cpuid.asm

global internal_cpuid

section .text
bits 64

; params:
;    rdi - cpuid call 
;    rsi - pointer to a continous 16 bytes of memory
;          which will be filled
internal_cpuid:
	; save frame pointer and callee-save ebx
	push rbp
	mov rbp, rsp
	push rbx

	; cpuid call - 0 = vendor id
	mov eax, rdi
	cpuid

	mov dword [rsi],    eax
	mov dword [rsi+4],  ebx
	mov dword [rsi+8],  ecx
	mov dword [rsi+12], edx

	pop rbx
	pop rbp

	ret

cpuid.rs

#[repr(C, packed)]
struct CpuIdResult {
    eax: u32,
    ebx: u32,
    ecx: u32,
    edx: u32
}

fn cpuid(id: u32) -> CpuIdResult {
    let mut result = CpuIdResult {
        eax: 0,
        ebx: 0,
        ecx: 0,
        edx: 0,
    };

    unsafe {
        internal_cpuid(&mut result);
    }

    result;
}


#[link(name = "cpuid")]
extern {
    pub fn internal_cpuid(ptr: *mut CpuIdResult);
}