Add support for artificial tail call frames
This patch teaches lldb to detect when there are missing frames in a
backtrace due to a sequence of tail calls, and to fill in the backtrace
with artificial tail call frames when this happens. This is only done
when the execution history can be determined from the call graph and
from the return PC addresses of calls on the stack. Ambiguous sequences
of tail calls (e.g anything involving tail calls and recursion) are
detected and ignored.
Depends on D49887.
Differential Revision: https://reviews.llvm.org/D50478
llvm-svn: 343900
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index ea13399..4f9e726 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -3742,6 +3742,60 @@
return vars_added;
}
+/// Collect call graph edges present in a function DIE.
+static std::vector<lldb_private::CallEdge>
+CollectCallEdges(DWARFDIE function_die) {
+ // Check if the function has a supported call site-related attribute.
+ // TODO: In the future it may be worthwhile to support call_all_source_calls.
+ uint64_t has_call_edges =
+ function_die.GetAttributeValueAsUnsigned(DW_AT_call_all_calls, 0);
+ if (!has_call_edges)
+ return {};
+
+ Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
+ LLDB_LOG(log, "CollectCallEdges: Found call site info in {0}",
+ function_die.GetPubname());
+
+ // Scan the DIE for TAG_call_site entries.
+ // TODO: A recursive scan of all blocks in the subprogram is needed in order
+ // to be DWARF5-compliant. This may need to be done lazily to be performant.
+ // For now, assume that all entries are nested directly under the subprogram
+ // (this is the kind of DWARF LLVM produces) and parse them eagerly.
+ std::vector<CallEdge> call_edges;
+ for (DWARFDIE child = function_die.GetFirstChild(); child.IsValid();
+ child = child.GetSibling()) {
+ if (child.Tag() != DW_TAG_call_site)
+ continue;
+
+ // Extract DW_AT_call_origin (the call target's DIE).
+ DWARFDIE call_origin = child.GetReferencedDIE(DW_AT_call_origin);
+ if (!call_origin.IsValid()) {
+ LLDB_LOG(log, "CollectCallEdges: Invalid call origin in {0}",
+ function_die.GetPubname());
+ continue;
+ }
+
+ // Extract DW_AT_call_return_pc (the PC the call returns to) if it's
+ // available. It should only ever be unavailable for tail call edges, in
+ // which case use LLDB_INVALID_ADDRESS.
+ addr_t return_pc = child.GetAttributeValueAsAddress(DW_AT_call_return_pc,
+ LLDB_INVALID_ADDRESS);
+
+ LLDB_LOG(log, "CollectCallEdges: Found call origin: {0} (retn-PC: {1:x})",
+ call_origin.GetPubname(), return_pc);
+ call_edges.emplace_back(call_origin.GetMangledName(), return_pc);
+ }
+ return call_edges;
+}
+
+std::vector<lldb_private::CallEdge>
+SymbolFileDWARF::ParseCallEdgesInFunction(UserID func_id) {
+ DWARFDIE func_die = GetDIEFromUID(func_id.GetID());
+ if (func_die.IsValid())
+ return CollectCallEdges(func_die);
+ return {};
+}
+
//------------------------------------------------------------------
// PluginInterface protocol
//------------------------------------------------------------------
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index b3fa8b5..abf4e39 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -317,6 +317,9 @@
DIEInDeclContext(const lldb_private::CompilerDeclContext *parent_decl_ctx,
const DWARFDIE &die);
+ std::vector<lldb_private::CallEdge>
+ ParseCallEdgesInFunction(UserID func_id) override;
+
void Dump(lldb_private::Stream &s) override;
protected:
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
index 39c70d1..4c91686 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
@@ -1060,6 +1060,15 @@
return type_list.GetSize() - initial_size;
}
+std::vector<lldb_private::CallEdge>
+SymbolFileDWARFDebugMap::ParseCallEdgesInFunction(UserID func_id) {
+ uint32_t oso_idx = GetOSOIndexFromUserID(func_id.GetID());
+ SymbolFileDWARF *oso_dwarf = GetSymbolFileByOSOIndex(oso_idx);
+ if (oso_dwarf)
+ return oso_dwarf->ParseCallEdgesInFunction(func_id);
+ return {};
+}
+
TypeSP SymbolFileDWARFDebugMap::FindDefinitionTypeForDWARFDeclContext(
const DWARFDeclContext &die_decl_ctx) {
TypeSP type_sp;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
index 550f74a..4bb9af0 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.h
@@ -122,6 +122,8 @@
size_t GetTypes(lldb_private::SymbolContextScope *sc_scope,
uint32_t type_mask,
lldb_private::TypeList &type_list) override;
+ std::vector<lldb_private::CallEdge>
+ ParseCallEdgesInFunction(lldb_private::UserID func_id) override;
//------------------------------------------------------------------
// PluginInterface protocol