2016-01-01 04:33:14 +00:00
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/* Copyright 2014-2016 Free Software Foundation, Inc.
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DWARF: Read constant-class addresses correctly
Starting with DWARF version 4, the description of the DW_AT_high_pc
attribute was amended to say:
if it is of class constant, the value is an unsigned integer offset
which when added to the low PC gives the address of the first
location past the last instruction associated with the entity.
A change was made in Apr 27th, 2012 to reflect that change:
| commit 91da14142c0171e58a91ad58a32fd010b700e761
| Author: Mark Wielaard <mjw@redhat.com>
| Date: Fri Apr 27 18:55:19 2012 +0000
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| * dwarf2read.c (dwarf2_get_pc_bounds): Check DW_AT_high_pc form to
| see whether it is an address or a constant offset from DW_AT_low_pc.
| (dwarf2_record_block_ranges): Likewise.
| (read_partial_die): Likewise.
Unfortunately, this new interpretation is now used regardless of
the CU's DWARF version. It turns out that one of WindRiver's compilers
(FTR: Diabdata 4.4) is generating DWARF version 2 info with
DW_AT_high_pc attributes improperly using the data4 form. Because of
that, we miscompute all high PCs incorrectly. This leads to a lot of
symtabs having overlapping ranges, which in turn causes havoc in
pc-to-symtab-and-line translations.
One visible effect is when inserting a breakpoint on a given function:
(gdb) b world
Breakpoint 1 at 0x4005c4
The source location of the breakpoint is missing. The output should be:
(gdb) b world
Breakpoint 1 at 0x4005c8: file dw2-rel-hi-pc-world.c, line 24.
What happens in this case is that the pc-to-SAL translation first
starts be trying to find the symtab associated to our PC using
each symtab's ranges. Because of the high_pc miscomputation,
many symtabs end up matching, and the heuristic trying to select
the most probable one unfortunately returns one that is unrelated
(it really had no change in this case to do any better). Once we
have the wrong symtab, the start searching the associated linetable,
where the addresses are correct, thus finding no match, and therefore
no SAL.
This patch is an attempt at handling the situation as gracefully
as we can, without guarantees. It introduces a new function
"attr_value_as_address" which uses the correct accessor for getting
the value of a given attribute. It then adjust the code throughout
this unit to use this function instead of assuming that addresses always
have the DW_FORM_addr format.
It also fixes the original issue of miscomputing the high_pc
by limiting the new interpretation of constant form DW_AT_high_pc
attributes to units using DWARF version 4 or later.
gdb/ChangeLog:
* dwarf2read.c (attr_value_as_address): New function.
(dwarf2_find_base_address, read_call_site_scope): Use
attr_value_as_address in place of DW_ADDR.
(dwarf2_get_pc_bounds): Use attr_value_as_address to get
the low and high addresses. Slight rework of the handling
of the high pc being a constant form, and limit it to
DWARF verson 4 or higher.
(dwarf2_record_block_ranges): Likewise.
(read_partial_die): Likewise.
(new_symbol_full): Use attr_value_as_address in place of DW_ADDR.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-abs-hi-pc-hello-dbg.S: New file.
* gdb.dwarf2/dw2-abs-hi-pc-hello.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc-world-dbg.S: New file.
* gdb.dwarf2/dw2-abs-hi-pc-world.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc.exp: New file.
Tested on x86_64-linux.
2014-02-15 15:09:58 +00:00
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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.section .debug_info
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.4byte .Ledebug_info0 - .Lsdebug_info0 /* Length of Compilation Unit Info */
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.Lsdebug_info0:
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.2byte 0x2 /* DWARF version number */
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.4byte .Ldebug_abbrev0 /* Offset Into Abbrev. Section */
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.byte 0x4 /* Pointer Size (in bytes) */
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.uleb128 0x1 /* (DIE (0xb) DW_TAG_compile_unit) */
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.ascii "GNU C 4.7.4 20140206 for GNAT Pro 7.3.0w (20140206)\0"
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.byte 0x1 /* DW_AT_language */
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.ascii "dw2-abs-hi-pc-hello.c\0" /* DW_AT_name */
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.ascii "/tmp\0" /* DW_AT_comp_dir */
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.4byte .hello_start /* DW_AT_low_pc */
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.4byte .hello_end /* DW_AT_high_pc */
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.4byte .Ldebug_line0 /* DW_AT_stmt_list */
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.uleb128 0x2 /* (DIE (0x2d) DW_TAG_subprogram) */
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.byte 0x1 /* DW_AT_external */
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.ascii "hello\0"
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.byte 0x1 /* DW_AT_decl_file (hello.c) */
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.byte 0x13 /* DW_AT_decl_line */
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.byte 0x1 /* DW_AT_prototyped */
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.4byte .hello_start /* DW_AT_low_pc */
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.4byte .hello_end /* DW_AT_high_pc */
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.byte 0 /* end of children of DIE 0xb */
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.Ledebug_info0:
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.section .debug_abbrev
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.Ldebug_abbrev0:
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.uleb128 0x1 /* (abbrev code) */
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.uleb128 0x11 /* (TAG: DW_TAG_compile_unit) */
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.byte 0x1 /* DW_children_yes */
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.uleb128 0x25 /* (DW_AT_producer) */
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.uleb128 0x8 /* (DW_FORM_string) */
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.uleb128 0x13 /* (DW_AT_language) */
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.uleb128 0xb /* (DW_FORM_data1) */
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.uleb128 0x3 /* (DW_AT_name) */
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.uleb128 0x8 /* (DW_FORM_string) */
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.uleb128 0x1b /* (DW_AT_comp_dir) */
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.uleb128 0x8 /* (DW_FORM_string) */
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.uleb128 0x11 /* (DW_AT_low_pc) */
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.uleb128 0x6 /* (DW_FORM_data4) */
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.uleb128 0x12 /* (DW_AT_high_pc) */
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.uleb128 0x6 /* (DW_FORM_data4) */
