How to execute an array of bytes as code on x86-64 under linux

execute-code-from-memory-x64-linux.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <sys/mman.h>
#include <unistd.h>

typedef int (*f)(int);
//typedef int (*f)();

//uint8_t code[] = {
//    0x89, 0xc1,
//    0x0f, 0xaf, 0xc0, 
//    0xc3 
//};

//uint8_t code[] = { 0xC3 };

//uint8_t code[] = { 0x48, 0xC7, 0xC0, 0x2A, 0x00, 0x00, 0x00, 0xC3 };

//0:  48 83 c7 01             add    rdi,0x1
//4:  48 89 f8                mov    rax,rdi
//7:  c3                      ret
uint8_t code[] = { 0x48, 0x83, 0xC7, 0x01, 0x48, 0x89, 0xF8, 0xC3 };

int main() {
    int pagesize = getpagesize();
    uint8_t* buffer = memalign(pagesize, pagesize);
    if (buffer == NULL) { printf("memalign\n"); exit(1); }
    printf("code size %d\n", sizeof(code));  
    memcpy(buffer, code, sizeof(code));
    
    if (mprotect(buffer, pagesize, PROT_EXEC) != 0) {
        printf("can not mprotect\n");
        exit(1);
    }
    
    //int r = ((f)buffer)();
    int r = ((f)buffer)(6);
    
    printf("%d", r);
    return 0;
}