2.5 OpenEuler 中C与汇编的混合编程（选做）待完善
a.c
#include <stdio.h>
extern int B();
int A(int x,int y)
{
int d, e,f;
d = 4;
e = 5;
f= 6;
f = B(d,e);
}
a.s
.text
.globl A
A：
pushl %ebp
movl %esp,%ebp
subl $24, %esp
movl $4,-12(%ebp) # d=4
movl $5,-8(%ebp) # e=5
movl $6, -4(%ebp) # f=6
subl $8,%esp
pushl -8(%ebp) # push e
pushl -12(%ebp) # push d
call B
addl $16,, %esp #clean stack
movl %eax,-4(%ebp) # f=return value in AX
leave
ret
2(1)
s.s
.global get_esp,get_ebp
get_esp:
movl %esp,%eax
ret
get_ebp:
movl %ebp,%eax
ret
#====================================
int main()
{
int ebp,esp;
ebp = get_ebp();
esp = get_esp();
printf("ebp=%8x esp=%8x\n",ebp,esp);
}
2(2)
sum.c
int main() # driver program to test mysum() function
{
int a,b,c;
a = 123; b = 456;
c = mysum(a, b);
printf("c=%d\n", c); // c should be 579
}
mysum.s
.text
.global mysum,printf
mysum:
pushl %ebp
movl %esp,ebp
movl 8(%ebp),eax
add1 12(%ebp),%eax
movl %ebp,%esp
pop %ebp
ret
3
sub.c
#include <stdio.h>
int a,b;
int main()
{
a = 100; b = 200;
sub();
}
Assembly Code
.text
.global sub, a, b, printf
sub：
pushl %ebp
movl %esp,%ebp
pushl b
pushl a
pushl $fmt # push VALUE (address) of fmt
call printf # printf(fmt,a,b);
addl $12, %esp
movl %ebp,%esp
popl %ebp
ret
.data
fmt： .asciz "a=%d b=%d\n"
