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llvm-project/lldb/source/Symbol/FuncUnwinders.cpp
Pavel Labath 22bbd7d690 FuncUnwinders: Add a new "SymbolFile" unwind plan 
Summary:
some unwind formats are specific to a single symbol file and so it does
not make sense for their parsing code live in the general Symbol library
(as is the case with eh_frame for instance). This is the case for the
unwind information in breakpad files, but the same will probably be true
for PDB unwind info (once we are able to parse that).

This patch adds the ability to fetch an unwind plan provided by a symbol
file plugin, as discussed in the RFC at
<http://lists.llvm.org/pipermail/lldb-dev/2019-February/014703.html>.
I've kept the set of changes to a minimum, as there is no way to test
them until we have a symbol file which implements this API -- that is
comming in a follow-up patch, which will also implicitly test this
change.

The interesting part here is the introduction of the
"RegisterInfoResolver" interface. The reason for this is that breakpad
needs to be able to resolve register names (which are present as strings
in the file) into register enums so that it can construct the unwind
plan. This is normally done via the RegisterContext class, handing this
over to the SymbolFile plugin would mean that it has full access to the
debugged process, which is not something we want it to have. So instead,
I create a facade, which only provides the ability to query register
names, and hide the RegisterContext behind the facade.

Also note that this only adds the ability to dump the unwind plan
created by the symbol file plugin -- the plan is not used for unwinding
yet -- this will be added in a third patch, which will add additional
tests which makes sure the unwinding works as a whole.

Reviewers: jasonmolenda, clayborg

Subscribers: markmentovai, amccarth, lldb-commits

Differential Revision: https://reviews.llvm.org/D61732

llvm-svn: 360409
2019-05-10 07:54:37 +00:00

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//===-- FuncUnwinders.cpp ----------------------------------*- 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
//
//===----------------------------------------------------------------------===//
#include "lldb/Symbol/FuncUnwinders.h"
#include "lldb/Core/Address.h"
#include "lldb/Core/AddressRange.h"
#include "lldb/Symbol/ArmUnwindInfo.h"
#include "lldb/Symbol/CompactUnwindInfo.h"
#include "lldb/Symbol/DWARFCallFrameInfo.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/SymbolFile.h"
#include "lldb/Symbol/UnwindPlan.h"
#include "lldb/Symbol/UnwindTable.h"
#include "lldb/Target/ABI.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/RegisterNumber.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Thread.h"
#include "lldb/Target/UnwindAssembly.h"
#include <memory>
using namespace lldb;
using namespace lldb_private;
/// constructor
FuncUnwinders::FuncUnwinders(UnwindTable &unwind_table, AddressRange range)
: m_unwind_table(unwind_table), m_range(range), m_mutex(),
m_unwind_plan_assembly_sp(), m_unwind_plan_eh_frame_sp(),
m_unwind_plan_eh_frame_augmented_sp(), m_unwind_plan_compact_unwind(),
m_unwind_plan_arm_unwind_sp(), m_unwind_plan_fast_sp(),
m_unwind_plan_arch_default_sp(),
m_unwind_plan_arch_default_at_func_entry_sp(),
m_tried_unwind_plan_assembly(false), m_tried_unwind_plan_eh_frame(false),
m_tried_unwind_plan_debug_frame(false),
m_tried_unwind_plan_eh_frame_augmented(false),
m_tried_unwind_plan_debug_frame_augmented(false),
m_tried_unwind_plan_compact_unwind(false),
m_tried_unwind_plan_arm_unwind(false),
m_tried_unwind_plan_symbol_file(false), m_tried_unwind_fast(false),
m_tried_unwind_arch_default(false),
m_tried_unwind_arch_default_at_func_entry(false),
m_first_non_prologue_insn() {}
/// destructor
FuncUnwinders::~FuncUnwinders() {}
UnwindPlanSP FuncUnwinders::GetUnwindPlanAtCallSite(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (UnwindPlanSP plan_sp = GetEHFrameUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetDebugFrameUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetCompactUnwindUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetArmUnwindUnwindPlan(target))
