Re: back into the thread....

[Mark Manning <mark4th@gmail.com>]

actually i lied. i get
"Cannot access memory at address 8" in this case

On Tue, Nov 12, 2013 at 5:47 PM, Sterling Augustine
<saugustine@google.com> wrote:
> 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;
> }



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