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Commit 2b22ae13 authored by Josh Gao's avatar Josh Gao
Browse files

tombstoned: don't generate tombstones for native backtraces. 

Previously, if an intercept ends before we ask for a file descriptor
when doing a backtrace, we'll create a tombstone file instead.

Bug: http://b/114139908
Bug: http://b/115349586
Test: debuggerd_test32
Change-Id: I23c7bb8ae5a982a4374a862d0a4f17bee03eb1d9
parent 6f9eeecd

debuggerd/debuggerd_test.cpp

+40 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <android-base/macros.h>

#include <android-base/parseint.h>

#include <android-base/properties.h>

#include <android-base/stringprintf.h>

#include <android-base/strings.h>

#include <android-base/test_utils.h>

#include <android-base/unique_fd.h>
@@ -1053,3 +1054,42 @@ TEST(tombstoned, intercept_any) { 
  ASSERT_TRUE(android::base::ReadFully(output_fd.get(), outbuf, sizeof(outbuf)));

  ASSERT_STREQ("any", outbuf);

}



TEST(tombstoned, interceptless_backtrace) {

  // Generate 50 backtraces, and then check to see that we haven't created 50 new tombstones.

  auto get_tombstone_timestamps = []() -> std::map<int, time_t> {

    std::map<int, time_t> result;

    for (int i = 0; i < 99; ++i) {

      std::string path = android::base::StringPrintf("/data/tombstones/tombstone_%02d", i);

      struct stat st;

      if (stat(path.c_str(), &st) == 0) {

        result[i] = st.st_mtim.tv_sec;

      }

    }

    return result;

  };



  auto before = get_tombstone_timestamps();

  for (int i = 0; i < 50; ++i) {

    raise_debugger_signal(kDebuggerdNativeBacktrace);

  }

  auto after = get_tombstone_timestamps();



  int diff = 0;

  for (int i = 0; i < 99; ++i) {

    if (after.count(i) == 0) {

      continue;

    }

    if (before.count(i) == 0) {

      ++diff;

      continue;

    }

    if (before[i] != after[i]) {

      ++diff;

    }

  }



  // We can't be sure that nothing's crash looping in the background.

  // This should be good enough, though...

  ASSERT_LT(diff, 10) << "too many new tombstones; is something crashing in the background?";

}

debuggerd/tombstoned/tombstoned.cpp

+7 −2
Original line number Diff line number Diff line
@@ -212,9 +212,14 @@ static void perform_request(Crash* crash) { 
  bool intercepted =

      intercept_manager->GetIntercept(crash->crash_pid, crash->crash_type, &output_fd);

  if (!intercepted) {

    if (crash->crash_type == kDebuggerdNativeBacktrace) {

      // Don't generate tombstones for native backtrace requests.

      output_fd.reset(open("/dev/null", O_WRONLY | O_CLOEXEC));

    } else {

      std::tie(crash->crash_tombstone_path, output_fd) = CrashQueue::for_crash(crash)->get_output();

      crash->crash_tombstone_fd.reset(dup(output_fd.get()));

    }

  }



  TombstonedCrashPacket response = {

    .packet_type = CrashPacketType::kPerformDump