[LLDB][Minidump] Support minidumps where there are multiple exception streams (#97470)

Currently, LLDB assumes all minidumps will have unique sections. This is
intuitive because almost all of the minidump sections are themselves
lists. Exceptions including Signals are unique in that they are all
individual sections with their own directory.

This means LLDB fails to load minidumps with multiple exceptions due to
them not being unique. This behavior is erroneous and this PR introduces
support for an arbitrary number of exception streams. Additionally, stop
info was calculated only for a single thread before, and now we properly
support mapping exceptions to threads.

~~This PR is starting in DRAFT because implementing testing is still
required.~~

Author: Jlalond

lldb/source/Plugins/Process/minidump/MinidumpParser.cpp

@@ -417,14 +417,9 @@ std::vector<const minidump::Module *> MinidumpParser::GetFilteredModuleList() {
   return filtered_modules;
 }
 
-const minidump::ExceptionStream *MinidumpParser::GetExceptionStream() {
-  auto ExpectedStream = GetMinidumpFile().getExceptionStream();
-  if (ExpectedStream)
-    return &*ExpectedStream;
-
-  LLDB_LOG_ERROR(GetLog(LLDBLog::Process), ExpectedStream.takeError(),
-                 "Failed to read minidump exception stream: {0}");
-  return nullptr;
+llvm::iterator_range<ExceptionStreamsIterator>
+MinidumpParser::GetExceptionStreams() {
+  return GetMinidumpFile().getExceptionStreams();
 }
 
 std::optional<minidump::Range>

lldb/source/Plugins/Process/minidump/MinidumpParser.h

@@ -48,6 +48,8 @@ struct Range {
 };
 
 using FallibleMemory64Iterator = llvm::object::MinidumpFile::FallibleMemory64Iterator;
+using ExceptionStreamsIterator =
+    llvm::object::MinidumpFile::ExceptionStreamsIterator;
 
 class MinidumpParser {
 public:
@@ -84,7 +86,7 @@ class MinidumpParser {
   // have the same name, it keeps the copy with the lowest load address.
   std::vector<const minidump::Module *> GetFilteredModuleList();
 
-  const llvm::minidump::ExceptionStream *GetExceptionStream();
+  llvm::iterator_range<ExceptionStreamsIterator> GetExceptionStreams();
 
   std::optional<Range> FindMemoryRange(lldb::addr_t addr);
 

lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp

@@ -157,8 +157,7 @@ ProcessMinidump::ProcessMinidump(lldb::TargetSP target_sp,
                                  const FileSpec &core_file,
                                  DataBufferSP core_data)
     : PostMortemProcess(target_sp, listener_sp, core_file),
-      m_core_data(std::move(core_data)), m_active_exception(nullptr),
-      m_is_wow64(false) {}
+      m_core_data(std::move(core_data)), m_is_wow64(false) {}
 
 ProcessMinidump::~ProcessMinidump() {
   Clear();
@@ -209,7 +208,20 @@ Status ProcessMinidump::DoLoadCore() {
   GetTarget().SetArchitecture(arch, true /*set_platform*/);
 
   m_thread_list = m_minidump_parser->GetThreads();
-  m_active_exception = m_minidump_parser->GetExceptionStream();
+  auto exception_stream_it = m_minidump_parser->GetExceptionStreams();
+  for (auto exception_stream : exception_stream_it) {
+    // If we can't read an exception stream skip it
+    // We should probably serve a warning
+    if (!exception_stream)
+      continue;
+
+    if (!m_exceptions_by_tid
+             .try_emplace(exception_stream->ThreadId, exception_stream.get())
+             .second) {
+      return Status::FromErrorStringWithFormatv(
+          "Duplicate exception stream for tid {0}", exception_stream->ThreadId);
+    }
+  }
 
   SetUnixSignals(UnixSignals::Create(GetArchitecture()));
 
