Loading machinecode from file into memory and executing in C -- mprotect failing
- by chartreusekitsune
Hi I'm trying to load raw machine code into memory and run it from within a C program, right now when the program executes it breaks when trying to run mprotect on the memory to make it executable. I'm also not entirely sure that if the memory does get set right it will execute. What I currently have is the following:
#include <memory.h>
#include <sys/mman.h>
#include <stdio.h>
int main ( int argc, char **argv )
{
FILE *fp;
int sz = 0;
char *membuf;
int output = 0;
fp = fopen(argv[1],"rb");
if(fp == NULL)
{
printf("Failed to open file, aborting!\n");
exit(1);
}
fseek(fp, 0L, SEEK_END);
sz = ftell(fp);
fseek(fp, 0L, SEEK_SET);
membuf = (char *)malloc(sz*sizeof(char));
if(membuf == NULL)
{
printf("Failed to allocate memory, aborting!\n");
exit(1);
}
memset(membuf, 0x90, sz*sizeof(char));
if( mprotect(membuf, sz*sizeof(char), PROT_EXEC | PROT_READ | PROT_WRITE) == -1)
{
printf("mprotect failed!!! aborting!\n");
exit(1);
}
if((sz*sizeof(char)) != fread(membuf, sz*sizeof(char), 1, fp))
{
printf("Read failed, aborting!\n");
exit(1);
}
__asm__
(
"call %%eax;"
: "=a" (output)
: "a" (membuf)
);
printf("Output = %x\n", output);
return 0;
}
