[Windows] Dump more information about access violation exception

[leonid.mashinskiy]

Summary

Dump more information about "access violation" and "in page error" exceptions to description.
Description now contains data about read/write violation type and actual address as described at https://docs.microsoft.com/en-us/windows/desktop/api/winnt/ns-winnt-_exception_record

[leonid.mashinskiy]

Thanks for review!

Please, commit this for me, because I have no commit access.

[amccarth]

Does this affect any existing tests? Is there a good way to test it?

[leonid.mashinskiy]

• added access violation exception message test

[leonid.mashinskiy]

In D60519#1461640, @amccarth wrote:

Does this affect any existing tests?

I didn't notice new failures and didn't find any existing tests for windows exceptions.

[stella.stamenova]

I ran local tests with this and a couple of the tests from the lldb suite failed:

lldb-Suite :: functionalities/inferior-crashing/TestInferiorCrashing.py
lldb-Suite :: functionalities/thread/crash_during_step/TestCrashDuringStep.py

Here's the error from one of them (they are the same):

##[error]CUSTOMBUILD(0,0): Error : test_step_inst_with_dwarf (TestCrashDuringStep.CrashDuringStepTestCase)
     1>CUSTOMBUILD : error : test_step_inst_with_dwarf (TestCrashDuringStep.CrashDuringStepTestCase) [e:\_work\32\b\LLVMBuild\check-all.vcxproj]
         
            Test thread creation during step-inst handling.
         
         ----------------------------------------------------------------------
         
         Traceback (most recent call last):
         
           File "E:\_work\32\s\llvm\tools\lldb\packages\Python\lldbsuite\test\lldbtest.py", line 1746, in test_method
         
             return attrvalue(self)
         
           File "E:\_work\32\s\llvm\tools\lldb\packages\Python\lldbsuite\test\decorators.py", line 114, in wrapper
         
             func(*args, **kwargs)
         
           File "E:\_work\32\s\llvm\tools\lldb\packages\Python\lldbsuite\test\functionalities\thread\crash_during_step\TestCrashDuringStep.py", line 51, in test_step_inst_with
         
             while process.GetState() == lldb.eStateStopped and not lldbutil.is_thread_crashed(self, thread):
         
           File "E:\_work\32\s\llvm\tools\lldb\packages\Python\lldbsuite\test\lldbutil.py", line 740, in is_thread_crashed
         
             return "Exception 0xc0000005" in thread.GetStopDescription(100)
         
           File "E:\_work\32\b\LLVMBuild\Release\lib\site-packages\lldb\__init__.py", line 11874, in GetStopDescription
         
             return _lldb.SBThread_GetStopDescription(self, dst)
         
         UnicodeDecodeError: 'utf-8' codec can't decode byte 0x97 in position 104: invalid start byte
         
         Config=x86_64-E:\_work\32\b\LLVMBuild\Release\bin\clang.exe

[leonid.mashinskiy]

• increased buffer size in GetStopDescription call to fit new message

[amccarth]

Thanks for the new test and the test fix. It's unfortunate that the tests are so sensitive to an arbitrary buffer size.

[leonid.mashinskiy]

Ping!
Are these changes accepted ?

[stella.stamenova]

Yes, sorry. I hadn't gotten around to testing it to make sure the failures were gone. Do you still need someone to commit for you?

[leonid.mashinskiy]

Thanks!
I think I can ask @aleksandr.urakov to land changes.

lldb/trunk/lit/Process/Windows/exception_access_violation.cpp

+// clang-format off
+
+// REQUIRES: system-windows
+// RUN: %build --compiler=clang-cl -o %t.exe -- %s
+// RUN: env LLDB_USE_NATIVE_PDB_READER=1 %lldb -f %t.exe -o "run" -- write | FileCheck --check-prefix=WRITE %s
+// RUN: env LLDB_USE_NATIVE_PDB_READER=1 %lldb -f %t.exe -o "run" -- read | FileCheck --check-prefix=READ %s
+
+#include <string.h>
+
+int access_violation_write(void* addr) {
+    *(int*)addr = 42;
+    return 0;
+}
+
+
+int access_violation_read(void* addr) {
+    volatile int ret = *(int*)addr;
+    return ret;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc < 2) {
+        return 1;
+    }
+    if (strcmp(argv[1], "write") == 0) {
+        return access_violation_write((void*)42);
+    }
+    if (strcmp(argv[1], "read") == 0) {
+        return access_violation_read((void*)42);
+    }
+    return 1;
+}
+
+
+// WRITE:     * thread #1, stop reason = Exception 0xc0000005 encountered at address {{.*}}: Access violation writing location 0x0000002a
+
+// READ:      * thread #1, stop reason = Exception 0xc0000005 encountered at address {{.*}}: Access violation reading location 0x0000002a