@@ -232,60 +244,57 @@ Status ProcessMinidump::DoDestroy() { return Status(); }
 
 void ProcessMinidump::RefreshStateAfterStop() {
 
-  if (!m_active_exception)
-    return;
-
-  constexpr uint32_t BreakpadDumpRequested = 0xFFFFFFFF;
-  if (m_active_exception->ExceptionRecord.ExceptionCode ==
-      BreakpadDumpRequested) {
-    // This "ExceptionCode" value is a sentinel that is sometimes used
-    // when generating a dump for a process that hasn't crashed.
-
-    // TODO: The definition and use of this "dump requested" constant
-    // in Breakpad are actually Linux-specific, and for similar use
-    // cases on Mac/Windows it defines different constants, referring
-    // to them as "simulated" exceptions; consider moving this check
-    // down to the OS-specific paths and checking each OS for its own
-    // constant.
-    return;
-  }
+  for (const auto &[_, exception_stream] : m_exceptions_by_tid) {
+    constexpr uint32_t BreakpadDumpRequested = 0xFFFFFFFF;
+    if (exception_stream.ExceptionRecord.ExceptionCode ==
+        BreakpadDumpRequested) {
+      // This "ExceptionCode" value is a sentinel that is sometimes used
+      // when generating a dump for a process that hasn't crashed.
+
+      // TODO: The definition and use of this "dump requested" constant
+      // in Breakpad are actually Linux-specific, and for similar use
+      // cases on Mac/Windows it defines different constants, referring
+      // to them as "simulated" exceptions; consider moving this check
+      // down to the OS-specific paths and checking each OS for its own
+      // constant.
+      return;
+    }
 
-  lldb::StopInfoSP stop_info;
-  lldb::ThreadSP stop_thread;
+    lldb::StopInfoSP stop_info;
+    lldb::ThreadSP stop_thread;
 
-  Process::m_thread_list.SetSelectedThreadByID(m_active_exception->ThreadId);
-  stop_thread = Process::m_thread_list.GetSelectedThread();
-  ArchSpec arch = GetArchitecture();
+    Process::m_thread_list.SetSelectedThreadByID(exception_stream.ThreadId);
+    stop_thread = Process::m_thread_list.GetSelectedThread();
+    ArchSpec arch = GetArchitecture();
 
-  if (arch.GetTriple().getOS() == llvm::Triple::Linux) {
-    uint32_t signo = m_active_exception->ExceptionRecord.ExceptionCode;
+    if (arch.GetTriple().getOS() == llvm::Triple::Linux) {
+      uint32_t signo = exception_stream.ExceptionRecord.ExceptionCode;
+      if (signo == 0) {
+        // No stop.
+        return;
+      }
 
-    if (signo == 0) {
-      // No stop.
-      return;
+      stop_info = StopInfo::CreateStopReasonWithSignal(*stop_thread, signo);
+    } else if (arch.GetTriple().getVendor() == llvm::Triple::Apple) {
+      stop_info = StopInfoMachException::CreateStopReasonWithMachException(
+          *stop_thread, exception_stream.ExceptionRecord.ExceptionCode, 2,
+          exception_stream.ExceptionRecord.ExceptionFlags,
+          exception_stream.ExceptionRecord.ExceptionAddress, 0);
+    } else {
+      std::string desc;
+      llvm::raw_string_ostream desc_stream(desc);
+      desc_stream << "Exception "
+                  << llvm::format_hex(
+                         exception_stream.ExceptionRecord.ExceptionCode, 8)
+                  << " encountered at address "
+                  << llvm::format_hex(
+                         exception_stream.ExceptionRecord.ExceptionAddress, 8);
+      stop_info = StopInfo::CreateStopReasonWithException(
+          *stop_thread, desc_stream.str().c_str());
     }
 
