UserspaceEmulator: Make symbolication work when .text isn't the first

... segment

This happens with binaries build with Clang or with a custom linker
script. If this is the case, offsets should be calculated not from the
base address of `.text`, but from the first section loaded for the
library.

This commit moves all UserspaceEmulator symbolication into a common
helper function and fixes a FIXME.

Userland/DevTools/UserspaceEmulator/Emulator.cpp

@@ -276,19 +276,10 @@ void Emulator::handle_repl()
     auto saved_eip = m_cpu.eip();
     m_cpu.save_base_eip();
     auto insn = X86::Instruction::from_stream(m_cpu, true, true);
-    // FIXME: This does not respect inlineing
+    // FIXME: This does not respect inlining
     //        another way of getting the current function is at need
-    if (auto const* region = load_library_from_address(m_cpu.base_eip())) {
-        auto separator_index = region->name().find(":").value();
-        String lib_name = region->name().substring(0, separator_index);
-        String lib_path = lib_name;
-        if (region->name().contains(".so"))
-            lib_path = String::formatted("/usr/lib/{}", lib_path);
-
-        auto it = m_dynamic_library_cache.find(lib_path);
-        auto& elf = it->value.debug_info->elf();
-        String symbol = elf.symbolicate(m_cpu.base_eip() - region->base());
-        outln("[{}]: {}", lib_name, symbol);
+    if (auto symbol = symbol_at(m_cpu.base_eip()); symbol.has_value()) {
+        outln("[{}]: {}", symbol->lib_name, symbol->symbol);
     }
 
     outln("==> {}", create_instruction_line(m_cpu.base_eip(), insn));
@@ -405,11 +396,11 @@ MmapRegion const* Emulator::load_library_from_address(FlatPtr address)
     auto const* region = find_text_region(address);
     if (!region)
         return {};
-    auto separator_index = region->name().find(':');
-    if (!separator_index.has_value())
+
+    String lib_name = region->lib_name();
+    if (lib_name.is_null())
         return {};
 
-    String lib_name = region->name().substring(0, separator_index.value());
     String lib_path = lib_name;
     if (region->name().contains(".so"))
         lib_path = String::formatted("/usr/lib/{}", lib_path);
@@ -426,30 +417,49 @@ MmapRegion const* Emulator::load_library_from_address(FlatPtr address)
     return region;
 }
 
-String Emulator::create_backtrace_line(FlatPtr address)
+MmapRegion const* Emulator::first_region_for_object(StringView name)
 {
-    auto minimal = String::formatted("=={{{}}}==    {:p}", getpid(), (void*)address);
-    auto const* region = load_library_from_address(address);
-    if (!region)
-        return minimal;
-    // FIXME: This is redundant
-    auto separator_index = region->name().find(":").value();
-    String lib_name = region->name().substring(0, separator_index);
-    String lib_path = lib_name;
-    if (region->name().contains(".so"))
-        lib_path = String::formatted("/usr/lib/{}", lib_path);
+    MmapRegion* ret = nullptr;
+    mmu().for_each_region_of_type<MmapRegion>([&](auto& region) {
+        if (region.lib_name() == name) {
+            ret = &region;
+            return IterationDecision::Break;
+        }
+        return IterationDecision::Continue;
+    });
+    return ret;
+}
 
-    auto it = m_dynamic_library_cache.find(lib_path);
-    auto& elf = it->value.debug_info->elf();
-    String symbol = elf.symbolicate(address - region->base());
+// FIXME: This disregards function inlining.
+Optional<Emulator::SymbolInfo> Emulator::symbol_at(FlatPtr address)
+{
+    auto const* address_region = load_library_from_address(address);
+    if (!address_region)
+        return {};
+    auto lib_name = address_region->lib_name();
+    auto const* first_region = (lib_name.is_null() || lib_name.is_empty()) ? address_region : first_region_for_object(lib_name);
+    VERIFY(first_region);
+    auto lib_path = lib_name.contains(".so"sv) ? String::formatted("/usr/lib/{}", lib_name) : lib_name;
 
-    auto line_without_source_info = String::formatted("=={{{}}}==    {:p}  [{}]: {}", getpid(), (void*)address, lib_name, symbol);
+    auto it = m_dynamic_library_cache.find(lib_path);
+    auto const& elf = it->value.debug_info->elf();
+    auto symbol = elf.symbolicate(address - first_region->base());
 
-    auto source_position = it->value.debug_info->get_source_position(address - region->base());
-    if (source_position.has_value())
-        return String::formatted("=={{{}}}==    {:p}  [{}]: {} (\e[34;1m{}\e[0m:{})", getpid(), (void*)address, lib_name, symbol, LexicalPath::basename(source_position.value().file_path), source_position.value().line_number);
+    auto source_position = it->value.debug_info->get_source_position(address - first_region->base());
+    return { { lib_name, symbol, source_position } };
+}
 
