diff options
Diffstat (limited to 'lib/builtins/enable_execute_stack.c')
-rw-r--r-- | lib/builtins/enable_execute_stack.c | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/lib/builtins/enable_execute_stack.c b/lib/builtins/enable_execute_stack.c new file mode 100644 index 000000000000..63d836b31d17 --- /dev/null +++ b/lib/builtins/enable_execute_stack.c @@ -0,0 +1,58 @@ +/* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------=== + * + * The LLVM Compiler Infrastructure + * + * This file is dual licensed under the MIT and the University of Illinois Open + * Source Licenses. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + */ + +#include "int_lib.h" + +#include <sys/mman.h> + +/* #include "config.h" + * FIXME: CMake - include when cmake system is ready. + * Remove #define HAVE_SYSCONF 1 line. + */ +#define HAVE_SYSCONF 1 + +#ifndef __APPLE__ +#include <unistd.h> +#endif /* __APPLE__ */ + +#if __LP64__ + #define TRAMPOLINE_SIZE 48 +#else + #define TRAMPOLINE_SIZE 40 +#endif + +/* + * 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. + */ + +COMPILER_RT_ABI void +__enable_execute_stack(void* addr) +{ + +#if __APPLE__ + /* On Darwin, pagesize is always 4096 bytes */ + const uintptr_t pageSize = 4096; +#elif !defined(HAVE_SYSCONF) +#error "HAVE_SYSCONF not defined! See enable_execute_stack.c" +#else + const uintptr_t pageSize = sysconf(_SC_PAGESIZE); +#endif /* __APPLE__ */ + + 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+TRAMPOLINE_SIZE+pageSize) & pageAlignMask); + size_t length = endPage - startPage; + (void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC); +} |