[MachCore] Report arm64 thread exception state

A MachO userspace corefile may contain LC_THREAD commands which specify
thread exception state.

For arm64* only (for now), report a human-readable version of this state
as the thread stop reason, instead of 'SIGSTOP'.

As a follow-up, similar functionality can be implemented for x86 cores
by translating the trapno/err exception registers.

rdar://82898146

Differential Revision: https://reviews.llvm.org/D109795

lldb/include/lldb/Target/AppleArm64ExceptionClass.def

@@ -0,0 +1,50 @@
+/*===-- AppleArm64ExceptionClass.def ---------------------------*- C++ -*-=== *\
+|*
+|* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+|* See https://llvm.org/LICENSE.txt for license information.
+|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+|*
+\*===----------------------------------------------------------------------===*/
+
+// Defines ESR exception classes for Apple arm64* targets.
+// These largely map 1:1 to the exception classes defined in ARM's architecture
+// reference manual, but there are some Apple-specific additions.
+
+#ifndef APPLE_ARM64_EXCEPTION_CLASS
+#error "APPLE_ARM64_EXCEPTION_CLASS(Name, Code) not defined."
+#endif
+
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_UNCATEGORIZED, 0x00)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_WFI_WFE, 0x01)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_MCR_MRC_CP15_TRAP, 0x03)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_MCRR_MRRC_CP15_TRAP, 0x04)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_MCR_MRC_CP14_TRAP, 0x05)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_LDC_STC_CP14_TRAP, 0x06)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_TRAP_SIMD_FP, 0x07)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_PTRAUTH_INSTR_TRAP, 0x09)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_MCRR_MRRC_CP14_TRAP, 0x0c)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_ILLEGAL_INSTR_SET, 0x0e)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SVC_32, 0x11)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SVC_64, 0x15)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_MSR_TRAP, 0x18)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_PAC_FAIL, 0x1C)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_IABORT_EL0, 0x20)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_IABORT_EL1, 0x21)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_PC_ALIGN, 0x22)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_DABORT_EL0, 0x24)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_DABORT_EL1, 0x25)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SP_ALIGN, 0x26)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_FLOATING_POINT_32, 0x28)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_FLOATING_POINT_64, 0x2C)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SERROR_INTERRUPT, 0x2F)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_BKPT_REG_MATCH_EL0, 0x30)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_BKPT_REG_MATCH_EL1, 0x31)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SW_STEP_DEBUG_EL0, 0x32)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_SW_STEP_DEBUG_EL1, 0x33)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_WATCHPT_MATCH_EL0, 0x34)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_WATCHPT_MATCH_EL1, 0x35)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_BKPT_AARCH32, 0x38)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_BRK_AARCH64, 0x3C)
+APPLE_ARM64_EXCEPTION_CLASS(ESR_EC_PRIV, 0x3F)
+
+#undef APPLE_ARM64_EXCEPTION_CLASS

lldb/include/lldb/Target/AppleArm64ExceptionClass.h

@@ -0,0 +1,50 @@
+//===-- AppleArm64ExceptionClass.h ------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_TARGET_APPLEARM64EXCEPTIONCLASS_H
+#define LLDB_TARGET_APPLEARM64EXCEPTIONCLASS_H
+
+#include <cstdint>
+
+namespace lldb_private {
+
+enum class AppleArm64ExceptionClass : unsigned {
+#define APPLE_ARM64_EXCEPTION_CLASS(Name, Code) Name = Code,
+#include "AppleArm64ExceptionClass.def"
+};
+
+/// Get the Apple ARM64 exception class encoded within \p esr.
+inline AppleArm64ExceptionClass getAppleArm64ExceptionClass(uint32_t esr) {
+  /*
+   * Exception Syndrome Register
+   *
+   *  31  26 25 24               0
+   * +------+--+------------------+
+   * |  EC  |IL|       ISS        |
+   * +------+--+------------------+
+   *
+   * EC  - Exception Class
+   * IL  - Instruction Length
+   * ISS - Instruction Specific Syndrome
+   */
+  return static_cast<AppleArm64ExceptionClass>(esr >> 26);
+}
+
+inline const char *toString(AppleArm64ExceptionClass EC) {
+  switch (EC) {
+#define APPLE_ARM64_EXCEPTION_CLASS(Name, Code)                                \
+  case AppleArm64ExceptionClass::Name:                                         \
+    return #Name;
+#include "AppleArm64ExceptionClass.def"
+  }
+  return "Unknown Exception Class";
+}
+
+} // namespace lldb_private
+
+#endif // LLDB_TARGET_APPLEARM64EXCEPTIONCLASS_H

