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old-cross-binutils/gdb/arch-utils.c
Maciej W. Rozycki 3e29f34a4e MIPS: Keep the ISA bit in compressed code addresses 
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.
2014-12-12 13:49:06 +00:00

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/* Dynamic architecture support for GDB, the GNU debugger.
Copyright (C) 1998-2014 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "arch-utils.h"
#include "buildsym.h"
#include "gdbcmd.h"
#include "inferior.h" /* enum CALL_DUMMY_LOCATION et al. */
#include "infrun.h"
#include "regcache.h"
#include "sim-regno.h"
#include "gdbcore.h"
#include "osabi.h"
#include "target-descriptions.h"
#include "objfiles.h"
#include "language.h"
#include "symtab.h"
#include "version.h"
#include "floatformat.h"
struct displaced_step_closure *
simple_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
size_t len = gdbarch_max_insn_length (gdbarch);
gdb_byte *buf = xmalloc (len);
read_memory (from, buf, len);
write_memory (to, buf, len);
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog, "displaced: copy %s->%s: ",
paddress (gdbarch, from), paddress (gdbarch, to));
displaced_step_dump_bytes (gdb_stdlog, buf, len);
}
return (struct displaced_step_closure *) buf;
}
void
simple_displaced_step_free_closure (struct gdbarch *gdbarch,
struct displaced_step_closure *closure)
{
xfree (closure);
}
int
default_displaced_step_hw_singlestep (struct gdbarch *gdbarch,
struct displaced_step_closure *closure)
{
return !gdbarch_software_single_step_p (gdbarch);
}
CORE_ADDR
displaced_step_at_entry_point (struct gdbarch *gdbarch)
{
CORE_ADDR addr;
int bp_len;
addr = entry_point_address ();
/* Inferior calls also use the entry point as a breakpoint location.
We don't want displaced stepping to interfere with those
breakpoints, so leave space. */
gdbarch_breakpoint_from_pc (gdbarch, &addr, &bp_len);
addr += bp_len * 2;
return addr;
}
int
legacy_register_sim_regno (struct gdbarch *gdbarch, int regnum)
{
/* Only makes sense to supply raw registers. */
gdb_assert (regnum >= 0 && regnum < gdbarch_num_regs (gdbarch));
/* NOTE: cagney/2002-05-13: The old code did it this way and it is
suspected that some GDB/SIM combinations may rely on this
behavour. The default should be one2one_register_sim_regno
(below). */
if (gdbarch_register_name (gdbarch, regnum) != NULL
&& gdbarch_register_name (gdbarch, regnum)[0] != '\0')
return regnum;
else
return LEGACY_SIM_REGNO_IGNORE;
}
CORE_ADDR
generic_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
{
return 0;
}
CORE_ADDR
generic_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc)
{
return 0;
}
int
generic_in_solib_return_trampoline (struct gdbarch *gdbarch,
CORE_ADDR pc, const char *name)
{
return 0;
}
int
generic_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc)
{
return 0;
}
/* Helper functions for gdbarch_inner_than */
int
core_addr_lessthan (CORE_ADDR lhs, CORE_ADDR rhs)
{
return (lhs < rhs);
}
int
core_addr_greaterthan (CORE_ADDR lhs, CORE_ADDR rhs)
{
return (lhs > rhs);
}
/* Misc helper functions for targets. */
CORE_ADDR
core_addr_identity (struct gdbarch *gdbarch, CORE_ADDR addr)
{
return addr;
}
CORE_ADDR
convert_from_func_ptr_addr_identity (struct gdbarch *gdbarch, CORE_ADDR addr,
struct target_ops *targ)
{
return addr;
}
int
no_op_reg_to_regnum (struct gdbarch *gdbarch, int reg)
{
return reg;
}
void
default_coff_make_msymbol_special (int val, struct minimal_symbol *msym)
{
return;
}
/* See arch-utils.h. */
void
default_make_symbol_special (struct symbol *sym, struct objfile *objfile)
{
return;
}
/* See arch-utils.h. */
CORE_ADDR
default_adjust_dwarf2_addr (CORE_ADDR pc)
{
return pc;
}
/* See arch-utils.h. */
CORE_ADDR
default_adjust_dwarf2_line (CORE_ADDR addr, int rel)
{
return addr;
}
int
cannot_register_not (struct gdbarch *gdbarch, int regnum)
