In C, an enum or structure defined inside other structure has global
scope just like it had been defined outside the struct in the first
place. However, in C++, such a nested structure is given a name that
is nested inside the structure. This patch moves such affected
structures/enums out to global scope, so that code using them works
the same in C++ as it works today in C.
gdb/ChangeLog:
2015-02-27 Tom Tromey <tromey@redhat.com>
Pedro Alves <palves@redhat.com>
* dwarf2-frame.c (enum cfa_how_kind, struct
dwarf2_frame_state_reg_info): Move out of struct
dwarf2_frame_state.
* dwarf2read.c (struct tu_stats): Move out of struct
dwarf2_per_objfile.
(struct file_entry): Move out of struct line_header.
(struct nextfield, struct nextfnfield, struct fnfieldlist, struct
typedef_field_list): Move out of struct field_info.
* gdbtypes.h (enum dynamic_prop_kind, union dynamic_prop_data):
Move out of struct dynamic_prop.
(union type_owner, union field_location, struct field, struct
range_bounds, union type_specific): Move out of struct main_type.
(struct fn_fieldlist, struct fn_field, struct typedef_field)
(VOFFSET_STATIC): Move out of struct cplus_struct_type.
(struct call_site_target, union call_site_parameter_u, struct
call_site_parameter): Move out of struct call_site.
* m32c-tdep.c (enum m32c_prologue_kind): Move out of struct
m32c_prologue.
(enum srcdest_kind): Move out of struct srcdest.
* main.c (enum cmdarg_kind): Move out of struct cmdarg.
* prologue-value.h (enum prologue_value_kind): Move out of struct
prologue_value.
* s390-linux-tdep.c (enum s390_abi_kind): Move out of struct
gdbarch_tdep.
* stabsread.c (struct nextfield, struct next_fnfieldlist): Move
out of struct field_info.
* symfile.h (struct other_sections): Move out of struct
section_addr_info.
* symtab.c (struct symbol_cache_slot): Move out struct
block_symbol_cache.
* target-descriptions.c (enum tdesc_type_kind): Move out of
typedef struct tdesc_type.
* tui/tui-data.h (enum tui_line_or_address_kind): Move out of
struct tui_line_or_address.
* value.c (enum internalvar_kind, union internalvar_data): Move
out of struct internalvar.
* xtensa-tdep.h (struct ctype_cache): Move out of struct
gdbarch_tdep.
GDB is currently broken on all SPARC targets when using GCC 4.9.
When trying to print any local variable:
(gdb) p x
can't compute CFA for this frame
This is related to the fact that the compiler now generates DWARF 4
debugging info by default, and in particular that it now emits
DW_OP_call_frame_cfa, which triggers a limitation in dwarf2_frame_cfa:
/* This restriction could be lifted if other unwinders are known to
compute the frame base in a way compatible with the DWARF
unwinder. */
if (!frame_unwinder_is (this_frame, &dwarf2_frame_unwind)
&& !frame_unwinder_is (this_frame, &dwarf2_tailcall_frame_unwind))
error (_("can't compute CFA for this frame"));
We couldn't append the dwarf2 unwinder to all SPARC targets because
it does not work properly with StackGhost:
https://www.sourceware.org/ml/gdb-patches/2014-07/msg00012.html
We also later discovered that using the DWARF2 unwinder means
using it for computing the function's return address, which
is buggy when it comes to functions returning a struct (where
the return address is saved-pc+12 instead of saved-pc+8).
This is because GCC is emitting the info about the return address
as %o7/%i7 instead of the actual return address. For functions
that have debugging info, we compensate by looking at the function's
return type and add the extra +4, but for function without debug
info, we're stuck.
EricB and I twisted the issue in all the directions we could think of,
and unfortunately couldn't find a way to make it work without
introduction one regression or another.
But, stepping back a little, just removing the restriction seems to work
well for us on all both sparc-elf and {sparc,sparc64}-solaris.
After reviewing the previous discussions about this test, I could
not figure out whether some unwinders were already known to have
incompatible CFAs or if the concern was purely theoretical:
https://www.sourceware.org/ml/gdb-patches/2009-06/msg00191.htmlhttps://www.sourceware.org/ml/gdb-patches/2009-07/msg00570.htmlhttps://www.sourceware.org/ml/gdb-patches/2009-09/msg00027.html
At the moment, we took the approach of trying it out, and see what
happens...
gdb/ChangeLog:
PR backtrace/16215:
* dwarf2-frame.c (dwarf2_frame_cfa): Remove the restriction
the frame unwinder must either be the dwarf2_frame_unwind
or the dwarf2_tailcall_frame_unwind. Verify that this_frame's
stack_addr is valid before calling get_frame_base. Throw
an error if not valid.
Tested on sparc-solaris and sparc-elf with AdaCore's testsuite
(the FSF testsuite crashes all of AdaCore's solaris machines).
This removes dwarf2_compile_expr_to_ax, replacing it with a utility
function that fetches the CFA data and adding the code to actually
compile to an agent expression directly into
dwarf2_compile_expr_to_ax. This refactoring lets a later patch reuse
the new dwarf2_fetch_cfa_info.
gdb/ChangeLog
2014-12-12 Tom Tromey <tromey@redhat.com>
* dwarf2loc.c (dwarf2_compile_expr_to_ax) <DW_OP_call_frame_cfa>:
Update.
* dwarf2-frame.c (dwarf2_fetch_cfa_info): New function, based on
dwarf2_compile_cfa_to_ax.
(dwarf2_compile_cfa_to_ax): Remove.
* dwarf2-frame.h (dwarf2_fetch_cfa_info): Declare.
(dwarf2_compile_cfa_to_ax): Remove.
1. Background information
The MIPS architecture, as originally designed and implemented in
mid-1980s has a uniform instruction word size that is 4 bytes, naturally
aligned. As such all MIPS instructions are located at addresses that
have their bits #1 and #0 set to zeroes, and any attempt to execute an
instruction from an address that has any of the two bits set to one
causes an address error exception. This may for example happen when a
jump-register instruction is executed whose register value used as the
jump target has any of these bits set.
Then in mid 1990s LSI sought a way to improve code density for their
TinyRISC family of MIPS cores and invented an alternatively encoded
instruction set in a joint effort with MIPS Technologies (then a
subsidiary of SGI). The new instruction set has been named the MIPS16
ASE (Application-Specific Extension) and uses a variable instruction
word size, which is 2 bytes (as the name of the ASE suggests) for most,
but there are a couple of exceptions that take 4 bytes, and then most of
the 2-byte instructions can be treated with a 2-byte extension prefix to
expand the range of the immediate operands used.
As a result instructions are no longer 4-byte aligned, instead they are
aligned to a multiple of 2. That left the bit #0 still unused for code
references, be it for the standard MIPS (i.e. as originally invented) or
for the MIPS16 instruction set, and based on that observation a clever
trick was invented that on one hand allowed the processor to be
seamlessly switched between the two instruction sets at any time at the
run time while on the other avoided the introduction of any special
control register to do that.
So it is the bit #0 of the instruction address that was chosen as the
selector and named the ISA bit. Any instruction executed at an even
address is interpreted as a standard MIPS instruction (the address still
has to have its bit #1 clear), any instruction executed at an odd
address is interpreted as a MIPS16 instruction.
To switch between modes ordinary jump instructions are used, such as
used for function calls and returns, specifically the bit #0 of the
source register used in jump-register instructions selects the execution
(ISA) mode for the following piece of code to be interpreted in.
Additionally new jump-immediate instructions were added that flipped the
ISA bit to select the opposite mode upon execution. They were
considered necessary to avoid the need to make register jumps in all
cases as the original jump-immediate instructions provided no way to
change the bit #0 at all.
This was all important for cases where standard MIPS and MIPS16 code had
to be mixed, either for compatibility with the existing binary code base
or to access resources not reachable from MIPS16 code (the MIPS16
instruction set only provides access to general-purpose registers, and
not for example floating-point unit registers or privileged coprocessor
0 registers) -- pieces of code in the opposite mode can be executed as
ordinary subroutine calls.
A similar approach has been more recently adopted for the MIPS16
replacement instruction set defined as the so called microMIPS ASE.
This is another instruction set encoding introduced to the MIPS
architecture. Just like the MIPS16 ASE, the microMIPS instruction set
uses a variable-length encoding, where each instruction takes a multiple
of 2 bytes. The ISA bit has been reused and for microMIPS-capable
processors selects between the standard MIPS and the microMIPS mode
instead.
2. Statement of the problem
To put it shortly, MIPS16 and microMIPS code pointers used by GDB are
different to these observed at the run time. This results in the same
expressions being evaluated producing different results in GDB and in
the program being debugged. Obviously it's the results obtained at the
run time that are correct (they define how the program behaves) and
therefore by definition the results obtained in GDB are incorrect.
A bit longer description will record that obviously at the run time the
ISA bit has to be set correctly (refer to background information above
if unsure why so) or the program will not run as expected. This is
recorded in all the executable file structures used at the run time: the
dynamic symbol table (but not always the static one!), the GOT, and
obviously in all the addresses embedded in code or data of the program
itself, calculated by applying the appropriate relocations at the static
link time.
While a program is being processed by GDB, the ISA bit is stripped off
from any code addresses, presumably to make them the same as the
respective raw memory byte address used by the processor to access the
instruction in the instruction fetch access cycle. This stripping is
actually performed outside GDB proper, in BFD, specifically
_bfd_mips_elf_symbol_processing (elfxx-mips.c, see the piece of code at
the very bottom of that function, starting with an: "If this is an
odd-valued function symbol, assume it's a MIPS16 or microMIPS one."
comment).
This function is also responsible for symbol table dumps made by
`objdump' too, so you'll never see the ISA bit reported there by that
tool, you need to use `readelf'.
This is however unlike what is ever done at the run time, the ISA bit
once present is never stripped off, for example a cast like this:
(short *) main
will not strip the ISA bit off and if the resulting pointer is intended
to be used to access instructions as data, for example for software
instruction decoding (like for fault recovery or emulation in a signal
handler) or for self-modifying code then the bit still has to be
stripped off by an explicit AND operation.
This is probably best illustrated with a simple real program example.
Let's consider the following simple program:
$ cat foobar.c
int __attribute__ ((mips16)) foo (void)
{
return 1;
}
int __attribute__ ((mips16)) bar (void)
{
return 2;
}
int __attribute__ ((nomips16)) foo32 (void)
{
return 3;
}
int (*foo32p) (void) = foo32;
int (*foop) (void) = foo;
int fooi = (int) foo;
int
main (void)
{
return foop ();
}
$
This is plain C with no odd tricks, except from the instruction mode
attributes. They are not necessary to trigger this problem, I just put
them here so that the program can be contained in a single source file
and to make it obvious which function is MIPS16 code and which is not.
Let's try it with Linux, so that everyone can repeat this experiment:
$ mips-linux-gnu-gcc -mips16 -g -O2 -o foobar foobar.c
$
Let's have a look at some interesting symbols:
$ mips-linux-gnu-readelf -s foobar | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 7 entries:
Symbol table '.symtab' contains 95 entries:
55: 00000000 0 FILE LOCAL DEFAULT ABS foobar.c
66: 0040068c 4 FUNC GLOBAL DEFAULT [MIPS16] 12 bar
68: 00410848 4 OBJECT GLOBAL DEFAULT 21 foo32p
70: 00410844 4 OBJECT GLOBAL DEFAULT 21 foop
78: 00400684 8 FUNC GLOBAL DEFAULT 12 foo32
80: 00400680 4 FUNC GLOBAL DEFAULT [MIPS16] 12 foo
88: 00410840 4 OBJECT GLOBAL DEFAULT 21 fooi
$
Hmm, no sight of the ISA bit, but notice how foo and bar (but not
foo32!) have been marked as MIPS16 functions (ELF symbol structure's
`st_other' field is used for that).
So let's try to run and poke at this program with GDB. I'll be using a
native system for simplicity (I'll be using ellipses here and there to
remove unrelated clutter):
$ ./foobar
$ echo $?
1
$
So far, so good.
$ gdb ./foobar
[...]
(gdb) break main
Breakpoint 1 at 0x400490: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar
Breakpoint 1, main () at foobar.c:23
23 return foop ();
(gdb)
Yay, it worked! OK, so let's poke at it:
(gdb) print main
$1 = {int (void)} 0x400490 <main>
(gdb) print foo32
$2 = {int (void)} 0x400684 <foo32>
(gdb) print foo32p
$3 = (int (*)(void)) 0x400684 <foo32>
(gdb) print bar
$4 = {int (void)} 0x40068c <bar>
(gdb) print foo
$5 = {int (void)} 0x400680 <foo>
(gdb) print foop
$6 = (int (*)(void)) 0x400681 <foo>
(gdb)
A-ha! Here's the difference and finally the ISA bit!
(gdb) print /x fooi
$7 = 0x400681
(gdb) p/x $pc
p/x $pc
$8 = 0x400491
(gdb)
And here as well...
(gdb) advance foo
foo () at foobar.c:4
4 }
(gdb) disassemble
Dump of assembler code for function foo:
0x00400680 <+0>: jr ra
0x00400682 <+2>: li v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0 foo () at foobar.c:4
main () at foobar.c:24
24 }
Value returned is $9 = 1
(gdb) continue
Continuing.
[Inferior 1 (process 14103) exited with code 01]
(gdb)
So let's be a bit inquisitive...
(gdb) run
Starting program: .../foobar
Breakpoint 1, main () at foobar.c:23
23 return foop ();
(gdb)
Actually we do not like to run foo here at all. Let's run bar instead!
(gdb) set foop = bar
(gdb) print foop
$10 = (int (*)(void)) 0x40068c <bar>
(gdb)
Hmm, no ISA bit. Is it going to work?
(gdb) advance bar
bar () at foobar.c:9
9 }
(gdb) p/x $pc
$11 = 0x40068c
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068c <+0>: jr ra
0x0040068e <+2>: li v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0 bar () at foobar.c:9
Program received signal SIGILL, Illegal instruction.
bar () at foobar.c:9
9 }
(gdb)
Oops!
(gdb) p/x $pc
$12 = 0x40068c
(gdb)
We're still there!
(gdb) continue
Continuing.
Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)
So let's try something else:
(gdb) run
Starting program: .../foobar
Breakpoint 1, main () at foobar.c:23
23 return foop ();
(gdb) set foop = foo
(gdb) advance foo
foo () at foobar.c:4
4 }
(gdb) disassemble
Dump of assembler code for function foo:
=> 0x00400680 <+0>: jr ra
0x00400682 <+2>: li v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0 foo () at foobar.c:4
Program received signal SIGILL, Illegal instruction.
foo () at foobar.c:4
4 }
(gdb) continue
Continuing.
Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)
The same problem!
(gdb) run
Starting program:
/net/build2-lucid-cs/scratch/macro/mips-linux-fsf-gcc/isa-bit/foobar
Breakpoint 1, main () at foobar.c:23
23 return foop ();
(gdb) set foop = foo32
(gdb) advance foo32
foo32 () at foobar.c:14
14 }
(gdb) disassemble
Dump of assembler code for function foo32:
=> 0x00400684 <+0>: jr ra
0x00400688 <+4>: li v0,3
End of assembler dump.
