diff options
Diffstat (limited to 'lib/enable_execute_stack.c')
-rw-r--r-- | lib/enable_execute_stack.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/lib/enable_execute_stack.c b/lib/enable_execute_stack.c new file mode 100644 index 000000000..2c1878238 --- /dev/null +++ b/lib/enable_execute_stack.c @@ -0,0 +1,36 @@ +//===-- 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 + abort(); +#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); +} + + |