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[lldb/DWARF] Use DW_AT_call_pc to determine artificial frame address 

lldb currently guesses the address to use when creating an artificial
frame (i.e., a frame constructed by determining the sequence of (tail)
calls which must have happened).

Guessing the address creates problems -- use the actual address provided
by the DW_AT_call_pc attribute instead.

Depends on D76336.

rdar://60307600

Differential Revision: https://reviews.llvm.org/D76337
This commit is contained in:
Vedant Kumar 2020-03-17 17:59:08 -07:00
parent f7052da6db
commit 6905394d15
5 changed files with 95 additions and 41 deletions
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25
lldb/include/lldb/Symbol/Function.h
View File

@ -284,19 +284,33 @@ public:
/// Like \ref GetReturnPCAddress, but returns an unresolved file address.
lldb::addr_t GetUnresolvedReturnPCAddress() const { return return_pc; }
/// Get the load PC address of the call instruction (or LLDB_INVALID_ADDRESS).
lldb::addr_t GetCallInstPC(Function &caller, Target &target) const;
/// Get the call site parameters available at this call edge.
llvm::ArrayRef<CallSiteParameter> GetCallSiteParameters() const {
return parameters;
}
protected:
CallEdge(lldb::addr_t return_pc, CallSiteParameterArray &&parameters)
: return_pc(return_pc), parameters(std::move(parameters)) {}
CallEdge(lldb::addr_t return_pc, lldb::addr_t call_inst_pc,
CallSiteParameterArray &&parameters)
: return_pc(return_pc), call_inst_pc(call_inst_pc),
parameters(std::move(parameters)) {}
/// Helper that finds the load address of \p unresolved_pc, a file address
/// which refers to an instruction within \p caller.
static lldb::addr_t GetLoadAddress(lldb::addr_t unresolved_pc,
Function &caller, Target &target);
/// An invalid address if this is a tail call. Otherwise, the return PC for
/// the call. Note that this is a file address which must be resolved.
lldb::addr_t return_pc;
/// The address of the call instruction. Usually an invalid address, unless
/// this is a tail call.
lldb::addr_t call_inst_pc;
CallSiteParameterArray parameters;
};
@ -308,8 +322,8 @@ public:
/// Construct a call edge using a symbol name to identify the callee, and a
/// return PC within the calling function to identify a specific call site.
DirectCallEdge(const char *symbol_name, lldb::addr_t return_pc,
CallSiteParameterArray &&parameters)
: CallEdge(return_pc, std::move(parameters)) {
lldb::addr_t call_inst_pc, CallSiteParameterArray &&parameters)
: CallEdge(return_pc, call_inst_pc, std::move(parameters)) {
lazy_callee.symbol_name = symbol_name;
}
@ -339,8 +353,9 @@ public:
/// Construct a call edge using a DWARFExpression to identify the callee, and
/// a return PC within the calling function to identify a specific call site.
IndirectCallEdge(DWARFExpression call_target, lldb::addr_t return_pc,
lldb::addr_t call_inst_pc,
CallSiteParameterArray &&parameters)
: CallEdge(return_pc, std::move(parameters)),
: CallEdge(return_pc, call_inst_pc, std::move(parameters)),
call_target(std::move(call_target)) {}
Function *GetCallee(ModuleList &images, ExecutionContext &exe_ctx) override;

23
lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
View File

@ -3737,6 +3737,7 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
llvm::Optional<DWARFDIE> call_origin;
llvm::Optional<DWARFExpression> call_target;
addr_t return_pc = LLDB_INVALID_ADDRESS;
addr_t call_inst_pc = LLDB_INVALID_ADDRESS;
DWARFAttributes attributes;
const size_t num_attributes = child.GetAttributes(attributes);
@ -3765,6 +3766,12 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
if (attr == DW_AT_call_return_pc)
return_pc = form_value.Address();
// Extract DW_AT_call_pc (the PC at the call/branch instruction). It
// should only ever be unavailable for non-tail calls, in which case use
// LLDB_INVALID_ADDRESS.
if (attr == DW_AT_call_pc)
call_inst_pc = form_value.Address();
// Extract DW_AT_call_target (the location of the address of the indirect
// call).
if (attr == DW_AT_call_target) {
@ -3787,10 +3794,11 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
continue;
}
// Adjust the return PC. It needs to be fixed up if the main executable
// Adjust any PC forms. It needs to be fixed up if the main executable
// contains a debug map (i.e. pointers to object files), because we need a
// file address relative to the executable's text section.
return_pc = FixupAddress(return_pc);
call_inst_pc = FixupAddress(call_inst_pc);
// Extract call site parameters.
CallSiteParameterArray parameters =
@ -3798,10 +3806,13 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
std::unique_ptr<CallEdge> edge;
if (call_origin) {
LLDB_LOG(log, "CollectCallEdges: Found call origin: {0} (retn-PC: {1:x})",
call_origin->GetPubname(), return_pc);
LLDB_LOG(log,
"CollectCallEdges: Found call origin: {0} (retn-PC: {1:x}) "
"(call-PC: {2:x})",
call_origin->GetPubname(), return_pc, call_inst_pc);
edge = std::make_unique<DirectCallEdge>(call_origin->GetMangledName(),
return_pc, std::move(parameters));
return_pc, call_inst_pc,
std::move(parameters));
} else {
if (log) {
StreamString call_target_desc;
@ -3810,8 +3821,8 @@ SymbolFileDWARF::CollectCallEdges(ModuleSP module, DWARFDIE function_die) {
LLDB_LOG(log, "CollectCallEdges: Found indirect call target: {0}",
call_target_desc.GetString());
}
edge = std::make_unique<IndirectCallEdge>(*call_target, return_pc,
std::move(parameters));
edge = std::make_unique<IndirectCallEdge>(
*call_target, return_pc, call_inst_pc, std::move(parameters));
}
if (log && parameters.size()) {