{
return 0;
}
/* Legacy version of target_virtual_frame_pointer(). Assumes that
there is an gdbarch_deprecated_fp_regnum and that it is the same,
cooked or raw. */
void
legacy_virtual_frame_pointer (struct gdbarch *gdbarch,
CORE_ADDR pc,
int *frame_regnum,
LONGEST *frame_offset)
{
/* FIXME: cagney/2002-09-13: This code is used when identifying the
frame pointer of the current PC. It is assuming that a single
register and an offset can determine this. I think it should
instead generate a byte code expression as that would work better
with things like Dwarf2's CFI. */
if (gdbarch_deprecated_fp_regnum (gdbarch) >= 0
&& gdbarch_deprecated_fp_regnum (gdbarch)
< gdbarch_num_regs (gdbarch))
*frame_regnum = gdbarch_deprecated_fp_regnum (gdbarch);
else if (gdbarch_sp_regnum (gdbarch) >= 0
&& gdbarch_sp_regnum (gdbarch)
< gdbarch_num_regs (gdbarch))
*frame_regnum = gdbarch_sp_regnum (gdbarch);
else
/* Should this be an internal error? I guess so, it is reflecting
an architectural limitation in the current design. */
internal_error (__FILE__, __LINE__,
_("No virtual frame pointer available"));
*frame_offset = 0;
}
int
generic_convert_register_p (struct gdbarch *gdbarch, int regnum,
struct type *type)
{
return 0;
}
int
default_stabs_argument_has_addr (struct gdbarch *gdbarch, struct type *type)
{
return 0;
}
int
generic_instruction_nullified (struct gdbarch *gdbarch,
struct regcache *regcache)
{
return 0;
}
int
default_remote_register_number (struct gdbarch *gdbarch,
int regno)
{
return regno;
}
/* See arch-utils.h. */
int
default_vsyscall_range (struct gdbarch *gdbarch, struct mem_range *range)
{
return 0;
}
/* Functions to manipulate the endianness of the target. */
static int target_byte_order_user = BFD_ENDIAN_UNKNOWN;
static const char endian_big[] = "big";
static const char endian_little[] = "little";
static const char endian_auto[] = "auto";
static const char *const endian_enum[] =
{
endian_big,
endian_little,
endian_auto,
NULL,
};
static const char *set_endian_string;
enum bfd_endian
selected_byte_order (void)
{
return target_byte_order_user;
}
/* Called by ``show endian''. */
static void
show_endian (struct ui_file *file, int from_tty, struct cmd_list_element *c,
const char *value)
{
if (target_byte_order_user == BFD_ENDIAN_UNKNOWN)
if (gdbarch_byte_order (get_current_arch ()) == BFD_ENDIAN_BIG)
fprintf_unfiltered (file, _("The target endianness is set automatically "
"(currently big endian)\n"));
else
fprintf_unfiltered (file, _("The target endianness is set automatically "
"(currently little endian)\n"));
else
if (target_byte_order_user == BFD_ENDIAN_BIG)
fprintf_unfiltered (file,
_("The target is assumed to be big endian\n"));
else
fprintf_unfiltered (file,
_("The target is assumed to be little endian\n"));
}
static void
set_endian (char *ignore_args, int from_tty, struct cmd_list_element *c)
{
struct gdbarch_info info;
gdbarch_info_init (&info);
if (set_endian_string == endian_auto)
{
target_byte_order_user = BFD_ENDIAN_UNKNOWN;
if (! gdbarch_update_p (info))
internal_error (__FILE__, __LINE__,
_("set_endian: architecture update failed"));
}
else if (set_endian_string == endian_little)
{
info.byte_order = BFD_ENDIAN_LITTLE;
if (! gdbarch_update_p (info))
printf_unfiltered (_("Little endian target not supported by GDB\n"));
else
target_byte_order_user = BFD_ENDIAN_LITTLE;
}
else if (set_endian_string == endian_big)
{
info.byte_order = BFD_ENDIAN_BIG;
if (! gdbarch_update_p (info))
printf_unfiltered (_("Big endian target not supported by GDB\n"));
else
target_byte_order_user = BFD_ENDIAN_BIG;
}
else
internal_error (__FILE__, __LINE__,
_("set_endian: bad value"));
show_endian (gdb_stdout, from_tty, NULL, NULL);
}
/* Given SELECTED, a currently selected BFD architecture, and
TARGET_DESC, the current target description, return what
architecture to use.
