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519 lines
19 KiB
519 lines
19 KiB
//===-- UnwindLLDB.cpp ----------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "lldb/Target/UnwindLLDB.h"
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#include "lldb/Core/Module.h"
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#include "lldb/Symbol/FuncUnwinders.h"
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#include "lldb/Symbol/Function.h"
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#include "lldb/Symbol/UnwindPlan.h"
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#include "lldb/Target/ABI.h"
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#include "lldb/Target/Process.h"
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#include "lldb/Target/RegisterContext.h"
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#include "lldb/Target/RegisterContextUnwind.h"
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#include "lldb/Target/Target.h"
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#include "lldb/Target/Thread.h"
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#include "lldb/Utility/Log.h"
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using namespace lldb;
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using namespace lldb_private;
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UnwindLLDB::UnwindLLDB(Thread &thread)
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: Unwind(thread), m_frames(), m_unwind_complete(false),
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m_user_supplied_trap_handler_functions() {
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ProcessSP process_sp(thread.GetProcess());
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if (process_sp) {
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Args args;
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process_sp->GetTarget().GetUserSpecifiedTrapHandlerNames(args);
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size_t count = args.GetArgumentCount();
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for (size_t i = 0; i < count; i++) {
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const char *func_name = args.GetArgumentAtIndex(i);
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m_user_supplied_trap_handler_functions.push_back(ConstString(func_name));
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}
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}
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}
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uint32_t UnwindLLDB::DoGetFrameCount() {
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if (!m_unwind_complete) {
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//#define DEBUG_FRAME_SPEED 1
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#if DEBUG_FRAME_SPEED
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#define FRAME_COUNT 10000
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using namespace std::chrono;
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auto time_value = steady_clock::now();
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#endif
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if (!AddFirstFrame())
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return 0;
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ProcessSP process_sp(m_thread.GetProcess());
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ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
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while (AddOneMoreFrame(abi)) {
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#if DEBUG_FRAME_SPEED
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if ((m_frames.size() % FRAME_COUNT) == 0) {
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const auto now = steady_clock::now();
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const auto delta_t = now - time_value;
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printf("%u frames in %.9f ms (%g frames/sec)\n", FRAME_COUNT,
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duration<double, std::milli>(delta_t).count(),
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(float)FRAME_COUNT / duration<double>(delta_t).count());
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time_value = now;
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}
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#endif
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}
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}
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return m_frames.size();
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}
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bool UnwindLLDB::AddFirstFrame() {
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if (m_frames.size() > 0)
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return true;
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ProcessSP process_sp(m_thread.GetProcess());
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ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
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// First, set up the 0th (initial) frame
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CursorSP first_cursor_sp(new Cursor());
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RegisterContextLLDBSP reg_ctx_sp(new RegisterContextUnwind(
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m_thread, RegisterContextLLDBSP(), first_cursor_sp->sctx, 0, *this));
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if (reg_ctx_sp.get() == nullptr)
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goto unwind_done;
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if (!reg_ctx_sp->IsValid())
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goto unwind_done;
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if (!reg_ctx_sp->GetCFA(first_cursor_sp->cfa))
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goto unwind_done;
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if (!reg_ctx_sp->ReadPC(first_cursor_sp->start_pc))
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goto unwind_done;
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// Everything checks out, so release the auto pointer value and let the
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// cursor own it in its shared pointer
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first_cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
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m_frames.push_back(first_cursor_sp);
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// Update the Full Unwind Plan for this frame if not valid
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UpdateUnwindPlanForFirstFrameIfInvalid(abi);
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return true;
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unwind_done:
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Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
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if (log) {
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LLDB_LOGF(log, "th%d Unwind of this thread is complete.",
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m_thread.GetIndexID());
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}
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m_unwind_complete = true;
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return false;
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}
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UnwindLLDB::CursorSP UnwindLLDB::GetOneMoreFrame(ABI *abi) {
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assert(m_frames.size() != 0 &&
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"Get one more frame called with empty frame list");
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// If we've already gotten to the end of the stack, don't bother to try
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// again...
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if (m_unwind_complete)
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return nullptr;
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Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
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CursorSP prev_frame = m_frames.back();
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uint32_t cur_idx = m_frames.size();
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CursorSP cursor_sp(new Cursor());
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RegisterContextLLDBSP reg_ctx_sp(new RegisterContextUnwind(
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m_thread, prev_frame->reg_ctx_lldb_sp, cursor_sp->sctx, cur_idx, *this));
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uint64_t max_stack_depth = m_thread.GetMaxBacktraceDepth();
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// We want to detect an unwind that cycles erroneously and stop backtracing.