23
lldb/source/Symbol/Function.cpp
View File

@ -120,27 +120,36 @@ size_t InlineFunctionInfo::MemorySize() const {
/// @name Call site related structures
/// @{
lldb::addr_t CallEdge::GetReturnPCAddress(Function &caller,
Target &target) const {
lldb::addr_t CallEdge::GetLoadAddress(lldb::addr_t unresolved_pc,
Function &caller, Target &target) {
Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
const Address &caller_start_addr = caller.GetAddressRange().GetBaseAddress();
ModuleSP caller_module_sp = caller_start_addr.GetModule();
if (!caller_module_sp) {
LLDB_LOG(log, "GetReturnPCAddress: cannot get Module for caller");
LLDB_LOG(log, "GetLoadAddress: cannot get Module for caller");
return LLDB_INVALID_ADDRESS;
}
SectionList *section_list = caller_module_sp->GetSectionList();
if (!section_list) {
LLDB_LOG(log, "GetReturnPCAddress: cannot get SectionList for Module");
LLDB_LOG(log, "GetLoadAddress: cannot get SectionList for Module");
return LLDB_INVALID_ADDRESS;
}
Address return_pc_addr = Address(return_pc, section_list);
lldb::addr_t ret_addr = return_pc_addr.GetLoadAddress(&target);
return ret_addr;
Address the_addr = Address(unresolved_pc, section_list);
lldb::addr_t load_addr = the_addr.GetLoadAddress(&target);
return load_addr;
}
lldb::addr_t CallEdge::GetReturnPCAddress(Function &caller,
Target &target) const {
return GetLoadAddress(return_pc, caller, target);
}
lldb::addr_t CallEdge::GetCallInstPC(Function &caller, Target &target) const {
return GetLoadAddress(call_inst_pc, caller, target);
}
void DirectCallEdge::ParseSymbolFileAndResolve(ModuleList &images) {

