DavidSpickett created this revision.
Herald added subscribers: kristof.beyls, mgorny.
DavidSpickett requested review of this revision.
Herald added a project: LLDB.
Herald added a subscriber: lldb-commits.
This adds a specific unwind plan for AArch64 Linux sigreturn frames.
Previously we assumed that the fp would be valid here but it is not.
https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/vdso/sigreturn.S
On Ubuntu Bionic it happened to point to an old frame info which meant
you got what looked like a correct backtrace. On Focal, the info is
completely invalid. (probably due to some code shuffling in libc)
This adds an UnwindPlan that knows that the sp in a sigreturn frame
points to an rt_sigframe from which we can offset to get saved
sp and pc values to backtrace correctly.
Based on LibUnwind's change: https://reviews.llvm.org/D90898
This also updates TestHandleAbort to check that common frames
between signal and signal handler backtrace are in fact the same.
Fixes https://bugs.llvm.org/show_bug.cgi?id=52165
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D112069
Files:
lldb/include/lldb/Symbol/AArch64UnwindInfo.h
lldb/source/Symbol/AArch64UnwindInfo.cpp
lldb/source/Symbol/CMakeLists.txt
lldb/source/Target/RegisterContextUnwind.cpp
lldb/test/API/functionalities/signal/handle-abrt/TestHandleAbort.py
Index: lldb/test/API/functionalities/signal/handle-abrt/TestHandleAbort.py
===================================================================
--- lldb/test/API/functionalities/signal/handle-abrt/TestHandleAbort.py
+++ lldb/test/API/functionalities/signal/handle-abrt/TestHandleAbort.py
@@ -16,8 +16,6 @@
NO_DEBUG_INFO_TESTCASE = True
@skipIfWindows # signals do not exist on Windows
- # Fails on Ubuntu Focal
- @skipIf(archs=["aarch64"], oslist=["linux"])
@expectedFailureNetBSD
def test_inferior_handle_sigabrt(self):
"""Inferior calls abort() and handles the resultant SIGABRT.
@@ -47,6 +45,9 @@
self.assertEqual(thread.GetStopReasonDataAtIndex(0),
signo, "The stop signal should be SIGABRT")
+ # Save the backtrace frames to compare to the handler backtrace later.
+ signal_frames = thread.get_thread_frames()
+
# Continue to breakpoint in abort handler
bkpt = target.FindBreakpointByID(
lldbutil.run_break_set_by_source_regexp(self, "Set a breakpoint here"))
@@ -58,13 +59,21 @@
frame = thread.GetFrameAtIndex(0)
self.assertEqual(frame.GetDisplayFunctionName(), "handler", "Unexpected break?")
+ handler_frames = thread.get_thread_frames()
+
# Expect that unwinding should find 'abort_caller'
- foundFoo = False
- for frame in thread:
+ found_caller = False
+ for frame in handler_frames:
if frame.GetDisplayFunctionName() == "abort_caller":
- foundFoo = True
+ found_caller = True
+ break
+
+ self.assertTrue(found_caller, "Unwinding did not find func that called abort")
- self.assertTrue(foundFoo, "Unwinding did not find func that called abort")
+ # Check that frames present in both backtraces have the same addresses.
+ # The signal handler backtrace has extra frames at the start.
+ self.assertEqual(signal_frames, handler_frames[-len(signal_frames):],
+ "Common frames for signal and signal handler backtrace do not match")
# Continue until we exit.
process.Continue()
Index: lldb/source/Target/RegisterContextUnwind.cpp
===================================================================
--- lldb/source/Target/RegisterContextUnwind.cpp
+++ lldb/source/Target/RegisterContextUnwind.cpp
@@ -12,6 +12,7 @@
#include "lldb/Core/Module.h"
#include "lldb/Core/Value.h"
#include "lldb/Expression/DWARFExpression.h"
+#include "lldb/Symbol/AArch64UnwindInfo.h"
#include "lldb/Symbol/ArmUnwindInfo.h"
#include "lldb/Symbol/CallFrameInfo.h"
#include "lldb/Symbol/DWARFCallFrameInfo.h"
@@ -900,6 +901,11 @@
// unwind out of sigtramp.
