2.5 OpenEuler 中C与汇编的混合编程（选做）

一、X86_64实践内容

2.5.1

1.代码如下：

/************a.c*************/
#include<stdio.h>

extern int B();

int A(int x,int y)
{
	int d,e,f;
	d =4; e =5; f=6;
	d=B(d,e);
}

经过汇编命令gcc -m32 -S a.c -o a.s

得到汇编文件

/************a.s*************/
.file	"a.c"
	.text
	.globl	A
	.type	A, @function
A:
.LFB0:
	.cfi_startproc
	endbr32
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	pushl	%ebx
	subl	$20, %esp
	.cfi_offset 3, -12
	call	__x86.get_pc_thunk.ax
	addl	$_GLOBAL_OFFSET_TABLE_, %eax
	movl	$4, -20(%ebp)
	movl	$5, -16(%ebp)
	movl	$6, -12(%ebp)
	subl	$8, %esp
	pushl	-16(%ebp)
	pushl	-20(%ebp)
	movl	%eax, %ebx
	call	B@PLT
	addl	$16, %esp
	movl	%eax, -20(%ebp)
	nop
	movl	-4(%ebp), %ebx
	leave
	.cfi_restore 5
	.cfi_restore 3
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	A, .-A
	.section	.text.__x86.get_pc_thunk.ax,"axG",@progbits,__x86.get_pc_thunk.ax,comdat
	.globl	__x86.get_pc_thunk.ax
	.hidden	__x86.get_pc_thunk.ax
	.type	__x86.get_pc_thunk.ax, @function
__x86.get_pc_thunk.ax:
.LFB1:
	.cfi_startproc
	movl	(%esp), %eax
	ret
	.cfi_endproc
.LFE1:
	.ident	"GCC: (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0"
	.section	.note.GNU-stack,"",@progbits
	.section	.note.gnu.property,"a"
	.align 4
	.long	 1f - 0f
	.long	 4f - 1f
	.long	 5
0:
	.string	 "GNU"
1:
	.align 4
	.long	 0xc0000002
	.long	 3f - 2f
2:
	.long	 0x3
3:
	.align 4
4:

2.5.2

1.代码如下：

/************s.c*************/
#include <stdio.h>
extern int get_ebp();
extern int get_esp();
int main()
{
    int ebp, esp;
    ebp = get_ebp();
    esp = get_esp();
    printf("ebp=%8x     esp=%8x\n",ebp,esp);
}

/************s.s*************/
		.global get_esp,get_ebp
get_esp:
		movl %esp,%eax
		ret
get_ebp:
		movl %ebp,%eax
		ret

经过汇编命令gcc -m32 s.s s.c -o s.out

得到汇编文件

2.5.3

/************smysum.s*************/
	.text
	.global mysum,printf
mysum:
#(1)Entry:
	pushl $ebp
	movl %esp,%ebp
#(2)Function Body code
	movl 8(%ebp),%eax
	addl 12(%ebp),%eax
#(3)Exit Code
	movl %ebp,%esp
	pop %ebp
	ret

/************smysum.c*************/
#include<stdio.h>
int main()
{
	int a,b,c;
	a = 123;b = 456;
	c = mysum(a,b);
	printf("c=%d\n",c);
}

汇编指令：gcc -m32 -o mysum.out mysum.s mysum.c

2.5.4

/************prt.c*************/
int a,b;
int main()
{
	a = 100;b = 200;
	sub();
}

/************prt.s*************/	
	.text
	.global sub,a,b,printf
sub:
	pushl %ebp
	movl %esp,%ebp
	
	pushl b
	pushl a
	pushl $fmt
	call printf
	addl $12,%esp
	
	movl %ebp,%esp
	popl %ebp
	ret
	
	
	    .data
fmt:	.asciz "a=%d b=%d\n"

汇编命令：gcc -m32 prt.c prt.s -o prt.out