(gdb) finish
Run till exit from #0 foo32 () at foobar.c:14
main () at foobar.c:24
24 }
Value returned is $14 = 3
(gdb) continue
Continuing.
[Inferior 1 (process 14113) exited with code 03]
(gdb)
That did work though, so it's the ISA bit only!
(gdb) quit
Enough!
That's the tip of the iceberg only though. So let's rebuild the
executable with some dynamic symbols:
$ mips-linux-gnu-gcc -mips16 -Wl,--export-dynamic -g -O2 -o foobar-dyn foobar.c
$ mips-linux-gnu-readelf -s foobar-dyn | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 32 entries:
6: 004009cd 4 FUNC GLOBAL DEFAULT 12 bar
8: 00410b88 4 OBJECT GLOBAL DEFAULT 21 foo32p
9: 00410b84 4 OBJECT GLOBAL DEFAULT 21 foop
15: 004009c4 8 FUNC GLOBAL DEFAULT 12 foo32
17: 004009c1 4 FUNC GLOBAL DEFAULT 12 foo
25: 00410b80 4 OBJECT GLOBAL DEFAULT 21 fooi
Symbol table '.symtab' contains 95 entries:
55: 00000000 0 FILE LOCAL DEFAULT ABS foobar.c
69: 004009cd 4 FUNC GLOBAL DEFAULT 12 bar
71: 00410b88 4 OBJECT GLOBAL DEFAULT 21 foo32p
72: 00410b84 4 OBJECT GLOBAL DEFAULT 21 foop
79: 004009c4 8 FUNC GLOBAL DEFAULT 12 foo32
81: 004009c1 4 FUNC GLOBAL DEFAULT 12 foo
89: 00410b80 4 OBJECT GLOBAL DEFAULT 21 fooi
$
OK, now the ISA bit is there for a change, but the MIPS16 `st_other'
attribute gone, hmm... What does `objdump' do then:
$ mips-linux-gnu-objdump -Tt foobar-dyn | egrep 'SYMBOL|foo|bar'
foobar-dyn: file format elf32-tradbigmips
SYMBOL TABLE:
00000000 l df *ABS* 00000000 foobar.c
004009cc g F .text 00000004 0xf0 bar
00410b88 g O .data 00000004 foo32p
00410b84 g O .data 00000004 foop
004009c4 g F .text 00000008 foo32
004009c0 g F .text 00000004 0xf0 foo
00410b80 g O .data 00000004 fooi
DYNAMIC SYMBOL TABLE:
004009cc g DF .text 00000004 Base 0xf0 bar
00410b88 g DO .data 00000004 Base foo32p
00410b84 g DO .data 00000004 Base foop
004009c4 g DF .text 00000008 Base foo32
004009c0 g DF .text 00000004 Base 0xf0 foo
00410b80 g DO .data 00000004 Base fooi
$
Hmm, the attribute (0xf0, printed raw) is back, and the ISA bit gone
again.
Let's have a look at some DWARF-2 records GDB uses (I'll be stripping
off a lot here for brevity) -- debug info:
$ mips-linux-gnu-readelf -wi foobar
Contents of the .debug_info section:
[...]
Compilation Unit @ offset 0x88:
Length: 0xbb (32-bit)
Version: 4
Abbrev Offset: 62
Pointer Size: 4
<0><93>: Abbrev Number: 1 (DW_TAG_compile_unit)
<94> DW_AT_producer : (indirect string, offset: 0x19e): GNU C 4.8.0 20120513 (experimental) -meb -mips16 -march=mips32r2 -mhard-float -mllsc -mplt -mno-synci -mno-shared -mabi=32 -g -O2
<98> DW_AT_language : 1 (ANSI C)
<99> DW_AT_name : (indirect string, offset: 0x190): foobar.c
<9d> DW_AT_comp_dir : (indirect string, offset: 0x225): [...]
<a1> DW_AT_ranges : 0x0
<a5> DW_AT_low_pc : 0x0
<a9> DW_AT_stmt_list : 0x27
<1><ad>: Abbrev Number: 2 (DW_TAG_subprogram)
<ae> DW_AT_external : 1
<ae> DW_AT_name : foo
<b2> DW_AT_decl_file : 1
<b3> DW_AT_decl_line : 1
<b4> DW_AT_prototyped : 1
<b4> DW_AT_type : <0xc2>
<b8> DW_AT_low_pc : 0x400680
<bc> DW_AT_high_pc : 0x400684
<c0> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<c2> DW_AT_GNU_all_call_sites: 1
<1><c2>: Abbrev Number: 3 (DW_TAG_base_type)
<c3> DW_AT_byte_size : 4
<c4> DW_AT_encoding : 5 (signed)
<c5> DW_AT_name : int
<1><c9>: Abbrev Number: 4 (DW_TAG_subprogram)
<ca> DW_AT_external : 1
<ca> DW_AT_name : (indirect string, offset: 0x18a): foo32
<ce> DW_AT_decl_file : 1
<cf> DW_AT_decl_line : 11
<d0> DW_AT_prototyped : 1
<d0> DW_AT_type : <0xc2>
<d4> DW_AT_low_pc : 0x400684
<d8> DW_AT_high_pc : 0x40068c
<dc> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<de> DW_AT_GNU_all_call_sites: 1
<1><de>: Abbrev Number: 2 (DW_TAG_subprogram)
<df> DW_AT_external : 1
<df> DW_AT_name : bar
<e3> DW_AT_decl_file : 1
<e4> DW_AT_decl_line : 6
<e5> DW_AT_prototyped : 1
<e5> DW_AT_type : <0xc2>
<e9> DW_AT_low_pc : 0x40068c
<ed> DW_AT_high_pc : 0x400690
<f1> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<f3> DW_AT_GNU_all_call_sites: 1
<1><f3>: Abbrev Number: 5 (DW_TAG_subprogram)
<f4> DW_AT_external : 1
<f4> DW_AT_name : (indirect string, offset: 0x199): main
<f8> DW_AT_decl_file : 1
<f9> DW_AT_decl_line : 21
<fa> DW_AT_prototyped : 1
<fa> DW_AT_type : <0xc2>
<fe> DW_AT_low_pc : 0x400490
<102> DW_AT_high_pc : 0x4004a4
<106> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<108> DW_AT_GNU_all_tail_call_sites: 1
[...]
$
-- no sign of the ISA bit anywhere -- frame info:
$ mips-linux-gnu-readelf -wf foobar
[...]
Contents of the .debug_frame section:
00000000 0000000c ffffffff CIE
Version: 1
Augmentation: ""
Code alignment factor: 1
Data alignment factor: -4
Return address column: 31
DW_CFA_def_cfa_register: r29
DW_CFA_nop
00000010 0000000c 00000000 FDE cie=00000000 pc=00400680..00400684
00000020 0000000c 00000000 FDE cie=00000000 pc=00400684..0040068c
00000030 0000000c 00000000 FDE cie=00000000 pc=0040068c..00400690
00000040 00000018 00000000 FDE cie=00000000 pc=00400490..004004a4
DW_CFA_advance_loc: 6 to 00400496
DW_CFA_def_cfa_offset: 32
DW_CFA_offset: r31 at cfa-4
DW_CFA_advance_loc: 6 to 0040049c
DW_CFA_restore: r31
DW_CFA_def_cfa_offset: 0
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
[...]
$
-- no sign of the ISA bit anywhere -- range info (GDB doesn't use arange):
$ mips-linux-gnu-readelf -wR foobar
Contents of the .debug_ranges section:
Offset Begin End
00000000 00400680 00400690
00000000 00400490 004004a4
00000000 <End of list>
$
-- no sign of the ISA bit anywhere -- line info:
$ mips-linux-gnu-readelf -wl foobar
Raw dump of debug contents of section .debug_line:
[...]
Offset: 0x27
Length: 78
DWARF Version: 2
Prologue Length: 31
Minimum Instruction Length: 1
Initial value of 'is_stmt': 1
Line Base: -5
Line Range: 14
Opcode Base: 13
Opcodes:
Opcode 1 has 0 args
Opcode 2 has 1 args
Opcode 3 has 1 args
Opcode 4 has 1 args
Opcode 5 has 1 args
Opcode 6 has 0 args
Opcode 7 has 0 args
Opcode 8 has 0 args
Opcode 9 has 1 args
Opcode 10 has 0 args
Opcode 11 has 0 args
Opcode 12 has 1 args
The Directory Table is empty.
The File Name Table:
Entry Dir Time Size Name
1 0 0 0 foobar.c
Line Number Statements:
Extended opcode 2: set Address to 0x400681
Special opcode 6: advance Address by 0 to 0x400681 and Line by 1 to 2
Special opcode 7: advance Address by 0 to 0x400681 and Line by 2 to 4
Special opcode 55: advance Address by 3 to 0x400684 and Line by 8 to 12
Special opcode 7: advance Address by 0 to 0x400684 and Line by 2 to 14
Advance Line by -7 to 7
Special opcode 131: advance Address by 9 to 0x40068d and Line by 0 to 7
Special opcode 7: advance Address by 0 to 0x40068d and Line by 2 to 9
Advance PC by 3 to 0x400690
Extended opcode 1: End of Sequence
Extended opcode 2: set Address to 0x400491
Advance Line by 21 to 22
Copy
Special opcode 6: advance Address by 0 to 0x400491 and Line by 1 to 23
Special opcode 60: advance Address by 4 to 0x400495 and Line by -1 to 22
Special opcode 34: advance Address by 2 to 0x400497 and Line by 1 to 23
Special opcode 62: advance Address by 4 to 0x40049b and Line by 1 to 24
Special opcode 32: advance Address by 2 to 0x40049d and Line by -1 to 23
Special opcode 6: advance Address by 0 to 0x40049d and Line by 1 to 24
Advance PC by 7 to 0x4004a4
Extended opcode 1: End of Sequence
[...]
-- a-ha, the ISA bit is there! However it's not always right for some
reason, I don't have a small test case to show it, but here's an excerpt
from MIPS16 libc, a prologue of a function:
00019630 <__libc_init_first>:
19630: e8a0 jrc ra
19632: 6500 nop
00019634 <_init>:
19634: f000 6a11 li v0,17
19638: f7d8 0b08 la v1,15e00 <_DYNAMIC+0x15c54>
1963c: f400 3240 sll v0,16
19640: e269 addu v0,v1
19642: 659a move gp,v0
19644: 64f6 save 48,ra,s0-s1
19646: 671c move s0,gp
19648: d204 sw v0,16(sp)
1964a: f352 984c lw v0,-27828(s0)
1964e: 6724 move s1,a0
and the corresponding DWARF-2 line info:
Line Number Statements:
Extended opcode 2: set Address to 0x19631
Advance Line by 44 to 45
Copy
Special opcode 8: advance Address by 0 to 0x19631 and Line by 3 to 48
Special opcode 66: advance Address by 4 to 0x19635 and Line by 5 to 53
Advance PC by constant 17 to 0x19646
Special opcode 25: advance Address by 1 to 0x19647 and Line by 6 to 59
Advance Line by -6 to 53
Special opcode 33: advance Address by 2 to 0x19649 and Line by 0 to 53
Special opcode 39: advance Address by 2 to 0x1964b and Line by 6 to 59
Advance Line by -6 to 53
Special opcode 61: advance Address by 4 to 0x1964f and Line by 0 to 53
-- see that "Advance PC by constant 17" there? It clears the ISA bit,
however code at 0x19646 is not standard MIPS code at all. For some
reason the constant is always 17, I've never seen DW_LNS_const_add_pc
used with any other value -- is that a binutils bug or what?
3. Solution:
I think we should retain the value of the ISA bit in code references,
that is effectively treat them as cookies as they indeed are (although
trivially calculated) rather than raw memory byte addresses.
In a perfect world both the static symbol table and the respective
DWARF-2 records should be fixed to include the ISA bit in all the cases.
I think however that this is infeasible.
All the uses of `_bfd_mips_elf_symbol_processing' can not necessarily be
tracked down. This function is used by `elf_slurp_symbol_table' that in
turn is used by `bfd_canonicalize_symtab' and
`bfd_canonicalize_dynamic_symtab', which are public interfaces.
Similarly DWARF-2 records are used outside GDB, one notable if a bit
questionable is the exception unwinder (libgcc/unwind-dw2.c) -- I have
identified at least bits in `execute_cfa_program' and
`uw_frame_state_for', both around the calls to `_Unwind_IsSignalFrame',
that would need an update as they effectively flip the ISA bit freely;
see also the comment about MASK_RETURN_ADDR in gcc/config/mips/mips.h.
But there may be more places. Any change in how DWARF-2 records are
produced would require an update there and would cause compatibility
problems with libgcc.a binaries already distributed; given that this is
a static library a complex change involving function renames would
likely be required.
I propose therefore to accept the existing inconsistencies and deal with
them entirely within GDB. I have figured out that the ISA bit lost in
various places can still be recovered as long as we have symbol
information -- that'll have the `st_other' attribute correctly set to
one of standard MIPS/MIPS16/microMIPS encoding.
Here's the resulting change. It adds a couple of new `gdbarch' hooks,
one to update symbol information with the ISA bit lost in
`_bfd_mips_elf_symbol_processing', and two other ones to adjust DWARF-2
records as they're processed. The ISA bit is set in each address
handled according to information retrieved from the symbol table for the
symbol spanning the address if any; limits are adjusted based on the
address they point to related to the respective base address.
Additionally minimal symbol information has to be adjusted accordingly
in its gdbarch hook.
With these changes in place some complications with ISA bit juggling in
the PC that never fully worked can be removed from the MIPS backend.
Conversely, the generic dynamic linker event special breakpoint symbol
handler has to be updated to call the minimal symbol gdbarch hook to
record that the symbol is a MIPS16 or microMIPS address if applicable or
the breakpoint will be set at the wrong address and either fail to work
or cause SIGTRAPs (this is because the symbol is handled early on and
bypasses regular symbol processing).
4. Results obtained
The change fixes the example above -- to repeat only the crucial steps:
(gdb) break main
Breakpoint 1 at 0x400491: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar
Breakpoint 1, main () at foobar.c:23
23 return foop ();
(gdb) print foo
$1 = {int (void)} 0x400681 <foo>
(gdb) set foop = bar
(gdb) advance bar
bar () at foobar.c:9
9 }
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068d <+0>: jr ra
0x0040068f <+2>: li v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0 bar () at foobar.c:9
main () at foobar.c:24
24 }
Value returned is $2 = 2
(gdb) continue
Continuing.
[Inferior 1 (process 14128) exited with code 02]
(gdb)
-- excellent!
