Initial import of compiler-rt.

 -


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@74292 91177308-0d34-0410-b5e6-96231b3b80d8

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);
+}
+
+