-    stop_info = StopInfo::CreateStopReasonWithSignal(
-        *stop_thread, signo);
-  } else if (arch.GetTriple().getVendor() == llvm::Triple::Apple) {
-    stop_info = StopInfoMachException::CreateStopReasonWithMachException(
-        *stop_thread, m_active_exception->ExceptionRecord.ExceptionCode, 2,
-        m_active_exception->ExceptionRecord.ExceptionFlags,
-        m_active_exception->ExceptionRecord.ExceptionAddress, 0);
-  } else {
-    std::string desc;
-    llvm::raw_string_ostream desc_stream(desc);
-    desc_stream << "Exception "
-                << llvm::format_hex(
-                       m_active_exception->ExceptionRecord.ExceptionCode, 8)
-                << " encountered at address "
-                << llvm::format_hex(
-                       m_active_exception->ExceptionRecord.ExceptionAddress, 8);
-    stop_info = StopInfo::CreateStopReasonWithException(
-        *stop_thread, desc_stream.str().c_str());
-  }
-
-  stop_thread->SetStopInfo(stop_info);
+    stop_thread->SetStopInfo(stop_info);
+  }
 }
 
 bool ProcessMinidump::IsAlive() { return true; }
@@ -387,10 +396,9 @@ bool ProcessMinidump::DoUpdateThreadList(ThreadList &old_thread_list,
     LocationDescriptor context_location = thread.Context;
 
     // If the minidump contains an exception context, use it
-    if (m_active_exception != nullptr &&
-        m_active_exception->ThreadId == thread.ThreadId) {
-      context_location = m_active_exception->ThreadContext;
-    }
+    if (auto it = m_exceptions_by_tid.find(thread.ThreadId);
+        it != m_exceptions_by_tid.end())
+      context_location = it->second.ThreadContext;
 
     llvm::ArrayRef<uint8_t> context;
     if (!m_is_wow64)

lldb/source/Plugins/Process/minidump/ProcessMinidump.h

@@ -107,7 +107,8 @@ class ProcessMinidump : public PostMortemProcess {
 private:
   lldb::DataBufferSP m_core_data;
   llvm::ArrayRef<minidump::Thread> m_thread_list;
-  const minidump::ExceptionStream *m_active_exception;
+  std::unordered_map<uint32_t, const minidump::ExceptionStream>
+      m_exceptions_by_tid;
   lldb::CommandObjectSP m_command_sp;
   bool m_is_wow64;
   std::optional<MemoryRegionInfos> m_memory_regions;

lldb/test/API/functionalities/postmortem/minidump-new/TestMiniDumpNew.py

@@ -505,8 +505,22 @@ def test_minidump_memory64list(self):
         self.assertEqual(region.GetRegionBase(), 0x7FFF12A84030)
         self.assertTrue(region.GetRegionEnd(), 0x7FFF12A84030 + 0x2FD0)
         self.assertTrue(region_info_list.GetMemoryRegionAtIndex(1, region))
-        self.assertEqual(region.GetRegionBase(), 0x00007fff12a87000)
-        self.assertTrue(region.GetRegionEnd(), 0x00007fff12a87000 + 0x00000018)
+        self.assertEqual(region.GetRegionBase(), 0x00007FFF12A87000)
+        self.assertTrue(region.GetRegionEnd(), 0x00007FFF12A87000 + 0x00000018)
         self.assertTrue(region_info_list.GetMemoryRegionAtIndex(2, region))
-        self.assertEqual(region.GetRegionBase(), 0x00007fff12a87018)
-        self.assertTrue(region.GetRegionEnd(), 0x00007fff12a87018 + 0x00000400)
+        self.assertEqual(region.GetRegionBase(), 0x00007FFF12A87018)
+        self.assertTrue(region.GetRegionEnd(), 0x00007FFF12A87018 + 0x00000400)
+
+    def test_multiple_exceptions_or_signals(self):
+        """Test that lldb can read the exception information from the Minidump."""
+        print("Starting to read multiple-sigsev.yaml")
+        self.process_from_yaml("multiple-sigsev.yaml")
+        print("Done reading multiple-sigsev.yaml")
+        self.check_state()
+        # This process crashed due to a segmentation fault in both it's threads.
+        self.assertEqual(self.process.GetNumThreads(), 2)
+        for i in range(2):
+            thread = self.process.GetThreadAtIndex(i)
+            self.assertStopReason(thread.GetStopReason(), lldb.eStopReasonSignal)
+            stop_description = thread.GetStopDescription(256)
+            self.assertIn("SIGSEGV", stop_description)

