Question

I have an array of hex codes that translate into assembly instructions and I want to create program in C that can execute these.

unsigned char rawData[5356] = {
    0x4C, 0x01, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64, 0x0C, 0x00, 0x00,
    0x3D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x01, 0x2E, 0x74, 0x65, 0x78,
    0x74, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0xB4, 0x05, 0x00, 0x00, 0xA4, 0x01, 0x00, 0x00, 0x68, 0x08, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x61, 0x00, 0x00, 0x00, 0x20, 0x00, 0x30, 0x60,
    0x2E, 0x64, 0x61, 0x74, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x40, 0x00, 0x30, 0xC0, 0x2E, 0x62, 0x73, 0x73, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x30, 0xC0, 0x2F, 0x34, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x14, 0x00, 0x00, 0x00, 0x58, 0x07, 0x00, 0x00, 0x32, 0x0C, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x20, 0x10, 0x30, 0x60,
    0x2F, 0x33, 0x32, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x6C, 0x07, 0x00, 0x00,...and so on

Answer 1

With the x86 it is possible.

Here’s a small sample. Allocate the page with write/exec privileges and copy your opcodes there.

#ifdef _WIN32
#include <windows.h>
#else
#include <sys/mman.h>
#include <unistd.h>
#endif


int main(){
    char opcodes[] = { ..... }; 

    #ifdef _WIN32

    HANDLE mem_handle = CreateFileMappingA( INVALID_HANDLE_VALUE, NULL, PAGE_EXECUTE_READWRITE, 0,  length, NULL);

    void* mem_map = MapViewOfFile( mem_handle, FILE_MAP_ALL_ACCESS | FILE_MAP_EXECUTE, 0x0, 0x0, length);

    #else // posix
    void* mem_map = mmap(NULL, sizeof(opcodes), PROT_EXEC|PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
    #endif

    memcpy(mem_map, opcodes, sizeof(opcodes));

    (( void(*)() )mem_map)();

    return 0;
}

For POSIX systems use the mmap() call.

Also read about trampolines. See the link: http://pages.cs.wisc.edu/~weinrich/papers/method_dispatch.pdf

You didn’t tell if this is a complete program or a single function. There might be problems with relative/absolute adressing.

Small remark: this code works also with PowerPC and ARMs with MMU enabled.