The change removes about 90 failures per MIPS16 multilib in mips-sde-elf
testing too, results for MIPS16 are now similar to that for standard
MIPS; microMIPS results are a bit worse because of host-I/O problems in
QEMU used instead of MIPSsim for microMIPS testing only:
=== gdb Summary ===
# of expected passes 14299
# of unexpected failures 187
# of expected failures 56
# of known failures 58
# of unresolved testcases 11
# of untested testcases 52
# of unsupported tests 174
MIPS16:
=== gdb Summary ===
# of expected passes 14298
# of unexpected failures 187
# of unexpected successes 2
# of expected failures 54
# of known failures 58
# of unresolved testcases 12
# of untested testcases 52
# of unsupported tests 174
microMIPS:
=== gdb Summary ===
# of expected passes 14149
# of unexpected failures 201
# of unexpected successes 2
# of expected failures 54
# of known failures 58
# of unresolved testcases 7
# of untested testcases 53
# of unsupported tests 175
2014-12-12 Maciej W. Rozycki <macro@codesourcery.com>
Maciej W. Rozycki <macro@mips.com>
Pedro Alves <pedro@codesourcery.com>
gdb/
* gdbarch.sh (elf_make_msymbol_special): Change type to `F',
remove `predefault' and `invalid_p' initializers.
(make_symbol_special): New architecture method.
(adjust_dwarf2_addr, adjust_dwarf2_line): Likewise.
(objfile, symbol): New declarations.
* arch-utils.h (default_elf_make_msymbol_special): Remove
prototype.
(default_make_symbol_special): New prototype.
(default_adjust_dwarf2_addr): Likewise.
(default_adjust_dwarf2_line): Likewise.
* mips-tdep.h (mips_unmake_compact_addr): New prototype.
* arch-utils.c (default_elf_make_msymbol_special): Remove
function.
(default_make_symbol_special): New function.
(default_adjust_dwarf2_addr): Likewise.
(default_adjust_dwarf2_line): Likewise.
* dwarf2-frame.c (decode_frame_entry_1): Call
`gdbarch_adjust_dwarf2_addr'.
* dwarf2loc.c (dwarf2_find_location_expression): Likewise.
* dwarf2read.c (create_addrmap_from_index): Likewise.
(process_psymtab_comp_unit_reader): Likewise.
(add_partial_symbol): Likewise.
(add_partial_subprogram): Likewise.
(process_full_comp_unit): Likewise.
(read_file_scope): Likewise.
(read_func_scope): Likewise. Call `gdbarch_make_symbol_special'.
(read_lexical_block_scope): Call `gdbarch_adjust_dwarf2_addr'.
(read_call_site_scope): Likewise.
(dwarf2_ranges_read): Likewise.
(dwarf2_record_block_ranges): Likewise.
(read_attribute_value): Likewise.
(dwarf_decode_lines_1): Call `gdbarch_adjust_dwarf2_line'.
(new_symbol_full): Call `gdbarch_adjust_dwarf2_addr'.
* elfread.c (elf_symtab_read): Don't call
`gdbarch_elf_make_msymbol_special' if unset.
* mips-linux-tdep.c (micromips_linux_sigframe_validate): Strip
the ISA bit from the PC.
* mips-tdep.c (mips_unmake_compact_addr): New function.
(mips_elf_make_msymbol_special): Set the ISA bit in the symbol's
address appropriately.
(mips_make_symbol_special): New function.
(mips_pc_is_mips): Set the ISA bit before symbol lookup.
(mips_pc_is_mips16): Likewise.
(mips_pc_is_micromips): Likewise.
(mips_pc_isa): Likewise.
(mips_adjust_dwarf2_addr): New function.
(mips_adjust_dwarf2_line): Likewise.
(mips_read_pc, mips_unwind_pc): Keep the ISA bit.
(mips_addr_bits_remove): Likewise.
(mips_skip_trampoline_code): Likewise.
(mips_write_pc): Don't set the ISA bit.
(mips_eabi_push_dummy_call): Likewise.
(mips_o64_push_dummy_call): Likewise.
(mips_gdbarch_init): Install `mips_make_symbol_special',
`mips_adjust_dwarf2_addr' and `mips_adjust_dwarf2_line' gdbarch
handlers.
* solib.c (gdb_bfd_lookup_symbol_from_symtab): Get
target-specific symbol address adjustments.
* gdbarch.h: Regenerate.
* gdbarch.c: Regenerate.
2014-12-12 Maciej W. Rozycki <macro@codesourcery.com>
gdb/testsuite/
* gdb.base/func-ptrs.c: New file.
* gdb.base/func-ptrs.exp: New file.
Currently "symtabs" in gdb are stored as a single linked list of
struct symtab that contains both symbol symtabs (the blockvectors)
and file symtabs (the linetables).
This has led to confusion, bugs, and performance issues.
This patch is conceptually very simple: split struct symtab into
two pieces: one part containing things common across the entire
compilation unit, and one part containing things specific to each
source file.
Example.
For the case of a program built out of these files:
foo.c
foo1.h
foo2.h
bar.c
foo1.h
bar.h
Today we have a single list of struct symtabs:
objfile -> foo.c -> foo1.h -> foo2.h -> bar.c -> foo1.h -> bar.h -> NULL
where "->" means the "next" pointer in struct symtab.
With this patch, that turns into:
objfile -> foo.c(cu) -> bar.c(cu) -> NULL
| |
v v
foo.c bar.c
| |
v v
foo1.h foo1.h
| |
v v
foo2.h bar.h
| |
v v
NULL NULL
where "foo.c(cu)" and "bar.c(cu)" are struct compunit_symtab objects,
and the files foo.c, etc. are struct symtab objects.
So now, for example, when we want to iterate over all blockvectors
we can now just iterate over the compunit_symtab list.
Plus a lot of the data that was either unused or replicated for each
symtab in a compilation unit now lives in struct compunit_symtab.
E.g., the objfile pointer, the producer string, etc.
I thought of moving "language" out of struct symtab but there is
logic to try to compute the language based on previously seen files,
and I think that's best left as is for now.
With my standard monster benchmark with -readnow (which I can't actually
do, but based on my calculations), whereas today the list requires
77MB to store all the struct symtabs, it now only requires 37MB.
A modest space savings given the gigabytes needed for all the debug info,
etc. Still, it's nice. Plus, whereas today we create a copy of dirname
for each source file symtab in a compilation unit, we now only create one
for the compunit.
So this patch is basically just a data structure reorg,
I don't expect significant performance improvements from it.
Notes:
1) A followup patch can do a similar split for struct partial_symtab.
I have left that until after I get the changes I want in to
better utilize .gdb_index (it may affect how we do partial syms).
2) Another followup patch *could* rename struct symtab.
The term "symtab" is ambiguous and has been a source of confusion.
In this patch I'm leaving it alone, calling it the "historical" name
of "filetabs", which is what they are now: just the file-name + line-table.
gdb/ChangeLog:
Split struct symtab into two: struct symtab and compunit_symtab.
* amd64-tdep.c (amd64_skip_xmm_prologue): Fetch producer from compunit.
* block.c (blockvector_for_pc_sect): Change "struct symtab *" argument
to "struct compunit_symtab *". All callers updated.
(set_block_compunit_symtab): Renamed from set_block_symtab. Change
"struct symtab *" argument to "struct compunit_symtab *".
All callers updated.
(get_block_compunit_symtab): Renamed from get_block_symtab. Change
result to "struct compunit_symtab *". All callers updated.
(find_iterator_compunit_symtab): Renamed from find_iterator_symtab.
Change result to "struct compunit_symtab *". All callers updated.
* block.h (struct global_block) <compunit_symtab>: Renamed from symtab.
hange type to "struct compunit_symtab *". All uses updated.
(struct block_iterator) <d.compunit_symtab>: Renamed from "d.symtab".
Change type to "struct compunit_symtab *". All uses updated.
* buildsym.c (struct buildsym_compunit): New struct.
(subfiles, buildsym_compdir, buildsym_objfile, main_subfile): Delete.
(buildsym_compunit): New static global.
(finish_block_internal): Update to fetch objfile from
buildsym_compunit.
(make_blockvector): Delete objfile argument.
(start_subfile): Rewrite to use buildsym_compunit. Don't initialize
debugformat, producer.
(start_buildsym_compunit): New function.
(free_buildsym_compunit): Renamed from free_subfiles_list.
All callers updated.
(patch_subfile_names): Rewrite to use buildsym_compunit.
(get_compunit_symtab): New function.
(get_macro_table): Delete argument comp_dir. All callers updated.
(start_symtab): Change result to "struct compunit_symtab *".
All callers updated. Create the subfile of the main source file.
(watch_main_source_file_lossage): Rewrite to use buildsym_compunit.
(reset_symtab_globals): Update.
(end_symtab_get_static_block): Update to use buildsym_compunit.
(end_symtab_without_blockvector): Rewrite.
(end_symtab_with_blockvector): Change result to
"struct compunit_symtab *". All callers updated.
Update to use buildsym_compunit. Don't set symtab->dirname,
instead set it in the compunit.
Explicitly make sure main symtab is first in its list.
Set debugformat, producer, blockvector, block_line_section, and
macrotable in the compunit.
(end_symtab_from_static_block): Change result to
"struct compunit_symtab *". All callers updated.
(end_symtab, end_expandable_symtab): Ditto.
(set_missing_symtab): Change symtab argument to
"struct compunit_symtab *". All callers updated.
(augment_type_symtab): Ditto.
(record_debugformat): Update to use buildsym_compunit.
(record_producer): Update to use buildsym_compunit.
* buildsym.h (struct subfile) <dirname>: Delete.
<producer, debugformat>: Delete.
<buildsym_compunit>: New member.
(get_compunit_symtab): Declare.
* dwarf2read.c (struct type_unit_group) <compunit_symtab>: Renamed
from primary_symtab. Change type to "struct compunit_symtab *".
All uses updated.
(dwarf2_start_symtab): Change result to "struct compunit_symtab *".
All callers updated.
(dwarf_decode_macros): Delete comp_dir argument. All callers updated.
(struct dwarf2_per_cu_quick_data) <compunit_symtab>: Renamed from
symtab. Change type to "struct compunit_symtab *". All uses updated.
(dw2_instantiate_symtab): Change result to "struct compunit_symtab *".
All callers updated.
(dw2_find_last_source_symtab): Ditto.
(dw2_lookup_symbol): Ditto.
(recursively_find_pc_sect_compunit_symtab): Renamed from
recursively_find_pc_sect_symtab. Change result to
"struct compunit_symtab *". All callers updated.
(dw2_find_pc_sect_compunit_symtab): Renamed from
dw2_find_pc_sect_symtab. Change result to
"struct compunit_symtab *". All callers updated.
(get_compunit_symtab): Renamed from get_symtab. Change result to
"struct compunit_symtab *". All callers updated.
(recursively_compute_inclusions): Change type of immediate_parent
argument to "struct compunit_symtab *". All callers updated.
(compute_compunit_symtab_includes): Renamed from
compute_symtab_includes. All callers updated. Rewrite to compute
includes of compunit_symtabs and not symtabs.
(process_full_comp_unit): Update to work with struct compunit_symtab.
(process_full_type_unit): Ditto.
(dwarf_decode_lines_1): Delete argument comp_dir. All callers updated.
(dwarf_decode_lines): Remove special case handling of main subfile.
(macro_start_file): Delete argument comp_dir. All callers updated.
(dwarf_decode_macro_bytes): Ditto.
* guile/scm-block.c (bkscm_print_block_syms_progress_smob): Update to
use struct compunit_symtab.
* i386-tdep.c (i386_skip_prologue): Fetch producer from compunit.
* jit.c (finalize_symtab): Build compunit_symtab.
* jv-lang.c (get_java_class_symtab): Change result to
"struct compunit_symtab *". All callers updated.
* macroscope.c (sal_macro_scope): Fetch macro table from compunit.
* macrotab.c (struct macro_table) <compunit_symtab>: Renamed from
comp_dir. Change type to "struct compunit_symtab *".
All uses updated.
(new_macro_table): Change comp_dir argument to cust,
"struct compunit_symtab *". All callers updated.
* maint.c (struct cmd_stats) <nr_compunit_symtabs>: Renamed from
nr_primary_symtabs. All uses updated.
(count_symtabs_and_blocks): Update to handle compunits.
(report_command_stats): Update output, "primary symtabs" renamed to
"compunits".
* mdebugread.c (new_symtab): Change result to
"struct compunit_symtab *". All callers updated.
(parse_procedure): Change type of search_symtab argument to
"struct compunit_symtab *". All callers updated.
* objfiles.c (objfile_relocate1): Loop over blockvectors in a
separate loop.
* objfiles.h (struct objfile) <compunit_symtabs>: Renamed from
symtabs. Change type to "struct compunit_symtab *". All uses updated.
(ALL_OBJFILE_FILETABS): Renamed from ALL_OBJFILE_SYMTABS.
All uses updated.
(ALL_OBJFILE_COMPUNITS): Renamed from ALL_OBJFILE_PRIMARY_SYMTABS.
All uses updated.
(ALL_FILETABS): Renamed from ALL_SYMTABS. All uses updated.
(ALL_COMPUNITS): Renamed from ALL_PRIMARY_SYMTABS. All uses updated.
* psympriv.h (struct partial_symtab) <compunit_symtab>: Renamed from
symtab. Change type to "struct compunit_symtab *". All uses updated.
* psymtab.c (psymtab_to_symtab): Change result type to
"struct compunit_symtab *". All callers updated.
(find_pc_sect_compunit_symtab_from_partial): Renamed from
find_pc_sect_symtab_from_partial. Change result type to
"struct compunit_symtab *". All callers updated.
(lookup_symbol_aux_psymtabs): Change result type to
"struct compunit_symtab *". All callers updated.
(find_last_source_symtab_from_partial): Ditto.
* python/py-symtab.c (stpy_get_producer): Fetch producer from compunit.
* source.c (forget_cached_source_info_for_objfile): Fetch debugformat
and macro_table from compunit.
* symfile-debug.c (debug_qf_find_last_source_symtab): Change result
type to "struct compunit_symtab *". All callers updated.
(debug_qf_lookup_symbol): Ditto.
(debug_qf_find_pc_sect_compunit_symtab): Renamed from
debug_qf_find_pc_sect_symtab, change result type to
"struct compunit_symtab *". All callers updated.
* symfile.c (allocate_symtab): Delete objfile argument.
New argument cust.
(allocate_compunit_symtab): New function.
(add_compunit_symtab_to_objfile): New function.
* symfile.h (struct quick_symbol_functions) <lookup_symbol>:
Change result type to "struct compunit_symtab *". All uses updated.
<find_pc_sect_compunit_symtab>: Renamed from find_pc_sect_symtab.
Change result type to "struct compunit_symtab *". All uses updated.
* symmisc.c (print_objfile_statistics): Compute blockvector count in
separate loop.
(dump_symtab_1): Update test for primary source symtab.
(maintenance_info_symtabs): Update to handle compunit symtabs.
(maintenance_check_symtabs): Ditto.
* symtab.c (set_primary_symtab): Delete.
(compunit_primary_filetab): New function.
(compunit_language): New function.
(iterate_over_some_symtabs): Change type of arguments "first",
"after_last" to "struct compunit_symtab *". All callers updated.
Update to loop over symtabs in each compunit.
(error_in_psymtab_expansion): Rename symtab argument to cust,
and change type to "struct compunit_symtab *". All callers updated.