lldb/test/API/functionalities/postmortem/minidump-new/multiple-sigsev.yaml

@@ -0,0 +1,39 @@
+--- !minidump
+Streams:
+  - Type:            ThreadList
+    Threads:
+      - Thread Id:       0x1B4F23
+        Context:         0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000B0010000000000033000000000000000000000006020100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000010A234EBFC7F000010A234EBFC7F00000000000000000000F09C34EBFC7F0000C0A91ABCE97F00000000000000000000A0163FBCE97F00004602000000000000921C40000000000030A434EBFC7F000000000000000000000000000000000000C61D4000000000007F0300000000000000000000000000000000000000000000801F0000FFFF0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000FFFF00FFFFFFFFFFFFFF00FFFFFFFF25252525252525252525252525252525000000000000000000000000000000000000000000000000000000000000000000FFFF00FFFFFFFFFFFFFF00FFFFFFFF0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000FF00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+        Stack:
+          Start of Memory Range: 0x7FFFFFFFD348
+          Content:         ''
+      - Thread Id:       0x1B6D22
+        Context:         0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000B0010000000000033000000000000000000000006020100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000010A234EBFC7F000010A234EBFC7F00000000000000000000F09C34EBFC7F0000C0A91ABCE97F00000000000000000000A0163FBCE97F00004602000000000000921C40000000000030A434EBFC7F000000000000000000000000000000000000C61D4000000000007F0300000000000000000000000000000000000000000000801F0000FFFF0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000FFFF00FFFFFFFFFFFFFF00FFFFFFFF25252525252525252525252525252525000000000000000000000000000000000000000000000000000000000000000000FFFF00FFFFFFFFFFFFFF00FFFFFFFF0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000FF00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+        Stack:
+          Start of Memory Range: 0x7FFFF75FDE28
+          Content:         ''
+  - Type:            ModuleList
+    Modules:
+      - Base of Image:   0x0000000000400000
+        Size of Image:   0x00017000
+        Module Name:     'a.out'
+        CodeView Record: ''
+  - Type:            SystemInfo
+    Processor Arch:  AMD64
+    Platform ID:     Linux
+    CSD Version:     'Linux 3.13'
+    CPU:
+      Vendor ID:       GenuineIntel
+      Version Info:    0x00000000
+      Feature Info:    0x00000000
+  - Type:            Exception
+    Thread ID:       0x1B4F23
+    Exception Record:
+      Exception Code:  0xB
+    Thread Context:  00000000
+  - Type:            Exception
+    Thread ID:       0x1B6D22
+    Exception Record:
+      Exception Code:  0xB
+    Thread Context:  00000000
+...

lldb/unittests/Process/minidump/MinidumpParserTest.cpp

@@ -251,10 +251,15 @@ TEST_F(MinidumpParserTest, GetFilteredModuleList) {
 
 TEST_F(MinidumpParserTest, GetExceptionStream) {
   SetUpData("linux-x86_64.dmp");
-  const llvm::minidump::ExceptionStream *exception_stream =
-      parser->GetExceptionStream();
-  ASSERT_NE(nullptr, exception_stream);
-  ASSERT_EQ(11UL, exception_stream->ExceptionRecord.ExceptionCode);
+  auto exception_streams = parser->GetExceptionStreams();
+  size_t count = 0;
+  for (auto exception_stream : exception_streams) {
+    ASSERT_THAT_EXPECTED(exception_stream, llvm::Succeeded());
+    ASSERT_EQ(16001UL, exception_stream->ThreadId);
+    count++;
+  }
+
+  ASSERT_THAT(1UL, count);
 }
 
 void check_mem_range_exists(MinidumpParser &parser, const uint64_t range_start,