Add basic infrastructure for protecting V8's heap when leaving the VM...

src/platform-linux.cc

Index: src/platform-linux.cc
===================================================================
--- src/platform-linux.cc	(revision 1577)
+++ src/platform-linux.cc	(working copy)
@@ -238,9 +238,9 @@
 
 void* OS::Allocate(const size_t requested,
                    size_t* allocated,
-                   bool executable) {
+                   bool is_executable) {
   const size_t msize = RoundUp(requested, sysconf(_SC_PAGESIZE));
-  int prot = PROT_READ | PROT_WRITE | (executable ? PROT_EXEC : 0);
+  int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   if (mbase == MAP_FAILED) {
     LOG(StringEvent("OS::Allocate", "mmap failed"));
@@ -252,12 +252,29 @@
 }
 
 
-void OS::Free(void* buf, const size_t length) {
+void OS::Free(void* address, const size_t size) {
   // TODO(1240712): munmap has a return value which is ignored here.

[Søren Thygesen Gjesse, 2009/03/24 11:43:55]

Move this issue to code.google.com/p/v8.

-  munmap(buf, length);
+  munmap(address, size);
 }
 
 
+#ifdef ENABLE_HEAP_PROTECTION
+
+void OS::Protect(void* address, size_t size) {
+  // TODO(1240712): mprotect has a return value which is ignored here.
+  mprotect(address, size, PROT_READ);
+}
+
+
+void OS::Unprotect(void* address, size_t size, bool is_executable) {
+  // TODO(1240712): mprotect has a return value which is ignored here.
+  int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
+  mprotect(address, size, prot);
+}
+
+#endif
+
+
 void OS::Sleep(int milliseconds) {
   unsigned int ms = static_cast<unsigned int>(milliseconds);
   usleep(1000 * ms);
@@ -271,7 +288,7 @@
 
 
 void OS::DebugBreak() {
-#if defined (__arm__) || defined(__thumb__)
+#ifdef ARM
   asm("bkpt 0");
 #else
   asm("int $3");
@@ -422,8 +439,8 @@
 }
 
 
-bool VirtualMemory::Commit(void* address, size_t size, bool executable) {
-  int prot = PROT_READ | PROT_WRITE | (executable ? PROT_EXEC : 0);
+bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
+  int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   if (MAP_FAILED == mmap(address, size, prot,
                          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
                          kMmapFd, kMmapFdOffset)) {