On Wed, 2022-03-30 at 22:03 +0300, Jarkko Sakkinen wrote: > On Wed, 2022-03-30 at 10:40 -0700, Reinette Chatre wrote: > > Could you please elaborate how the compiler will fix it up? > > Sure. > > Here's the disassembly of the RBX version: > > [0x000021a9]> pi 1 > lea rax, [rbx + loc.encl_stack] > > Here's the same with s/RBX/RIP/: > > [0x000021a9]> pi 5 > lea rax, loc.encl_stack > Compiler will substitute correct offset relative to the RIP, > well, because it can and it makes sense. > > It is treated differently than other registers, e.g. when > LEA is assembled. > > BR, Jarkko To demonstrate this I did a couple of simple sessions with Rizin (fork/continuation/something of Radare2): jarkko@suppilovahvero ~/Downloads (main)> rizin test_encl.rbx.elf -- Temporally drop the verbosity prefixing the commands with ':' [0x00002000]> aaa [x] Analyze all flags starting with sym. and entry0 (aa) [x] Analyze function calls (aac) [x] Analyze len bytes of instructions for references (aar) [x] Check for classes [x] Type matching analysis for all functions (aaft) [x] Propagate noreturn information [x] Use -AA or aaaa to perform additional experimental analysis. [0x00002000]> /ad lea 0x0000206e # 7: lea rax, [rip + 0xf8b] 0x0000206f # 6: lea eax, [rip + 0xf8b] 0x0000207e # 1: leave 0x000020a1 # 7: lea rcx, [rip + 0xf58] 0x000020a2 # 6: lea ecx, [rip + 0xf58] 0x000020b4 # 1: leave 0x000020ee # 1: leave 0x00002128 # 1: leave 0x00002145 # 7: lea rax, [rip - 0x102] 0x00002146 # 6: lea eax, [rip - 0x102] 0x00002150 # 7: lea rax, [rip - 0xd7] 0x00002151 # 6: lea eax, [rip - 0xd7] 0x0000215b # 7: lea rax, [rip - 0xac] 0x0000215c # 6: lea eax, [rip - 0xac] 0x00002166 # 7: lea rax, [rip - 0x7d] 0x00002167 # 6: lea eax, [rip - 0x7d] 0x00002171 # 7: lea rax, [rip - 0x4e] 0x00002172 # 6: lea eax, [rip - 0x4e] 0x000021a7 # 1: leave 0x000021a9 # 7: lea rax, [rbx + loc.encl_stack] 0x000021aa # 6: lea eax, [rbx + loc.encl_stack] [0x00002000]> s 0x21a9 [0x000021a9]> pi 1 lea rax, [rbx + loc.encl_stack] [0x000021a9]> jarkko@suppilovahvero ~/Downloads (main)> rizin test_encl.elf -- Use V! to enter into the visual panels mode (dwm style) [0x00002000]> aaa [x] Analyze all flags starting with sym. and entry0 (aa) [x] Analyze function calls (aac) [x] Analyze len bytes of instructions for references (aar) [x] Check for classes [x] Type matching analysis for all functions (aaft) [x] Propagate noreturn information [x] Use -AA or aaaa to perform additional experimental analysis. [0x00002000]> /ad lea 0x0000206e # 7: lea rax, [rip + 0xf8b] 0x0000206f # 6: lea eax, [rip + 0xf8b] 0x0000207e # 1: leave 0x000020a1 # 7: lea rcx, [rip + 0xf58] 0x000020a2 # 6: lea ecx, [rip + 0xf58] 0x000020b4 # 1: leave 0x000020ee # 1: leave 0x00002128 # 1: leave 0x00002145 # 7: lea rax, [rip - 0x102] 0x00002146 # 6: lea eax, [rip - 0x102] 0x00002150 # 7: lea rax, [rip - 0xd7] 0x00002151 # 6: lea eax, [rip - 0xd7] 0x0000215b # 7: lea rax, [rip - 0xac] 0x0000215c # 6: lea eax, [rip - 0xac] 0x00002166 # 7: lea rax, [rip - 0x7d] 0x00002167 # 6: lea eax, [rip - 0x7d] 0x00002171 # 7: lea rax, [rip - 0x4e] 0x00002172 # 6: lea eax, [rip - 0x4e] 0x000021a7 # 1: leave 0x000021a9 # 7: lea rax, [rip + 0x5e50] 0x000021aa # 6: lea eax, [rip + 0x5e50] [0x00002000]> s 0x21a9 [0x000021a9]> pi 1 lea rax, loc.encl_stack [0x000021a9]> BR, Jarkko
