Hi,
I am working on an Elf64 parser to find symbol.
Im working on 'libc.so' and found some strange things about how
objdump/gdb resolve the PLT symbols.
Here is what I get from my own parser:
==============================
-------------------------------------
# Plt addr for 'realloc'
>>> get_symbol_addr('realloc')
'0x1f4b0'
# Got addr for 'realloc'
>>> get_symbol_addr('realloc.got')
'0x3a4028
-------------------------------------
Here is what objdump find:
==========================
000000000001f490 <realloc@plt>:
1f490: ff 25 82 4b 38 00 jmpq *0x384b82(%rip) # 3a4018
# So I have differents values:
# me | objdump
# PLT : 0x1f4b0 | 0x1f490
# GOT : 0x3a4028 | 0x3a4018
But Here is the infos from readelf about the GOT reloc :
Objdump rela.plt info :
======================
# It seems to be same offset that mine.
000003a4028 01e800000007 R_X86_64_JUMP_SLO 000000000007c110 realloc + 0
Even weirder !
Info extracted from GDB:
===================
-------------------------------------
(gdb) info proc map
......
0x7ffff7a33000 0x7ffff7bd4000 0x1a1000 0x0 /usr/lib/libc-2.18.so
# Let's disas MY 'realloc' PLT entry.
(gdb) x/i 0x7ffff7a33000 + 0x1f4b0
0x7ffff7a524b0 <__tls_get_addr@plt>: jmpq *0x384b72(%rip)
# 0x7ffff7dd7028
# __tls_get_addr : it seems I was wrong : but let's follow the GOT !
(gdb) x/gx 0x7ffff7dd7028
0x7ffff7dd7028: 0x00007ffff7aaf110
# (following the GOT)
(gdb) x/i 0x00007ffff7aaf110
0x7ffff7aaf110 <realloc>: push %r15
-------------------------------------
So, according to GDB, the PLT entry <__tls_get_addr@plt> resolve into <realloc>.
It seems to be a bug in BFD.
If I am missing something: please tell me.
Thanks,
--
Clement "Hakril" Rouault
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