Introduce CheckASLR() in sanitizers

Summary:
At least the ASan, MSan, TSan sanitizers require disabled ASLR on a NetBSD.

Introduce a generic CheckASLR() routine, that implements a check for the
current process. This flag depends on the global or per-process settings.

There is no simple way to disable ASLR in the build process from the
level of a sanitizer or during the runtime execution.

With ASLR enabled sanitizers that operate over the process virtual address
space can misbehave usually breaking with cryptic messages.

This check is dummy for !NetBSD.

Sponsored by <The NetBSD Foundation>

Reviewers: vitalybuka, joerg

Reviewed By: vitalybuka

Subscribers: cryptoad, kubamracek, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D47442

llvm-svn: 333985

compiler-rt/lib/asan/asan_rtl.cc

@@ -384,6 +384,7 @@ static void AsanInitInternal() {
   asan_init_is_running = true;
 
   CacheBinaryName();
+  CheckASLR();
 
   // Initialize flags. This must be done early, because most of the
   // initialization steps look at flags().

compiler-rt/lib/msan/msan.cc

@@ -397,6 +397,7 @@ void __msan_init() {
   InitTlsSize();
 
   CacheBinaryName();
+  CheckASLR();
   InitializeFlags();
 
   // Install tool-specific callbacks in sanitizer_common.

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -221,6 +221,7 @@ bool SetEnv(const char *name, const char *value);
 
 u32 GetUid();
 void ReExec();
+void CheckASLR();
 char **GetArgv();
 void PrintCmdline();
 bool StackSizeIsUnlimited();

compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cc

@@ -87,6 +87,7 @@ void GetThreadStackTopAndBottom(bool, uptr *stack_top, uptr *stack_bottom) {
 }
 
 void MaybeReexec() {}
+void CheckASLR() {}
 void PlatformPrepareForSandboxing(__sanitizer_sandbox_arguments *args) {}
 void DisableCoreDumperIfNecessary() {}
 void InstallDeadlySignalHandlers(SignalHandlerType handler) {}

compiler-rt/lib/sanitizer_common/sanitizer_linux.cc

@@ -1954,6 +1954,30 @@ void MaybeReexec() {
   // No need to re-exec on Linux.
 }
 
+void CheckASLR() {
+#if SANITIZER_NETBSD
+  int mib[3];
+  int paxflags;
+  size_t len = sizeof(paxflags);
+
+  mib[0] = CTL_PROC;
+  mib[1] = internal_getpid();
+  mib[2] = PROC_PID_PAXFLAGS;
+
+  if (UNLIKELY(sysctl(mib, 3, &paxflags, &len, NULL, 0) == -1)) {
+    Printf("sysctl failed\n");
+    Die();
+  }
+
+  if (UNLIKELY(paxflags & CTL_PROC_PAXFLAGS_ASLR)) {
+    Printf("This sanitizer is not compatible with enabled ASLR\n");
+    Die();
+  }
+#else
+  // Do nothing
+#endif
+}
+
 void PrintModuleMap() { }
 
 void CheckNoDeepBind(const char *filename, int flag) {

compiler-rt/lib/sanitizer_common/sanitizer_mac.cc

@@ -340,6 +340,10 @@ void ReExec() {
   UNIMPLEMENTED();
 }
 
+void CheckASLR() {
+  // Do nothing
+}
+
 uptr GetPageSize() {
   return sysconf(_SC_PAGESIZE);
 }

compiler-rt/lib/sanitizer_common/sanitizer_win.cc

@@ -1025,6 +1025,10 @@ void MaybeReexec() {
   // No need to re-exec on Windows.
 }
 
+void CheckASLR() {
+  // Do nothing
+}
+
 char **GetArgv() {
   // FIXME: Actually implement this function.
   return 0;

compiler-rt/lib/tsan/rtl/tsan_rtl.cc

@@ -354,6 +354,7 @@ void Initialize(ThreadState *thr) {
   ctx = new(ctx_placeholder) Context;
   const char *options = GetEnv(SANITIZER_GO ? "GORACE" : "TSAN_OPTIONS");
   CacheBinaryName();
+  CheckASLR();
   InitializeFlags(&ctx->flags, options);
   AvoidCVE_2016_2143();
   InitializePlatformEarly();