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/* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===
*
* The LLVM Compiler Infrastructure
*
* This file is dual licensed under the MIT and the University of Illinois Open
* Source Licenses. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*/
#include "int_lib.h"
#ifndef _WIN32
#include <sys/mman.h>
#endif
/* #include "config.h"
* FIXME: CMake - include when cmake system is ready.
* Remove #define HAVE_SYSCONF 1 line.
*/
#define HAVE_SYSCONF 1
#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#else
#ifndef __APPLE__
#include <unistd.h>
#endif /* __APPLE__ */
#endif /* _WIN32 */
#if __LP64__
#define TRAMPOLINE_SIZE 48
#else
#define TRAMPOLINE_SIZE 40
#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.
*/
COMPILER_RT_ABI void
__enable_execute_stack(void* addr)
{
#if _WIN32
MEMORY_BASIC_INFORMATION mbi;
if (!VirtualQuery (addr, &mbi, sizeof(mbi)))
return; /* We should probably assert here because there is no return value */
VirtualProtect (mbi.BaseAddress, mbi.RegionSize, PAGE_EXECUTE_READWRITE, &mbi.Protect);
#else
#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+TRAMPOLINE_SIZE+pageSize) & pageAlignMask);
size_t length = endPage - startPage;
(void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC);
#endif
}
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