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// Don't want this maximum unwind limit to be too low -- if you have a
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// backtrace with an "infinitely recursing" bug, it will crash when the stack
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// blows out and the first 35,000 frames are uninteresting - it's the top
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// most 5 frames that you actually care about. So you can't just cap the
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// unwind at 10,000 or something. Realistically anything over around 200,000
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// is going to blow out the stack space. If we're still unwinding at that
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// point, we're probably never going to finish.
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if (cur_idx >= max_stack_depth) {
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LLDB_LOGF(log,
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"%*sFrame %d unwound too many frames, assuming unwind has "
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"gone astray, stopping.",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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if (reg_ctx_sp.get() == nullptr) {
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// If the RegisterContextUnwind has a fallback UnwindPlan, it will switch to
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// that and return true. Subsequent calls to TryFallbackUnwindPlan() will
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// return false.
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
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// still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log, "%*sFrame %d did not get a RegisterContext, stopping.",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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if (!reg_ctx_sp->IsValid()) {
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// We failed to get a valid RegisterContext. See if the regctx below this
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// on the stack has a fallback unwind plan it can use. Subsequent calls to
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// TryFallbackUnwindPlan() will return false.
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
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// still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log,
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"%*sFrame %d invalid RegisterContext for this frame, "
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"stopping stack walk",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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if (!reg_ctx_sp->GetCFA(cursor_sp->cfa)) {
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// If the RegisterContextUnwind has a fallback UnwindPlan, it will switch to
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// that and return true. Subsequent calls to TryFallbackUnwindPlan() will
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// return false.
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
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// still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log,
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"%*sFrame %d did not get CFA for this frame, stopping stack walk",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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if (abi && !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
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// On Mac OS X, the _sigtramp asynchronous signal trampoline frame may not
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// have its (constructed) CFA aligned correctly -- don't do the abi
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// alignment check for these.
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if (!reg_ctx_sp->IsTrapHandlerFrame()) {
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// See if we can find a fallback unwind plan for THIS frame. It may be
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// that the UnwindPlan we're using for THIS frame was bad and gave us a
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// bad CFA. If that's not it, then see if we can change the UnwindPlan
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// for the frame below us ("NEXT") -- see if using that other UnwindPlan
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// gets us a better unwind state.
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if (!reg_ctx_sp->TryFallbackUnwindPlan() ||
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!reg_ctx_sp->GetCFA(cursor_sp->cfa) ||
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!abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of
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// prev_frame still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log,
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"%*sFrame %d did not get a valid CFA for this frame, "
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"stopping stack walk",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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} else {
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LLDB_LOGF(log,
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"%*sFrame %d had a bad CFA value but we switched the "
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"UnwindPlan being used and got one that looks more "
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"realistic.",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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}
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}
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}
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if (!reg_ctx_sp->ReadPC(cursor_sp->start_pc)) {
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// If the RegisterContextUnwind has a fallback UnwindPlan, it will switch to
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// that and return true. Subsequent calls to TryFallbackUnwindPlan() will
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// return false.
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
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// still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log,
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"%*sFrame %d did not get PC for this frame, stopping stack walk",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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if (abi && !abi->CodeAddressIsValid(cursor_sp->start_pc)) {
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// If the RegisterContextUnwind has a fallback UnwindPlan, it will switch to
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// that and return true. Subsequent calls to TryFallbackUnwindPlan() will
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// return false.
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if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// TryFallbackUnwindPlan for prev_frame succeeded and updated
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// reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
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// still needs to be updated. Hence updating it.
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if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
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return nullptr;
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return GetOneMoreFrame(abi);
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}
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LLDB_LOGF(log, "%*sFrame %d did not get a valid PC, stopping stack walk",
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cur_idx < 100 ? cur_idx : 100, "", cur_idx);
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return nullptr;
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}
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// Infinite loop where the current cursor is the same as the previous one...
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if (prev_frame->start_pc == cursor_sp->start_pc &&
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prev_frame->cfa == cursor_sp->cfa) {
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LLDB_LOGF(log,
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"th%d pc of this frame is the same as the previous frame and "
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"CFAs for both frames are identical -- stopping unwind",
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m_thread.GetIndexID());
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return nullptr;
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}
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cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
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return cursor_sp;
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}
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void UnwindLLDB::UpdateUnwindPlanForFirstFrameIfInvalid(ABI *abi) {
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// This function is called for First Frame only.
