1 /* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===
3 * The LLVM Compiler Infrastructure
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
8 * ===----------------------------------------------------------------------===
17 /* #include "config.h"
18 * FIXME: CMake - include when cmake system is ready.
19 * Remove #define HAVE_SYSCONF 1 line.
21 #define HAVE_SYSCONF 1
24 #define WIN32_LEAN_AND_MEAN
29 #endif /* __APPLE__ */
33 #define TRAMPOLINE_SIZE 48
35 #define TRAMPOLINE_SIZE 40
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.
47 __enable_execute_stack(void* addr)
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);
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"
62 const uintptr_t pageSize = sysconf(_SC_PAGESIZE);
63 #endif /* __APPLE__ */
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);