bits 32
	section .text

F_ID equ 0x200000

	global read_cpuid_
read_cpuid_:
	; determine if cpuid is available
	pushf
	pop eax
	mov edx, eax	; keep a copy of the original eflags in edx
	xor eax, F_ID
	push eax
	popf
	pushf
	pop eax
	cmp edx, eax
	jnz .havecpuid
	; failed to flip ID bit, CPUID not supported
	mov eax, -1
	ret
.havecpuid:
	push ebp
	mov ebp, esp
	push ebx
	push edi
	sub esp, 8
	mov edi, [ebp + 8]

	xor eax, eax
	mov [esp], eax	; current index
	cpuid

	mov [edi], eax
	; clamp to the size of our cpuid_info structure
	cmp eax, 1
	jbe .skipclamp
	mov eax, 1
	mov [esp + 4], eax	; maximum index
.skipclamp:

	mov [edi + 4], ebx
	mov [edi + 8], edx
	mov [edi + 12], ecx
	add edi, 16

cpuid_loop:
	mov eax, [esp]
	inc eax
	cmp eax, [esp + 4]
	ja cpuid_done
	mov [esp], eax
	cpuid
	mov [edi], eax
	mov [edi + 4], ebx
	mov [edi + 8], edx
	mov [edi + 12], ecx
	add edi, 16
	jmp cpuid_loop

cpuid_done:
	add esp, 8
	pop edi
	pop ebx
	pop ebp
	xor eax, eax
	ret