minidump: Add ability to attach (breakpad) symbol files to placeholder modules

This re-commits r354263, which was because it uncovered with handling of
modules with empty (zero) UUIDs. This would cause us to treat two
modules as intentical even though they were not. This caused an assert
in PlaceholderObjectFile::SetLoadAddress to fire, because we were trying
to load the module twice even though it was designed to be only loaded
at a specific address. (The same problem also existed with the previous
implementation, but it had no asserts to warn us about this.) These
issues have now been fixed in r356896.

windows bot. The issue there was that ObjectFilePECOFF vended its base
address through the incorrect interface. SymbolFilePDB depended on that,
which lead to assertion failures when SymbolFilePDB was attempting to
use the placeholder object files as a base. This has been fixed in
r354258

The original commit message was:

The reason this wasn't working was that ProcessMinidump was creating odd
object-file-less modules, and SymbolFileBreakpad required the module to
have an associated object file because it needed to get its base
address.

This fixes that by introducing a PlaceholderObjectFile to serve as a
dummy object file. The general idea for this is taken from D55142, but
I've reworked it a bit to avoid the need for the PlaceholderModule
class. Now that we have an object file, our modules are sufficiently
similar to regular modules that we can use the regular Module class
almost out of the box -- the only thing I needed to tweak was the
Module::CreateModuleFromObjectFile functon to set the module's FileSpec
in addition to it's architecture. This wasn't needed for ObjectFileJIT
(the other user of CreateModuleFromObjectFile), but it shouldn't hurt it
either, and the change seems like a straightforward extension of this
function.

Reviewers: clayborg, lemo, amccarth

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D57751

llvm-svn: 357060

lldb/include/lldb/Core/Module.h

@@ -163,15 +163,19 @@ public:
     lldb::ModuleSP module_sp(new Module());
     module_sp->m_objfile_sp =
         std::make_shared<ObjFilePlugin>(module_sp, std::forward<Args>(args)...);
+    module_sp->m_did_load_objfile.store(true, std::memory_order_relaxed);
 
-    // Once we get the object file, update our module with the object file's
-    // architecture since it might differ in vendor/os if some parts were
-    // unknown.
-    if (ArchSpec arch = module_sp->m_objfile_sp->GetArchitecture()) {
-      module_sp->m_arch = arch;
-      return module_sp;
-    }
+    // Once we get the object file, set module ArchSpec to the one we get from
+    // the object file. If the object file does not have an architecture, we
+    // consider the creation a failure.
+    ArchSpec arch = module_sp->m_objfile_sp->GetArchitecture();
+    if (!arch)
       return nullptr;
+    module_sp->m_arch = arch;
+
+    // Also copy the object file's FileSpec.
+    module_sp->m_file = module_sp->m_objfile_sp->GetFileSpec();
+    return module_sp;
   }
 
   //------------------------------------------------------------------

lldb/lit/Minidump/Inputs/linux-x86_64.syms

@@ -0,0 +1,4 @@
+MODULE Linux x86_64 3B285CE327C387C262DB788BF5A4078B0 linux-x86_64
+INFO CODE_ID E35C283BC327C28762DB788BF5A4078BE2351448
+FUNC 3d0 18 0 crash()
+FUNC 3f0 10 0 _start

lldb/lit/Minidump/breakpad-symbols.test

@@ -0,0 +1,26 @@
+# Test that we can attach breakpad symbols to the "placeholder" modules created
+# for minidump files.
+#
+# The minidump input for this test taken from packages/Python/lldbsuite/test/functionalities/postmortem/minidump-new
+
+# RUN: %lldb -c %S/Inputs/linux-x86_64.dmp \
+# RUN:   -o "target symbols add -s /tmp/test/linux-x86_64 %S/Inputs/linux-x86_64.syms" \
+# RUN:   -s %s -o exit | FileCheck %s
+
+image list
+# CHECK-LABEL: image list
+# CHECK: E35C283B-C327-C287-62DB-788BF5A4078B-E2351448 0x0000000000400000 /tmp/test/linux-x86_64
+
+image dump symtab /tmp/test/linux-x86_64
+# CHECK-LABEL: image dump symtab /tmp/test/linux-x86_64
+# CHECK: Symtab, file = /tmp/test/linux-x86_64, num_symbols = 2:
+# CHECK: [    0]      0   X Code            0x00000000004003d0 0x00000000004003d0 0x0000000000000018 0x00000000 crash()
+# CHECK: [    1]      0   X Code            0x00000000004003f0 0x00000000004003f0 0x0000000000000010 0x00000000 _start
+
+image lookup -a 0x4003f3
+# CHECK-LABEL: image lookup -a 0x4003f3
+# CHECK: Summary: linux-x86_64`_start + 3
+
+image dump objfile /tmp/test/linux-x86_64
+# CHECK-LABEL: image dump objfile /tmp/test/linux-x86_64
+# CHECK: Placeholder object file for /tmp/test/linux-x86_64 loaded at [0x400000-0x401000)

lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp

@@ -41,51 +41,81 @@ using namespace lldb;
 using namespace lldb_private;
 using namespace minidump;
 
