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

5 files changed, 34 insertions, 0 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common.h b/compiler-rt/lib/sanitizer_common/sanitizer_common.h
index 150c97ea4f1..4246d2e7002 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common.h
+++ b/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();
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cc b/compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cc
index 85191d95eae..fa5c82a249d 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cc
+++ b/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) {}
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
index 5adacc5efdb..a5b9dd00898 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
+++ b/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) {
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
index b0376a47072..c613a6af11c 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
+++ b/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);
 }
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_win.cc b/compiler-rt/lib/sanitizer_common/sanitizer_win.cc
index f59420cbd2a..47fad3f1895 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_win.cc
+++ b/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;