gcc inline assembler - filling a structure

[Vincent De Groote <list.encelade@xxxxxxxxx>]

Hello,

I would like to execute the cpuid instruction on a x86

So I declared

typedef unsigned long int register_t;

struct response_t {
  register_t eax;
  register_t ebx;
   register_t ecx;
   register_t edx;
};

void cpuid ( register_t command, struct response_t * response )  {

...

}

How can I, in assembler, assign the value of a register (for example
ebx) to the response->ebx field ?

I also would like to wrap such function under a preprocessor #ifdef
directive, to check the target machine.
Is there a preprocessor definition I can use for this (a target like
x86) ?  I cannot find the list of all preprocessor definitions defined
by gcc.


Thanks for your replies and your time

Vincent De Groote