Re: back into the thread....

[Sterling Augustine <saugustine@google.com>]

On Tue, Nov 12, 2013 at 2:42 PM, Sterling Augustine
<saugustine@google.com> wrote:
> This feature clearly works.
>

.. This time with a couple of cleanups. The old example definitely
works, this just eliminates an extraneous call to malloc and an
uninitialized variable.

include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <string.h>
#include <malloc.h>

const char bytes[] = { 0x89, 0xf8, 0xc3 };
#define EXEC_BYTES sizeof(bytes)

typedef int(*function_ptr)(int);

int main(int argc, char *argv[])
{
  int test_val = 5;
  int return_val;
  function_ptr dst;
  if (posix_memalign((void **) &dst, 4096*8, EXEC_BYTES) != 0) {
    printf("can't allocate.\n");
    exit (-1);
  }
  if (mprotect(dst, EXEC_BYTES, PROT_READ|PROT_WRITE|PROT_EXEC) != 0) {
    printf("can't mprotect\n");
    exit (-1);
  }

  if (argc > 1)
    test_val = atoi(argv[1]);

  memcpy(dst, bytes, EXEC_BYTES);

  return_val = dst(test_val);
  printf("return val was %d\n", return_val);
  return 0;
}