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assert(m_frames.size() == 1 && "No. of cursor frames are not 1");
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bool old_m_unwind_complete = m_unwind_complete;
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CursorSP old_m_candidate_frame = m_candidate_frame;
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// Try to unwind 2 more frames using the Unwinder. It uses Full UnwindPlan
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// and if Full UnwindPlan fails, then uses FallBack UnwindPlan. Also update
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// the cfa of Frame 0 (if required).
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AddOneMoreFrame(abi);
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// Remove all the frames added by above function as the purpose of using
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// above function was just to check whether Unwinder of Frame 0 works or not.
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for (uint32_t i = 1; i < m_frames.size(); i++)
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m_frames.pop_back();
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// Restore status after calling AddOneMoreFrame
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m_unwind_complete = old_m_unwind_complete;
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m_candidate_frame = old_m_candidate_frame;
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return;
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}
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bool UnwindLLDB::AddOneMoreFrame(ABI *abi) {
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Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
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// Frame zero is a little different
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if (m_frames.empty())
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return false;
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// If we've already gotten to the end of the stack, don't bother to try
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// again...
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if (m_unwind_complete)
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return false;
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CursorSP new_frame = m_candidate_frame;
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if (new_frame == nullptr)
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new_frame = GetOneMoreFrame(abi);
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if (new_frame == nullptr) {
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LLDB_LOGF(log, "th%d Unwind of this thread is complete.",
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m_thread.GetIndexID());
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m_unwind_complete = true;
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return false;
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}
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m_frames.push_back(new_frame);
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// If we can get one more frame further then accept that we get back a
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// correct frame.
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m_candidate_frame = GetOneMoreFrame(abi);
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if (m_candidate_frame)
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return true;
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// We can't go further from the frame returned by GetOneMore frame. Lets try
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// to get a different frame with using the fallback unwind plan.
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if (!m_frames[m_frames.size() - 2]
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->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
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// We don't have a valid fallback unwind plan. Accept the frame as it is.
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// This is a valid situation when we are at the bottom of the stack.
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return true;
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}
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// Remove the possibly incorrect frame from the frame list and try to add a
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// different one with the newly selected fallback unwind plan.
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m_frames.pop_back();
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CursorSP new_frame_v2 = GetOneMoreFrame(abi);
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if (new_frame_v2 == nullptr) {
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// We haven't got a new frame from the fallback unwind plan. Accept the
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// frame from the original unwind plan. This is a valid situation when we
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// are at the bottom of the stack.
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m_frames.push_back(new_frame);
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return true;
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}
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// Push the new frame to the list and try to continue from this frame. If we
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// can get a new frame then accept it as the correct one.
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m_frames.push_back(new_frame_v2);
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m_candidate_frame = GetOneMoreFrame(abi);
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if (m_candidate_frame) {
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// If control reached here then TryFallbackUnwindPlan had succeeded for
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// Cursor::m_frames[m_frames.size() - 2]. It also succeeded to Unwind next
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// 2 frames i.e. m_frames[m_frames.size() - 1] and a frame after that. For
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// Cursor::m_frames[m_frames.size() - 2], reg_ctx_lldb_sp field was already
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// updated during TryFallbackUnwindPlan call above. However, cfa field
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// still needs to be updated. Hence updating it here and then returning.
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return m_frames[m_frames.size() - 2]->reg_ctx_lldb_sp->GetCFA(
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m_frames[m_frames.size() - 2]->cfa);
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}
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// The new frame hasn't helped in unwinding. Fall back to the original one as
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// the default unwind plan is usually more reliable then the fallback one.
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m_frames.pop_back();
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m_frames.push_back(new_frame);
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return true;
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}
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bool UnwindLLDB::DoGetFrameInfoAtIndex(uint32_t idx, addr_t &cfa, addr_t &pc,
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bool &behaves_like_zeroth_frame) {
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if (m_frames.size() == 0) {
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if (!AddFirstFrame())
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return false;
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}
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ProcessSP process_sp(m_thread.GetProcess());
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ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
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while (idx >= m_frames.size() && AddOneMoreFrame(abi))
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;
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if (idx < m_frames.size()) {
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cfa = m_frames[idx]->cfa;
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pc = m_frames[idx]->start_pc;
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if (idx == 0) {
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// Frame zero always behaves like it.
