[Bug gold/16794] New: gold doesn't include the "implicit addend" when processing REL relocations to mergable sections

[rafael.espindola at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16794

            Bug ID: 16794
           Summary: gold doesn't include the "implicit addend" when
                    processing REL relocations to mergable sections
           Product: binutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gold
          Assignee: ian at airs dot com
          Reporter: rafael.espindola at gmail dot com
                CC: ccoutant at google dot com

Created attachment 7516
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7516&action=edit
testcase

The attached testcase has both 32 and 64 bit versions of a test. The file
test.o contains relocations to a mergeable section. In the 32 bit case it has:


00000012  00000509 R_386_GOTOFF      00000000   .rodata.str1.1
0000001c  00000509 R_386_GOTOFF      00000000   .rodata.str1.1

The "implicit addend" are in the two lea instructions:

objdump  -d test.o

  10:    8d 83 07 00 00 00        lea    0x7(%ebx),%eax
  16:    89 44 24 04              mov    %eax,0x4(%esp)
  1a:    8d 83 00 00 00 00        lea    0x0(%ebx),%eax

On the gold produced output, the distance between the two is still 7 (0x11ac-
0x11a5)

 80484e0:       8d 83 5b ee ff ff       lea    -0x11a5(%ebx),%eax
 80484e6:       89 44 24 04             mov    %eax,0x4(%esp)
 80484ea:       8d 83 54 ee ff ff       lea    -0x11ac(%ebx),%eax

The the actual section has been modified to merge the strings, so that is no
longer valid.

Using bfd ld, the offset is updated:

 8048460:       8d 83 4d ee ff ff       lea    -0x11b3(%ebx),%eax
 8048466:       89 44 24 04             mov    %eax,0x4(%esp)
 804846a:       8d 83 4c ee ff ff       lea    -0x11b4(%ebx),%ea

Everything works on 64 bits. I assume that is because it uses RELA relocations.
In 64 bits the test.o file has

000000000003  000500000002 R_X86_64_PC32     0000000000000000 .rodata.str1.1 +
0
00000000000a  000500000002 R_X86_64_PC32     0000000000000000 .rodata.str1.1 +
7


   0:    48 8d 3d 00 00 00 00     lea    0x0(%rip),%rdi
   7:    48 8d 35 00 00 00 00     lea    0x0(%rip),%rsi

and the final binary is update correctly

  400530:       48 8d 3d ad 00 00 00    lea    0xad(%rip),%rdi
  400537:       48 8d 35 a7 00 00 00    lea    0xa7(%rip),%rsi

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