lldb/trunk/packages/Python/lldbsuite/test/lldbutil.py

def is_thread_crashed(test, thread):
     reported depends on the platform."""
     if test.platformIsDarwin():
         return thread.GetStopReason(
         ) == lldb.eStopReasonException and "EXC_BAD_ACCESS" in thread.GetStopDescription(100)
     elif test.getPlatform() == "linux":
         return thread.GetStopReason() == lldb.eStopReasonSignal and thread.GetStopReasonDataAtIndex(
             0) == thread.GetProcess().GetUnixSignals().GetSignalNumberFromName("SIGSEGV")
     elif test.getPlatform() == "windows":
-        return "Exception 0xc0000005" in thread.GetStopDescription(100)
+        return "Exception 0xc0000005" in thread.GetStopDescription(200)
     else:
         return "invalid address" in thread.GetStopDescription(100)
 
 
 def get_crashed_threads(test, process):
     threads = []
     if process.GetState() != lldb.eStateStopped:
         return threads

lldb/trunk/source/Plugins/Process/Windows/Common/ExceptionRecord.h

public:
   bool IsContinuable() const { return m_continuable; }
   const ExceptionRecord *GetNextException() const {
     return m_next_exception.get();
   }
   lldb::addr_t GetExceptionAddress() const { return m_exception_addr; }
 
   lldb::tid_t GetThreadID() const { return m_thread_id; }
 
+  const std::vector<ULONG_PTR>& GetExceptionArguments() const { return m_arguments; }
+
 private:
   DWORD m_code;
   bool m_continuable;
   std::shared_ptr<ExceptionRecord> m_next_exception;
   lldb::addr_t m_exception_addr;
   lldb::tid_t m_thread_id;
   std::vector<ULONG_PTR> m_arguments;
 };
 }
 
 #endif

lldb/trunk/source/Plugins/Process/Windows/Common/ProcessWindows.cpp

void ProcessWindows::DidAttach(ArchSpec &arch_spec) {
 
   // The initial stop won't broadcast the state change event, so account for
   // that here.
   if (m_session_data && GetPrivateState() == eStateStopped &&
       m_session_data->m_stop_at_entry)
     RefreshStateAfterStop();
 }
 
+static void
+DumpAdditionalExceptionInformation(llvm::raw_ostream &stream,
+                                   const ExceptionRecordSP &exception) {
+  // Decode additional exception information for specific exception types based
+  // on
+  // https://docs.microsoft.com/en-us/windows/desktop/api/winnt/ns-winnt-_exception_record
+
+  const int addr_min_width = 2 + 8; // "0x" + 4 address bytes
+
+  const std::vector<ULONG_PTR> &args = exception->GetExceptionArguments();
+  switch (exception->GetExceptionCode()) {
+  case EXCEPTION_ACCESS_VIOLATION: {
+    if (args.size() < 2)
+      break;
+
+    stream << ": ";
+    const int access_violation_code = args[0];
+    const lldb::addr_t access_violation_address = args[1];
+    switch (access_violation_code) {
+    case 0:
+      stream << "Access violation reading";
+      break;
+    case 1:
+      stream << "Access violation writing";
+      break;
+    case 8:
+      stream << "User-mode data execution prevention (DEP) violation at";
+      break;
+    default:
+      stream << "Unknown access violation (code " << access_violation_code
+             << ") at";
+      break;
+    }
+    stream << " location "
+           << llvm::format_hex(access_violation_address, addr_min_width);
+    break;
+  }
+  case EXCEPTION_IN_PAGE_ERROR: {
+    if (args.size() < 3)
+      break;
+
+    stream << ": ";
+    const int page_load_error_code = args[0];
+    const lldb::addr_t page_load_error_address = args[1];
+    const DWORD underlying_code = args[2];
+    switch (page_load_error_code) {
+    case 0:
+      stream << "In page error reading";
+      break;
+    case 1:
+      stream << "In page error writing";
+      break;
+    case 8:
+      stream << "User-mode data execution prevention (DEP) violation at";
+      break;
+    default:
+      stream << "Unknown page loading error (code " << page_load_error_code
+             << ") at";
+      break;
+    }
+    stream << " location "
+           << llvm::format_hex(page_load_error_address, addr_min_width)
+           << " (status code " << llvm::format_hex(underlying_code, 8) << ")";
+    break;
+  }
+  }
+}
+
 void ProcessWindows::RefreshStateAfterStop() {
   Log *log = ProcessWindowsLog::GetLogIfAny(WINDOWS_LOG_EXCEPTION);
   llvm::sys::ScopedLock lock(m_mutex);
 
   if (!m_session_data) {
     LLDB_LOG(log, "no active session.  Returning...");
     return;
   }
void ProcessWindows::RefreshStateAfterStop() {
 
   default: {
     std::string desc;
     llvm::raw_string_ostream desc_stream(desc);
     desc_stream << "Exception "
                 << llvm::format_hex(active_exception->GetExceptionCode(), 8)
                 << " encountered at address "
                 << llvm::format_hex(active_exception->GetExceptionAddress(), 8);
+    DumpAdditionalExceptionInformation(desc_stream, active_exception);
+
     stop_info = StopInfo::CreateStopReasonWithException(
         *stop_thread, desc_stream.str().c_str());
     stop_thread->SetStopInfo(stop_info);
     LLDB_LOG(log, "{0}", desc_stream.str());
     return;
   }
   }
 }