blob: b349d2f312b427fd93fb4629604fb547507fbe72 [file] [log] [blame]
/* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===
*
* The LLVM Compiler Infrastructure
*
* This file is distributed under the University of Illinois Open Source
* License. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*/
#include <stdint.h>
#include <sys/mman.h>
/* #include "config.h"
* FIXME: CMake - include when cmake system is ready.
* Remove #define HAVE_SYSCONF 1 line.
*/
#define HAVE_SYSCONF 1
#ifndef __APPLE__
#include <unistd.h>
#endif /* __APPLE__ */
/*
* The compiler generates calls to __enable_execute_stack() when creating
* trampoline functions on the stack for use with nested functions.
* It is expected to mark the page(s) containing the address
* and the next 48 bytes as executable. Since the stack is normally rw-
* that means changing the protection on those page(s) to rwx.
*/
void __enable_execute_stack(void* addr)
{
#if __APPLE__
/* On Darwin, pagesize is always 4096 bytes */
const uintptr_t pageSize = 4096;
#elif !defined(HAVE_SYSCONF)
#error "HAVE_SYSCONF not defined! See enable_execute_stack.c"
#else
const uintptr_t pageSize = sysconf(_SC_PAGESIZE);
#endif /* __APPLE__ */
const uintptr_t pageAlignMask = ~(pageSize-1);
uintptr_t p = (uintptr_t)addr;
unsigned char* startPage = (unsigned char*)(p & pageAlignMask);
unsigned char* endPage = (unsigned char*)((p+48+pageSize) & pageAlignMask);
size_t length = endPage - startPage;
(void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC);
}