44
lldb/source/Target/StackFrameList.cpp
View File

@ -236,13 +236,17 @@ void StackFrameList::GetOnlyConcreteFramesUpTo(uint32_t end_idx,
m_frames.resize(num_frames);
}
/// A sequence of calls that comprise some portion of a backtrace. Each frame
/// is represented as a pair of a callee (Function *) and an address within the
/// callee.
using CallSequence = std::vector<std::pair<Function *, addr_t>>;
/// Find the unique path through the call graph from \p begin (with return PC
/// \p return_pc) to \p end. On success this path is stored into \p path, and
/// on failure \p path is unchanged.
static void FindInterveningFrames(Function &begin, Function &end,
ExecutionContext &exe_ctx, Target &target,
addr_t return_pc,
std::vector<Function *> &path,
addr_t return_pc, CallSequence &path,
ModuleList &images, Log *log) {
LLDB_LOG(log, "Finding frames between {0} and {1}, retn-pc={2:x}",
begin.GetDisplayName(), end.GetDisplayName(), return_pc);
@ -275,24 +279,27 @@ static void FindInterveningFrames(Function &begin, Function &end,
// Fully explore the set of functions reachable from the first edge via tail
// calls in order to detect ambiguous executions.
struct DFS {
std::vector<Function *> active_path = {};
std::vector<Function *> solution_path = {};
CallSequence active_path = {};
CallSequence solution_path = {};
llvm::SmallPtrSet<Function *, 2> visited_nodes = {};
bool ambiguous = false;
Function *end;
ModuleList &images;
Target &target;
ExecutionContext &context;
DFS(Function *end, ModuleList &images, ExecutionContext &context)
: end(end), images(images), context(context) {}
DFS(Function *end, ModuleList &images, Target &target,
ExecutionContext &context)
: end(end), images(images), target(target), context(context) {}
void search(Function &first_callee, std::vector<Function *> &path) {
dfs(first_callee);
void search(CallEdge &first_edge, Function &first_callee,
CallSequence &path) {
dfs(first_edge, first_callee);
if (!ambiguous)
path = std::move(solution_path);
}
void dfs(Function &callee) {
void dfs(CallEdge &current_edge, Function &callee) {
// Found a path to the target function.
if (&callee == end) {
if (solution_path.empty())
@ -312,13 +319,16 @@ static void FindInterveningFrames(Function &begin, Function &end,
}
// Search the calls made from this callee.
active_path.push_back(&callee);
active_path.emplace_back(&callee, LLDB_INVALID_ADDRESS);
for (const auto &edge : callee.GetTailCallingEdges()) {
Function *next_callee = edge->GetCallee(images, context);
if (!next_callee)
continue;
dfs(*next_callee);
addr_t tail_call_pc = edge->GetCallInstPC(callee, target);
active_path.back().second = tail_call_pc;
dfs(*edge, *next_callee);
if (ambiguous)
return;
}
@ -326,7 +336,7 @@ static void FindInterveningFrames(Function &begin, Function &end,
}
};
DFS(&end, images, exe_ctx).search(*first_callee, path);
DFS(&end, images, target, exe_ctx).search(*first_edge, *first_callee, path);
}
/// Given that \p next_frame will be appended to the frame list, synthesize
@ -379,7 +389,7 @@ void StackFrameList::SynthesizeTailCallFrames(StackFrame &next_frame) {
// Try to find the unique sequence of (tail) calls which led from next_frame
// to prev_frame.
std::vector<Function *> path;
CallSequence path;
addr_t return_pc = next_reg_ctx_sp->GetPC();
Target &target = *target_sp.get();
ModuleList &images = next_frame.CalculateTarget()->GetImages();
@ -389,13 +399,13 @@ void StackFrameList::SynthesizeTailCallFrames(StackFrame &next_frame) {
path, images, log);
// Push synthetic tail call frames.
for (Function *callee : llvm::reverse(path)) {
for (auto calleeInfo : llvm::reverse(path)) {
Function *callee = calleeInfo.first;
uint32_t frame_idx = m_frames.size();
uint32_t concrete_frame_idx = next_frame.GetConcreteFrameIndex();
addr_t cfa = LLDB_INVALID_ADDRESS;
bool cfa_is_valid = false;
addr_t pc =
callee->GetAddressRange().GetBaseAddress().GetLoadAddress(&target);
addr_t pc = calleeInfo.second;
constexpr bool behaves_like_zeroth_frame = false;
SymbolContext sc;
callee->CalculateSymbolContext(&sc);
@ -404,7 +414,7 @@ void StackFrameList::SynthesizeTailCallFrames(StackFrame &next_frame) {
cfa_is_valid, pc, StackFrame::Kind::Artificial,
behaves_like_zeroth_frame, &sc);
m_frames.push_back(synth_frame);
LLDB_LOG(log, "Pushed frame {0}", callee->GetDisplayName());
LLDB_LOG(log, "Pushed frame {0} at {1:x}", callee->GetDisplayName(), pc);
}
// If any frames were created, adjust next_frame's index.

21
lldb/test/API/functionalities/tail_call_frames/unambiguous_sequence/main.cpp
View File

@ -3,19 +3,28 @@ volatile int x;
void __attribute__((noinline)) sink() {
x++; //% self.filecheck("bt", "main.cpp", "-implicit-check-not=artificial")
// CHECK: frame #0: 0x{{[0-9a-f]+}} a.out`sink() at main.cpp:[[@LINE-1]]:4 [opt]
// CHECK-NEXT: frame #1: 0x{{[0-9a-f]+}} a.out`func3{{.*}} [opt] [artificial]
// CHECK-NEXT: frame #2: 0x{{[0-9a-f]+}} a.out`func2{{.*}} [opt]
// CHECK-NEXT: frame #3: 0x{{[0-9a-f]+}} a.out`func1{{.*}} [opt] [artificial]
// CHECK-NEXT: frame #1: 0x{{[0-9a-f]+}} a.out`func3() at main.cpp:14:3 [opt] [artificial]
// CHECK-NEXT: frame #2: 0x{{[0-9a-f]+}} a.out`func2() {{.*}} [opt]
// CHECK-NEXT: frame #3: 0x{{[0-9a-f]+}} a.out`func1() at main.cpp:23:3 [opt] [artificial]
// CHECK-NEXT: frame #4: 0x{{[0-9a-f]+}} a.out`main{{.*}} [opt]
}
void __attribute__((noinline)) func3() { sink(); /* tail */ }
void __attribute__((noinline)) func3() {
x++;
sink(); /* tail */
}
void __attribute__((disable_tail_calls, noinline)) func2() { func3(); /* regular */ }
void __attribute__((disable_tail_calls, noinline)) func2() {
func3(); /* regular */
}
void __attribute__((noinline)) func1() { func2(); /* tail */ }
void __attribute__((noinline)) func1() {
x++;
func2(); /* tail */
}
int __attribute__((disable_tail_calls)) main() {
// DEBUG: self.runCmd("log enable lldb step -f /tmp/lldbstep.log")
func1(); /* regular */
return 0;
}