lldb/include/lldb/module.modulemap

@@ -119,6 +119,7 @@ module lldb_Wrapper {
     requires cplusplus
 
     umbrella "Target"
+    textual header "Target/AppleArm64ExceptionClass.def"
     module * { export * }
   }
 }

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

@@ -745,13 +745,14 @@ class RegisterContextDarwin_arm64_Mach : public RegisterContextDarwin_arm64 {
       PrintRegisterValue(reg_ctx, "sp", nullptr, 8, data);
       PrintRegisterValue(reg_ctx, "pc", nullptr, 8, data);
       PrintRegisterValue(reg_ctx, "cpsr", nullptr, 4, data);
+      data.PutHex32(0); // uint32_t pad at the end
 
       // Write out the EXC registers
-      //            data.PutHex32 (EXCRegSet);
-      //            data.PutHex32 (EXCWordCount);
-      //            WriteRegister (reg_ctx, "far", NULL, 8, data);
-      //            WriteRegister (reg_ctx, "esr", NULL, 4, data);
-      //            WriteRegister (reg_ctx, "exception", NULL, 4, data);
+      data.PutHex32(EXCRegSet);
+      data.PutHex32(EXCWordCount);
+      PrintRegisterValue(reg_ctx, "far", NULL, 8, data);
+      PrintRegisterValue(reg_ctx, "esr", NULL, 4, data);
+      PrintRegisterValue(reg_ctx, "exception", NULL, 4, data);
       return true;
     }
     return false;

lldb/source/Plugins/Process/mach-core/ThreadMachCore.cpp

@@ -9,14 +9,17 @@
 #include "ThreadMachCore.h"
 
 #include "lldb/Breakpoint/Watchpoint.h"
+#include "lldb/Host/SafeMachO.h"
 #include "lldb/Symbol/ObjectFile.h"
+#include "lldb/Target/AppleArm64ExceptionClass.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StopInfo.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Unwind.h"
 #include "lldb/Utility/ArchSpec.h"
 #include "lldb/Utility/DataExtractor.h"
+#include "lldb/Utility/RegisterValue.h"
 #include "lldb/Utility/State.h"
 #include "lldb/Utility/StreamString.h"
 
@@ -88,10 +91,55 @@ ThreadMachCore::CreateRegisterContextForFrame(StackFrame *frame) {
   return reg_ctx_sp;
 }
 