SELECTED may be NULL, in which case we return the architecture
associated with TARGET_DESC. If SELECTED specifies a variant
of the architecture associtated with TARGET_DESC, return the
more specific of the two.
If SELECTED is a different architecture, but it is accepted as
compatible by the target, we can use the target architecture.
If SELECTED is obviously incompatible, warn the user. */
static const struct bfd_arch_info *
choose_architecture_for_target (const struct target_desc *target_desc,
const struct bfd_arch_info *selected)
{
const struct bfd_arch_info *from_target = tdesc_architecture (target_desc);
const struct bfd_arch_info *compat1, *compat2;
if (selected == NULL)
return from_target;
if (from_target == NULL)
return selected;
/* struct bfd_arch_info objects are singletons: that is, there's
supposed to be exactly one instance for a given machine. So you
can tell whether two are equivalent by comparing pointers. */
if (from_target == selected)
return selected;
/* BFD's 'A->compatible (A, B)' functions return zero if A and B are
incompatible. But if they are compatible, it returns the 'more
featureful' of the two arches. That is, if A can run code
written for B, but B can't run code written for A, then it'll
return A.
Some targets (e.g. MIPS as of 2006-12-04) don't fully
implement this, instead always returning NULL or the first
argument. We detect that case by checking both directions. */
compat1 = selected->compatible (selected, from_target);
compat2 = from_target->compatible (from_target, selected);
if (compat1 == NULL && compat2 == NULL)
{
/* BFD considers the architectures incompatible. Check our
target description whether it accepts SELECTED as compatible
anyway. */
if (tdesc_compatible_p (target_desc, selected))
return from_target;
warning (_("Selected architecture %s is not compatible "
"with reported target architecture %s"),
selected->printable_name, from_target->printable_name);
return selected;
}
if (compat1 == NULL)
return compat2;
if (compat2 == NULL)
return compat1;
if (compat1 == compat2)
return compat1;
/* If the two didn't match, but one of them was a default
architecture, assume the more specific one is correct. This
handles the case where an executable or target description just
says "mips", but the other knows which MIPS variant. */
if (compat1->the_default)
return compat2;
if (compat2->the_default)
return compat1;
/* We have no idea which one is better. This is a bug, but not
a critical problem; warn the user. */
warning (_("Selected architecture %s is ambiguous with "
"reported target architecture %s"),
selected->printable_name, from_target->printable_name);
return selected;
}
/* Functions to manipulate the architecture of the target. */
enum set_arch { set_arch_auto, set_arch_manual };
static const struct bfd_arch_info *target_architecture_user;
static const char *set_architecture_string;
const char *
selected_architecture_name (void)
{
if (target_architecture_user == NULL)
return NULL;
else
return set_architecture_string;
}
/* Called if the user enters ``show architecture'' without an
argument. */
static void
show_architecture (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
if (target_architecture_user == NULL)
fprintf_filtered (file, _("The target architecture is set "
"automatically (currently %s)\n"),
gdbarch_bfd_arch_info (get_current_arch ())->printable_name);
else
fprintf_filtered (file, _("The target architecture is assumed to be %s\n"),
set_architecture_string);
}
/* Called if the user enters ``set architecture'' with or without an
argument. */
static void
