Hi Atif, In target-i386/translate.c, there are many variants of mov i.e.
case 0x89: /* mov Gv, Ev */ case 0xc7: /* mov Ev, Iv */ case 0x8b: /* mov Ev, Gv */ case 0x8e: /* mov seg, Gv */
That's true. I forgot the fact that mov %eax,%eax can be both: 0x89 0xC0 0x8B 0xC0 It's up to the compiler to choose which one to use. which one do you think will be called when "mov %eax, %eax" instruction is
translated. I printed the value of modrm inside the case 0x89 but the value remains the same whether I use %eax or %ebx. Secondly, How can I extract the source and destination registers from modrm.
modrm is the byte following the 0x89 or 0x8B opcode. After modrm = ldub_code(s->pc++); you can decode it this way (in binary): XXYYYZZZ XX --> Indexing mode YYY --> Destination register ZZZ --> Source register 0xC0 is the value you are looking for 11 000 000 --> (no indexing)(%eax)(%eax). You can find more information here: http://pdos.csail.mit.edu/6.828/2005/readings/i386/s17_02.htm One more thing: you may want to check operand size. It's on "ot" variable, and its meaning (from translate.c): enum { OT_BYTE = 0, OT_WORD, OT_LONG, OT_QUAD, }; being 8, 16, 32 and 64 bits respectively. Regards, Eduardo
