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//===-- 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>
#ifndef __APPLE__
#include <unistd.h>
#endif
//
// 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;
#else
// FIXME: We should have a configure check for this.
const uintptr_t pageSize = getpagesize();
#endif
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);
mprotect(startPage, endPage-startPage, PROT_READ | PROT_WRITE | PROT_EXEC);
}
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