set_architecture (char *ignore_args, int from_tty, struct cmd_list_element *c)
{
struct gdbarch_info info;
gdbarch_info_init (&info);
if (strcmp (set_architecture_string, "auto") == 0)
{
target_architecture_user = NULL;
if (!gdbarch_update_p (info))
internal_error (__FILE__, __LINE__,
_("could not select an architecture automatically"));
}
else
{
info.bfd_arch_info = bfd_scan_arch (set_architecture_string);
if (info.bfd_arch_info == NULL)
internal_error (__FILE__, __LINE__,
_("set_architecture: bfd_scan_arch failed"));
if (gdbarch_update_p (info))
target_architecture_user = info.bfd_arch_info;
else
printf_unfiltered (_("Architecture `%s' not recognized.\n"),
set_architecture_string);
}
show_architecture (gdb_stdout, from_tty, NULL, NULL);
}
/* Try to select a global architecture that matches "info". Return
non-zero if the attempt succeeds. */
int
gdbarch_update_p (struct gdbarch_info info)
{
struct gdbarch *new_gdbarch;
/* Check for the current file. */
if (info.abfd == NULL)
info.abfd = exec_bfd;
if (info.abfd == NULL)
info.abfd = core_bfd;
/* Check for the current target description. */
if (info.target_desc == NULL)
info.target_desc = target_current_description ();
new_gdbarch = gdbarch_find_by_info (info);
/* If there no architecture by that name, reject the request. */
if (new_gdbarch == NULL)
{
if (gdbarch_debug)
fprintf_unfiltered (gdb_stdlog, "gdbarch_update_p: "
"Architecture not found\n");
return 0;
}
/* If it is the same old architecture, accept the request (but don't
swap anything). */
if (new_gdbarch == target_gdbarch ())
{
if (gdbarch_debug)
fprintf_unfiltered (gdb_stdlog, "gdbarch_update_p: "
"Architecture %s (%s) unchanged\n",
host_address_to_string (new_gdbarch),
gdbarch_bfd_arch_info (new_gdbarch)->printable_name);
return 1;
}
/* It's a new architecture, swap it in. */
if (gdbarch_debug)
fprintf_unfiltered (gdb_stdlog, "gdbarch_update_p: "
"New architecture %s (%s) selected\n",
host_address_to_string (new_gdbarch),
gdbarch_bfd_arch_info (new_gdbarch)->printable_name);
set_target_gdbarch (new_gdbarch);
return 1;
}
/* Return the architecture for ABFD. If no suitable architecture
could be find, return NULL. */
struct gdbarch *
gdbarch_from_bfd (bfd *abfd)
{
struct gdbarch_info info;
gdbarch_info_init (&info);
info.abfd = abfd;
return gdbarch_find_by_info (info);
}
/* Set the dynamic target-system-dependent parameters (architecture,
byte-order) using information found in the BFD */
void
set_gdbarch_from_file (bfd *abfd)
{
struct gdbarch_info info;
struct gdbarch *gdbarch;
gdbarch_info_init (&info);
info.abfd = abfd;
info.target_desc = target_current_description ();
gdbarch = gdbarch_find_by_info (info);
if (gdbarch == NULL)
error (_("Architecture of file not recognized."));
set_target_gdbarch (gdbarch);
}
/* Initialize the current architecture. Update the ``set
architecture'' command so that it specifies a list of valid
architectures. */
#ifdef DEFAULT_BFD_ARCH
extern const bfd_arch_info_type DEFAULT_BFD_ARCH;
static const bfd_arch_info_type *default_bfd_arch = &DEFAULT_BFD_ARCH;
#else
static const bfd_arch_info_type *default_bfd_arch;
#endif
#ifdef DEFAULT_BFD_VEC
extern const bfd_target DEFAULT_BFD_VEC;
static const bfd_target *default_bfd_vec = &DEFAULT_BFD_VEC;
#else
static const bfd_target *default_bfd_vec;
#endif
static int default_byte_order = BFD_ENDIAN_UNKNOWN;
void
initialize_current_architecture (void)
{
const char **arches = gdbarch_printable_names ();
struct gdbarch_info info;
/* determine a default architecture and byte order. */
gdbarch_info_init (&info);
/* Find a default architecture. */