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.uleb128 0x10 /* (DW_AT_stmt_list) */
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.uleb128 0x6 /* (DW_FORM_data4) */
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.byte 0
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.byte 0
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.uleb128 0x2 /* (abbrev code) */
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.uleb128 0x2e /* (TAG: DW_TAG_subprogram) */
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.byte 0 /* DW_children_no */
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.uleb128 0x3f /* (DW_AT_external) */
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.uleb128 0xc /* (DW_FORM_flag) */
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.uleb128 0x3 /* (DW_AT_name) */
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.uleb128 0x8 /* (DW_FORM_string) */
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.uleb128 0x3a /* (DW_AT_decl_file) */
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.uleb128 0xb /* (DW_FORM_data1) */
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.uleb128 0x3b /* (DW_AT_decl_line) */
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.uleb128 0xb /* (DW_FORM_data1) */
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.uleb128 0x27 /* (DW_AT_prototyped) */
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.uleb128 0xc /* (DW_FORM_flag) */
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.uleb128 0x11 /* (DW_AT_low_pc) */
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.uleb128 0x6 /* (DW_FORM_data4) */
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.uleb128 0x12 /* (DW_AT_high_pc) */
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.uleb128 0x6 /* (DW_FORM_data4) */
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.byte 0
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.byte 0
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.byte 0
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.section .debug_line
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.Ldebug_line0:
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.4byte LELT-LSLT /* Length of Source Line Info */
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LSLT:
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.2byte 0x2 /* DWARF Version */
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.4byte LELTP-LASLTP /* Prolog Length */
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LASLTP:
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.byte 0x1 /* Minimum Instruction Length */
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.byte 0x1 /* Default is_stmt_start flag */
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.byte 0x1 /* Line Base Value (Special Opcodes) */
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.byte 0x1 /* Line Range Value (Special Opcodes) */
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.byte 0xd /* Special Opcode Base */
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.byte 0 /* opcode: 0x1 has 0 args */
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.byte 0x1 /* opcode: 0x2 has 1 args */
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.byte 0x1 /* opcode: 0x3 has 1 args */
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.byte 0x1 /* opcode: 0x4 has 1 args */
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.byte 0x1 /* opcode: 0x5 has 1 args */
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.byte 0 /* opcode: 0x6 has 0 args */
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.byte 0 /* opcode: 0x7 has 0 args */
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.byte 0 /* opcode: 0x8 has 0 args */
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.byte 0x1 /* opcode: 0x9 has 1 args */
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.byte 0 /* opcode: 0xa has 0 args */
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.byte 0 /* opcode: 0xb has 0 args */
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.byte 0x1 /* opcode: 0xc has 1 args */
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.byte 0 /* End directory table */
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.ascii "dw2-abs-hi-pc-hello.c\0" /* File Entry: 0x1 */
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.uleb128 0
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.uleb128 0
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.uleb128 0
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.byte 0 /* End file name table */
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LELTP:
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.byte 0 /* set address to .hello_start */
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.uleb128 0x5
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.byte 0x2
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.4byte .hello_start
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.byte 0x3 /* DW_LNS_advance_line */
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.sleb128 22 /* ... to 23 */
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.byte 0x5 /* column 0 */
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.uleb128 0 /* 0 */
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.byte 1 /* DW_LNS_copy */
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.byte 0 /* set address to .hello0 */
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.uleb128 0x5
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.byte 0x2
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.4byte .hello0
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.byte 0x3 /* DW_LNS_advance_line */
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.sleb128 1 /* ... to 24 */
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.byte 0x5 /* column 0 */
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.uleb128 0 /* 0 */
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.byte 1 /* DW_LNS_copy */
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.byte 0 /* set address to .hello1 */
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.uleb128 0x5
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.byte 0x2
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.4byte .hello1
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.byte 0x3 /* DW_LNS_advance_line */
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.sleb128 1 /* ... to 25 */
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.byte 0x5 /* column 0 */
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.uleb128 0 /* 0 */
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.byte 1 /* DW_LNS_copy */
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.byte 0 /* set address to .hello_end */
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.uleb128 0x5
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.byte 0x2
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.4byte .hello_end
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.byte 0 /* end sequence */
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.uleb128 0x1
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.byte 0x1
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LELT:
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