Hi, This is regarding GOT in PIC code. I have built a shared object library with simple hello function printing the contents of a global variable (say p). When I use objdump the code shows the function referencing the variable address from a GOT table index. (see dump below). The code is such that the offset of GOT from SP is already decided at link time in the shared object file (0x1b1c, as I can see from objdump). This makes me ask - 1. Does the dynamic linker map the physical pages for .data segments such that GOT is at a fixed offset from code in logical address space? is this true? 2. Aren't the variables themselves at a fixed offset from GOT (since GOT is part of data segment)? So, can't the code just access the data relative to PC with a single indirection? 000004cc <hello>: 4cc: 55 push ebp 4cd: 89 e5 mov ebp,esp 4cf: 53 push ebx 4d0: 83 ec 14 sub esp,0x14 4d3: e8 ef ff ff ff call 4c7 <__i686.get_pc_thunk.bx> 4d8: 81 c3 1c 1b 00 00 add ebx,0x1b1c <----------------------offset 4de: 8b 83 f4 ff ff ff mov eax,DWORD PTR [ebx-0xc] 4e4: 8b 00 mov eax,DWORD PTR [eax] 4e6: 89 c1 mov ecx,eax 4e8: 8b 83 f8 ff ff ff mov eax,DWORD PTR [ebx-0x8] 4ee: 8b 10 mov edx,DWORD PTR [eax] 4f0: 8d 83 90 e5 ff ff lea eax,[ebx-0x1a70] 4f6: 89 4c 24 08 mov DWORD PTR [esp+0x8],ecx 4fa: 89 54 24 04 mov DWORD PTR [esp+0x4],edx 4fe: 89 04 24 mov DWORD PTR [esp],eax 501: e8 d2 fe ff ff call 3d8 <printf@plt> 506: 83 c4 14 add esp,0x14 509: 5b pop ebx 50a: 5d pop ebp 50b: c3 ret Regards, Chethan
