What does the following C code do?

void id(unsigned info, unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx) {
*eax = info;
asm volatile(
"mov %%ebx, %%edi;"
"cpuid;"
"mov %%ebx, %%esi;"
"mov %%edi, %%ebx;"
:"+a" (*eax), "=S" (*ebx), "=c" (*ecx), "=d" (*edx)
: :"edi");
}

Question

What does the following C code do?

void id(unsigned info, unsigned *eax, unsigned *ebx, unsigned *ecx, unsigned *edx) {
    *eax = info;
    asm volatile(
        "mov %%ebx, %%edi;"
        "cpuid;"
        "mov %%ebx, %%esi;"
        "mov %%edi, %%ebx;"
    :"+a" (*eax), "=S" (*ebx), "=c" (*ecx), "=d" (*edx)
            : :"edi");
}

anonymous · Answer

that look like things I see in assembly language

anonymous · Answer

Yeah C often supports inline assembly

anonymous · Answer

esi and edi are used often for memeory to memory transfer

anonymous · Answer

I have 0% knowledge of assembly, so I don't know how that code ended up there :(

anonymous · Answer

from what I can see , you are just moving data around the register

anonymous · Answer

what's the cpuid statement do?

anonymous · Answer

figure out information about processor , I suppose

anonymous · Answer

http://ideone.com/cPBS3

anonymous · Answer

typical output

anonymous · Answer

almost meaningless to me though :(

anonymous · Answer

If you haven't http://en.wikipedia.org/wiki/CPUID

anonymous · Answer

everything makes sense now