(find_pc_sect_compunit_symtab): Renamed from find_pc_sect_symtab.
Change result type to "struct compunit_symtab *". All callers updated.
(find_pc_compunit_symtab): Renamed from find_pc_symtab.
Change result type to "struct compunit_symtab *". All callers updated.
(find_pc_sect_line): Only loop over symtabs within selected compunit
instead of all symtabs in the objfile.
* symtab.h (struct symtab) <blockvector>: Moved to compunit_symtab.
<compunit_symtab> New member.
<block_line_section>: Moved to compunit_symtab.
<locations_valid>: Ditto.
<epilogue_unwind_valid>: Ditto.
<macro_table>: Ditto.
<dirname>: Ditto.
<debugformat>: Ditto.
<producer>: Ditto.
<objfile>: Ditto.
<call_site_htab>: Ditto.
<includes>: Ditto.
<user>: Ditto.
<primary>: Delete
(SYMTAB_COMPUNIT): New macro.
(SYMTAB_BLOCKVECTOR): Update definition.
(SYMTAB_OBJFILE): Update definition.
(SYMTAB_DIRNAME): Update definition.
(struct compunit_symtab): New type. Common members among all source
symtabs within a compilation unit moved here. All uses updated.
(COMPUNIT_OBJFILE): New macro.
(COMPUNIT_FILETABS): New macro.
(COMPUNIT_DEBUGFORMAT): New macro.
(COMPUNIT_PRODUCER): New macro.
(COMPUNIT_DIRNAME): New macro.
(COMPUNIT_BLOCKVECTOR): New macro.
(COMPUNIT_BLOCK_LINE_SECTION): New macro.
(COMPUNIT_LOCATIONS_VALID): New macro.
(COMPUNIT_EPILOGUE_UNWIND_VALID): New macro.
(COMPUNIT_CALL_SITE_HTAB): New macro.
(COMPUNIT_MACRO_TABLE): New macro.
(ALL_COMPUNIT_FILETABS): New macro.
(compunit_symtab_ptr): New typedef.
(DEF_VEC_P (compunit_symtab_ptr)): New vector type.
gdb/testsuite/ChangeLog:
* gdb.base/maint.exp: Update expected output.
This patch fixes a problem that prevented use of the Dwarf unwinders on SPU,
because dwarf2-frame.c common code did not support the situation where the
stack and/or frame pointer is maintained in a *vector* register. This is
because read_addr_from_reg is hard-coded to assume that such pointers can
be read from registers via a simple get_frame_register / unpack_pointer
operation.
Now, there *is* a routine address_from_register that calls into the
appropriate tdep routines to handle pointer values in "weird" registers
like on SPU, but it turns out I cannot simply change dwarf2-frame.c to
use address_from_register. This is because address_from_register uses
value_from_register to create a (temporary) value, and that routine
at some point calls get_frame_id in order to set up that value's
VALUE_FRAME_ID entry.
However, the dwarf2-frame.c read_addr_from_reg routine will be called
during early unwinding (to unwind the frame's CFA), at which point the
frame's ID is not actually known yet! This would cause an assert.
On the other hand, we may notice that VALUE_FRAME_ID is only needed in the
value returned by value_from_register if that value is later used as an
lvalue. But this is obviously never done to the temporary value used in
address_from_register. So, if we could change address_from_register to
not call value_from_register but instead accept constructing a value
that doesn't have VALUE_FRAME_ID set, things should be fine.
To do that, we can change the value_from_register callback to accept
a FRAME_ID instead of a FRAME; the only existing uses of the FRAME
argument were either to extract its frame ID, or its gdbarch. (To
keep a way of getting at the latter, we also change the callback's
type from "f" to "m".) Together with the required follow-on changes
in the existing value_from_register implementations (including the
default one), this seems to fix the problem.
As another minor interface cleanup, I've removed the explicit TYPE
argument from address_from_register. This routine really always
uses a default pointer type, and in the new implementation it -to
some extent- relies on that fact, in that it will now no longer
handle types that require gdbarch_convert_register_p handling.
gdb:
2014-04-17 Ulrich Weigand <uweigand@de.ibm.com>
* gdbarch.sh (value_from_register): Make class "m" instead of "f".
Replace FRAME argument with FRAME_ID.
* gdbarch.c, gdbarch.h: Regenerate.
* findvar.c (default_value_from_register): Add GDBARCH argument;
replace FRAME by FRAME_ID. No longer call get_frame_id.
(value_from_register): Update call to gdbarch_value_from_register.
* value.h (default_value_from_register): Update prototype.
* s390-linux-tdep.c (s390_value_from_register): Update interface
and call to default_value_from_register.
* spu-tdep.c (spu_value_from_register): Likewise.
* findvar.c (address_from_register): Remove TYPE argument.
Do not call value_from_register; use gdbarch_value_from_register
with null_frame_id instead.
* value.h (address_from_register): Update prototype.
* dwarf2-frame.c (read_addr_from_reg): Use address_from_register.
* dwarf2loc.c (dwarf_expr_read_addr_from_reg): Update for
address_from_register interface change.
Extend the always failing unwinder to provide the PC based on the call
structure detected in the branch trace.
The unwinder supports normal frames and tailcall frames.
Inline frames are not supported.
2014-01-16 Markus Metzger <markus.t.metzger@intel.com>
* record.h (record_btrace_frame_unwind)
(record_btrace_tailcall_frame_unwind): New declarations.
* dwarf2-frame: Include record.h
(dwarf2_frame_cfa): Throw an error for btrace frames.
* record-btrace.c: Include hashtab.h.
(btrace_get_bfun_name): New.
(btrace_call_history): Call btrace_get_bfun_name.
(struct btrace_frame_cache): New.
(bfcache): New.
(bfcache_hash, bfcache_eq, bfcache_new): New.
(btrace_get_frame_function): New.
(record_btrace_frame_unwind_stop_reason): Allow unwinding.
(record_btrace_frame_this_id): Compute own id.
(record_btrace_frame_prev_register): Provide PC, throw_error
for all other registers.
(record_btrace_frame_sniffer): Detect btrace frames.
(record_btrace_tailcall_frame_sniffer): New.
(record_btrace_frame_dealloc_cache): New.
(record_btrace_frame_unwind): Add new functions.
(record_btrace_tailcall_frame_unwind): New.
(_initialize_record_btrace): Allocate cache.
* btrace.c (btrace_clear): Call reinit_frame_cache.
* NEWS: Announce it.
testsuite/
* gdb.btrace/record_goto.exp: Add backtrace test.
* gdb.btrace/tailcall.exp: Add backtrace test.
Swap the unwind stop reason check and the unwinder check to allow
non-dwarf2 frame types to fail with a recoverable error.
gdb/
2013-02-11 Jan Kratochvil <jan.kratochvil@redhat.com>
* dwarf2-frame.c (dwarf2_frame_cfa): Move UNWIND_UNAVAILABLE check
earlier.
Like when stepping, the current stack frame location is expected to be
printed as result of tfind command, if that results in moving to a
different function. In tfind_1 we see:
if (from_tty
&& (has_stack_frames () || traceframe_number >= 0))
{
enum print_what print_what;
/* NOTE: in imitation of the step command, try to determine
whether we have made a transition from one function to
another. If so, we'll print the "stack frame" (ie. the new
function and it's arguments) -- otherwise we'll just show the
new source line. */
if (frame_id_eq (old_frame_id,
get_frame_id (get_current_frame ())))
print_what = SRC_LINE;
else
print_what = SRC_AND_LOC;
print_stack_frame (get_selected_frame (NULL), 1, print_what, 1);
do_displays ();
}
However, when we haven't collected any registers in the tracepoint
(collect $regs), that doesn't actually work:
(gdb) tstart
(gdb) info tracepoints
Num Type Disp Enb Address What
1 tracepoint keep y 0x080483b7 in func0
at ../.././../git/gdb/testsuite/gdb.trace/circ.c:28
collect testload
installed on target
2 tracepoint keep y 0x080483bc in func1
at ../.././../git/gdb/testsuite/gdb.trace/circ.c:32
collect testload
installed on target
(gdb) c
Continuing.
Breakpoint 3, end () at ../.././../git/gdb/testsuite/gdb.trace/circ.c:72
72 }
(gdb) tstop
(gdb) tfind start
Found trace frame 0, tracepoint 1
#0 func0 () at ../.././../git/gdb/testsuite/gdb.trace/circ.c:28
28 }
(gdb) tfind
Found trace frame 1, tracepoint 2
32 }
(gdb)
When we don't have info about the stack available
(UNWIND_UNAVAILABLE), frames end up with outer_frame_id as frame ID.
And in the scenario above, the issue is that both frames before and
after the second tfind (the frames for func0 an func1) have the same
id (outer_frame_id), so the frame_id_eq check returns false, even
though the frames were of different functions. GDB knows that,
because the PC is inferred from the tracepoint's address, even if no
registers were collected.
To fix this, this patch adds support for frame ids with a valid code
address, but <unavailable> stack address, and then makes the unwinders
use that instead of the catch-all outer_frame_id for such frames. The
frame_id_eq check in tfind_1 then automatically does the right thing
as expected.
I tested with --directory=gdb.trace/ , before/after the patch, and
compared the resulting gdb.logs, then adjusted the tests to expect the
extra output that came out. Turns out that was only circ.exp, the
original test that actually brought this issue to light.
Tested on x86_64 Fedora 17, native and gdbserver.
gdb/
2013-12-17 Pedro Alves <palves@redhat.com>
* frame.h (enum frame_id_stack_status): New enum.
(struct frame_id) <stack_addr>: Adjust comment.
<stack_addr_p>: Delete field, replaced with ...
<stack_status>: ... this new field.
(frame_id_build_unavailable_stack): Declare.
* frame.c (frame_addr_hash, fprint_field, outer_frame_id)
(frame_id_build_special): Adjust.
(frame_id_build_unavailable_stack): New function.
(frame_id_build, frame_id_build_wild): Adjust.
(frame_id_p, frame_id_eq, frame_id_inner): Adjust to take into
account frames with unavailable stack.
* amd64-tdep.c (amd64_frame_this_id)
(amd64_sigtramp_frame_this_id, amd64_epilogue_frame_this_id): Use
frame_id_build_unavailable_stack.
* dwarf2-frame.c (dwarf2_frame_this_id): Likewise.
* i386-tdep.c (i386_frame_this_id, i386_epilogue_frame_this_id)
(i386_sigtramp_frame_this_id): Likewise.
gdb/testsuite/
2013-12-17 Pedro Alves <palves@redhat.com>
* gdb.trace/circ.exp: Expect frame info to be printed when
switching between frames with unavailable stack, but different
functions.
This reverts da2b2fdf57 and some
follow-up patches. They were incorrect.
2013-11-26 Tom Tromey <tromey@redhat.com>
* dwarf2-frame.c (dwarf2_frame_cache): Revert patch from
2013-11-22.
2013-11-26 Tom Tromey <tromey@redhat.com>
* gdb.dwarf2/dw2-unspecified-ret-addr.S: Remove.
* gdb.dwarf2/dw2-unspecified-ret-addr.c: Remove.
* gdb.dwarf2/dw2-unspecified-ret-addr.exp: Remove.
Debugging PR 16155 further, I found that the DWARF unwinder found the
function in question, but thought it had no registers saved
(fs->regs.num_regs == 0).
It seems to me that if a frame does not specify the return address
column, or if the return address column is explicitly marked as
DWARF2_FRAME_REG_UNSPECIFIED, then we should set the
"undefined_retaddr" flag and let the DWARF unwinder gracefully stop.
This patch implements that idea.
With this patch the backtrace works properly:
(gdb) bt
#0 0x0000007fb7ed485c in nanosleep () from /lib64/libc.so.6
#1 0x0000007fb7ed4508 in sleep () from /lib64/libc.so.6
#2 0x00000000004008bc in thread_function (arg=0x4) at threadapply.c:73
#3 0x0000007fb7fad950 in start_thread () from /lib64/libpthread.so.0
#4 0x0000007fb7f0956c in clone () from /lib64/libc.so.6
2013-11-22 Tom Tromey <tromey@redhat.com>
PR backtrace/16155:
* dwarf2-frame.c (dwarf2_frame_cache): Set undefined_retaddr if
the return address column is unspecified.
2013-11-22 Tom Tromey <tromey@redhat.com>
* gdb.dwarf2/dw2-bad-cfi.c: New file.
* gdb.dwarf2/dw2-bad-cfi.exp: New file.
* gdb.dwarf2/dw2-bad-cfi.S: New file.
Two rationales, same patch.
TL;DR 1:
dwarf2_frame_cache recursion is evil. dwarf2_frame_cache calls
dwarf2_tailcall_sniffer_first which then recurses into
dwarf2_frame_cache.
TL;DR 2:
An unwinder trying to unwind is evil. dwarf2_frame_sniffer calls
dwarf2_frame_cache which calls dwarf2_tailcall_sniffer_first which
then tries to unwind the PC of the previous frame.
Avoid all that by deferring dwarf2_tailcall_sniffer_first until it's
really necessary.
Rationale 1
===========
A frame sniffer should not try to unwind, because that bypasses all
the validation checks done by get_prev_frame. The UNWIND_SAME_ID
scenario is one such case where GDB is currently broken because (in
part) of this (the next patch adds a test that would fail without
this).