+static bool IsCrashExceptionClass(AppleArm64ExceptionClass EC) {
+  switch (EC) {
+  case AppleArm64ExceptionClass::ESR_EC_UNCATEGORIZED:
+  case AppleArm64ExceptionClass::ESR_EC_SVC_32:
+  case AppleArm64ExceptionClass::ESR_EC_SVC_64:
+    // In the ARM exception model, a process takes an exception when asking the
+    // kernel to service a system call. Don't treat this like a crash.
+    return false;
+  default:
+    return true;
+  }
+}
+
 bool ThreadMachCore::CalculateStopInfo() {
   ProcessSP process_sp(GetProcess());
   if (process_sp) {
-    SetStopInfo(StopInfo::CreateStopReasonWithSignal(*this, SIGSTOP));
+    StopInfoSP stop_info;
+    RegisterContextSP reg_ctx_sp = GetRegisterContext();
+
+    if (reg_ctx_sp) {
+      Target &target = process_sp->GetTarget();
+      const ArchSpec arch_spec = target.GetArchitecture();
+      const uint32_t cputype = arch_spec.GetMachOCPUType();
+
+      if (cputype == llvm::MachO::CPU_TYPE_ARM64 ||
+          cputype == llvm::MachO::CPU_TYPE_ARM64_32) {
+        const RegisterInfo *esr_info = reg_ctx_sp->GetRegisterInfoByName("esr");
+        const RegisterInfo *far_info = reg_ctx_sp->GetRegisterInfoByName("far");
+        RegisterValue esr, far;
+        if (reg_ctx_sp->ReadRegister(esr_info, esr) &&
+            reg_ctx_sp->ReadRegister(far_info, far)) {
+          const uint32_t esr_val = esr.GetAsUInt32();
+          const AppleArm64ExceptionClass exception_class =
+              getAppleArm64ExceptionClass(esr_val);
+          if (IsCrashExceptionClass(exception_class)) {
+            StreamString S;
+            S.Printf("%s (fault address: 0x%" PRIx64 ")",
+                     toString(exception_class), far.GetAsUInt64());
+            stop_info =
+                StopInfo::CreateStopReasonWithException(*this, S.GetData());
+          }
+        }
+      }
+    }
+
+    // Set a stop reason for crashing threads only so that they get selected
+    // preferentially.
+    if (stop_info)
+      SetStopInfo(stop_info);
     return true;
   }
   return false;

lldb/test/API/macosx/corefile-exception-reason/Makefile

@@ -0,0 +1,3 @@
+CXX_SOURCES = main.cpp
+
+include Makefile.rules

lldb/test/API/macosx/corefile-exception-reason/TestCorefileExceptionReason.py

@@ -0,0 +1,43 @@
+"""Test that lldb can report the exception reason for threads in a corefile."""
+
+import os
+import re
+import subprocess
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestCorefileExceptionReason(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @skipIfOutOfTreeDebugserver  # newer debugserver required for these qMemoryRegionInfo types
+    @no_debug_info_test
+    @skipUnlessDarwin
+    @skipIf(archs=no_match(['arm64','arm64e']))
+    def test(self):
+
+        corefile = self.getBuildArtifact("process.core")
+        self.build()
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+            self, "// break here", lldb.SBFileSpec("main.cpp"))
+
+        self.runCmd("continue")
+
+        self.runCmd("process save-core -s stack " + corefile)
+        process.Kill()
+        self.dbg.DeleteTarget(target)
+
+        # Now load the corefile
+        target = self.dbg.CreateTarget('')
+        process = target.LoadCore(corefile)
+        thread = process.GetSelectedThread()
+        self.assertTrue(process.GetSelectedThread().IsValid())
+        if self.TraceOn():
+            self.runCmd("image list")
+            self.runCmd("bt")
+            self.runCmd("fr v")
+
+        self.assertTrue(thread.GetStopDescription(256) == "ESR_EC_DABORT_EL0 (fault address: 0x0)")

lldb/test/API/macosx/corefile-exception-reason/main.cpp

@@ -0,0 +1,24 @@
+#include <stdlib.h>
+#include <thread>
+#include <unistd.h>
+#include <vector>
+
+void *sleep_worker(void *in) {
+  sleep(30);
+  sleep(30);
+  return nullptr;
+}
+
+void *crash_worker(void *in) {
+  sleep(1);
+  volatile int *p = nullptr; // break here
+  return (void *)*p;
+}
+
+int main() {
+  std::vector<std::thread> threads;
+  threads.push_back(std::move(std::thread(crash_worker, nullptr)));
+  for (int i = 0; i < 15; i++)
+    threads.push_back(std::move(std::thread(sleep_worker, nullptr)));
+  sleep(10);
+}