What is the difference between .got and .got.plt section?

Question

What is the difference between .got and .got.plt section in ELF format?

Answer 1

My previous comment turns to be right:

I think .got is for relocations regarding global 'variables' while .got.plt is a auxiliary section to act together with .plt when resolving procedures absolute addresses.

The example below makes things a bit clear.

These are the relocations for my 32 bits i686-linux /lib/libm.so

Relocation section '.rel.dyn' at offset 0x32b8 contains 8 entries:  Offset     Info    Type            Sym.Value  Sym. Name 00025030  00000008 R_386_RELATIVE    00024fd8  00005706 R_386_GLOB_DAT    00025034   _LIB_VERSION 00024fdc  00000406 R_386_GLOB_DAT    00000000   __gmon_start__ 00024fe0  00000506 R_386_GLOB_DAT    00000000   _Jv_RegisterClasses 00024fe4  00000806 R_386_GLOB_DAT    00000000   _rtld_global_ro 00024fe8  00000906 R_386_GLOB_DAT    00000000   stderr 00024fec  00013006 R_386_GLOB_DAT    0002507c   signgam 00024ff0  00000e06 R_386_GLOB_DAT    00000000   __cxa_finalize  Relocation section '.rel.plt' at offset 0x32f8 contains 12 entries:  Offset     Info    Type            Sym.Value  Sym. Name 00025000  00000107 R_386_JUMP_SLOT   00000000   fputs 00025004  00000207 R_386_JUMP_SLOT   00000000   __errno_location 00025008  00000307 R_386_JUMP_SLOT   00000000   sprintf 0002500c  00000407 R_386_JUMP_SLOT   00000000   __gmon_start__ 00025010  00000607 R_386_JUMP_SLOT   00000000   strtod 00025014  00000707 R_386_JUMP_SLOT   00000000   __assert_fail 00025018  00000a07 R_386_JUMP_SLOT   00000000   strlen 0002501c  00000b07 R_386_JUMP_SLOT   00000000   strtof 00025020  00000c07 R_386_JUMP_SLOT   00000000   fwrite 00025024  00000d07 R_386_JUMP_SLOT   00000000   strtold 00025028  00005e07 R_386_JUMP_SLOT   00005970   matherr 0002502c  00000e07 R_386_JUMP_SLOT   00000000   __cxa_finalize 

Look that as you noted there are two relocation sections, namely .rel.dyn and .rel.plt. You can see that all relocations for .rel.plt are of type R_386_JUMP_SLOT which means that they are branch relocations on the other hand almost all relocations in .rel.dyn are R_386_GLOB_DAT which means relocation for global variables.

Another subtle difference exist between .symtab and .dynsym. While the first contain references for all symbols used during static link editing the later contain only those symbols needed for dynamic linking. Thus, the relocations mentioned above refer only to .dynsym section.