GDB goes into an infinite loop in value_fetch_lazy, here:
while (VALUE_LVAL (new_val) == lval_register && value_lazy (new_val))
{
frame = frame_find_by_id (VALUE_FRAME_ID (new_val));
...
new_val = get_frame_register_value (frame, regnum);
}
(top-gdb) bt
#0 value_fetch_lazy (val=0x11516d0) at ../../src/gdb/value.c:3510
#1 0x0000000000584bd8 in value_optimized_out (value=0x11516d0) at ../../src/gdb/value.c:1096
#2 0x00000000006fe7a1 in frame_register_unwind (frame=0x1492600, regnum=16, optimizedp=0x7fffffffcdec, unavailablep=0x7fffffffcde8, lvalp=0x7fffffffcdd8, addrp=
0x7fffffffcde0, realnump=0x7fffffffcddc, bufferp=0x7fffffffce10 "@\316\377\377\377\177") at ../../src/gdb/frame.c:940
#3 0x00000000006fea3a in frame_unwind_register (frame=0x1492600, regnum=16, buf=0x7fffffffce10 "@\316\377\377\377\177") at ../../src/gdb/frame.c:990
#4 0x0000000000473b9b in i386_unwind_pc (gdbarch=0xf54660, next_frame=0x1492600) at ../../src/gdb/i386-tdep.c:1771
#5 0x0000000000601dfa in gdbarch_unwind_pc (gdbarch=0xf54660, next_frame=0x1492600) at ../../src/gdb/gdbarch.c:2870
#6 0x0000000000693db5 in dwarf2_tailcall_sniffer_first (this_frame=0x1492600, tailcall_cachep=0x14926f0, entry_cfa_sp_offsetp=0x7fffffffcf00)
at ../../src/gdb/dwarf2-frame-tailcall.c:389
#7 0x0000000000690928 in dwarf2_frame_cache (this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/dwarf2-frame.c:1245
#8 0x0000000000690f46 in dwarf2_frame_sniffer (self=0x8e4980, this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/dwarf2-frame.c:1423
#9 0x000000000070203b in frame_unwind_find_by_frame (this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/frame-unwind.c:112
#10 0x00000000006fd681 in get_frame_id (fi=0x1492600) at ../../src/gdb/frame.c:408
#11 0x00000000007006c2 in get_prev_frame_1 (this_frame=0xdc1860) at ../../src/gdb/frame.c:1826
#12 0x0000000000700b7a in get_prev_frame (this_frame=0xdc1860) at ../../src/gdb/frame.c:2056
#13 0x0000000000514588 in frame_info_to_frame_object (frame=0xdc1860) at ../../src/gdb/python/py-frame.c:322
#14 0x000000000051784c in bootstrap_python_frame_filters (frame=0xdc1860, frame_low=0, frame_high=-1) at ../../src/gdb/python/py-framefilter.c:1396
#15 0x0000000000517a6f in apply_frame_filter (frame=0xdc1860, flags=7, args_type=CLI_SCALAR_VALUES, out=0xed7a90, frame_low=0, frame_high=-1)
at ../../src/gdb/python/py-framefilter.c:1492
#16 0x00000000005e77b0 in backtrace_command_1 (count_exp=0x0, show_locals=0, no_filters=0, from_tty=1) at ../../src/gdb/stack.c:1777
#17 0x00000000005e7c0f in backtrace_command (arg=0x0, from_tty=1) at ../../src/gdb/stack.c:1891
#18 0x00000000004e37a7 in do_cfunc (c=0xda4fa0, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:107
#19 0x00000000004e683c in cmd_func (cmd=0xda4fa0, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:1882
#20 0x00000000006f35ed in execute_command (p=0xcc66c2 "", from_tty=1) at ../../src/gdb/top.c:468
#21 0x00000000005f8853 in command_handler (command=0xcc66c0 "bt") at ../../src/gdb/event-top.c:435
#22 0x00000000005f8e12 in command_line_handler (rl=0xfe05f0 "@") at ../../src/gdb/event-top.c:632
#23 0x000000000074d2c6 in rl_callback_read_char () at ../../src/readline/callback.c:220
#24 0x00000000005f8375 in rl_callback_read_char_wrapper (client_data=0x0) at ../../src/gdb/event-top.c:164
#25 0x00000000005f876a in stdin_event_handler (error=0, client_data=0x0) at ../../src/gdb/event-top.c:375
#26 0x00000000005f72fa in handle_file_event (data=...) at ../../src/gdb/event-loop.c:768
#27 0x00000000005f67a3 in process_event () at ../../src/gdb/event-loop.c:342
#28 0x00000000005f686a in gdb_do_one_event () at ../../src/gdb/event-loop.c:406
#29 0x00000000005f68bb in start_event_loop () at ../../src/gdb/event-loop.c:431
#30 0x00000000005f83a7 in cli_command_loop (data=0x0) at ../../src/gdb/event-top.c:179
#31 0x00000000005eeed3 in current_interp_command_loop () at ../../src/gdb/interps.c:327
#32 0x00000000005ef8ff in captured_command_loop (data=0x0) at ../../src/gdb/main.c:267
#33 0x00000000005ed2f6 in catch_errors (func=0x5ef8e4 <captured_command_loop>, func_args=0x0, errstring=0x8b6554 "", mask=RETURN_MASK_ALL)
at ../../src/gdb/exceptions.c:524
#34 0x00000000005f0d21 in captured_main (data=0x7fffffffd9e0) at ../../src/gdb/main.c:1067
#35 0x00000000005ed2f6 in catch_errors (func=0x5efb9b <captured_main>, func_args=0x7fffffffd9e0, errstring=0x8b6554 "", mask=RETURN_MASK_ALL)
at ../../src/gdb/exceptions.c:524
#36 0x00000000005f0d57 in gdb_main (args=0x7fffffffd9e0) at ../../src/gdb/main.c:1076
#37 0x000000000045bb6a in main (argc=4, argv=0x7fffffffdae8) at ../../src/gdb/gdb.c:34
(top-gdb)
GDB is trying to unwind the PC register of the previous frame (frame
#5 above), starting from the frame being sniffed (the THIS frame).
But the THIS frame's unwinder says the PC of the previous frame is
actually the same as the previous's frame's next frame (which is the
same frame we started with, the THIS frame), therefore it returns an
lval_register lazy value with frame set to THIS frame. And so the
value_fetch_lazy loop never ends.
Rationale 2
===========
As an experiment, I tried making dwarf2-frame.c:read_addr_from_reg use
address_from_register. That caused a bunch of regressions, but it
actually took me a long while to figure out what was going on. Turns
out dwarf2-frame.c:read_addr_from_reg is called while computing the
frame's CFA, from within dwarf2_frame_cache. address_from_register
wants to create a register with frame_id set to the frame being
constructed. To create the frame id, we again call dwarf2_frame_cache,
which given:
static struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
{
...
if (*this_cache)
return *this_cache;
returns an incomplete object to the caller:
static void
dwarf2_frame_this_id (struct frame_info *this_frame, void **this_cache,
struct frame_id *this_id)
{
struct dwarf2_frame_cache *cache =
dwarf2_frame_cache (this_frame, this_cache);
...
(*this_id) = frame_id_build (cache->cfa, get_frame_func (this_frame));
}
As cache->cfa is still 0 (we were trying to compute it!), and
get_frame_id recalls this id from here on, we end up with a broken
frame id in recorded for this frame. Later, when inspecting locals,
the dwarf machinery needs to know the selected frame's base, which
calls get_frame_base:
CORE_ADDR
get_frame_base (struct frame_info *fi)
{
return get_frame_id (fi).stack_addr;
}
which as seen above then returns 0 ...
So I gave up using address_from_register.
But, the pain of investigating this made me want to have GDB itself
assert that recursion never happens here. So I wrote a patch to do
that. But, it triggers on current mainline, because
dwarf2_tailcall_sniffer_first, called from dwarf2_frame_cache, unwinds
the this_frame.
A sniffer shouldn't be trying to unwind, exactly because of this sort
of tricky issue. The patch defers calling
dwarf2_tailcall_sniffer_first until it's really necessary, in
dwarf2_frame_prev_register (thus actually outside the sniffer path).
As this makes the call to dwarf2_frame_sniffer in dwarf2_frame_cache
unnecessary again, the patch removes that too.
Tested on x86_64 Fedora 17.
gdb/
2013-11-22 Pedro Alves <palves@redhat.com>
PR 16155
* dwarf2-frame.c (struct dwarf2_frame_cache)
<checked_tailcall_bottom, entry_cfa_sp_offset,
entry_cfa_sp_offset_p>: New fields.
(dwarf2_frame_cache): Adjust to use the new cache fields instead
of locals. Don't call dwarf2_tailcall_sniffer_first here.
(dwarf2_frame_prev_register): Call it here, but only once.
Two rationales, same patch.
TL;DR 1:
dwarf2_frame_cache recursion is evil. dwarf2_frame_cache calls
dwarf2_tailcall_sniffer_first which then recurses into
dwarf2_frame_cache.
TL;DR 2:
An unwinder trying to unwind is evil. dwarf2_frame_sniffer calls
dwarf2_frame_cache which calls dwarf2_tailcall_sniffer_first which
then tries to unwind the PC of the previous frame.
Avoid all that by deferring dwarf2_tailcall_sniffer_first until it's
really necessary.
Rationale 1
===========
A frame sniffer should not try to unwind, because that bypasses all
the validation checks done by get_prev_frame. The UNWIND_SAME_ID
scenario is one such case where GDB is currently broken because (in
part) of this (the next patch adds a test that would fail without
this).
GDB goes into an infinite loop in value_fetch_lazy, here:
while (VALUE_LVAL (new_val) == lval_register && value_lazy (new_val))
{
frame = frame_find_by_id (VALUE_FRAME_ID (new_val));
...
new_val = get_frame_register_value (frame, regnum);
}
(top-gdb) bt
#0 value_fetch_lazy (val=0x11516d0) at ../../src/gdb/value.c:3510
#1 0x0000000000584bd8 in value_optimized_out (value=0x11516d0) at ../../src/gdb/value.c:1096
#2 0x00000000006fe7a1 in frame_register_unwind (frame=0x1492600, regnum=16, optimizedp=0x7fffffffcdec, unavailablep=0x7fffffffcde8, lvalp=0x7fffffffcdd8, addrp=
0x7fffffffcde0, realnump=0x7fffffffcddc, bufferp=0x7fffffffce10 "@\316\377\377\377\177") at ../../src/gdb/frame.c:940
#3 0x00000000006fea3a in frame_unwind_register (frame=0x1492600, regnum=16, buf=0x7fffffffce10 "@\316\377\377\377\177") at ../../src/gdb/frame.c:990
#4 0x0000000000473b9b in i386_unwind_pc (gdbarch=0xf54660, next_frame=0x1492600) at ../../src/gdb/i386-tdep.c:1771
#5 0x0000000000601dfa in gdbarch_unwind_pc (gdbarch=0xf54660, next_frame=0x1492600) at ../../src/gdb/gdbarch.c:2870
#6 0x0000000000693db5 in dwarf2_tailcall_sniffer_first (this_frame=0x1492600, tailcall_cachep=0x14926f0, entry_cfa_sp_offsetp=0x7fffffffcf00)
at ../../src/gdb/dwarf2-frame-tailcall.c:389
#7 0x0000000000690928 in dwarf2_frame_cache (this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/dwarf2-frame.c:1245
#8 0x0000000000690f46 in dwarf2_frame_sniffer (self=0x8e4980, this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/dwarf2-frame.c:1423
#9 0x000000000070203b in frame_unwind_find_by_frame (this_frame=0x1492600, this_cache=0x1492618) at ../../src/gdb/frame-unwind.c:112
#10 0x00000000006fd681 in get_frame_id (fi=0x1492600) at ../../src/gdb/frame.c:408
#11 0x00000000007006c2 in get_prev_frame_1 (this_frame=0xdc1860) at ../../src/gdb/frame.c:1826
#12 0x0000000000700b7a in get_prev_frame (this_frame=0xdc1860) at ../../src/gdb/frame.c:2056
#13 0x0000000000514588 in frame_info_to_frame_object (frame=0xdc1860) at ../../src/gdb/python/py-frame.c:322
#14 0x000000000051784c in bootstrap_python_frame_filters (frame=0xdc1860, frame_low=0, frame_high=-1) at ../../src/gdb/python/py-framefilter.c:1396
#15 0x0000000000517a6f in apply_frame_filter (frame=0xdc1860, flags=7, args_type=CLI_SCALAR_VALUES, out=0xed7a90, frame_low=0, frame_high=-1)
at ../../src/gdb/python/py-framefilter.c:1492
#16 0x00000000005e77b0 in backtrace_command_1 (count_exp=0x0, show_locals=0, no_filters=0, from_tty=1) at ../../src/gdb/stack.c:1777
#17 0x00000000005e7c0f in backtrace_command (arg=0x0, from_tty=1) at ../../src/gdb/stack.c:1891
#18 0x00000000004e37a7 in do_cfunc (c=0xda4fa0, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:107
#19 0x00000000004e683c in cmd_func (cmd=0xda4fa0, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:1882
#20 0x00000000006f35ed in execute_command (p=0xcc66c2 "", from_tty=1) at ../../src/gdb/top.c:468
#21 0x00000000005f8853 in command_handler (command=0xcc66c0 "bt") at ../../src/gdb/event-top.c:435
#22 0x00000000005f8e12 in command_line_handler (rl=0xfe05f0 "@") at ../../src/gdb/event-top.c:632
#23 0x000000000074d2c6 in rl_callback_read_char () at ../../src/readline/callback.c:220
#24 0x00000000005f8375 in rl_callback_read_char_wrapper (client_data=0x0) at ../../src/gdb/event-top.c:164
#25 0x00000000005f876a in stdin_event_handler (error=0, client_data=0x0) at ../../src/gdb/event-top.c:375
#26 0x00000000005f72fa in handle_file_event (data=...) at ../../src/gdb/event-loop.c:768
#27 0x00000000005f67a3 in process_event () at ../../src/gdb/event-loop.c:342
#28 0x00000000005f686a in gdb_do_one_event () at ../../src/gdb/event-loop.c:406
#29 0x00000000005f68bb in start_event_loop () at ../../src/gdb/event-loop.c:431
#30 0x00000000005f83a7 in cli_command_loop (data=0x0) at ../../src/gdb/event-top.c:179
#31 0x00000000005eeed3 in current_interp_command_loop () at ../../src/gdb/interps.c:327
#32 0x00000000005ef8ff in captured_command_loop (data=0x0) at ../../src/gdb/main.c:267
#33 0x00000000005ed2f6 in catch_errors (func=0x5ef8e4 <captured_command_loop>, func_args=0x0, errstring=0x8b6554 "", mask=RETURN_MASK_ALL)
at ../../src/gdb/exceptions.c:524
#34 0x00000000005f0d21 in captured_main (data=0x7fffffffd9e0) at ../../src/gdb/main.c:1067
#35 0x00000000005ed2f6 in catch_errors (func=0x5efb9b <captured_main>, func_args=0x7fffffffd9e0, errstring=0x8b6554 "", mask=RETURN_MASK_ALL)
at ../../src/gdb/exceptions.c:524
#36 0x00000000005f0d57 in gdb_main (args=0x7fffffffd9e0) at ../../src/gdb/main.c:1076
#37 0x000000000045bb6a in main (argc=4, argv=0x7fffffffdae8) at ../../src/gdb/gdb.c:34
(top-gdb)
GDB is trying to unwind the PC register of the previous frame (frame
#5 above), starting from the frame being sniffed (the THIS frame).
But the THIS frame's unwinder says the PC of the previous frame is
actually the same as the previous's frame's next frame (which is the
same frame we started with, the THIS frame), therefore it returns an
lval_register lazy value with frame set to THIS frame. And so the
value_fetch_lazy loop never ends.
Rationale 2
===========
As an experiment, I tried making dwarf2-frame.c:read_addr_from_reg use
address_from_register. That caused a bunch of regressions, but it
actually took me a long while to figure out what was going on. Turns
out dwarf2-frame.c:read_addr_from_reg is called while computing the
frame's CFA, from within dwarf2_frame_cache. address_from_register
wants to create a register with frame_id set to the frame being
constructed. To create the frame id, we again call dwarf2_frame_cache,
which given:
static struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
{
...
if (*this_cache)
return *this_cache;
returns an incomplete object to the caller:
static void
dwarf2_frame_this_id (struct frame_info *this_frame, void **this_cache,
struct frame_id *this_id)
{
struct dwarf2_frame_cache *cache =
dwarf2_frame_cache (this_frame, this_cache);
...
