https://github.com/da-viper created https://github.com/llvm/llvm-project/pull/178695
The mold linker adds a function symbol to the symbol table (.symtab) for every shared library exported function. So if we try to step into a library, lldb will fail because the symbol at the address is not a trampline function. Example: ```cpp lib.c int lib_add(int a, int b); ``` when we link the library to an executable, mold will create the normal trampoline functions in the .plt section but add an extra symbol in symbol table `lib_add$plt`. I cannot think of a way to add another symbol in the trampoline's file address without linking with mold. Is there a way to write a test for this ? >From 8ef6eac983b5f31ddb75825180e1bd056f1a19d9 Mon Sep 17 00:00:00 2001 From: Ebuka Ezike <[email protected]> Date: Thu, 29 Jan 2026 16:17:05 +0000 Subject: [PATCH] [lldb] Improve trampoline function detection The mold linker adds a function symbol to the symbol table (.symtab) for every shared library exported function. So if we try to step into a library, lldb will fail because the symbol at the address is not a trampline function. Example: ```cpp lib.c int lib_add(int a, int b); ``` when we link the library to an executable, mold will create the normal trampoline functions in the .plt section but add an extra symbol in symbol table `lib_add$plt`. This patch adds a new method Module::FindSymbolsContainingFileAddress() to find symbols of a specific type that contain a given file address. --- lldb/include/lldb/Core/Module.h | 4 +++ lldb/source/Core/Module.cpp | 17 ++++++++++++ .../POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp | 27 +++++++++++++++++-- 3 files changed, 46 insertions(+), 2 deletions(-) diff --git a/lldb/include/lldb/Core/Module.h b/lldb/include/lldb/Core/Module.h index 643b9a5c3bf54..87d828fb41eed 100644 --- a/lldb/include/lldb/Core/Module.h +++ b/lldb/include/lldb/Core/Module.h @@ -265,6 +265,10 @@ class Module : public std::enable_shared_from_this<Module>, lldb::SymbolType symbol_type, SymbolContextList &sc_list); + void FindSymbolsContainingFileAddress(const Address &addr, + lldb::SymbolType symbol_type, + SymbolContextList &sc_list); + void FindSymbolsMatchingRegExAndType( const RegularExpression ®ex, lldb::SymbolType symbol_type, SymbolContextList &sc_list, diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp index 486af1a053344..436c4ce027d84 100644 --- a/lldb/source/Core/Module.cpp +++ b/lldb/source/Core/Module.cpp @@ -1316,6 +1316,23 @@ void Module::FindSymbolsWithNameAndType(ConstString name, } } +void Module::FindSymbolsContainingFileAddress(const Address &addr, + lldb::SymbolType symbol_type, + SymbolContextList &sc_list) { + if (Symtab *symtab = GetSymtab()) { + std::vector<uint32_t> symbol_indexes; + symtab->ForEachSymbolContainingFileAddress( + addr.GetFileAddress(), [&, symbol_type](Symbol *match_sym) { + if (const lldb::SymbolType curr_type = match_sym->GetType(); + curr_type == lldb::eSymbolTypeAny || curr_type == symbol_type) { + symbol_indexes.push_back(symtab->GetIndexForSymbol(match_sym)); + } + return true; + }); + SymbolIndicesToSymbolContextList(symtab, symbol_indexes, sc_list); + } +} + void Module::FindSymbolsMatchingRegExAndType( const RegularExpression ®ex, SymbolType symbol_type, SymbolContextList &sc_list, Mangled::NamePreference mangling_preference) { diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp index 6705ac139f0fb..8802b4b7cd27b 100644 --- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp +++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp @@ -540,11 +540,34 @@ DynamicLoaderPOSIXDYLD::GetStepThroughTrampolinePlan(Thread &thread, StackFrame *frame = thread.GetStackFrameAtIndex(0).get(); const SymbolContext &context = frame->GetSymbolContext(eSymbolContextSymbol); - const Symbol *sym = context.symbol; - if (sym == nullptr || !sym->IsTrampoline()) + Symbol *sym = context.symbol; + if (sym == nullptr) return thread_plan_sp; + if (!sym->IsTrampoline()) { + if (sym->GetType() != lldb::eSymbolTypeCode) + return thread_plan_sp; + + SymbolContextList addr_ctx_list; + context.module_sp->FindSymbolsContainingFileAddress( + context.GetFunctionOrSymbolAddress(), eSymbolTypeTrampoline, + addr_ctx_list); + if (addr_ctx_list.IsEmpty()) + return thread_plan_sp; + + for (const auto &sym_ctx : addr_ctx_list.SymbolContexts()) { + if (sym_ctx.symbol != nullptr) { + sym = sym_ctx.symbol; + break; + } + } + + // may not find a match + if (sym == nullptr) + return thread_plan_sp; + } + ConstString sym_name = sym->GetMangled().GetName(Mangled::ePreferMangled); if (!sym_name) return thread_plan_sp; _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