if (default_bfd_arch == NULL)
{
/* Choose the architecture by taking the first one
alphabetically. */
const char *chosen = arches[0];
const char **arch;
for (arch = arches; *arch != NULL; arch++)
{
if (strcmp (*arch, chosen) < 0)
chosen = *arch;
}
if (chosen == NULL)
internal_error (__FILE__, __LINE__,
_("initialize_current_architecture: No arch"));
default_bfd_arch = bfd_scan_arch (chosen);
if (default_bfd_arch == NULL)
internal_error (__FILE__, __LINE__,
_("initialize_current_architecture: Arch not found"));
}
info.bfd_arch_info = default_bfd_arch;
/* Take several guesses at a byte order. */
if (default_byte_order == BFD_ENDIAN_UNKNOWN
&& default_bfd_vec != NULL)
{
/* Extract BFD's default vector's byte order. */
switch (default_bfd_vec->byteorder)
{
case BFD_ENDIAN_BIG:
default_byte_order = BFD_ENDIAN_BIG;
break;
case BFD_ENDIAN_LITTLE:
default_byte_order = BFD_ENDIAN_LITTLE;
break;
default:
break;
}
}
if (default_byte_order == BFD_ENDIAN_UNKNOWN)
{
/* look for ``*el-*'' in the target name. */
const char *chp;
chp = strchr (target_name, '-');
if (chp != NULL
&& chp - 2 >= target_name
&& strncmp (chp - 2, "el", 2) == 0)
default_byte_order = BFD_ENDIAN_LITTLE;
}
if (default_byte_order == BFD_ENDIAN_UNKNOWN)
{
/* Wire it to big-endian!!! */
default_byte_order = BFD_ENDIAN_BIG;
}
info.byte_order = default_byte_order;
info.byte_order_for_code = info.byte_order;
if (! gdbarch_update_p (info))
internal_error (__FILE__, __LINE__,
_("initialize_current_architecture: Selection of "
"initial architecture failed"));
/* Create the ``set architecture'' command appending ``auto'' to the
list of architectures. */
{
/* Append ``auto''. */
int nr;
for (nr = 0; arches[nr] != NULL; nr++);
arches = xrealloc (arches, sizeof (char*) * (nr + 2));
arches[nr + 0] = "auto";
arches[nr + 1] = NULL;
add_setshow_enum_cmd ("architecture", class_support,
arches, &set_architecture_string,
_("Set architecture of target."),
_("Show architecture of target."), NULL,
set_architecture, show_architecture,
&setlist, &showlist);
add_alias_cmd ("processor", "architecture", class_support, 1, &setlist);
}
}
/* Initialize a gdbarch info to values that will be automatically
overridden. Note: Originally, this ``struct info'' was initialized
using memset(0). Unfortunately, that ran into problems, namely
BFD_ENDIAN_BIG is zero. An explicit initialization function that
can explicitly set each field to a well defined value is used. */
void
gdbarch_info_init (struct gdbarch_info *info)
{
memset (info, 0, sizeof (struct gdbarch_info));
info->byte_order = BFD_ENDIAN_UNKNOWN;
info->byte_order_for_code = info->byte_order;
info->osabi = GDB_OSABI_UNINITIALIZED;
}
/* Similar to init, but this time fill in the blanks. Information is
obtained from the global "set ..." options and explicitly
initialized INFO fields. */
void
gdbarch_info_fill (struct gdbarch_info *info)
{
/* "(gdb) set architecture ...". */
if (info->bfd_arch_info == NULL
&& target_architecture_user)
info->bfd_arch_info = target_architecture_user;
/* From the file. */
if (info->bfd_arch_info == NULL
&& info->abfd != NULL
&& bfd_get_arch (info->abfd) != bfd_arch_unknown
&& bfd_get_arch (info->abfd) != bfd_arch_obscure)
info->bfd_arch_info = bfd_get_arch_info (info->abfd);
/* From the target. */
if (info->target_desc != NULL)
info->bfd_arch_info = choose_architecture_for_target
(info->target_desc, info->bfd_arch_info);
/* From the default. */
if (info->bfd_arch_info == NULL)
info->bfd_arch_info = default_bfd_arch;
/* "(gdb) set byte-order ...". */
if (info->byte_order == BFD_ENDIAN_UNKNOWN