(*this_id) = frame_id_build (cache->cfa, get_frame_func (this_frame));
}
As cache->cfa is still 0 (we were trying to compute it!), and
get_frame_id recalls this id from here on, we end up with a broken
frame id in recorded for this frame. Later, when inspecting locals,
the dwarf machinery needs to know the selected frame's base, which
calls get_frame_base:
CORE_ADDR
get_frame_base (struct frame_info *fi)
{
return get_frame_id (fi).stack_addr;
}
which as seen above then returns 0 ...
So I gave up using address_from_register.
But, the pain of investigating this made me want to have GDB itself
assert that recursion never happens here. So I wrote a patch to do
that. But, it triggers on current mainline, because
dwarf2_tailcall_sniffer_first, called from dwarf2_frame_cache, unwinds
the this_frame.
A sniffer shouldn't be trying to unwind, exactly because of this sort
of tricky issue. The patch defers calling
dwarf2_tailcall_sniffer_first until it's really necessary, in
dwarf2_frame_prev_register (thus actually outside the sniffer path).
As this makes the call to dwarf2_frame_sniffer in dwarf2_frame_cache
unnecessary again, the patch removes that too.
Tested on x86_64 Fedora 17.
gdb/
2013-11-22 Pedro Alves <palves@redhat.com>
PR 16155
* dwarf2-frame.c (struct dwarf2_frame_cache)
<checked_tailcall_bottom, entry_cfa_sp_offset,
entry_cfa_sp_offset_p>: New fields.
(dwarf2_frame_cache): Adjust to use the new cache fields instead
of locals. Don't call dwarf2_tailcall_sniffer_first here.
(dwarf2_frame_prev_register): Call it here, but only once.
This removes gdb_string.h. This patch is purely mechanical. I
created it by running the two commands:
git rm common/gdb_string.h
perl -pi -e's/"gdb_string.h"/<string.h>/;' *.[chyl] */*.[chyl]
2013-11-18 Tom Tromey <tromey@redhat.com>
* common/gdb_string.h: Remove.
* aarch64-tdep.c: Use string.h, not gdb_string.h.
* ada-exp.y: Use string.h, not gdb_string.h.
* ada-lang.c: Use string.h, not gdb_string.h.
* ada-lex.l: Use string.h, not gdb_string.h.
* ada-typeprint.c: Use string.h, not gdb_string.h.
* ada-valprint.c: Use string.h, not gdb_string.h.
* aix-thread.c: Use string.h, not gdb_string.h.
* alpha-linux-tdep.c: Use string.h, not gdb_string.h.
* alpha-mdebug-tdep.c: Use string.h, not gdb_string.h.
* alpha-nat.c: Use string.h, not gdb_string.h.
* alpha-osf1-tdep.c: Use string.h, not gdb_string.h.
* alpha-tdep.c: Use string.h, not gdb_string.h.
* alphanbsd-tdep.c: Use string.h, not gdb_string.h.
* amd64-dicos-tdep.c: Use string.h, not gdb_string.h.
* amd64-linux-nat.c: Use string.h, not gdb_string.h.
* amd64-linux-tdep.c: Use string.h, not gdb_string.h.
* amd64-nat.c: Use string.h, not gdb_string.h.
* amd64-sol2-tdep.c: Use string.h, not gdb_string.h.
* amd64fbsd-tdep.c: Use string.h, not gdb_string.h.
* amd64obsd-tdep.c: Use string.h, not gdb_string.h.
* arch-utils.c: Use string.h, not gdb_string.h.
* arm-linux-nat.c: Use string.h, not gdb_string.h.
* arm-linux-tdep.c: Use string.h, not gdb_string.h.
* arm-tdep.c: Use string.h, not gdb_string.h.
* arm-wince-tdep.c: Use string.h, not gdb_string.h.
* armbsd-tdep.c: Use string.h, not gdb_string.h.
* armnbsd-nat.c: Use string.h, not gdb_string.h.
* armnbsd-tdep.c: Use string.h, not gdb_string.h.
* armobsd-tdep.c: Use string.h, not gdb_string.h.
* avr-tdep.c: Use string.h, not gdb_string.h.
* ax-gdb.c: Use string.h, not gdb_string.h.
* ax-general.c: Use string.h, not gdb_string.h.
* bcache.c: Use string.h, not gdb_string.h.
* bfin-tdep.c: Use string.h, not gdb_string.h.
* breakpoint.c: Use string.h, not gdb_string.h.
* build-id.c: Use string.h, not gdb_string.h.
* buildsym.c: Use string.h, not gdb_string.h.
* c-exp.y: Use string.h, not gdb_string.h.
* c-lang.c: Use string.h, not gdb_string.h.
* c-typeprint.c: Use string.h, not gdb_string.h.
* c-valprint.c: Use string.h, not gdb_string.h.
* charset.c: Use string.h, not gdb_string.h.
* cli-out.c: Use string.h, not gdb_string.h.
* cli/cli-cmds.c: Use string.h, not gdb_string.h.
* cli/cli-decode.c: Use string.h, not gdb_string.h.
* cli/cli-dump.c: Use string.h, not gdb_string.h.
* cli/cli-interp.c: Use string.h, not gdb_string.h.
* cli/cli-logging.c: Use string.h, not gdb_string.h.
* cli/cli-script.c: Use string.h, not gdb_string.h.
* cli/cli-setshow.c: Use string.h, not gdb_string.h.
* cli/cli-utils.c: Use string.h, not gdb_string.h.
* coffread.c: Use string.h, not gdb_string.h.
* common/common-utils.c: Use string.h, not gdb_string.h.
* common/filestuff.c: Use string.h, not gdb_string.h.
* common/linux-procfs.c: Use string.h, not gdb_string.h.
* common/linux-ptrace.c: Use string.h, not gdb_string.h.
* common/signals.c: Use string.h, not gdb_string.h.
* common/vec.h: Use string.h, not gdb_string.h.
* core-regset.c: Use string.h, not gdb_string.h.
* corefile.c: Use string.h, not gdb_string.h.
* corelow.c: Use string.h, not gdb_string.h.
* cp-abi.c: Use string.h, not gdb_string.h.
* cp-support.c: Use string.h, not gdb_string.h.
* cp-valprint.c: Use string.h, not gdb_string.h.
* cris-tdep.c: Use string.h, not gdb_string.h.
* d-lang.c: Use string.h, not gdb_string.h.
* dbxread.c: Use string.h, not gdb_string.h.
* dcache.c: Use string.h, not gdb_string.h.
* demangle.c: Use string.h, not gdb_string.h.
* dicos-tdep.c: Use string.h, not gdb_string.h.
* disasm.c: Use string.h, not gdb_string.h.
* doublest.c: Use string.h, not gdb_string.h.
* dsrec.c: Use string.h, not gdb_string.h.
* dummy-frame.c: Use string.h, not gdb_string.h.
* dwarf2-frame.c: Use string.h, not gdb_string.h.
* dwarf2loc.c: Use string.h, not gdb_string.h.
* dwarf2read.c: Use string.h, not gdb_string.h.
* elfread.c: Use string.h, not gdb_string.h.
* environ.c: Use string.h, not gdb_string.h.
* eval.c: Use string.h, not gdb_string.h.
* event-loop.c: Use string.h, not gdb_string.h.
* exceptions.c: Use string.h, not gdb_string.h.
* exec.c: Use string.h, not gdb_string.h.
* expprint.c: Use string.h, not gdb_string.h.
* f-exp.y: Use string.h, not gdb_string.h.
* f-lang.c: Use string.h, not gdb_string.h.
* f-typeprint.c: Use string.h, not gdb_string.h.
* f-valprint.c: Use string.h, not gdb_string.h.
* fbsd-nat.c: Use string.h, not gdb_string.h.
* findcmd.c: Use string.h, not gdb_string.h.
* findvar.c: Use string.h, not gdb_string.h.
* fork-child.c: Use string.h, not gdb_string.h.
* frame.c: Use string.h, not gdb_string.h.
* frv-linux-tdep.c: Use string.h, not gdb_string.h.
* frv-tdep.c: Use string.h, not gdb_string.h.
* gdb.c: Use string.h, not gdb_string.h.
* gdb_bfd.c: Use string.h, not gdb_string.h.
* gdbarch.c: Use string.h, not gdb_string.h.
* gdbtypes.c: Use string.h, not gdb_string.h.
* gnu-nat.c: Use string.h, not gdb_string.h.
* gnu-v2-abi.c: Use string.h, not gdb_string.h.
* gnu-v3-abi.c: Use string.h, not gdb_string.h.
* go-exp.y: Use string.h, not gdb_string.h.
* go-lang.c: Use string.h, not gdb_string.h.
* go32-nat.c: Use string.h, not gdb_string.h.
* hppa-hpux-tdep.c: Use string.h, not gdb_string.h.
* hppa-linux-nat.c: Use string.h, not gdb_string.h.
* hppanbsd-tdep.c: Use string.h, not gdb_string.h.
* hppaobsd-tdep.c: Use string.h, not gdb_string.h.
* i386-cygwin-tdep.c: Use string.h, not gdb_string.h.
* i386-dicos-tdep.c: Use string.h, not gdb_string.h.
* i386-linux-nat.c: Use string.h, not gdb_string.h.
* i386-linux-tdep.c: Use string.h, not gdb_string.h.
* i386-nto-tdep.c: Use string.h, not gdb_string.h.
* i386-sol2-tdep.c: Use string.h, not gdb_string.h.
* i386-tdep.c: Use string.h, not gdb_string.h.
* i386bsd-tdep.c: Use string.h, not gdb_string.h.
* i386gnu-nat.c: Use string.h, not gdb_string.h.
* i386nbsd-tdep.c: Use string.h, not gdb_string.h.
* i386obsd-tdep.c: Use string.h, not gdb_string.h.
* i387-tdep.c: Use string.h, not gdb_string.h.
* ia64-libunwind-tdep.c: Use string.h, not gdb_string.h.
* ia64-linux-nat.c: Use string.h, not gdb_string.h.
* inf-child.c: Use string.h, not gdb_string.h.
* inf-ptrace.c: Use string.h, not gdb_string.h.
* inf-ttrace.c: Use string.h, not gdb_string.h.
* infcall.c: Use string.h, not gdb_string.h.
* infcmd.c: Use string.h, not gdb_string.h.
* inflow.c: Use string.h, not gdb_string.h.
* infrun.c: Use string.h, not gdb_string.h.
* interps.c: Use string.h, not gdb_string.h.
* iq2000-tdep.c: Use string.h, not gdb_string.h.
* irix5-nat.c: Use string.h, not gdb_string.h.
* jv-exp.y: Use string.h, not gdb_string.h.
* jv-lang.c: Use string.h, not gdb_string.h.
* jv-typeprint.c: Use string.h, not gdb_string.h.
* jv-valprint.c: Use string.h, not gdb_string.h.
* language.c: Use string.h, not gdb_string.h.
* linux-fork.c: Use string.h, not gdb_string.h.
* linux-nat.c: Use string.h, not gdb_string.h.
* lm32-tdep.c: Use string.h, not gdb_string.h.
* m2-exp.y: Use string.h, not gdb_string.h.
* m2-typeprint.c: Use string.h, not gdb_string.h.
* m32c-tdep.c: Use string.h, not gdb_string.h.
* m32r-linux-nat.c: Use string.h, not gdb_string.h.
* m32r-linux-tdep.c: Use string.h, not gdb_string.h.
* m32r-rom.c: Use string.h, not gdb_string.h.
* m32r-tdep.c: Use string.h, not gdb_string.h.
* m68hc11-tdep.c: Use string.h, not gdb_string.h.
* m68k-tdep.c: Use string.h, not gdb_string.h.
* m68kbsd-tdep.c: Use string.h, not gdb_string.h.
* m68klinux-nat.c: Use string.h, not gdb_string.h.
* m68klinux-tdep.c: Use string.h, not gdb_string.h.
* m88k-tdep.c: Use string.h, not gdb_string.h.
* macrocmd.c: Use string.h, not gdb_string.h.
* main.c: Use string.h, not gdb_string.h.
* mdebugread.c: Use string.h, not gdb_string.h.
* mem-break.c: Use string.h, not gdb_string.h.
* memattr.c: Use string.h, not gdb_string.h.
* memory-map.c: Use string.h, not gdb_string.h.
* mep-tdep.c: Use string.h, not gdb_string.h.
* mi/mi-cmd-break.c: Use string.h, not gdb_string.h.
* mi/mi-cmd-disas.c: Use string.h, not gdb_string.h.
* mi/mi-cmd-env.c: Use string.h, not gdb_string.h.
* mi/mi-cmd-stack.c: Use string.h, not gdb_string.h.
* mi/mi-cmd-var.c: Use string.h, not gdb_string.h.
* mi/mi-cmds.c: Use string.h, not gdb_string.h.
* mi/mi-console.c: Use string.h, not gdb_string.h.
* mi/mi-getopt.c: Use string.h, not gdb_string.h.
* mi/mi-interp.c: Use string.h, not gdb_string.h.
* mi/mi-main.c: Use string.h, not gdb_string.h.
* mi/mi-parse.c: Use string.h, not gdb_string.h.
* microblaze-rom.c: Use string.h, not gdb_string.h.
* microblaze-tdep.c: Use string.h, not gdb_string.h.
* mingw-hdep.c: Use string.h, not gdb_string.h.
* minidebug.c: Use string.h, not gdb_string.h.
* minsyms.c: Use string.h, not gdb_string.h.
* mips-irix-tdep.c: Use string.h, not gdb_string.h.
* mips-linux-tdep.c: Use string.h, not gdb_string.h.
* mips-tdep.c: Use string.h, not gdb_string.h.
* mips64obsd-tdep.c: Use string.h, not gdb_string.h.
* mipsnbsd-tdep.c: Use string.h, not gdb_string.h.
* mipsread.c: Use string.h, not gdb_string.h.
* mn10300-linux-tdep.c: Use string.h, not gdb_string.h.
* mn10300-tdep.c: Use string.h, not gdb_string.h.
* monitor.c: Use string.h, not gdb_string.h.
* moxie-tdep.c: Use string.h, not gdb_string.h.
* mt-tdep.c: Use string.h, not gdb_string.h.
* nbsd-tdep.c: Use string.h, not gdb_string.h.
* nios2-linux-tdep.c: Use string.h, not gdb_string.h.
* nto-procfs.c: Use string.h, not gdb_string.h.
* nto-tdep.c: Use string.h, not gdb_string.h.
* objc-lang.c: Use string.h, not gdb_string.h.
* objfiles.c: Use string.h, not gdb_string.h.
* opencl-lang.c: Use string.h, not gdb_string.h.
* osabi.c: Use string.h, not gdb_string.h.
* osdata.c: Use string.h, not gdb_string.h.
* p-exp.y: Use string.h, not gdb_string.h.
* p-lang.c: Use string.h, not gdb_string.h.
* p-typeprint.c: Use string.h, not gdb_string.h.
* parse.c: Use string.h, not gdb_string.h.
* posix-hdep.c: Use string.h, not gdb_string.h.
* ppc-linux-nat.c: Use string.h, not gdb_string.h.
* ppc-sysv-tdep.c: Use string.h, not gdb_string.h.