-    return line_without_source_info;
+String Emulator::create_backtrace_line(FlatPtr address)
+{
+    auto maybe_symbol = symbol_at(address);
+    if (!maybe_symbol.has_value()) {
+        return String::formatted("=={{{}}}==    {:p}", getpid(), address);
+    } else if (!maybe_symbol->source_position.has_value()) {
+        return String::formatted("=={{{}}}==    {:p}  [{}]: {}", getpid(), address, maybe_symbol->lib_name, maybe_symbol->symbol);
+    } else {
+        auto const& source_position = maybe_symbol->source_position.value();
+        return String::formatted("=={{{}}}==    {:p}  [{}]: {} (\e[34;1m{}\e[0m:{})", getpid(), address, maybe_symbol->lib_name, maybe_symbol->symbol, LexicalPath::basename(source_position.file_path), source_position.line_number);
+    }
 }
 
 void Emulator::dump_backtrace(Vector<FlatPtr> const& backtrace)
@@ -486,26 +496,11 @@ void Emulator::emit_profile_event(AK::OutputStream& output, StringView event_nam
 
 String Emulator::create_instruction_line(FlatPtr address, X86::Instruction insn)
 {
-    auto minimal = String::formatted("{:p}: {}", (void*)address, insn.to_string(address));
-    auto const* region = load_library_from_address(address);
-    if (!region)
-        return minimal;
-    // FIXME: This is redundant
-    auto separator_index = region->name().find(":").value();
-    String lib_name = region->name().substring(0, separator_index);
-    String lib_path = lib_name;
-    if (region->name().contains(".so"))
-        lib_path = String::formatted("/usr/lib/{}", lib_path);
-
-    auto it = m_dynamic_library_cache.find(lib_path);
-    auto& elf = it->value.debug_info->elf();
-    String symbol = elf.symbolicate(address - region->base());
-
-    auto source_position = it->value.debug_info->get_source_position(address - region->base());
-    if (!source_position.has_value())
-        return minimal;
-
-    return String::formatted("{:p}: {} \e[34;1m{}\e[0m:{}", (void*)address, insn.to_string(address), LexicalPath::basename(source_position.value().file_path), source_position.value().line_number);
+    auto symbol = symbol_at(address);
+    if (!symbol.has_value() || !symbol->source_position.has_value())
+        return String::formatted("{:p}: {}", address, insn.to_string(address));
+    else
+        return String::formatted("{:p}: {} \e[34;1m{}\e[0m:{}", address, insn.to_string(address), LexicalPath::basename(symbol->source_position->file_path), symbol->source_position.value().line_number);
 }
 
 static void emulator_signal_handler(int signum)

Userland/DevTools/UserspaceEmulator/Emulator.h

@@ -79,6 +79,14 @@ public:
             pause();
     }
 
+    struct SymbolInfo {
+        String lib_name;
+        String symbol;
+        Optional<Debug::DebugInfo::SourcePosition> source_position;
+    };
+
+    Optional<SymbolInfo> symbol_at(FlatPtr address);
+
     void dump_regions() const;
 
 private:
@@ -211,7 +219,7 @@ private:
     void dispatch_one_pending_signal();
     MmapRegion const* find_text_region(FlatPtr address);
     MmapRegion const* load_library_from_address(FlatPtr address);
-    String symbol_at(FlatPtr address);
+    MmapRegion const* first_region_for_object(StringView name);
     String create_backtrace_line(FlatPtr address);
     String create_instruction_line(FlatPtr address, X86::Instruction insn);
 

Userland/DevTools/UserspaceEmulator/MmapRegion.h

@@ -52,6 +52,15 @@ public:
     void set_malloc_metadata(Badge<MallocTracer>, NonnullOwnPtr<MallocRegionMetadata> metadata) { m_malloc_metadata = move(metadata); }
 
     const String& name() const { return m_name; }
+    String lib_name() const
+    {
+        if (m_name.contains("Loader.so"sv))
+            return "Loader.so";
+        auto const maybe_separator = m_name.find(':');
+        if (!maybe_separator.has_value())
+            return {};
+        return m_name.substring(0, *maybe_separator);
+    }
     void set_name(String name) { m_name = move(name); }
 
 private:

Userland/DevTools/UserspaceEmulator/SoftMMU.h

@@ -71,6 +71,16 @@ public:
         }
     }
 
+    template<typename Type, typename Callback>
+    void for_each_region_of_type(Callback callback)
+    {
+        return for_each_region([callback](auto& region) {
+            if (!is<Type>(region))
+                return IterationDecision::Continue;
+            return callback(static_cast<Type&>(region));
+        });
+    }
+
     template<typename Callback>
     void for_regions_in(X86::LogicalAddress address, size_t size, Callback callback)
     {