And this code (pulled from the Pi forum, written by ???) demonstrates -
#include <stdio.h>
#include <sys/mman.h>
#include <stdint.h>
#include <stdlib.h>
int inc(int x){ //increments x
uint32_t *ret = mmap(NULL,
2 * sizeof(uint32_t), // Space for 16 instructions. (More than enough.)
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS,
-1,0);
if (ret == MAP_FAILED) {
printf("Could not mmap a memory buffer with the proper permissions.\n");
return -1;
}
*(ret + 0) = 0xE2800001; //add r0 r0 #1 := r0 += 1
*(ret + 1) = 0xE12FFF1E; //bx lr := jump back to inc()
__clear_cache((char*) ret, (char*) (ret+2));
int(*f)(int) = (int (*)(int)) ret;
return (*f)(x);
}
int main(){
printf("%d\n",inc(6)); //expect '7' to be printed
exit(0);}
tim
--
tim Rowledge;
[hidden email];
http://www.rowledge.org/timStrange OpCodes: YVR: Branch to Vancouver
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