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behaves_like_zeroth_frame = true;
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} else if (m_frames[idx - 1]->reg_ctx_lldb_sp->IsTrapHandlerFrame()) {
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// This could be an asynchronous signal, thus the
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// pc might point to the interrupted instruction rather
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// than a post-call instruction
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behaves_like_zeroth_frame = true;
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} else if (m_frames[idx]->reg_ctx_lldb_sp->IsTrapHandlerFrame()) {
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// This frame may result from signal processing installing
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// a pointer to the first byte of a signal-return trampoline
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// in the return address slot of the frame below, so this
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// too behaves like the zeroth frame (i.e. the pc might not
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// be pointing just past a call in it)
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behaves_like_zeroth_frame = true;
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} else {
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behaves_like_zeroth_frame = false;
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}
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return true;
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}
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return false;
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}
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lldb::RegisterContextSP
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UnwindLLDB::DoCreateRegisterContextForFrame(StackFrame *frame) {
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lldb::RegisterContextSP reg_ctx_sp;
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uint32_t idx = frame->GetConcreteFrameIndex();
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if (idx == 0) {
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return m_thread.GetRegisterContext();
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}
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if (m_frames.size() == 0) {
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if (!AddFirstFrame())
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return reg_ctx_sp;
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}
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ProcessSP process_sp(m_thread.GetProcess());
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ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
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while (idx >= m_frames.size()) {
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if (!AddOneMoreFrame(abi))
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break;
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}
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|
const uint32_t num_frames = m_frames.size();
|
|
if (idx < num_frames) {
|
|
Cursor *frame_cursor = m_frames[idx].get();
|
|
reg_ctx_sp = frame_cursor->reg_ctx_lldb_sp;
|
|
}
|
|
return reg_ctx_sp;
|
|
}
|
|
|
|
UnwindLLDB::RegisterContextLLDBSP
|
|
UnwindLLDB::GetRegisterContextForFrameNum(uint32_t frame_num) {
|
|
RegisterContextLLDBSP reg_ctx_sp;
|
|
if (frame_num < m_frames.size())
|
|
reg_ctx_sp = m_frames[frame_num]->reg_ctx_lldb_sp;
|
|
return reg_ctx_sp;
|
|
}
|
|
|
|
bool UnwindLLDB::SearchForSavedLocationForRegister(
|
|
uint32_t lldb_regnum, lldb_private::UnwindLLDB::RegisterLocation ®loc,
|
|
uint32_t starting_frame_num, bool pc_reg) {
|
|
int64_t frame_num = starting_frame_num;
|
|
if (static_cast<size_t>(frame_num) >= m_frames.size())
|
|
return false;
|
|
|
|
// Never interrogate more than one level while looking for the saved pc
|
|
// value. If the value isn't saved by frame_num, none of the frames lower on
|
|
// the stack will have a useful value.
|
|
if (pc_reg) {
|
|
UnwindLLDB::RegisterSearchResult result;
|
|
result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
|
|
lldb_regnum, regloc);
|
|
return result == UnwindLLDB::RegisterSearchResult::eRegisterFound;
|
|
}
|
|
while (frame_num >= 0) {
|
|
UnwindLLDB::RegisterSearchResult result;
|
|
result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
|
|
lldb_regnum, regloc);
|
|
|
|
// We descended down to the live register context aka stack frame 0 and are
|
|
// reading the value out of a live register.
|
|
if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
|
|
regloc.type ==
|
|
UnwindLLDB::RegisterLocation::eRegisterInLiveRegisterContext) {
|
|
return true;
|
|
}
|
|
|
|
// If we have unwind instructions saying that register N is saved in
|
|
// register M in the middle of the stack (and N can equal M here, meaning
|
|
// the register was not used in this function), then change the register
|
|
// number we're looking for to M and keep looking for a concrete location
|
|
// down the stack, or an actual value from a live RegisterContext at frame
|
|
// 0.
|
|
if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
|
|
regloc.type == UnwindLLDB::RegisterLocation::eRegisterInRegister &&
|
|
frame_num > 0) {
|
|
result = UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
|
|
lldb_regnum = regloc.location.register_number;
|
|
}
|
|
|
|
if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound)
|
|
return true;
|
|
if (result == UnwindLLDB::RegisterSearchResult::eRegisterIsVolatile)
|
|
return false;
|
|
frame_num--;
|
|
}
|
|
return false;
|
|
}
|