* ppcfbsd-tdep.c: Use string.h, not gdb_string.h.
* ppcnbsd-tdep.c: Use string.h, not gdb_string.h.
* ppcobsd-tdep.c: Use string.h, not gdb_string.h.
* printcmd.c: Use string.h, not gdb_string.h.
* procfs.c: Use string.h, not gdb_string.h.
* prologue-value.c: Use string.h, not gdb_string.h.
* python/py-auto-load.c: Use string.h, not gdb_string.h.
* python/py-gdb-readline.c: Use string.h, not gdb_string.h.
* ravenscar-thread.c: Use string.h, not gdb_string.h.
* regcache.c: Use string.h, not gdb_string.h.
* registry.c: Use string.h, not gdb_string.h.
* remote-fileio.c: Use string.h, not gdb_string.h.
* remote-m32r-sdi.c: Use string.h, not gdb_string.h.
* remote-mips.c: Use string.h, not gdb_string.h.
* remote-sim.c: Use string.h, not gdb_string.h.
* remote.c: Use string.h, not gdb_string.h.
* reverse.c: Use string.h, not gdb_string.h.
* rs6000-aix-tdep.c: Use string.h, not gdb_string.h.
* ser-base.c: Use string.h, not gdb_string.h.
* ser-go32.c: Use string.h, not gdb_string.h.
* ser-mingw.c: Use string.h, not gdb_string.h.
* ser-pipe.c: Use string.h, not gdb_string.h.
* ser-tcp.c: Use string.h, not gdb_string.h.
* ser-unix.c: Use string.h, not gdb_string.h.
* serial.c: Use string.h, not gdb_string.h.
* sh-tdep.c: Use string.h, not gdb_string.h.
* sh64-tdep.c: Use string.h, not gdb_string.h.
* shnbsd-tdep.c: Use string.h, not gdb_string.h.
* skip.c: Use string.h, not gdb_string.h.
* sol-thread.c: Use string.h, not gdb_string.h.
* solib-dsbt.c: Use string.h, not gdb_string.h.
* solib-frv.c: Use string.h, not gdb_string.h.
* solib-osf.c: Use string.h, not gdb_string.h.
* solib-spu.c: Use string.h, not gdb_string.h.
* solib-target.c: Use string.h, not gdb_string.h.
* solib.c: Use string.h, not gdb_string.h.
* somread.c: Use string.h, not gdb_string.h.
* source.c: Use string.h, not gdb_string.h.
* sparc-nat.c: Use string.h, not gdb_string.h.
* sparc-sol2-tdep.c: Use string.h, not gdb_string.h.
* sparc-tdep.c: Use string.h, not gdb_string.h.
* sparc64-tdep.c: Use string.h, not gdb_string.h.
* sparc64fbsd-tdep.c: Use string.h, not gdb_string.h.
* sparc64nbsd-tdep.c: Use string.h, not gdb_string.h.
* sparcnbsd-tdep.c: Use string.h, not gdb_string.h.
* spu-linux-nat.c: Use string.h, not gdb_string.h.
* spu-multiarch.c: Use string.h, not gdb_string.h.
* spu-tdep.c: Use string.h, not gdb_string.h.
* stabsread.c: Use string.h, not gdb_string.h.
* stack.c: Use string.h, not gdb_string.h.
* std-regs.c: Use string.h, not gdb_string.h.
* symfile.c: Use string.h, not gdb_string.h.
* symmisc.c: Use string.h, not gdb_string.h.
* symtab.c: Use string.h, not gdb_string.h.
* target.c: Use string.h, not gdb_string.h.
* thread.c: Use string.h, not gdb_string.h.
* tilegx-linux-nat.c: Use string.h, not gdb_string.h.
* tilegx-tdep.c: Use string.h, not gdb_string.h.
* top.c: Use string.h, not gdb_string.h.
* tracepoint.c: Use string.h, not gdb_string.h.
* tui/tui-command.c: Use string.h, not gdb_string.h.
* tui/tui-data.c: Use string.h, not gdb_string.h.
* tui/tui-disasm.c: Use string.h, not gdb_string.h.
* tui/tui-file.c: Use string.h, not gdb_string.h.
* tui/tui-layout.c: Use string.h, not gdb_string.h.
* tui/tui-out.c: Use string.h, not gdb_string.h.
* tui/tui-regs.c: Use string.h, not gdb_string.h.
* tui/tui-source.c: Use string.h, not gdb_string.h.
* tui/tui-stack.c: Use string.h, not gdb_string.h.
* tui/tui-win.c: Use string.h, not gdb_string.h.
* tui/tui-windata.c: Use string.h, not gdb_string.h.
* tui/tui-winsource.c: Use string.h, not gdb_string.h.
* typeprint.c: Use string.h, not gdb_string.h.
* ui-file.c: Use string.h, not gdb_string.h.
* ui-out.c: Use string.h, not gdb_string.h.
* user-regs.c: Use string.h, not gdb_string.h.
* utils.c: Use string.h, not gdb_string.h.
* v850-tdep.c: Use string.h, not gdb_string.h.
* valarith.c: Use string.h, not gdb_string.h.
* valops.c: Use string.h, not gdb_string.h.
* valprint.c: Use string.h, not gdb_string.h.
* value.c: Use string.h, not gdb_string.h.
* varobj.c: Use string.h, not gdb_string.h.
* vax-tdep.c: Use string.h, not gdb_string.h.
* vaxnbsd-tdep.c: Use string.h, not gdb_string.h.
* vaxobsd-tdep.c: Use string.h, not gdb_string.h.
* windows-nat.c: Use string.h, not gdb_string.h.
* xcoffread.c: Use string.h, not gdb_string.h.
* xml-support.c: Use string.h, not gdb_string.h.
* xstormy16-tdep.c: Use string.h, not gdb_string.h.
* xtensa-linux-nat.c: Use string.h, not gdb_string.h.
Since 'struct dwarf_expr_context_funcs::read_addr_from_reg' is now
only used for addresses, we can make it use unpack_pointer. And since
we now have 'struct dwarf_expr_context_funcs'::get_reg_value, there's
no need for speculation about using values here.
Tested on x86_64 Fedora 17.
gdb/
2013-11-18 Pedro Alves <palves@redhat.com>
* dwarf2-frame.c (read_addr_from_reg): Remove stale comment and
use unpack_pointer.
This is to help make it slightly clearer how this method is expected
to extract data from the given register.
gdb/ChangeLog:
* dwarf2expr.h (struct dwarf_expr_context_funcs)
<read_addr_from_reg>: Renames "read_reg".
* dwarf2-frame.c (read_addr_from_reg): Renames "read_reg".
Adjust comment.
(dwarf2_frame_ctx_funcs, execute_stack_op, dwarf2_frame_cache):
Use read_addr_from_reg in place of read_reg.
* dwarf2expr.c (execute_stack_op): Use read_addr_from_reg
in place of read_reg.
* dwarf2loc.c (dwarf_expr_read_addr_from_reg): Renames
dwarf_expr_read_reg.
(dwarf_expr_ctx_funcs): Replace dwarf_expr_read_reg
with dwarf_expr_read_addr_from_reg.
(needs_frame_read_addr_from_reg): Renames needs_frame_read_reg.
(needs_frame_ctx_funcs): Replace needs_frame_read_reg with
needs_frame_read_addr_from_reg.
Consider the following code, compiled at -O2 on ppc-linux:
procedure Increment (Val : in out Float; Msg : String);
The implementation does not really matter in this case). In our example,
this function is being called from a function with Param_1 set to 99.0.
Trying to break inside that function, and running until reaching that
breakpoint yields:
(gdb) b increment
Breakpoint 1 at 0x100014b4: file callee.adb, line 6.
(gdb) run
Starting program: /[...]/foo
Breakpoint 1, callee.increment (val=99.0, val@entry=0.0, msg=...)
at callee.adb:6
6 if Val > 200.0 then
The @entry value for parameter "val" is incorrect, it should be 99.0.
The associated call-site parameter DIE looks like this:
.uleb128 0xc # (DIE (0x115) DW_TAG_GNU_call_site_parameter)
.byte 0x2 # DW_AT_location
.byte 0x90 # DW_OP_regx
.uleb128 0x21
.byte 0x3 # DW_AT_GNU_call_site_value
.byte 0xf5 # DW_OP_GNU_regval_type
.uleb128 0x3f
.uleb128 0x25
The DW_AT_GNU_call_site_value uses a DW_OP_GNU_regval_type
operation, referencing register 0x3f=63, which is $f31,
an 8-byte floating register. In that register, the value is
stored using the usual 8-byte float format:
(gdb) info float
f31 99.0 (raw 0x4058c00000000000)
The current code evaluating DW_OP_GNU_regval_type operations
currently is (dwarf2expr.c:execute_stack_op):
result = (ctx->funcs->read_reg) (ctx->baton, reg);
result_val = value_from_ulongest (address_type, result);
result_val = value_from_contents (type,
value_contents_all (result_val));
What the ctx->funcs->read_reg function does is read the contents
of the register as if it contained an address. The rest of the code
continues that assumption, thinking it's OK to then use that to
create an address/ulongest struct value, which we then re-type
to the type specified by DW_OP_GNU_regval_type.
We're getting 0.0 above because the read_reg implementations
end up treating the contents of the FP register as an integral,
reading only 4 out of the 8 bytes. Being a big-endian target,
we read the high-order ones, which gives us zero.
This patch fixes the problem by introducing a new callback to
read the contents of a register as a given type, and then adjust
the handling of DW_OP_GNU_regval_type to use that new callback.
gdb/ChangeLog:
* dwarf2expr.h (struct dwarf_expr_context_funcs) <read_reg>:
Extend the documentation a bit.
<get_reg_value>: New field.
* dwarf2loc.c (dwarf_expr_get_reg_value)
(needs_frame_get_reg_value): New functions.
(dwarf_expr_ctx_funcs, needs_frame_ctx_funcs): Add "get_reg_value"
callback.
* dwarf2-frame.c (get_reg_value): New function.
(dwarf2_frame_ctx_funcs): Add "get_reg_value" callback.
* dwarf2expr.c (execute_stack_op) <DW_OP_GNU_regval_type>:
Use new callback to compute result_val.
gdb/testsuite/ChangeLog:
* gdb.ada/O2_float_param: New testcase.
The 'bytes_read' change should be obvious. As for the other hunk,
we're passing the address of the signed 'offset' to safe_read_uleb128,
which expects unsigned. Fix it by passing the address of the unsigned
'utmp' instead, like already done on other spots in the file.
gdb/
2013-04-19 Pedro Alves <palves@redhat.com>
* dwarf2-frame.c (execute_cfa_program): Make 'bytes_read' local
unsigned. Pass 'tmp' to safe_read_uleb128 instead of the signed
'offset', and adjust.
const.
* dwarf2read.c (struct dwarf2_section_info) <buffer>: Now const.
(struct die_reader_specs) <buffer>: Likewise.
(die_reader_func_ftype): Make 'info_ptr' const.
(struct line_header) <include_dirs, statement_program_start,
statement_program_end>: Now const.
(struct file_entry) <name>: Likewise.
(struct partial_die_info) <sibling>: Likewise.
(struct dwarf_block) <data>: Likewise.
(dwarf2_read_section): Remove cast.
(dwarf2_get_section_info): Make 'bufp' const.
(read_index_from_section): Constify.
(dw2_get_file_names_reader): Make 'info_ptr' const.
(dw2_get_primary_filename_reader): Likewise.
(read_comp_unit_head): Make 'info_ptr' and return type const.
(read_and_check_comp_unit_head, read_and_check_type_unit_head):
Likewise.
(read_abbrev_offset): Constify.
(dwarf2_create_include_psymtab): Make 'name' const.
(create_debug_types_hash_table): Update.
(read_cutu_die_from_dwo): Make 'result_info_ptr' const.
(init_cutu_and_read_dies, init_cutu_and_read_dies_no_follow):
Constify.
(process_psymtab_comp_unit_reader, build_type_psymtabs_reader)
(load_partial_comp_unit_reader): Make 'info_ptr' const.
(read_comp_units_from_section): Constify.
(peek_abbrev_code, peek_die_abbrev, skip_children, skip_one_die)
(locate_pdi_sibling, load_full_comp_unit_reader): Make 'info_ptr'
const.
(dwarf2_compute_name, setup_type_unit_groups): Constify.
(create_dwo_debug_info_hash_table): Make 'info_ptr' const.
(create_dwp_hash_table, dwarf2_ranges_read)
(dwarf2_record_block_ranges): Constify.
(read_die_and_children, read_die_and_siblings_1)
(read_die_and_siblings): Make 'info_ptr' and 'new_info_ptr'
const.
(read_full_die_1, read_full_die): Make 'info_ptr' const.
(abbrev_table_read_table): Constify.
(load_partial_dies): Make 'info_ptr' const.
(read_partial_die, read_attribute_value, read_attribute): Make
'info_ptr' and return type const.
(read_address, read_initial_length)
(read_checked_initial_length_and_offset, read_offset)
(read_offset_1, read_n_bytes, read_direct_string): Make 'buf'
const.
(read_direct_string): Make 'buf' and return type const.
(read_indirect_string_at_offset, read_indirect_string_from_dwz)
(read_indirect_string): Make return type const.
(read_unsigned_leb128, read_signed_leb128): Make 'buf' const.
(read_addr_index_from_leb128, dwarf2_read_addr_index_reader): Make
'info_ptr' const.
(read_str_index): Make return type const.
(add_include_dir): Make 'include_dir' const.
(add_file_name): Make 'name' const.
(dwarf_decode_line_header): Constify.
(psymtab_include_file_name): Make return type const.
(dwarf_decode_lines_1, dwarf_decode_lines): Constify.
(dwarf2_start_subfile): Make 'filename' const.
(dwarf2_const_value_attr): Make 'bytes' const.
(read_signatured_type_reader): Make 'info_ptr' const.
(decode_locdesc): Constify.
(skip_form_bytes): Make 'bytes', 'buffer_end', and return type
const.
(skip_unknown_opcode): Make 'opcode_definitions', 'mac_ptr',
'mac_end', and return type const.
(dwarf_parse_macro_header): Make 'mac_ptr' and return type const.
(dwarf_decode_macro_bytes): Make 'mac_ptr', 'mac_end', and return
type const.
(per_cu_header_read_in): Constify.
* symfile.h (dwarf2_get_section_info): Update.
Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.
* configure.ac (CC_HAS_LONG_LONG): Replace by AC_MSG_ERROR.
* defs.h (LONGEST, ULONGEST): Remove conditionalization for
CC_HAS_LONG_LONG.
* dwarf2-frame.c (DW64_CIE_ID): Likewise.
* dwarf2read.c (extract_cu_value): Remove the function.
(create_cus_from_index_list): Make the return type void, inline the
extract_cu_value caller, include new gdb_static_assert.
(create_cus_from_index): Make the return type void, update the function
comment, update the create_cus_from_index_list caller.
(create_signatured_type_table_from_index): Make the return type void,
inline the extract_cu_value caller, include new gdb_static_assert.
