Bug 16910 - Failed to relocate attributes of debug information when the sym is wrapped
Summary: Failed to relocate attributes of debug information when the sym is wrapped
Status: RESOLVED FIXED
Alias: None
Product: binutils
Classification: Unclassified
Component: ld (show other bugs)
Version: 2.25
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-05-06 03:06 UTC by Yao Qi
Modified: 2014-06-11 10:04 UTC (History)
1 user (show)

See Also:
Host:
Target:
Build:
Last reconfirmed:

Attachments
dwz.S (780 bytes, text/plain)
2014-05-06 03:10 UTC, Yao Qi 		Details
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Description Yao Qi 2014-05-06 03:06:29 UTC 
We find this bug when we run gdb test gdb.dwarf2/dwz.exp.  Here are the steps to reproduce this bug:

1. Compile and link
$ gcc 1.c -c -o 1.o
$ gcc 2.c -c -o 2.o
$ gcc dwz.S -c -o dwz.o
$ build-x86/ld/ld-new 1.o dwz.o 2.o --wrap main -o 1.exe

2. Examine the address of main and __wrap_main
$ readelf -s 1.exe | grep main
    10: 08048088    18 FUNC    GLOBAL DEFAULT    1 __wrap_main
    12: 08048074    20 FUNC    GLOBAL DEFAULT    1 main

3. Examine the DW_AT_low_pc attribute for main,
$ readelf -wi ./1.exe
Contents of the .debug_info section:                                                                                                                          

  Compilation Unit @ offset 0x0:
   Length:        0x17 (32-bit)
   Version:       4
   Abbrev Offset: 0x0
   Pointer Size:  4
 <0><b>: Abbrev Number: 2 (DW_TAG_partial_unit)
 <1><c>: Abbrev Number: 3 (DW_TAG_subprogram)
    <d>   DW_AT_name        : main
    <12>   DW_AT_low_pc      : 0x8048088  <------- [1]
    <16>   DW_AT_high_pc     : 0x8048092

As we can see, DW_AT_low_pc should be the address of main instead of __wrap_main, otherwise, GDB will be confused.  We find this problem on both x86 and arm targets.
Comment 1 Yao Qi 2014-05-06 03:10:17 UTC 
Created attachment 7587 [details]
dwz.S

$ cat 1.c 
int
main (void)
{
  return 0;
}

$ cat 2.c 
int
__wrap_main (void)
{
  __real_main ();
  return 0;
}
Comment 2 Alan Modra 2014-06-10 13:41:00 UTC 
commit b71c404358dbc78d3e84c4299c6139c5291ac441
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Jun 10 23:07:52 2014 +0930

    add pr number to changelog

commit 7b8e2718e4412ddc1e42c6a68166de919eb62221
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Jun 10 23:02:55 2014 +0930

    missing changelog entries for 8a5da09b9

commit 8a5da09b9e326a19e78b20a1021a5148ea0484b0
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Jun 10 21:50:21 2014 +0930

    Unwrap symbols for debug information
    
    Fixes issues with dwz multi-file (-m) and ld's -wrap option.
    Symbols referenced from DWARF debug info in a separate file, eg. to
    specify low and high pc, must use the real symbol.  The DWARF info
    is specifying attributes of the real function, not one interposed
    with --wrap.
    
    include/
        * bfdlink.h (unwrap_hash_lookup): Declare.
    bfd/
        * linker.c (unwrap_hash_lookup): New function.
        * elf-bfd (RELOC_FOR_GLOBAL_SYMBOL): Call unwrap_hash_lookup.
        * elf32-i370.c (i370_elf_relocate_section): Likewise.
        * elf32-m32c.c (m32c_elf_relocate_section): Likewise.
        * elf32-m32r.c (m32r_elf_relocate_section): Likewise.
        * elf32-score.c (s3_bfd_score_elf_relocate_section): Likewise.
        * elf32-score7.c (s7_bfd_score_elf_relocate_section): Likewise.
        * elf32-spu.c (spu_elf_relocate_section): Likewise.
        * elf64-hppa.c (elf64_hppa_relocate_section): Likewise.
Comment 3 Alan Modra 2014-06-11 10:04:08 UTC 
commit 7ed689ad61de0cbfe4e5a6f18f097776128202e4
Author: Alan Modra <amodra@gmail.com>
Date:   Wed Jun 11 19:11:12 2014 +0930

    Fix silly thinko
    
        * linker.c (unwrap_hash_lookup): Add missing parens.