llvm/compiler-rt/test/builtins/Unit/enable_execute_stack_test.c

// REQUIRES: native-run
// RUN: %clang_builtins %s %librt -o %t && %run_nomprotect %t
// REQUIRES: librt_has_enable_execute_stack

#include <stdio.h>
#include <string.h>
#include <stdint.h>
extern void __clear_cache(void* start, void* end);
extern void __enable_execute_stack(void* addr);

typedef int (*pfunc)(void);

// Make these static to avoid ILT jumps for incremental linking on Windows.
static int func1() { return 1; }
static int func2() { return 2; }

void *__attribute__((noinline))
memcpy_f(void *dst, const void *src, size_t n) {
// ARM and MIPS naturally align functions, but use the LSB for ISA selection
// (THUMB, MIPS16/uMIPS respectively).  Ensure that the ISA bit is ignored in
// the memcpy
#if defined(__arm__) || defined(__mips__)
  return (void *)((uintptr_t)memcpy(dst, (void *)((uintptr_t)src & ~1), n) |
                  ((uintptr_t)src & 1));
#else
  return memcpy(dst, (void *)((uintptr_t)src), n);
#endif
}

int main()
{
#if defined(__ve__)
    unsigned char execution_buffer[128] __attribute__((__aligned__(8)));
#else
    unsigned char execution_buffer[128];
#endif
    // mark stack page containing execution_buffer to be executable
    __enable_execute_stack(execution_buffer);
	
    // verify you can copy and execute a function
    pfunc f1 = (pfunc)memcpy_f(execution_buffer, func1, 128);
    __clear_cache(execution_buffer, &execution_buffer[128]);
    printf("f1: %p\n", f1);
    if ((*f1)() != 1)
        return 1;

    // verify you can overwrite a function with another
    pfunc f2 = (pfunc)memcpy_f(execution_buffer, func2, 128);
    __clear_cache(execution_buffer, &execution_buffer[128]);
    if ((*f2)() != 2)
        return 1;

    return 0;
}