return plan_sp;
return nullptr;
}
UnwindPlanSP FuncUnwinders::GetCompactUnwindUnwindPlan(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_compact_unwind.size() > 0)
return m_unwind_plan_compact_unwind[0]; // FIXME support multiple compact
// unwind plans for one func
if (m_tried_unwind_plan_compact_unwind)
return UnwindPlanSP();
m_tried_unwind_plan_compact_unwind = true;
if (m_range.GetBaseAddress().IsValid()) {
Address current_pc(m_range.GetBaseAddress());
CompactUnwindInfo *compact_unwind = m_unwind_table.GetCompactUnwindInfo();
if (compact_unwind) {
UnwindPlanSP unwind_plan_sp(new UnwindPlan(lldb::eRegisterKindGeneric));
if (compact_unwind->GetUnwindPlan(target, current_pc, *unwind_plan_sp)) {
m_unwind_plan_compact_unwind.push_back(unwind_plan_sp);
return m_unwind_plan_compact_unwind[0]; // FIXME support multiple
// compact unwind plans for one
// func
}
}
}
return UnwindPlanSP();
}
UnwindPlanSP FuncUnwinders::GetEHFrameUnwindPlan(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_eh_frame_sp.get() || m_tried_unwind_plan_eh_frame)
return m_unwind_plan_eh_frame_sp;
m_tried_unwind_plan_eh_frame = true;
if (m_range.GetBaseAddress().IsValid()) {
DWARFCallFrameInfo *eh_frame = m_unwind_table.GetEHFrameInfo();
if (eh_frame) {
m_unwind_plan_eh_frame_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!eh_frame->GetUnwindPlan(m_range, *m_unwind_plan_eh_frame_sp))
m_unwind_plan_eh_frame_sp.reset();
}
}
return m_unwind_plan_eh_frame_sp;
}
UnwindPlanSP FuncUnwinders::GetDebugFrameUnwindPlan(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_debug_frame_sp || m_tried_unwind_plan_debug_frame)
return m_unwind_plan_debug_frame_sp;
m_tried_unwind_plan_debug_frame = true;
if (m_range.GetBaseAddress().IsValid()) {
DWARFCallFrameInfo *debug_frame = m_unwind_table.GetDebugFrameInfo();
if (debug_frame) {
m_unwind_plan_debug_frame_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!debug_frame->GetUnwindPlan(m_range, *m_unwind_plan_debug_frame_sp))
m_unwind_plan_debug_frame_sp.reset();
}
}
return m_unwind_plan_debug_frame_sp;
}
UnwindPlanSP FuncUnwinders::GetArmUnwindUnwindPlan(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_arm_unwind_sp.get() || m_tried_unwind_plan_arm_unwind)
return m_unwind_plan_arm_unwind_sp;
m_tried_unwind_plan_arm_unwind = true;
if (m_range.GetBaseAddress().IsValid()) {
Address current_pc(m_range.GetBaseAddress());
ArmUnwindInfo *arm_unwind_info = m_unwind_table.GetArmUnwindInfo();
if (arm_unwind_info) {
m_unwind_plan_arm_unwind_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!arm_unwind_info->GetUnwindPlan(target, current_pc,
*m_unwind_plan_arm_unwind_sp))
m_unwind_plan_arm_unwind_sp.reset();
}
}
return m_unwind_plan_arm_unwind_sp;
}
namespace {
class RegisterContextToInfo: public SymbolFile::RegisterInfoResolver {
public:
RegisterContextToInfo(RegisterContext &ctx) : m_ctx(ctx) {}
const RegisterInfo *ResolveName(llvm::StringRef name) const {
return m_ctx.GetRegisterInfoByName(name);
}
const RegisterInfo *ResolveNumber(lldb::RegisterKind kind,
uint32_t number) const {
return m_ctx.GetRegisterInfo(kind, number);
}
private:
RegisterContext &m_ctx;
};
} // namespace
UnwindPlanSP FuncUnwinders::GetSymbolFileUnwindPlan(Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_symbol_file_sp.get() || m_tried_unwind_plan_symbol_file)
return m_unwind_plan_symbol_file_sp;
m_tried_unwind_plan_symbol_file = true;
if (SymbolFile *symfile = m_unwind_table.GetSymbolFile()) {
m_unwind_plan_symbol_file_sp = symfile->GetUnwindPlan(
m_range.GetBaseAddress(),
RegisterContextToInfo(*thread.GetRegisterContext()));
}
return m_unwind_plan_symbol_file_sp;
}
UnwindPlanSP FuncUnwinders::GetEHFrameAugmentedUnwindPlan(Target &target,
Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_eh_frame_augmented_sp.get() ||
m_tried_unwind_plan_eh_frame_augmented)
return m_unwind_plan_eh_frame_augmented_sp;
// Only supported on x86 architectures where we get eh_frame from the
// compiler that describes the prologue instructions perfectly, and sometimes
// the epilogue instructions too.
