ios_jit_test.c

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

typedef void(*gen_func)();
typedef void(*call_func)();

#define write_ptr(code, offset, addr) do{*((uintptr_t*)(code + offset)) = (uintptr_t)(addr);}while(0)

static void*
_gen_call(uint8_t* code, size_t size) {
  size_t* p = (size_t*)mmap(NULL, size + sizeof(size_t), PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);

  assert(p != MAP_FAILED);
  *p++ = size;
  memcpy(p, code, size);
  
  assert(mprotect(p-1, size + sizeof(size_t), PROT_EXEC | PROT_READ)==0);
  return p;
}

static void
_free_call(void* p) {
  size_t* _p = p;
  _p--;
  assert(munmap(_p, *_p)==0);
}


void
gen_x64(gen_func f) {
  uint8_t code[] = {
    0x55,                 // pushq %rbp
    0x48, 0x89, 0xe5,     // movq %rsp, %rbp
    
    0x48, 0xb9,           // movabsq #imm, %rcx
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,   // #imm
    
    0xff, 0xd1,           // callq  *%rcx
    
    0x5d,                 // popq %rbp
    0xc3,                 // ret
  };
  
  write_ptr(code, 6, f);
  gen_func p = _gen_call(code, sizeof(code));
  p();
  _free_call(p);
}


void
gen_x32(gen_func f) {
  uint8_t code[] = {
    0x55,                     // pushl  %ebp
    0x89, 0xe5,               // movl %esp, %ebp
    0x83, 0xec, 0x08,         // subl $0x8, %esp
    
    0xb8,                     // movl #imm, eax
    0x00, 0x00, 0x00, 0x00,   // #imm
    
    0xff, 0xd0,               // call eax
    0x83, 0xc4, 0x08,         // addl  $0x8, %esp
    0x5d,                     // popq %rbp
    0xc3,                     // ret
  };
  
  write_ptr(code, 7, f);
  gen_func p = _gen_call(code, sizeof(code));
  p();
  _free_call(p);
}


/*
static void
func(gen_func f) {
  f();
}
 */
void
gen_arm64(gen_func f) {
  uint32_t code[] = {
      0xa9bf7bfd,   // stp	fp, lr, [sp, #-16]!
      0x910003fd,   // mov	 fp, sp
      0xd10043ff,   // sub	sp, sp, #16
      0xf90007e0,   // str	x0, [sp, #8]
      0xf94007e0,   // ldr	x0, [sp, #8]
      0xd63f0000,   // blr	x0
      0x910003bf,   // mov	 sp, fp
      0xa8c17bfd,   // ldp	fp, lr, [sp], #16
      0xd65f03c0,   // ret
  };
  
  call_func p = (call_func)_gen_call((uint8_t*)code, sizeof(code));
  p(f);
  _free_call(p);
}