| //===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include <stdint.h> |
| #include <sys/mman.h> |
| |
| |
| // |
| // 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. |
| // |
| void __enable_execute_stack(void* addr) |
| { |
| #if __APPLE__ |
| // On Darwin, pagesize is always 4096 bytes |
| const uintptr_t pageSize = 4096; |
| #else |
| // FIXME: We should have a configure check for this. |
| const uintptr_t pagesize = getpagesize(); |
| #endif |
| 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+48+pageSize) & pageAlignMask); |
| mprotect(startPage, endPage-startPage, PROT_READ | PROT_WRITE | PROT_EXEC); |
| } |
| |
| |