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

Summary:
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: 353677

1 files changed, 75 insertions, 43 deletions

diff --git a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
index ef94f47b4a4..80b73d6185e 100644
--- a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
+++ b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
@@ -41,51 +41,84 @@ 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());
-  }
-
-  // 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);
-    target.GetSectionLoadList().SetSectionLoadAddress(
-        section_sp, module->base_of_image);
+  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_ap = llvm::make_unique<Symtab>(this);
+  }
+
+  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; }
+  Symtab *GetSymtab() override { return m_symtab_ap.get(); }
+  bool IsStripped() override { return true; }
+  ByteOrder GetByteOrder() const override { return m_arch.GetByteOrder(); }
+
+  uint32_t GetAddressByteSize() const override {
+    return m_arch.GetAddressByteSize();
+  }
+
+  bool GetUUID(UUID *uuid) override {
+    *uuid = m_uuid;
+    return true;
+  }
+
+  Address GetBaseAddress() override {
+    return Address(m_sections_ap->GetSectionAtIndex(0), 0);
   }
 
-ObjectFile *GetObjectFile() override { return nullptr; }
+  void CreateSections(SectionList &unified_section_list) override {
+    m_sections_ap = 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);
+    m_sections_ap->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_ap->GetNumSections(0) == 1);
 
-  SectionList *GetSectionList() override {
-    return Module::GetUnifiedSectionList();
+    target.GetSectionLoadList().SetSectionLoadAddress(
+        m_sections_ap->GetSectionAtIndex(0), m_base);
+    return true;
   }
+
+  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");
@@ -357,6 +390,7 @@ 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()) {
@@ -373,10 +407,8 @@ 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);
     }