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 #ifndef _WIN32 14 #include <sys/mman.h> 15 #endif 16 17 /* #include "config.h" 18 * FIXME: CMake - include when cmake system is ready. 19 * Remove #define HAVE_SYSCONF 1 line. 20 */ 21 #define HAVE_SYSCONF 1 22 23 #ifdef _WIN32 24 #define WIN32_LEAN_AND_MEAN 25 #include <Windows.h> 26 #else 27 #ifndef __APPLE__ 28 #include <unistd.h> 29 #endif /* __APPLE__ */ 30 #endif /* _WIN32 */ 31 32 #if __LP64__ 33 #define TRAMPOLINE_SIZE 48 34 #else 35 #define TRAMPOLINE_SIZE 40 36 #endif 37 38 /* 39 * The compiler generates calls to __enable_execute_stack() when creating 40 * trampoline functions on the stack for use with nested functions. 41 * It is expected to mark the page(s) containing the address 42 * and the next 48 bytes as executable. Since the stack is normally rw- 43 * that means changing the protection on those page(s) to rwx. 44 */ 45 46 COMPILER_RT_ABI void 47 __enable_execute_stack(void* addr) 48 { 49 50 #if _WIN32 51 MEMORY_BASIC_INFORMATION mbi; 52 if (!VirtualQuery (addr, &mbi, sizeof(mbi))) 53 return; /* We should probably assert here because there is no return value */ 54 VirtualProtect (mbi.BaseAddress, mbi.RegionSize, PAGE_EXECUTE_READWRITE, &mbi.Protect); 55 #else 56 #if __APPLE__ 57 /* On Darwin, pagesize is always 4096 bytes */ 58 const uintptr_t pageSize = 4096; 59 #elif !defined(HAVE_SYSCONF) 60 #error "HAVE_SYSCONF not defined! See enable_execute_stack.c" 61 #else 62 const uintptr_t pageSize = sysconf(_SC_PAGESIZE); 63 #endif /* __APPLE__ */ 64 65 const uintptr_t pageAlignMask = ~(pageSize-1); 66 uintptr_t p = (uintptr_t)addr; 67 unsigned char* startPage = (unsigned char*)(p & pageAlignMask); 68 unsigned char* endPage = (unsigned char*)((p+TRAMPOLINE_SIZE+pageSize) & pageAlignMask); 69 size_t length = endPage - startPage; 70 (void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC); 71 #endif 72 } 73
