stacktrace_test.cc

// 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 <stddef.h>
#include <stdint.h>

#include <algorithm>

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"
#include "absl/types/span.h"

namespace {

using ::testing::Contains;

struct StackTrace {
  static constexpr int kStackCount = 64;
  int depth;
  void* result[kStackCount];
  uintptr_t frames[kStackCount];
  int sizes[kStackCount];
};

// This test is currently only known to pass on Linux x86_64/aarch64.
#if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__))
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

#if ABSL_HAVE_BUILTIN(__builtin_frame_address)
struct FrameInfo {
  const void* return_address;
  uintptr_t frame_address;
};

// Returns the canonical frame address and return address for the current stack
// frame, while capturing the stack trace at the same time.
// This performs any platform-specific adjustments necessary to convert from the
// compiler built-ins to the expected API outputs.
ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS     // May read random elements from stack.
    ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY  // May read random elements from stack.
        ABSL_ATTRIBUTE_NOINLINE static FrameInfo
        CaptureBacktraceNoInline(StackTrace& backtrace) {
  FrameInfo result;
  result.return_address = __builtin_return_address(0);
  // Large enough to cover all realistic slots the return address could be in
  const int kMaxReturnAddressIndex = 5;
  void* const* bfa = static_cast<void* const*>(__builtin_frame_address(0));
  backtrace.depth = absl::internal_stacktrace::GetStackFramesWithContext(
      backtrace.result, backtrace.frames, backtrace.sizes,
      StackTrace::kStackCount, /*skip_count=*/0,
      /*uc=*/nullptr, /*min_dropped_frames=*/nullptr);
  // Make sure the return address is at a reasonable location in the frame
  ptrdiff_t i;
  for (i = 0; i < kMaxReturnAddressIndex; ++i) {
    // Avoid std::find() here, since it lacks no-sanitize attributes.
    if (bfa[i] == result.return_address) {
      break;
    }
  }
  result.frame_address =
      i < kMaxReturnAddressIndex
          ? reinterpret_cast<uintptr_t>(
                bfa + i + 1 /* get the Canonical Frame Address (CFA) */)
          : 0;
  return result;
}

TEST(StackTrace, CanonicalFrameAddresses) {
  // Now capture a stack trace and verify that the return addresses and frame
  // addresses line up for one frame.
  StackTrace backtrace;
  const auto [return_address, frame_address] =
      CaptureBacktraceNoInline(backtrace);
  auto return_addresses = absl::MakeSpan(backtrace.result)
                              .subspan(0, static_cast<size_t>(backtrace.depth));
  auto frame_addresses = absl::MakeSpan(backtrace.frames)
                             .subspan(0, static_cast<size_t>(backtrace.depth));

  // Many platforms don't support this by default.
  bool support_is_expected = false;

  if (support_is_expected) {
    // If all zeros were returned, that is valid per the function's contract.
    // It just means we don't support returning frame addresses on this
    // platform.
    bool supported = static_cast<size_t>(std::count(frame_addresses.begin(),
                                                    frame_addresses.end(), 0)) <
                     frame_addresses.size();
    EXPECT_TRUE(supported);
    if (supported) {
      ASSERT_TRUE(frame_address)
          << "unable to obtain frame address corresponding to return address";
      EXPECT_THAT(return_addresses, Contains(return_address).Times(1));
      EXPECT_THAT(frame_addresses, Contains(frame_address).Times(1));
      ptrdiff_t ifound = std::find(return_addresses.begin(),
                                   return_addresses.end(), return_address) -
                         return_addresses.begin();
      // Make sure we found the frame in the first place.
      ASSERT_LT(ifound, backtrace.depth);
      // Make sure the frame address actually corresponds to the return
      // address.
      EXPECT_EQ(frame_addresses[static_cast<size_t>(ifound)], frame_address);
      // Make sure the addresses only appear once.
    }
  }
}
#endif

}  // namespace