From c611e5ce1de222eb995f5aeabf3fa8cd57ae124b Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Fri, 20 Jan 2023 00:47:33 -0800
Subject: absl: add a stack unwinding test END_PUBLIC

absl: relax frame size check in x86 stack unwinding

Currently the unwinder stops whenever it sees a frame >100000 bytes.
There may be such legitimate frames, the default stack size is O(megabytes).
Only do this check if we are not within the thread stack bounds.
The thread stack is assumed to be readable, so the worst thing that can happen
if the large stack frame is actually bogus is that we will add one/few wrong frames and stop.

PiperOrigin-RevId: 503374764
Change-Id: Icabb55d6468b12a42bf026c37c98dbe84977e659
---
 absl/debugging/stacktrace_test.cc | 47 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 absl/debugging/stacktrace_test.cc

(limited to 'absl/debugging/stacktrace_test.cc')

diff --git a/absl/debugging/stacktrace_test.cc b/absl/debugging/stacktrace_test.cc
new file mode 100644
index 00000000..78ce7ad0
--- /dev/null
+++ b/absl/debugging/stacktrace_test.cc
@@ -0,0 +1,47 @@
+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/stacktrace.h"
+
+#include "gtest/gtest.h"
+#include "absl/base/macros.h"
+#include "absl/base/optimization.h"
+
+namespace {
+
+// This test is currently only known to pass on linux/x86_64.
+#if defined(__linux__) && defined(__x86_64__)
+ABSL_ATTRIBUTE_NOINLINE void Unwind(void* p) {
+  ABSL_ATTRIBUTE_UNUSED static void* volatile sink = p;
+  constexpr int kSize = 16;
+  void* stack[kSize];
+  int frames[kSize];
+  absl::GetStackTrace(stack, kSize, 0);
+  absl::GetStackFrames(stack, frames, kSize, 0);
+}
+
+ABSL_ATTRIBUTE_NOINLINE void HugeFrame() {
+  char buffer[1 << 20];
+  Unwind(buffer);
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+TEST(StackTrace, HugeFrame) {
+  // Ensure that the unwinder is not confused by very large stack frames.
+  HugeFrame();
+  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+#endif
+
+}  // namespace
-- 
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