if (target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_32_i386 &&
target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_64_x86_64 &&
target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_64_x86_64h) {
m_tried_unwind_plan_eh_frame_augmented = true;
return m_unwind_plan_eh_frame_augmented_sp;
}
m_tried_unwind_plan_eh_frame_augmented = true;
UnwindPlanSP eh_frame_plan = GetEHFrameUnwindPlan(target);
if (!eh_frame_plan)
return m_unwind_plan_eh_frame_augmented_sp;
m_unwind_plan_eh_frame_augmented_sp =
std::make_shared<UnwindPlan>(*eh_frame_plan);
// Augment the eh_frame instructions with epilogue descriptions if necessary
// so the UnwindPlan can be used at any instruction in the function.
UnwindAssemblySP assembly_profiler_sp(GetUnwindAssemblyProfiler(target));
if (assembly_profiler_sp) {
if (!assembly_profiler_sp->AugmentUnwindPlanFromCallSite(
m_range, thread, *m_unwind_plan_eh_frame_augmented_sp)) {
m_unwind_plan_eh_frame_augmented_sp.reset();
}
} else {
m_unwind_plan_eh_frame_augmented_sp.reset();
}
return m_unwind_plan_eh_frame_augmented_sp;
}
UnwindPlanSP FuncUnwinders::GetDebugFrameAugmentedUnwindPlan(Target &target,
Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_debug_frame_augmented_sp.get() ||
m_tried_unwind_plan_debug_frame_augmented)
return m_unwind_plan_debug_frame_augmented_sp;
// Only supported on x86 architectures where we get debug_frame from the
// compiler that describes the prologue instructions perfectly, and sometimes
// the epilogue instructions too.
if (target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_32_i386 &&
target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_64_x86_64 &&
target.GetArchitecture().GetCore() != ArchSpec::eCore_x86_64_x86_64h) {
m_tried_unwind_plan_debug_frame_augmented = true;
return m_unwind_plan_debug_frame_augmented_sp;
}
m_tried_unwind_plan_debug_frame_augmented = true;
UnwindPlanSP debug_frame_plan = GetDebugFrameUnwindPlan(target);
if (!debug_frame_plan)
return m_unwind_plan_debug_frame_augmented_sp;
m_unwind_plan_debug_frame_augmented_sp =
std::make_shared<UnwindPlan>(*debug_frame_plan);
// Augment the debug_frame instructions with epilogue descriptions if
// necessary so the UnwindPlan can be used at any instruction in the
// function.
UnwindAssemblySP assembly_profiler_sp(GetUnwindAssemblyProfiler(target));
if (assembly_profiler_sp) {
if (!assembly_profiler_sp->AugmentUnwindPlanFromCallSite(
m_range, thread, *m_unwind_plan_debug_frame_augmented_sp)) {
m_unwind_plan_debug_frame_augmented_sp.reset();
}
} else
m_unwind_plan_debug_frame_augmented_sp.reset();
return m_unwind_plan_debug_frame_augmented_sp;
}
UnwindPlanSP FuncUnwinders::GetAssemblyUnwindPlan(Target &target,
Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_assembly_sp.get() || m_tried_unwind_plan_assembly ||
!m_unwind_table.GetAllowAssemblyEmulationUnwindPlans()) {
return m_unwind_plan_assembly_sp;
}
m_tried_unwind_plan_assembly = true;
UnwindAssemblySP assembly_profiler_sp(GetUnwindAssemblyProfiler(target));
if (assembly_profiler_sp) {
m_unwind_plan_assembly_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!assembly_profiler_sp->GetNonCallSiteUnwindPlanFromAssembly(
m_range, thread, *m_unwind_plan_assembly_sp)) {
m_unwind_plan_assembly_sp.reset();
}
}
return m_unwind_plan_assembly_sp;
}
// This method compares the pc unwind rule in the first row of two UnwindPlans.