if (m_frame_type == eTrapHandlerFrame && process) {
m_fast_unwind_plan_sp.reset();
+
+ unwind_plan_sp = GetAArch64LinuxTrapHandlerUnwindPlan(process->GetTarget());
+ if (unwind_plan_sp)
+ return unwind_plan_sp;
+
unwind_plan_sp =
func_unwinders_sp->GetEHFrameUnwindPlan(process->GetTarget());
if (!unwind_plan_sp)
Index: lldb/source/Symbol/CMakeLists.txt
===================================================================
--- lldb/source/Symbol/CMakeLists.txt
+++ lldb/source/Symbol/CMakeLists.txt
@@ -7,6 +7,7 @@
endif()
add_lldb_library(lldbSymbol
+ AArch64UnwindInfo.cpp
ArmUnwindInfo.cpp
Block.cpp
CompactUnwindInfo.cpp
Index: lldb/source/Symbol/AArch64UnwindInfo.cpp
===================================================================
--- /dev/null
+++ lldb/source/Symbol/AArch64UnwindInfo.cpp
@@ -0,0 +1,63 @@
+//===-- AArch64UnwindInfo.cpp ---------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Symbol/AArch64UnwindInfo.h"
+#include "Utility/ARM64_DWARF_Registers.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+lldb::UnwindPlanSP
+lldb_private::GetAArch64LinuxTrapHandlerUnwindPlan(const Target &target) {
+ lldb::UnwindPlanSP unwind_plan_sp;
+ ArchSpec arch = target.GetArchitecture();
+ llvm::Triple::ArchType machine = arch.GetMachine();
+
+ if ((machine != llvm::Triple::ArchType::aarch64 &&
+ machine != llvm::Triple::ArchType::aarch64_be &&
+ machine != llvm::Triple::ArchType::aarch64_32) ||
+ arch.GetTriple().getOS() != llvm::Triple::OSType::Linux)
+ return unwind_plan_sp;
+
+ UnwindPlan::RowSP row = std::make_shared<UnwindPlan::Row>();
+ row->SetOffset(0);
+
+ // In the signal trampoline frame, sp points to an rt_sigframe[1], which is:
+ // - 128-byte siginfo struct
+ // - ucontext struct:
+ // - 8-byte long (uc_flags)
+ // - 8-byte pointer (uc_link)
+ // - 24-byte stack_t
+ // - 128-byte signal set
+ // - 8 bytes of padding because sigcontext has 16-byte alignment
+ // - sigcontext/mcontext_t
+ // [1]
+ // https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/signal.c
+ int32_t offset = 128 + 8 + 8 + 24 + 128 + 8;
+ // Then sigcontext[2] is:
+ // - 8 byte fault address
+ // - 31 8 byte registers
+ // - 8 byte sp
+ // - 8 byte pc
+ // [2]
+ // https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/sigcontext.h
+ offset += 8 + (31 * 8);
+ row->GetCFAValue().SetIsRegisterPlusOffset(arm64_dwarf::sp, offset);
+ row->SetRegisterLocationToAtCFAPlusOffset(arm64_dwarf::fp, 0, false);
+ row->SetRegisterLocationToAtCFAPlusOffset(arm64_dwarf::pc, 8, false);
+
+ unwind_plan_sp = std::make_shared<UnwindPlan>(eRegisterKindGeneric);
+ unwind_plan_sp->AppendRow(row);
+ unwind_plan_sp->SetSourceName("AArch64 Linux sigcontext");
+ unwind_plan_sp->SetSourcedFromCompiler(eLazyBoolYes);
+ unwind_plan_sp->SetUnwindPlanValidAtAllInstructions(eLazyBoolNo);
+ unwind_plan_sp->SetUnwindPlanForSignalTrap(eLazyBoolYes);
+ unwind_plan_sp->SetRegisterKind(eRegisterKindDWARF);
+
+ return unwind_plan_sp;
+}
Index: lldb/include/lldb/Symbol/AArch64UnwindInfo.h
===================================================================
--- /dev/null
+++ lldb/include/lldb/Symbol/AArch64UnwindInfo.h
@@ -0,0 +1,26 @@
+//===-- AArch64UnwindInfo.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_SYMBOL_AARCH64UNWINDINFO_H
+#define LLDB_SYMBOL_AARCH64UNWINDINFO_H
+
+#include "lldb/Symbol/UnwindPlan.h"
+#include "lldb/Target/Target.h"
+#include "lldb/lldb-forward.h"
+#include "lldb/lldb-private.h"
+
+namespace lldb_private {
+
+// If target is AArch64 Linux return a shared pointer to
+// an UnwindPlan. Otherwise return an invalid shared pointer.
+// We assume the caller has checked that they are in a trap handler frame.
+lldb::UnwindPlanSP GetAArch64LinuxTrapHandlerUnwindPlan(const Target &target);
+
+} // namespace lldb_private
+
+#endif // LLDB_SYMBOL_AARCH64UNWINDINFO_H
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