汇编函数调用的参数传递

32bit 汇编函数调用参数传递是通过堆栈来实现的。

.section .data
output:
    .asciz "The processor Vendor ID is %s\n"
.section .bss
    .lcomm buffer,12
.section .text
.globl main
main:
    movl $0,%eax
    cpuid
    movl $buffer, %edi
    movl %ebx, (%edi)
    movl %edx, 4(%edi)
    movl %ecx, 8(%edi)
    pushl $buffer    #第二个参数先进栈，第一个后进栈，这样pop的时候第一个就会先出来,反正就是参数从右到左进栈
    pushl $output
    call printf
    addl $8, %esp    #前面push了现在要堆栈平衡
    pushl $0
    call exit

64bit的参数传递会首先用到寄存器，寄存器不够，才用对堆栈

LINUX下面INTERGER参数（包括bool,char,short,int,long,long long)从左到右依次放到寄存器%rdi,%rsi,%rdx,%rcx,%r8,%r9，超过6个放堆栈里；SSE型的参数（float,double)，从左到右依次放到vector registers(%xmm0-%xmm7)

注意%rax的作用

1)temporary register;
2)with variable arguments passes information about the number of vector registers used;
3)1st return register
特别注意第二点
For calls that may call functions that use varargs or stdargs (prototype-lesscalls or calls to functions containing ellipsis (. . . ) in the declaration) %al is usedas hidden argument to specify the number of vector registers used.
对于变长参数的函数，要用%al指明用到的vector registers（存放float,double等类型）的个数 ，比如printf

.section .data
output:
    .asciz "The processor Vendor ID is %s\n"
.section .bss
    .lcomm buffer, 12
.section .text
.globl main
main:
    movl $0,%eax
    cpuid
    movl $buffer,%edi
    movl %ebx,(%edi)
    movl %edx,4(%edi)
    movl %ecx,8(%edi)
    movq $output,%rdi
    movq $buffer,%rsi
    movq $0,%rax    #没有用到vector registers，所以%al是0
    call printf
    mov $0,%ax   #这里的ax是返回值
    call exit

 

Windows下面INTERGER参数从左到右依次放到rcx,rdx,r8,r9，超过4个放堆栈里，由于现在不搞windows，这个就不说了