// If they have the same way of getting the pc value (e.g. "CFA - 8" + "CFA is
// sp"), then it will return LazyBoolTrue.
LazyBool FuncUnwinders::CompareUnwindPlansForIdenticalInitialPCLocation(
Thread &thread, const UnwindPlanSP &a, const UnwindPlanSP &b) {
LazyBool plans_are_identical = eLazyBoolCalculate;
RegisterNumber pc_reg(thread, eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC);
uint32_t pc_reg_lldb_regnum = pc_reg.GetAsKind(eRegisterKindLLDB);
if (a.get() && b.get()) {
UnwindPlan::RowSP a_first_row = a->GetRowAtIndex(0);
UnwindPlan::RowSP b_first_row = b->GetRowAtIndex(0);
if (a_first_row.get() && b_first_row.get()) {
UnwindPlan::Row::RegisterLocation a_pc_regloc;
UnwindPlan::Row::RegisterLocation b_pc_regloc;
a_first_row->GetRegisterInfo(pc_reg_lldb_regnum, a_pc_regloc);
b_first_row->GetRegisterInfo(pc_reg_lldb_regnum, b_pc_regloc);
plans_are_identical = eLazyBoolYes;
if (a_first_row->GetCFAValue() != b_first_row->GetCFAValue()) {
plans_are_identical = eLazyBoolNo;
}
if (a_pc_regloc != b_pc_regloc) {
plans_are_identical = eLazyBoolNo;
}
}
}
return plans_are_identical;
}
UnwindPlanSP FuncUnwinders::GetUnwindPlanAtNonCallSite(Target &target,
Thread &thread) {
UnwindPlanSP eh_frame_sp = GetEHFrameUnwindPlan(target);
if (!eh_frame_sp)
eh_frame_sp = GetDebugFrameUnwindPlan(target);
UnwindPlanSP arch_default_at_entry_sp =
GetUnwindPlanArchitectureDefaultAtFunctionEntry(thread);
UnwindPlanSP arch_default_sp = GetUnwindPlanArchitectureDefault(thread);
UnwindPlanSP assembly_sp = GetAssemblyUnwindPlan(target, thread);
// This point of this code is to detect when a function is using a non-
// standard ABI, and the eh_frame correctly describes that alternate ABI.
// This is addressing a specific situation on x86_64 linux systems where one
// function in a library pushes a value on the stack and jumps to another
// function. So using an assembly instruction based unwind will not work
// when you're in the second function - the stack has been modified in a non-
// ABI way. But we have eh_frame that correctly describes how to unwind from
// this location. So we're looking to see if the initial pc register save
// location from the eh_frame is different from the assembly unwind, the arch
// default unwind, and the arch default at initial function entry.
//
// We may have eh_frame that describes the entire function -- or we may have
// eh_frame that only describes the unwind after the prologue has executed --
// so we need to check both the arch default (once the prologue has executed)
// and the arch default at initial function entry. And we may be running on
// a target where we have only some of the assembly/arch default unwind plans
// available.
