clousure_bind

clousure_bind.c

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

void do_something(void* param) {
    printf("%p\n", param);
}

void (*clousure_bind(void(* function)(void*), void* context))(void) {
    int pagesize = getpagesize();
    if (pagesize < 0) {
        perror("getpagesize");
        return NULL;
    }
    unsigned char* ret = memalign(pagesize, pagesize);
    void (*oret)(void) = (void (*)(void))ret;
    // push %rbq
    // mov %rsp,%rbp
    memcpy(ret, "\x55\x48\x89\xe5\x48\xbf", 6);
    ret += 6;
    // movabs %[context],%rdi
    memcpy(ret, &context, 8);
    ret += 8;
    // movabs %[function],$rax
    memcpy(ret, "\x48\xb8", 2);
    ret += 2;
    memcpy(ret, &function, 8);
    ret += 8;
    // callq *%rax
    // nop
    // pop %rbq
    // retq
    memcpy(ret, "\xff\xd0\x90\x5d\xc3", 5);
    ret += 5;
    if (mprotect(oret, pagesize, PROT_EXEC | PROT_WRITE | PROT_READ) < 0) {
        perror("mprotect");
        return NULL;
    }
    return oret;
}

int main(void) {
    void (*fp1)(void) = clousure_bind(do_something, (void*)0x123456789abcdef0UL);
    void (*fp2)(void) = clousure_bind(do_something, (void*)0x1145141919810UL);
    if (fp1 != NULL) {
        fp1();
    }
    if (fp2 != NULL) {
        fp2();
    }
    free((void*)fp1);
    free((void*)fp2);
    return 0;
}