Jason Molenda 2aa020f49b
[lldb][NFC] Module, ModuleSpec, GetSectionData use DataExtractorSP (#178347)
In a PR last month I changed the ObjectFile CreateInstance etc methods
to accept an optional DataExtractorSP instead of a DataBufferSP, and
retain the extractor in a shared pointer internally in all of the
ObjectFile subclasses. This is laying the groundwork for using a
VirtualDataExtractor for some Mach-O binaries on macOS, where the
segments of the binary are out-of-order in actual memory, and we add a
lookup table to make it appear that the TEXT segment is at offset 0 in
the Extractor, etc. Working on the actual implementation, I realized we
were still using DataBufferSP's in ModuleSpec and Module, as well as in
ObjectFile::GetModuleSpecifications.

I originally was making a much larger NFC change where I had all
ObjectFile subclasses operating on DataExtractors throughout their
implementation, as well as in the DWARF parser. It was a very large
patchset. Many subclasses start with their DataExtractor, then create
smaller DataExtractors for parts of the binary image - the string table,
the symbol table, etc., for processing.

After consideration and discussion with Jonas, we agreed that a
segment/section of a binary will never require a lookup table to access
the bytes within it, so I changed
VirtualDataExtractor::GetSubsetExtractorSP to (1) require that the
Subset be contained within a single lookup table entry, and (2) return a
simple DataExtractor bounded on that byte range. By doing this, I was
able to remove all of my very-invasive changes to the ObjectFile
subclass internals; it's only when they are operating on the entire
binary image that care is needed.

One pattern that subclasses like ObjectFileBreakpad use is to take an
ArrayRef of the DataBuffer for a binary, then create a StringRef of
that, then look for strings in it. With a VirtualDataExtractor and
out-of-order binary segments, with gaps between them, this allows us to
search the entire buffer looking for a string, and segfault when it gets
to an unmapped region of the buffer. I added a
VirtualDataExtractor::GetSubsetExtractorSP(0) which gets the largest
contiguous memory region starting at offset 0 for this use case, and I
added a comment about what was being done there because I know it is not
obvious, and people not working on macOS wouldn't be familiar with the
requirement. (when we have a ModuleSpec with a DataExtractor, any of the
ObjectFile subclasses get a shot at Creating, so they all have to be
able to iterate on these)

rdar://148939795
2026-01-29 15:36:40 -08:00

156 lines
4.6 KiB
C++

//===-- ObjectFileMinidump.cpp --------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "ObjectFileMinidump.h"
#include "MinidumpFileBuilder.h"
#include "lldb/Core/ModuleSpec.h"
#include "lldb/Core/PluginManager.h"
#include "lldb/Core/Section.h"
#include "lldb/Target/Process.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "llvm/Support/FileSystem.h"
using namespace lldb;
using namespace lldb_private;
LLDB_PLUGIN_DEFINE(ObjectFileMinidump)
void ObjectFileMinidump::Initialize() {
PluginManager::RegisterPlugin(
GetPluginNameStatic(), GetPluginDescriptionStatic(), CreateInstance,
CreateMemoryInstance, GetModuleSpecifications, SaveCore);
}
void ObjectFileMinidump::Terminate() {
PluginManager::UnregisterPlugin(CreateInstance);
}
ObjectFile *ObjectFileMinidump::CreateInstance(
const lldb::ModuleSP &module_sp, lldb::DataExtractorSP extractor_sp,
lldb::offset_t data_offset, const lldb_private::FileSpec *file,
lldb::offset_t offset, lldb::offset_t length) {
return nullptr;
}
ObjectFile *ObjectFileMinidump::CreateMemoryInstance(
const lldb::ModuleSP &module_sp, WritableDataBufferSP data_sp,
const ProcessSP &process_sp, lldb::addr_t header_addr) {
return nullptr;
}
size_t ObjectFileMinidump::GetModuleSpecifications(
const lldb_private::FileSpec &file, lldb::DataExtractorSP &extractor_sp,
lldb::offset_t data_offset, lldb::offset_t file_offset,
lldb::offset_t length, lldb_private::ModuleSpecList &specs) {
specs.Clear();
return 0;
}
struct DumpFailRemoveHolder {
DumpFailRemoveHolder(MinidumpFileBuilder &builder) : m_builder(builder) {}
~DumpFailRemoveHolder() {
if (!m_success)
m_builder.DeleteFile();
}
void SetSuccess() { m_success = true; }
private:
MinidumpFileBuilder &m_builder;
bool m_success = false;
};
bool ObjectFileMinidump::SaveCore(const lldb::ProcessSP &process_sp,
lldb_private::SaveCoreOptions &options,
lldb_private::Status &error) {
// Output file and process_sp are both checked in PluginManager::SaveCore.
assert(options.GetOutputFile().has_value());
assert(process_sp);
// Minidump defaults to stacks only.
if (options.GetStyle() == SaveCoreStyle::eSaveCoreUnspecified)
options.SetStyle(SaveCoreStyle::eSaveCoreStackOnly);
llvm::Expected<lldb::FileUP> maybe_core_file = FileSystem::Instance().Open(
options.GetOutputFile().value(),
File::eOpenOptionWriteOnly | File::eOpenOptionCanCreate);
if (!maybe_core_file) {
error = Status::FromError(maybe_core_file.takeError());
return false;
}
MinidumpFileBuilder builder(std::move(maybe_core_file.get()), process_sp,
options);
DumpFailRemoveHolder request(builder);
Log *log = GetLog(LLDBLog::Object);
error = builder.AddHeaderAndCalculateDirectories();
if (error.Fail()) {
LLDB_LOGF(log, "AddHeaderAndCalculateDirectories failed: %s",
error.AsCString());
return false;
};
error = builder.AddSystemInfo();
if (error.Fail()) {
LLDB_LOGF(log, "AddSystemInfo failed: %s", error.AsCString());
return false;
}
error = builder.AddModuleList();
if (error.Fail()) {
LLDB_LOGF(log, "AddModuleList failed: %s", error.AsCString());
return false;
}
error = builder.AddMiscInfo();
if (error.Fail()) {
LLDB_LOGF(log, "AddMiscInfo failed: %s", error.AsCString());
return false;
}
error = builder.AddThreadList();
if (error.Fail()) {
LLDB_LOGF(log, "AddThreadList failed: %s", error.AsCString());
return false;
}
error = builder.AddLinuxFileStreams();
if (error.Fail()) {
LLDB_LOGF(log, "AddLinuxFileStreams failed: %s", error.AsCString());
return false;
}
// Add any exceptions but only if there are any in any threads.
error = builder.AddExceptions();
if (error.Fail()) {
LLDB_LOGF(log, "AddExceptions failed: %s", error.AsCString());
return false;
}
// Note: add memory HAS to be the last thing we do. It can overflow into 64b
// land and many RVA's only support 32b
error = builder.AddMemoryList();
if (error.Fail()) {
LLDB_LOGF(log, "AddMemoryList failed: %s", error.AsCString());
return false;
}
error = builder.DumpFile();
if (error.Fail()) {
LLDB_LOGF(log, "DumpFile failed: %s", error.AsCString());
return false;
}
request.SetSuccess();
return true;
}