(dwarf2_read_index): Update the create_cus_from_index and
create_signatured_type_table_from_index caller.
* printcmd.c (ui_printf): Remove conditionalizations for
CC_HAS_LONG_LONG.
* config.in: Regenerate.
* configure: Regenerate.
gdb/doc/
* gdbint.texinfo (Host Definition): Remove CC_HAS_LONG_LONG.
The problem is trying to unwind from a function where %ebp is NOT
used as the frame pointer, and the size of the frame changes over
the lifetime of that function.
For instance, trying to unwind past the GNAT runtime function
called system.tasking.rendezvous.timed_selective_wait on x86-linux,
one can get:
(gdb) bt
[...]
#3 0x0805364b in system.tasking.rendezvous.timed_selective_wait ()
#4 0xb7fe5068 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
Looking at the CFI, we find the following initial instructions...
> DW_CFA_def_cfa: %esp+4 (r4 ofs 4)
> DW_CFA_offset: %eip at cfa-4 (r8 = %eip)
... and the associated FDE:
> 00001be4 00000054 00001be8 FDE cie=00000000 pc=08053310..08053951
[...]
> DW_CFA_advance_loc: 8 to 080534ad
> DW_CFA_def_cfa_offset: 112
> DW_CFA_advance_loc2: 414 to 0805364b
> DW_CFA_def_cfa_offset: 108
[...]
The problem is that the DWARF frame unwinder executed the FDE until
the row for PC == 0x0805364b. But in reality, our program hasn't
executed the instruction at that address yet (it is the return address).
So GDB executed a little too much of the FDE, giving us the wrong
offset for the frame base, and thus the wrong address where %eip
got saved.
This patch fixes the problem by using a more correct PC as the bound
for executing the FDE.
gdb/ChangeLog:
* dwarf2-frame.c (dwarf2_frame_cache): Use
get_frame_address_in_block instead of get_frame_pc as
the bound for executing the frame's FDE.
gdb/testsuite/ChangeLog:
* gdb.ada/rdv_wait: New testcase.
"const gdb_byte *".
(struct dwarf2_fde): Make instructions, end "const gdb_byte *".
(execute_cfa_program): Update to match API of leb128 functions.
(read_1_byte, read_4_bytes, read_8_bytes): Make buf parameter
"const gdb_byte *".
(read_unsigned_leb128, read_signed_leb128): Delete.
(read_initial_length): Change type of buf argument to
"const gdb_byte *".
(read_encoded_value): Update to match API of leb128 functions.
(decode_frame_entry): Change result to "const gdb_byte *", and
similarly for "start" parameter.
(decode_frame_entry_1): Ditto. Use new leb128 reader functions.
(dwarf2_build_frame_info): Change local frame_ptr to
"const gdb_byte *".
* dwarf2expr.c (safe_read_uleb128, safe_read_sleb128): Replaces
read_uleb128, read_sleb128. All callers updated.
(safe_skip_leb128): New function.
(dwarf_block_to_dwarf_reg): Update to match API of leb128 functions.
Call gdb_read_uleb128, gdb_skip_leb128 instead of read_uleb128.
(dwarf_block_to_dwarf_reg_deref): Update to match API of leb128
functions. Call gdb_read_uleb128, gdb_read_sleb128 instead of
read_uleb128, read_sleb128.
(dwarf_block_to_fb_offset, dwarf_block_to_sp_offset): Ditto.
(execute_stack_op): Update to match API of leb128 functions.
* dwarf2expr.h: #include "leb128.h".
(read_uleb128, read_sleb128): Delete.
(gdb_read_uleb128, gdb_read_sleb128, gdb_skip_leb128): New functions.
(safe_read_uleb128, safe_read_sleb128, safe_skip_leb128): Declare.
* dwarf2loc.c (debug_loc_kind): New enum.
(decode_debug_loc_addresses): New function.
(decode_debug_loc_dwo_addresses): New function.
(dwarf2_find_location_expression): Rewrite.
(dwarf2_compile_expr_to_ax): Update to match API of leb128 functions.
(locexpr_describe_location_piece): Ditto.
(disassemble_dwarf_expression): Ditto.
(locexpr_describe_location_1): Ditto.
(loclist_describe_location): Rewrite.
* dwarf2loc.h (dwarf2_loclist_baton): New member "from_dwo".
* dwarf2read.c (die_reader_specs): New member "buffer_end".
(dwarf2_section_buffer_overflow_complaint): Renamed from
dwarf2_macros_too_long_complaint. All callers updated.
(skip_leb128): Delete.
(init_cu_die_reader): Initialize reader->buffer_end.
(skip_one_die): Replace call to skip_leb128 with safe_skip_leb128.
(skip_form_bytes): New arg buffer_end. All callers updated.
Replace call to skip_leb128 with gdb_skip_leb128.
(skip_unknown_opcode): New arg mac_end. All callers updated.
(fill_in_loclist_baton): Initialize baton->from_dwo.
* symfile.c (default_symfile_relocate): Use sectp->owner instead of
objfile->obfd.
* symfile.h (dwarf2_debug_sections): New member addr.
* dwarf2expr.c (execute_stack_op): New case DW_OP_GNU_addr_index.
(ctx_no_get_addr_index): New function.
* dwarf2expr.h (dwarf_expr_context_funcs): New member get_addr_index.
(ctx_no_get_addr_index): Declare.
* dwarf2-frame.c (dwarf2_frame_ctx_funcs): Update.
* dwarf2loc.c (dwarf_expr_get_addr_index): New function.
(dwarf_expr_ctx_funcs): Update.
(needs_get_addr_index): New function.
(needs_frame_ctx_funcs): Update.
* dwarf2loc.h (dwarf2_read_addr_index): Declare.
* dwarf2read.c: #include "gdbcore.h".
(dwarf2_per_objfile): New members addr, dwo_files.
(dwarf2_elf_names): Add entry for addr.
(struct dwo_section_names): New type.
(dwo_section_names): New static global.
(dwarf2_cu): New members dwo_unit, addr_base, have_addr_base.
(dwarf2_per_cu_data): New member is_debug_types, all boolean uses of
old debug_types_section member updated to use this.
Rename member debug_types_section to info_or_types_section,
all uses updated.
(signatured_type): Rename member type_offset to type_offset_in_tu,
all uses updated. New member type_offset_in_section.
(struct dwo_sections): New type.
(struct dwo_unit): New type.
(struct dwo_file): New type.
(die_reader_specs): New member dwo_file.
(dwarf2_locate_sections): Watch for .debug_addr.
(zlib_decompress_section): Use sectp->owner instead of objfile->obfd.
(dwarf2_read_section): Get bfd of section from bfd's asection,
instead of objfile.
(create_cus_from_index): Initialize the_cu->info_or_types_section.
(create_signatured_type_table_from_index): Initialize
sig_type->info_or_types_section.
(dw2_get_file_names): Statement lists for type units with DWO files
live in the DWO file.
(create_debug_types_hash_table): New function.
(create_all_type_units): Rewrite.
(init_cu_die_reader): New arg dwo_file, all callers updated.
(init_and_read_dies_worker): Get section from
this_cu->info_or_types_section. Set sig_type->type_offset_in_section.
Watch for DW_AT_GNU_dwo_name and if present lookup the file and
continue reading the CU/TU from there.
(init_cutu_and_read_dies_no_follow): New arg dwo_file, all callers
updated. Get section from this_cu->info_or_types_section.
(create_all_comp_units): Initialize this_cu->info_or_types_section.
(skip_one_die): New cases DW_FORM_GNU_addr_index,
DW_FORM_GNU_str_index.
(hash_dwo_file, eq_dwo_file): New functions.
(allocate_dwo_file_hash_table): New function.
(hash_dwo_unit, eq_dwo_unit): New functions.
(allocate_dwo_unit_table): New function.
(dwarf2_locate_dwo_sections): New function.
(struct create_dwo_info_table_data): New type.
(create_debug_info_hash_table_reader): New function.
(create_debug_info_hash_table): New function.
(try_open_dwo_file, open_dwo_file, init_dwo_file): New function.
(lookup_dwo_file): New function.
(lookup_dwo_comp_unit, lookup_dwo_type_unit): New functions.
(free_dwo_file, free_dwo_file_cleanup): New functions.
(free_dwo_file_from_slot, free_dwo_files): New functions.
(dwarf2_get_pc_bounds): Handle DW_FORM_GNU_addr_index.
(dwarf2_record_block_ranges): Ditto.
(read_partial_die): Ditto.
(process_enumeration_scope): Update to use type_offset_in_section.
(read_full_die_1): New function.
(read_full_die): Rewrite.
(read_attribute_value): New cases DW_FORM_GNU_addr_index,
DW_FORM_GNU_str_index.
(read_addr_index_1, read_addr_index): New functions.
(read_addr_index_from_leb128): New function.
(struct dwarf2_read_addr_index_data): New type.
(dwarf2_read_addr_index_reader): New function.
(dwarf2_read_addr_index): New function.
(read_str_index): New function.
(leb128_size): New function.
(dwarf_decode_line_header): Delete arg abfd, all callers updated.
If processing a type unit from a DWO file, get the line section
from the DWO file.
(var_decode_location): Watch for DW_OP_GNU_addr_index.
(dwarf2_const_value_attr): New cases DW_FORM_GNU_addr_index,
DW_FORM_GNU_str_index.
(lookup_die_type): Check whether section offset of type's die is
known before looking it up. Remove assert. Condition can
legimately happen for inter-cu type references.
(dwarf_attr_name): Handle Fission attributes.
(dwarf_form_name): Handle Fission forms.
(dump_die_shallow): New cases DW_FORM_GNU_addr_index,
DW_FORM_GNU_str_index.
(follow_die_sig): Update to use type_offset_in_section.
(decode_locdesc): New case DW_OP_GNU_addr_index.
(skip_form_bytes): New cases DW_FORM_GNU_addr_index,
DW_FORM_GNU_str_index.
(cu_debug_loc_section): New function.
(fill_in_loclist_baton, dwarf2_symbol_mark_computed): Call it.
(dwarf2_per_objfile_free): Unmap .debug_addr section.
Free DWO files if present.
* xcoffread.c (dwarf2_xcoff_names): Add .debug_addr.
testsuite/
* gdb.dwarf2/dw2-intercu.S (.Ltype_int2_in_cu2): Renamed from
.Ltype_int_in_cu2. Use name "int2" instead of "int".
All uses updated.
* gdb.dwarf2/dw2-intercu.exp: Add "ptype int2" ahead of
"ptype func_cu1" to expand cu2 before cu1.
Implement basic support for DW_TAG_GNU_call_site.
* block.c: Include gdbtypes.h and exceptions.h.
(call_site_for_pc): New function.
* block.h (call_site_for_pc): New declaration.
* defs.h: Include hashtab.h.
(make_cleanup_htab_delete, core_addr_hash, core_addr_eq): New
declarations.
* dwarf2-frame.c (dwarf2_frame_ctx_funcs): Install
ctx_no_push_dwarf_reg_entry_value.
* dwarf2expr.c (read_uleb128, read_sleb128): Support R as NULL.
(dwarf_block_to_dwarf_reg): New function.
(execute_stack_op) <DW_OP_GNU_entry_value>: Implement it.
(ctx_no_push_dwarf_reg_entry_value): New function.
* dwarf2expr.h (struct dwarf_expr_context_funcs): New field
push_dwarf_reg_entry_value.
(ctx_no_push_dwarf_reg_entry_value, dwarf_block_to_dwarf_reg): New
declarations.
* dwarf2loc.c: Include gdbcmd.h.
(dwarf_expr_ctx_funcs): New forward declaration.
(entry_values_debug, show_entry_values_debug, call_site_to_target_addr)
(dwarf_expr_reg_to_entry_parameter)
(dwarf_expr_push_dwarf_reg_entry_value): New.
(dwarf_expr_ctx_funcs): Install dwarf_expr_push_dwarf_reg_entry_value.
(dwarf2_evaluate_loc_desc_full): Handle NO_ENTRY_VALUE_ERROR.
(needs_dwarf_reg_entry_value): New function.
(needs_frame_ctx_funcs): Install it.
(_initialize_dwarf2loc): New function.
* dwarf2loc.h (entry_values_debug): New declaration.
* dwarf2read.c (struct dwarf2_cu): New field call_site_htab.
(read_call_site_scope): New forward declaration.
(process_full_comp_unit): Copy call_site_htab.
(process_die): Support DW_TAG_GNU_call_site.
(read_call_site_scope): New function.
(dwarf2_get_pc_bounds): Support NULL HIGHPC.
(dwarf_tag_name): Support DW_TAG_GNU_call_site.
(cleanup_htab): Delete.
(write_psymtabs_to_index): Use make_cleanup_htab_delete instead of it.
* exceptions.h (enum errors): New NO_ENTRY_VALUE_ERROR.
* gdb-gdb.py (StructMainTypePrettyPrinter): Support
FIELD_LOC_KIND_DWARF_BLOCK.
* gdbtypes.h (enum field_loc_kind): New entry
FIELD_LOC_KIND_DWARF_BLOCK.
(struct main_type): New loc entry dwarf_block.
(struct call_site, FIELD_DWARF_BLOCK, SET_FIELD_DWARF_BLOCK)
(TYPE_FIELD_DWARF_BLOCK): New.
* python/py-type.c: Include dwarf2loc.h.
(check_types_equal): Support FIELD_LOC_KIND_DWARF_BLOCK. New
internal_error call on unknown FIELD_LOC_KIND.
* symtab.h (struct symtab): New field call_site_htab.
* utils.c (do_htab_delete_cleanup, make_cleanup_htab_delete)
(core_addr_hash, core_addr_eq): New functions.
gdb/testsuite/
Implement basic support for DW_TAG_GNU_call_site.
* gdb.arch/Makefile.in (EXECUTABLES): Add amd64-entry-value.
* gdb.arch/amd64-entry-value.cc: New file.
* gdb.arch/amd64-entry-value.exp: New file.
We don't need to read the .eh_frame section from the separate
object files, because this data is already present in the
main executable (it needs to, or the program wouldn't work).
We discovered this investigating a problem with the 'next' command,
which was due to unwind failures, which came from the fact that
the .eh_frame was incorrectly relocated.
gdb/ChangeLog (Tristan Gingold):
* dwarf2-frame.c (dwarf2_build_frame_info): Do not load .eh_frame
section in separate object files.
* symfile.h (enum dwarf2_section_enum): New type.
(dwarf2_get_section_info): New prototype.
* dwarf2read.c (dwarf2_get_section_info): Replace parameter
section_name by sect. Use a switch to select the info.
* dwarf2-frame.c (warf2_get_section_info): Remove prototype.
(dwarf2_build_frame_info): Adjust calls to dwarf2_get_section_info.
Tom Tromey
Joel Brobecker
Maciej W. Rozycki
Doug Evans
Gary Benson
Ulrich Weigand
Markus Metzger
Pedro Alves
Jan Kratochvil
Aleksandar Ristovski
Joel Brobecker
Doug Evans
Sergio Durigan Junior
Fawzi Mohamed
Tristan Gingold