[libc++] Add a CI job running MSAN

[ldionne]

Summary

For some reason, we've been going without a MSAN CI job, even though
even run-buildbot defined a generic-msan job. This must have been an
oversight that went unnoticed. Thanks to @EricWF for the catch.

[philnik]

I'm not sure this will be that easy. MSAN is tricky. According to documentation, even libc has to be instrumented for this to work properly. See https://clang.llvm.org/docs/MemorySanitizer.html#id11. And AFAIK we don't build libc on the nodes.

[ldionne]

Add markup for failing tests in libunwind. I still think it's worth enabling for the libc++ tests.

[ldionne]

In D120851#3355702, @philnik wrote:

I'm not sure this will be that easy. MSAN is tricky. According to documentation, even libc has to be instrumented for this to work properly. See https://clang.llvm.org/docs/MemorySanitizer.html#id11. And AFAIK we don't build libc on the nodes.

It also says they implement various interceptors for common libc functionality, and we don't use anything super fancy, so perhaps we'll be good! So far it looks like only libunwind is having trouble.

[arichardson]

My guess is that all that's needed here are MSAN annotations around the functions written in inline assembly (saving/restoring all registers).

[ldionne]

In D120851#3417681, @arichardson wrote:

My guess is that all that's needed here are MSAN annotations around the functions written in inline assembly (saving/restoring all registers).

I'm really not familiar with those -- would you like to take a look? You can commandeer if you'd like.

[ldionne]

Otherwise, I'll ship this once CI is green and we can tackle post-commit.

libcxx/utils/ci/buildkite-pipeline.yml

- label: "UBSAN"
         queue: "libcxx-builders"
         os: "linux"
       retry:
         automatic:
           - exit_status: -1  # Agent was lost
             limit: 2
       timeout_in_minutes: 120
 
+    - label: "MSAN"
+      command: "libcxx/utils/ci/run-buildbot generic-msan"
+      artifact_paths:
+        - "**/test-results.xml"
+        - "**/*.abilist"
+      agents:
+        queue: "libcxx-builders"
+        os: "linux"
+      retry:
+        automatic:
+          - exit_status: -1  # Agent was lost
+            limit: 2
+      timeout_in_minutes: 120
+
   # Tests with the various supported ways to build libc++.
   - label: "Bootstrapping build"
     command: "libcxx/utils/ci/run-buildbot bootstrapping-build"
     artifact_paths:
       - "**/test-results.xml"
       - "**/*.abilist"
     agents:
       queue: "libcxx-builders"

libunwind/test/forceunwind.pass.cpp

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // REQUIRES: linux
 
+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 // Basic test for _Unwind_ForcedUnwind.
 // See libcxxabi/test/forced_unwind* tests too.
 
 #include <assert.h>
 #include <dlfcn.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdio.h>

libunwind/test/libunwind_01.pass.cpp

 // TODO: Investigate these failures on x86_64 macOS back deployment
 // UNSUPPORTED: target=x86_64-apple-darwin{{.+}}
 
+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 #include <libunwind.h>
 #include <stdlib.h>
 #include <string.h>
 
 void backtrace(int lower_bound) {
   unw_context_t context;
   unw_getcontext(&context);
 

libunwind/test/libunwind_02.pass.cpp

+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 #include <assert.h>
 #include <stdlib.h>
 #include <unwind.h>
 
 #define EXPECTED_NUM_FRAMES 50
 #define NUM_FRAMES_UPPER_BOUND 100
 
 _Unwind_Reason_Code callback(_Unwind_Context *context, void *cnt) {

libunwind/test/remember_state_leak.pass.sh.s

 # REQUIRES: target={{x86_64-.+-linux-gnu}}
+
+// Inline assembly isn't supported by Memory Sanitizer
+// UNSUPPORTED: msan
+
 # RUN: %{build} -no-pie
 # RUN: %{run}
 
 # The following assembly is a translation of this code:
 #
 #   _Unwind_Reason_Code callback(int, _Unwind_Action, long unsigned int,
 #                                _Unwind_Exception*, _Unwind_Context*, void*) {
 #     return _Unwind_Reason_Code(0);

libunwind/test/signal_frame.pass.cpp

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // Ensure that functions marked as signal frames are reported as such.
 
 // TODO: Investigate this failure on macOS
 // XFAIL: target={{.+}}-apple-darwin{{.+}}
 
+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 // UNSUPPORTED: libunwind-arm-ehabi
 
 // The AIX assembler does not support CFI directives, which
 // are necessary to run this test.
 // UNSUPPORTED: target=powerpc{{(64)?}}-ibm-aix
 
 #include <assert.h>
 #include <stdlib.h>

libunwind/test/signal_unwind.pass.cpp

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // Ensure that the unwinder can cope with the signal handler.
 // REQUIRES: linux && (target={{aarch64-.+}} || target={{x86_64-.+}})
 
+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 #include <assert.h>
 #include <dlfcn.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <unistd.h>

libunwind/test/unwind_leaffunction.pass.cpp

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // Ensure that leaf function can be unwund.
 // REQUIRES: linux && (target={{aarch64-.+}} || target={{x86_64-.+}})
 
+// TODO: Figure out why this fails with Memory Sanitizer.
+// XFAIL: msan
+
 #include <assert.h>
 #include <dlfcn.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <unistd.h>