if (CompareUnwindPlansForIdenticalInitialPCLocation(
thread, eh_frame_sp, arch_default_at_entry_sp) == eLazyBoolNo &&
CompareUnwindPlansForIdenticalInitialPCLocation(
thread, eh_frame_sp, arch_default_sp) == eLazyBoolNo &&
CompareUnwindPlansForIdenticalInitialPCLocation(
thread, assembly_sp, arch_default_sp) == eLazyBoolNo) {
return eh_frame_sp;
}
if (UnwindPlanSP plan_sp = GetEHFrameAugmentedUnwindPlan(target, thread))
return plan_sp;
if (UnwindPlanSP plan_sp = GetDebugFrameAugmentedUnwindPlan(target, thread))
return plan_sp;
return assembly_sp;
}
UnwindPlanSP FuncUnwinders::GetUnwindPlanFastUnwind(Target &target,
Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_fast_sp.get() || m_tried_unwind_fast)
return m_unwind_plan_fast_sp;
m_tried_unwind_fast = true;
UnwindAssemblySP assembly_profiler_sp(GetUnwindAssemblyProfiler(target));
if (assembly_profiler_sp) {
m_unwind_plan_fast_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!assembly_profiler_sp->GetFastUnwindPlan(m_range, thread,
*m_unwind_plan_fast_sp)) {
m_unwind_plan_fast_sp.reset();
}
}
return m_unwind_plan_fast_sp;
}
UnwindPlanSP FuncUnwinders::GetUnwindPlanArchitectureDefault(Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_arch_default_sp.get() || m_tried_unwind_arch_default)
return m_unwind_plan_arch_default_sp;
m_tried_unwind_arch_default = true;
Address current_pc;
ProcessSP process_sp(thread.CalculateProcess());
if (process_sp) {
ABI *abi = process_sp->GetABI().get();
if (abi) {
m_unwind_plan_arch_default_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!abi->CreateDefaultUnwindPlan(*m_unwind_plan_arch_default_sp)) {
m_unwind_plan_arch_default_sp.reset();
}
}
}
return m_unwind_plan_arch_default_sp;
}
UnwindPlanSP
FuncUnwinders::GetUnwindPlanArchitectureDefaultAtFunctionEntry(Thread &thread) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_unwind_plan_arch_default_at_func_entry_sp.get() ||
m_tried_unwind_arch_default_at_func_entry)
return m_unwind_plan_arch_default_at_func_entry_sp;
m_tried_unwind_arch_default_at_func_entry = true;
Address current_pc;
ProcessSP process_sp(thread.CalculateProcess());
if (process_sp) {
ABI *abi = process_sp->GetABI().get();
if (abi) {
m_unwind_plan_arch_default_at_func_entry_sp =
std::make_shared<UnwindPlan>(lldb::eRegisterKindGeneric);
if (!abi->CreateFunctionEntryUnwindPlan(
*m_unwind_plan_arch_default_at_func_entry_sp)) {
m_unwind_plan_arch_default_at_func_entry_sp.reset();
}
}
}
return m_unwind_plan_arch_default_at_func_entry_sp;
}
Address &FuncUnwinders::GetFirstNonPrologueInsn(Target &target) {
std::lock_guard<std::recursive_mutex> guard(m_mutex);
if (m_first_non_prologue_insn.IsValid())
return m_first_non_prologue_insn;
ExecutionContext exe_ctx(target.shared_from_this(), false);
UnwindAssemblySP assembly_profiler_sp(GetUnwindAssemblyProfiler(target));
if (assembly_profiler_sp)
assembly_profiler_sp->FirstNonPrologueInsn(m_range, exe_ctx,
m_first_non_prologue_insn);
return m_first_non_prologue_insn;
}
const Address &FuncUnwinders::GetFunctionStartAddress() const {
return m_range.GetBaseAddress();
}
lldb::UnwindAssemblySP
FuncUnwinders::GetUnwindAssemblyProfiler(Target &target) {
UnwindAssemblySP assembly_profiler_sp;
if (ArchSpec arch = m_unwind_table.GetArchitecture()) {
arch.MergeFrom(target.GetArchitecture());
assembly_profiler_sp = UnwindAssembly::FindPlugin(arch);
}
return assembly_profiler_sp;
}
Address FuncUnwinders::GetLSDAAddress(Target &target) {
Address lsda_addr;
UnwindPlanSP unwind_plan_sp = GetEHFrameUnwindPlan(target);
if (unwind_plan_sp.get() == nullptr) {
unwind_plan_sp = GetCompactUnwindUnwindPlan(target);
}
if (unwind_plan_sp.get() && unwind_plan_sp->GetLSDAAddress().IsValid()) {
lsda_addr = unwind_plan_sp->GetLSDAAddress();
}
return lsda_addr;
}
Address FuncUnwinders::GetPersonalityRoutinePtrAddress(Target &target) {
Address personality_addr;
UnwindPlanSP unwind_plan_sp = GetEHFrameUnwindPlan(target);
if (unwind_plan_sp.get() == nullptr) {
unwind_plan_sp = GetCompactUnwindUnwindPlan(target);
}
if (unwind_plan_sp.get() &&
unwind_plan_sp->GetPersonalityFunctionPtr().IsValid()) {
personality_addr = unwind_plan_sp->GetPersonalityFunctionPtr();
}
return personality_addr;
}
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