-//------------------------------------------------------------------
-/// A placeholder module used for minidumps, where the original
-/// object files may not be available (so we can't parse the object
-/// files to extract the set of sections/segments)
-///
-/// This placeholder module has a single synthetic section (.module_image)
-/// which represents the module memory range covering the whole module.
-//------------------------------------------------------------------
-class PlaceholderModule : public Module {
+namespace {
+
+/// A minimal ObjectFile implementation providing a dummy object file for the
+/// cases when the real module binary is not available. This allows the module
+/// to show up in "image list" and symbols to be added to it.
+class PlaceholderObjectFile : public ObjectFile {
 public:
-  PlaceholderModule(const ModuleSpec &module_spec) :
-    Module(module_spec.GetFileSpec(), module_spec.GetArchitecture()) {
-    if (module_spec.GetUUID().IsValid())
-      SetUUID(module_spec.GetUUID());
+  PlaceholderObjectFile(const lldb::ModuleSP &module_sp,
+                        const ModuleSpec &module_spec, lldb::offset_t base,
+                        lldb::offset_t size)
+      : ObjectFile(module_sp, &module_spec.GetFileSpec(), /*file_offset*/ 0,
+                   /*length*/ 0, /*data_sp*/ nullptr, /*data_offset*/ 0),
+        m_arch(module_spec.GetArchitecture()), m_uuid(module_spec.GetUUID()),
+        m_base(base), m_size(size) {
+    m_symtab_up = llvm::make_unique<Symtab>(this);
   }
 
-  // Creates a synthetic module section covering the whole module image (and
-  // sets the section load address as well)
-  void CreateImageSection(const MinidumpModule *module, Target& target) {
-    const ConstString section_name(".module_image");
-    lldb::SectionSP section_sp(new Section(
-        shared_from_this(),     // Module to which this section belongs.
-        nullptr,                // ObjectFile
-        0,                      // Section ID.
-        section_name,           // Section name.
-        eSectionTypeContainer,  // Section type.
-        module->base_of_image,  // VM address.
-        module->size_of_image,  // VM size in bytes of this section.
-        0,                      // Offset of this section in the file.
-        module->size_of_image,  // Size of the section as found in the file.
-        12,                     // Alignment of the section (log2)
-        0,                      // Flags for this section.
-        1));                    // Number of host bytes per target byte
-    section_sp->SetPermissions(ePermissionsExecutable | ePermissionsReadable);
-    GetSectionList()->AddSection(section_sp);
+  ConstString GetPluginName() override { return ConstString("placeholder"); }
+  uint32_t GetPluginVersion() override { return 1; }
+  bool ParseHeader() override { return true; }
+  Type CalculateType() override { return eTypeUnknown; }
+  Strata CalculateStrata() override { return eStrataUnknown; }
+  uint32_t GetDependentModules(FileSpecList &file_list) override { return 0; }
+  bool IsExecutable() const override { return false; }
+  ArchSpec GetArchitecture() override { return m_arch; }
+  UUID GetUUID() override { return m_uuid; }
+  Symtab *GetSymtab() override { return m_symtab_up.get(); }
+  bool IsStripped() override { return true; }
+  ByteOrder GetByteOrder() const override { return m_arch.GetByteOrder(); }
+
+  uint32_t GetAddressByteSize() const override {
+    return m_arch.GetAddressByteSize();
+  }
+
+  Address GetBaseAddress() override {
+    return Address(m_sections_up->GetSectionAtIndex(0), 0);
+  }
+
+  void CreateSections(SectionList &unified_section_list) override {
+    m_sections_up = llvm::make_unique<SectionList>();
+    auto section_sp = std::make_shared<Section>(
+        GetModule(), this, /*sect_id*/ 0, ConstString(".module_image"),
+        eSectionTypeOther, m_base, m_size, /*file_offset*/ 0, /*file_size*/ 0,
+        /*log2align*/ 0, /*flags*/ 0);
+    section_sp->SetPermissions(ePermissionsReadable | ePermissionsExecutable);
+    m_sections_up->AddSection(section_sp);
+    unified_section_list.AddSection(std::move(section_sp));
+  }
+
+  bool SetLoadAddress(Target &target, addr_t value,
+                      bool value_is_offset) override {
+    assert(!value_is_offset);
+    assert(value == m_base);
+
+    // Create sections if they haven't been created already.
+    GetModule()->GetSectionList();
+    assert(m_sections_up->GetNumSections(0) == 1);
+
     target.GetSectionLoadList().SetSectionLoadAddress(
-        section_sp, module->base_of_image);
+        m_sections_up->GetSectionAtIndex(0), m_base);
+    return true;
   }
 
-ObjectFile *GetObjectFile() override { return nullptr; }
-
-  SectionList *GetSectionList() override {
-    return Module::GetUnifiedSectionList();
+  void Dump(Stream *s) override {
+    s->Format("Placeholder object file for {0} loaded at [{1:x}-{2:x})\n",
+              GetFileSpec(), m_base, m_base + m_size);
   }
+
+private:
+  ArchSpec m_arch;
+  UUID m_uuid;
+  lldb::offset_t m_base;
+  lldb::offset_t m_size;
 };
+} // namespace
 
 ConstString ProcessMinidump::GetPluginNameStatic() {
   static ConstString g_name("minidump");
@@ -348,6 +378,7 @@ void ProcessMinidump::ReadModuleList() {
     auto file_spec = FileSpec(name.getValue(), GetArchitecture().GetTriple());
     FileSystem::Instance().Resolve(file_spec);
     ModuleSpec module_spec(file_spec, uuid);
+    module_spec.GetArchitecture() = GetArchitecture();
     Status error;
     lldb::ModuleSP module_sp = GetTarget().GetSharedModule(module_spec, &error);
     if (!module_sp || error.Fail()) {
@@ -364,10 +395,8 @@ void ProcessMinidump::ReadModuleList() {
                     name.getValue().c_str());
       }
 
-      auto placeholder_module =
-          std::make_shared<PlaceholderModule>(module_spec);
-      placeholder_module->CreateImageSection(module, GetTarget());
-      module_sp = placeholder_module;
+      module_sp = Module::CreateModuleFromObjectFile<PlaceholderObjectFile>(
+          module_spec, module->base_of_image, module->size_of_image);
       GetTarget().GetImages().Append(module_sp);
     }