1 //===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "int_lib.h" 10 11 #ifndef _WIN32 12 #include <sys/mman.h> 13 #endif 14 15 // #include "config.h" 16 // FIXME: CMake - include when cmake system is ready. 17 // Remove #define HAVE_SYSCONF 1 line. 18 #define HAVE_SYSCONF 1 19 20 #ifdef _WIN32 21 #define WIN32_LEAN_AND_MEAN 22 #include <windows.h> 23 #else 24 #ifndef __APPLE__ 25 #include <unistd.h> 26 #endif // __APPLE__ 27 #endif // _WIN32 28 29 #if __LP64__ 30 #define TRAMPOLINE_SIZE 48 31 #else 32 #define TRAMPOLINE_SIZE 40 33 #endif 34 35 // The compiler generates calls to __enable_execute_stack() when creating 36 // trampoline functions on the stack for use with nested functions. 37 // It is expected to mark the page(s) containing the address 38 // and the next 48 bytes as executable. Since the stack is normally rw- 39 // that means changing the protection on those page(s) to rwx. 40 41 COMPILER_RT_ABI void __enable_execute_stack(void *addr) { 42 43 #if _WIN32 44 MEMORY_BASIC_INFORMATION mbi; 45 if (!VirtualQuery(addr, &mbi, sizeof(mbi))) 46 return; // We should probably assert here because there is no return value 47 VirtualProtect(mbi.BaseAddress, mbi.RegionSize, PAGE_EXECUTE_READWRITE, 48 &mbi.Protect); 49 #else 50 #if __APPLE__ 51 // On Darwin, pagesize is always 4096 bytes 52 const uintptr_t pageSize = 4096; 53 #elif !defined(HAVE_SYSCONF) 54 #error "HAVE_SYSCONF not defined! See enable_execute_stack.c" 55 #else 56 const uintptr_t pageSize = sysconf(_SC_PAGESIZE); 57 #endif // __APPLE__ 58 59 const uintptr_t pageAlignMask = ~(pageSize - 1); 60 uintptr_t p = (uintptr_t)addr; 61 unsigned char *startPage = (unsigned char *)(p & pageAlignMask); 62 unsigned char *endPage = 63 (unsigned char *)((p + TRAMPOLINE_SIZE + pageSize) & pageAlignMask); 64 size_t length = endPage - startPage; 65 (void)mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC); 66 #endif 67 } 68