1/* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------=== 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is dual licensed under the MIT and the University of Illinois Open 6 * Source Licenses. See LICENSE.TXT for details. 7 * 8 * ===----------------------------------------------------------------------=== 9 */ 10 11#include "int_lib.h" 12 13#include <sys/mman.h> 14 15/* #include "config.h" 16 * FIXME: CMake - include when cmake system is ready. 17 * Remove #define HAVE_SYSCONF 1 line. 18 */ 19#define HAVE_SYSCONF 1 20 21#ifndef __APPLE__ 22#include <unistd.h> 23#endif /* __APPLE__ */ 24 25#if __LP64__ 26 #define TRAMPOLINE_SIZE 48 27#else 28 #define TRAMPOLINE_SIZE 40 29#endif 30 31/* 32 * The compiler generates calls to __enable_execute_stack() when creating 33 * trampoline functions on the stack for use with nested functions. 34 * It is expected to mark the page(s) containing the address 35 * and the next 48 bytes as executable. Since the stack is normally rw- 36 * that means changing the protection on those page(s) to rwx. 37 */ 38 39COMPILER_RT_ABI void 40__enable_execute_stack(void* addr) 41{ 42 43#if __APPLE__ 44 /* On Darwin, pagesize is always 4096 bytes */ 45 const uintptr_t pageSize = 4096; 46#elif !defined(HAVE_SYSCONF) 47#error "HAVE_SYSCONF not defined! See enable_execute_stack.c" 48#else 49 const uintptr_t pageSize = sysconf(_SC_PAGESIZE); 50#endif /* __APPLE__ */ 51 52 const uintptr_t pageAlignMask = ~(pageSize-1); 53 uintptr_t p = (uintptr_t)addr; 54 unsigned char* startPage = (unsigned char*)(p & pageAlignMask); 55 unsigned char* endPage = (unsigned char*)((p+TRAMPOLINE_SIZE+pageSize) & pageAlignMask); 56 size_t length = endPage - startPage; 57 (void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC); 58} 59