depexec.c

#include <sys/mman.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>

/* from objdump  - S
int foo(int a, int b)
{
  401110:	55                   	push   %rbp
  401111:	48 89 e5             	mov    %rsp,%rbp
  401114:	89 7d fc             	mov    %edi,-0x4(%rbp)
  401117:	89 75 f8             	mov    %esi,-0x8(%rbp)
    return a+b;
  40111a:	8b 45 fc             	mov    -0x4(%rbp),%eax
  40111d:	03 45 f8             	add    -0x8(%rbp),%eax
  401120:	5d                   	pop    %rbp
  401121:	c3                   	retq
  401122:	66 2e 0f 1f 84 00 00 	nopw   %cs:0x0(%rax,%rax,1)
  401129:	00 00 00
  40112c:	0f 1f 40 00          	nopl   0x0(%rax)
*/

int foo(int a, int b)
{
    return a+b;
}

int main()
{
    unsigned char code[] =
    {
            0x55,
            0x48, 0x89, 0xe5,
            0x89, 0x7d, 0xfc,
            0x89, 0x75, 0xf8,
            0x8b, 0x45, 0xfc,
            0x03, 0x45, 0xf8,
            0x5d, 0xc3
    };

    size_t pagesize = sysconf(_SC_PAGESIZE);
    uintptr_t pagestart = ((uintptr_t) &code) & -pagesize;
    if(mprotect((void*) pagestart, pagesize, PROT_READ|PROT_WRITE|PROT_EXEC)){
        perror("mprotect");
        return 1;
    }

    int c = ((int(*)())code)(100, 200);  //execute instruction
    printf("Successfully executed![%d]\n", c);
}