&& target_byte_order_user != BFD_ENDIAN_UNKNOWN)
info->byte_order = target_byte_order_user;
/* From the INFO struct. */
if (info->byte_order == BFD_ENDIAN_UNKNOWN
&& info->abfd != NULL)
info->byte_order = (bfd_big_endian (info->abfd) ? BFD_ENDIAN_BIG
: bfd_little_endian (info->abfd) ? BFD_ENDIAN_LITTLE
: BFD_ENDIAN_UNKNOWN);
/* From the default. */
if (info->byte_order == BFD_ENDIAN_UNKNOWN)
info->byte_order = default_byte_order;
info->byte_order_for_code = info->byte_order;
/* "(gdb) set osabi ...". Handled by gdbarch_lookup_osabi. */
/* From the manual override, or from file. */
if (info->osabi == GDB_OSABI_UNINITIALIZED)
info->osabi = gdbarch_lookup_osabi (info->abfd);
/* From the target. */
if (info->osabi == GDB_OSABI_UNKNOWN && info->target_desc != NULL)
info->osabi = tdesc_osabi (info->target_desc);
/* From the configured default. */
#ifdef GDB_OSABI_DEFAULT
if (info->osabi == GDB_OSABI_UNKNOWN)
info->osabi = GDB_OSABI_DEFAULT;
#endif
/* Must have at least filled in the architecture. */
gdb_assert (info->bfd_arch_info != NULL);
}
/* Return "current" architecture. If the target is running, this is
the architecture of the selected frame. Otherwise, the "current"
architecture defaults to the target architecture.
This function should normally be called solely by the command
interpreter routines to determine the architecture to execute a
command in. */
struct gdbarch *
get_current_arch (void)
{
if (has_stack_frames ())
return get_frame_arch (get_selected_frame (NULL));
else
return target_gdbarch ();
}
int
default_has_shared_address_space (struct gdbarch *gdbarch)
{
/* Simply say no. In most unix-like targets each inferior/process
has its own address space. */
return 0;
}
int
default_fast_tracepoint_valid_at (struct gdbarch *gdbarch,
CORE_ADDR addr, int *isize, char **msg)
{
/* We don't know if maybe the target has some way to do fast
tracepoints that doesn't need gdbarch, so always say yes. */
if (msg)
*msg = NULL;
return 1;
}
void
default_remote_breakpoint_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pcptr,
int *kindptr)
{
gdbarch_breakpoint_from_pc (gdbarch, pcptr, kindptr);
}
void
default_gen_return_address (struct gdbarch *gdbarch,
struct agent_expr *ax, struct axs_value *value,
CORE_ADDR scope)
{
error (_("This architecture has no method to collect a return address."));
}
int
default_return_in_first_hidden_param_p (struct gdbarch *gdbarch,
struct type *type)
{
/* Usually, the return value's address is stored the in the "first hidden"
parameter if the return value should be passed by reference, as
specified in ABI. */
return language_pass_by_reference (type);
}
int default_insn_is_call (struct gdbarch *gdbarch, CORE_ADDR addr)
{
return 0;
}
int default_insn_is_ret (struct gdbarch *gdbarch, CORE_ADDR addr)
{
return 0;
}
int default_insn_is_jump (struct gdbarch *gdbarch, CORE_ADDR addr)
{
return 0;
}
void
default_skip_permanent_breakpoint (struct regcache *regcache)
{
struct gdbarch *gdbarch = get_regcache_arch (regcache);
CORE_ADDR current_pc = regcache_read_pc (regcache);
const gdb_byte *bp_insn;
int bp_len;
bp_insn = gdbarch_breakpoint_from_pc (gdbarch, &current_pc, &bp_len);
current_pc += bp_len;
regcache_write_pc (regcache, current_pc);
}
/* -Wmissing-prototypes */
extern initialize_file_ftype _initialize_gdbarch_utils;
void
_initialize_gdbarch_utils (void)
{
add_setshow_enum_cmd ("endian", class_support,
endian_enum, &set_endian_string,
_("Set endianness of target."),
_("Show endianness of target."),
NULL, set_endian, show_endian,
&setlist, &showlist);
}
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