Improve LLDB's handling of non-local minidumps
Normally, LLDB is creating a high-fidelity representation of a live
process, including a list of modules and sections, with the
associated memory address ranges. In order to build the module and
section map LLDB tries to locate the local module image (object file)
and will parse it.
This does not work for postmortem debugging scenarios where the crash
dump (minidump in this case) was captured on a different machine.
Fortunately the minidump format encodes enough information about
each module's memory range to allow us to create placeholder modules.
This enables most LLDB functionality involving address-to-module
translations.
Also, we may want to completly disable the search for matching
local object files if we load minidumps unless we can prove that the
local image matches the one from the crash origin.
(not part of this change, see: llvm.org/pr35193)
Example: Identify the module from a stack frame PC:
Before:
thread #1, stop reason = Exception 0xc0000005 encountered at address 0x164d14
frame #0: 0x00164d14
frame #1: 0x00167c79
frame #2: 0x00167e6d
frame #3: 0x7510336a
frame #4: 0x77759882
frame #5: 0x77759855
After:
thread #1, stop reason = Exception 0xc0000005 encountered at address 0x164d14
frame #0: 0x00164d14 C:\Users\amccarth\Documents\Visual Studio 2013\Projects\fizzbuzz\Debug\fizzbuzz.exe
frame #1: 0x00167c79 C:\Users\amccarth\Documents\Visual Studio 2013\Projects\fizzbuzz\Debug\fizzbuzz.exe
frame #2: 0x00167e6d C:\Users\amccarth\Documents\Visual Studio 2013\Projects\fizzbuzz\Debug\fizzbuzz.exe
frame #3: 0x7510336a C:\Windows\SysWOW64\kernel32.dll
frame #4: 0x77759882 C:\Windows\SysWOW64\ntdll.dll
frame #5: 0x77759855 C:\Windows\SysWOW64\ntdll.dll
Example: target modules list
Before:
error: the target has no associated executable images
After:
[ 0] C:\Windows\System32\MSVCP120D.dll
[ 1] C:\Windows\SysWOW64\kernel32.dll
[ 2] C:\Users\amccarth\Documents\Visual Studio 2013\Projects\fizzbuzz\Debug\fizzbuzz.exe
[ 3] C:\Windows\System32\MSVCR120D.dll
[ 4] C:\Windows\SysWOW64\KERNELBASE.dll
[ 5] C:\Windows\SysWOW64\ntdll.dll
NOTE: the minidump format also includes the debug info GUID, so we can
fill-in the module UUID from it, but this part was excluded from this change
to keep the changes simple (the LLDB UUID is hardcoded to be either 16 or
20 bytes, while the CodeView GUIDs are normally 24 bytes)
Differential Revision: https://reviews.llvm.org/D45700
llvm-svn: 330302
diff --git a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
index d4d65c0..6bfe0e7 100644
--- a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
+++ b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
@@ -19,6 +19,7 @@
#include "lldb/Core/State.h"
#include "lldb/Target/DynamicLoader.h"
#include "lldb/Target/MemoryRegionInfo.h"
+#include "lldb/Target/SectionLoadList.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/UnixSignals.h"
#include "lldb/Utility/DataBufferLLVM.h"
@@ -31,9 +32,53 @@
// C includes
// C++ includes
+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 {
+public:
+ PlaceholderModule(const FileSpec &file_spec, const ArchSpec &arch) :
+ Module(file_spec, arch) {}
+
+ // 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);
+ }
+
+ ObjectFile *GetObjectFile() override { return nullptr; }
+
+ SectionList *GetSectionList() override {
+ return Module::GetUnifiedSectionList();
+ }
+};
+
ConstString ProcessMinidump::GetPluginNameStatic() {
static ConstString g_name("minidump");
return g_name;
@@ -281,7 +326,18 @@
Status error;
lldb::ModuleSP module_sp = GetTarget().GetSharedModule(module_spec, &error);
if (!module_sp || error.Fail()) {
- continue;
+ // We failed to locate a matching local object file. Fortunately,
+ // the minidump format encodes enough information about each module's
+ // memory range to allow us to create placeholder modules.
+ //
+ // This enables most LLDB functionality involving address-to-module
+ // translations (ex. identifing the module for a stack frame PC) and
+ // modules/sections commands (ex. target modules list, ...)
+ auto placeholder_module =
+ std::make_shared<PlaceholderModule>(file_spec, GetArchitecture());
+ placeholder_module->CreateImageSection(module, GetTarget());
+ module_sp = placeholder_module;
+ GetTarget().GetImages().Append(module_sp);
}
if (log) {