[Bug gold/14536] Unnecessary GOT usages

[ccoutant at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14536

--- Comment #1 from Cary Coutant <ccoutant at google dot com> 2012-08-31 
21:19:20 UTC ---
I think this is related to the discussion here:

   http://sourceware.org/ml/binutils/2011-03/msg00220.html.

-cary


On Fri, Aug 31, 2012 at 2:11 PM, hjl.tools at gmail dot com
<address@hidden> wrote:
> http://sourceware.org/bugzilla/show_bug.cgi?id=14536
>
>              Bug #: 14536
>            Summary: Unnecessary GOT usages
>            Product: binutils
>            Version: 2.23 (HEAD)
>             Status: NEW
>           Severity: normal
>           Priority: P2
>          Component: gold
>         AssignedTo: address@hidden
>         ReportedBy: address@hidden
>                 CC: address@hidden
>     Classification: Unclassified
>
>
> On Linux/x86, gold gives
> address@hidden symbolic-6]$ cat foo.S
>     .text
>     .globl    foo
>     .type    foo, @function
> foo:
>     ret
>     .size    foo, .-foo
>     .globl    _start
>     .type    _start, @function
> _start:
> #ifdef __x86_64__
>     movq    address@hidden(%rip), %rax
> #else
>     movl    address@hidden(%ecx), %eax
> #endif
>     .size    _start, .-_start
> address@hidden symbolic-6]$ cat foo.t
> {
>   global:
>   _start;
>   local:
>   *;
> };
> address@hidden symbolic-6]$ make
> gcc -m32    -c -o foo.o foo.S
> ./ld -m elf_i386 -Bsymbolic -shared -o libfoo.so foo.o
> ./ld -m elf_i386 -pie -o pie foo.o
> ./ld -m elf_i386 -o static foo.o
> ./ld -m elf_i386 -shared -o shared foo.o --version-script foo.t
> objdump -dw libfoo.so
>
> libfoo.so:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 0000016c <foo>:
>  16c:    c3                       ret
>
> 0000016d <_start>:
>  16d:    8b 81 fc ff ff ff        mov    -0x4(%ecx),%eax
> objdump -dw pie
>
> pie:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 00000114 <foo>:
>  114:    c3                       ret
>
> 00000115 <_start>:
>  115:    8b 81 fc ff ff ff        mov    -0x4(%ecx),%eax
> objdump -dw static
>
> static:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 08048074 <foo>:
>  8048074:    c3                       ret
>
> 08048075 <_start>:
>  8048075:    8b 81 fc ff ff ff        mov    -0x4(%ecx),%eax
> objdump -dw shared
>
> shared:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 000000f8 <foo>:
>   f8:    c3                       ret
>
> 000000f9 <_start>:
>   f9:    8b 81 fc ff ff ff        mov    -0x4(%ecx),%eax
> readelf -SW libfoo.so | grep ".got " || true
>   [ 7] .got              PROGBITS        00001204 000204 000004 00  WA  0   0
> 4
> readelf -SW pie | grep ".got " || true
>   [ 8] .got              PROGBITS        000011a4 0001a4 000004 00  WA  0   0
> 4
> readelf -SW static | grep ".got " || true
>   [ 2] .got              PROGBITS        0804907c 00007c 000004 00  WA  0   0
> 4
> readelf -SW shared | grep ".got " || true
>   [ 7] .got              PROGBITS        00001180 000180 000004 00  WA  0   0
> 4
> address@hidden symbolic-6]$
>
> bfd linker gave
>
> address@hidden symbolic-6]$ make LD=./ld.bfd
> gcc -m32    -c -o foo.o foo.S
> ./ld.bfd -m elf_i386 -Bsymbolic -shared -o libfoo.so foo.o
> ./ld.bfd -m elf_i386 -pie -o pie foo.o
> ./ld.bfd -m elf_i386 -o static foo.o
> ./ld.bfd -m elf_i386 -shared -o shared foo.o --version-script foo.t
> objdump -dw libfoo.so
>
> libfoo.so:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 00000140 <foo>:
>  140:    c3                       ret
>
> 00000141 <_start>:
>  141:    8d 81 98 ef ff ff        lea    -0x1068(%ecx),%eax
> objdump -dw pie
>
> pie:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 00000168 <foo>:
>  168:    c3                       ret
>
> 00000169 <_start>:
>  169:    8d 81 98 ef ff ff        lea    -0x1068(%ecx),%eax
> objdump -dw static
>
> static:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 08048074 <foo>:
>  8048074:    c3                       ret
>
> 08048075 <_start>:
>  8048075:    8d 81 f8 ef ff ff        lea    -0x1008(%ecx),%eax
> objdump -dw shared
>
> shared:     file format elf32-i386
>
>
> Disassembly of section .text:
>
> 000000d0 <foo>:
>   d0:    c3                       ret
>
> 000000d1 <_start>:
>   d1:    8d 81 a0 ef ff ff        lea    -0x1060(%ecx),%eax
> readelf -SW libfoo.so | grep ".got " || true
> readelf -SW pie | grep ".got " || true
> readelf -SW static | grep ".got " || true
> readelf -SW shared | grep ".got " || true
> address@hidden symbolic-6]$
>
> The same goes for Linux/x86-64.
>
> --
> Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
> ------- You are receiving this mail because: -------
> You are on the CC list for the bug.

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.