Re: Jit Implementation

bartc wrote:
> #include <stdio.h> #include <stdlib.h>
>
> int main(void){
>
> char* program; int (*fnptr)(void); int a;
>
> program = malloc(1000); /* Space for the code */
>
> program[0] = 0xB8; /* mov eax,1234h */ program[1] =
> 0x34; program[2] = 0x12; program[3] = 0; program[4] = 0; program[5]
> = 0xC3; /* ret */
>
> fnptr = (int (*)(void)) program;
>
> a = fnptr(); /* call the code */
>
> printf("Result = %X\n",a); /* show result */ }
>
> (If this shows "1234", then you're past the main hurdle.)
Some many find this useful, to get this working on linux i had to do this:


#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#include <errno.h>
#include <sys/mman.h>


int main( int argc, char *argv[] )
{
    int (*fnptr)(void); int retval= 0; size_t c_len= 1024;


    char *c_buffer = mmap( NULL, c_len, PROT_EXEC | PROT_READ | PROT_WRITE,
                          MAP_ANONYMOUS | MAP_PRIVATE , -1, 0 );


    *(c_buffer) = 0xB8; /* mov eax,1234h */
    *(c_buffer+1) = 0x34;
    *(c_buffer+2) = 0x12;
    *(c_buffer+3) = 0;
    *(c_buffer+4) = 0;
    *(c_buffer+5) = 0xC3; /* ret */


    fnptr = (int (*)(void)) c_buffer;
    retval = fnptr( ); /* call the code */


    printf("Result = %X\n", retval ); /* show result */
    munmap( c_buffer, c_len );


    return 0;
}


Hope some may find it useful. Have you any good pointers to references
for the operand values for this instruction set? I guess its in the
intel manuals but which ones are most useful or relevant?


- --Phil

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