DWARF parsing and writing support using LLVM (#2520)

This imports LLVM code for DWARF handling. That code has the
Apache 2 license like us. It's also the same code used to
emit DWARF in the common toolchain, so it seems like a safe choice.

This adds two passes: --dwarfdump which runs the same code LLVM
runs for llvm-dwarfdump. This shows we can parse it ok, and will
be useful for debugging. And --dwarfupdate writes out the DWARF
sections (unchanged from what we read, so it just roundtrips - for
updating we need #2515).

This puts LLVM in thirdparty which is added here.

All the LLVM code is behind USE_LLVM_DWARF, which is on
by default, but off in JS for now, as it increases code size by 20%.

This current approach imports the LLVM files directly. This is not
how they are intended to be used, so it required a bunch of
local changes - more than I expected actually, for the platform-specific
stuff. For now this seems to work, so it may be good enough, but
in the long term we may want to switch to linking against libllvm.
A downside to doing that is that binaryen users would need to
have an LLVM build, and even in the waterfall builds we'd have a
problem - while we ship LLVM there anyhow, we constantly update
it, which means that binaryen would need to be on latest llvm all
the time too (which otherwise, given DWARF is quite stable, we
might not need to constantly update).

An even larger issue is that as I did this work I learned about how
DWARF works in LLVM, and while the reading code is easy to
reuse, the writing code is trickier. The main code path is heavily
integrated with the MC layer, which we don't have - we might want
to create a "fake MC layer" for that, but it sounds hard. Instead,
there is the YAML path which is used mostly for testing, and which
can convert DWARF to and from YAML and from binary. Using
the non-YAML parts there, we can convert binary DWARF to
the YAML layer's nice Info data, then convert that to binary. This
works, however, this is not the path LLVM uses normally, and it
supports only some basic DWARF sections - I had to add ranges
support, in fact. So if we need more complex things, we may end
up needing to use the MC layer approach, or consider some other
DWARF library. However, hopefully that should not affect the core
binaryen code which just calls a library for DWARF stuff.

Helps #2400

1 files changed, 216 insertions, 0 deletions

diff --git a/third_party/llvm-project/include/llvm/Object/Minidump.h b/third_party/llvm-project/include/llvm/Object/Minidump.h
new file mode 100644
index 000000000..4429493af
--- /dev/null
+++ b/third_party/llvm-project/include/llvm/Object/Minidump.h
@@ -0,0 +1,216 @@
+//===- Minidump.h - Minidump object file implementation ---------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_MINIDUMP_H
+#define LLVM_OBJECT_MINIDUMP_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/iterator.h"
+#include "llvm/BinaryFormat/Minidump.h"
+#include "llvm/Object/Binary.h"
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+namespace object {
+
+/// A class providing access to the contents of a minidump file.
+class MinidumpFile : public Binary {
+public:
+  /// Construct a new MinidumpFile object from the given memory buffer. Returns
+  /// an error if this file cannot be identified as a minidump file, or if its
+  /// contents are badly corrupted (i.e. we cannot read the stream directory).
+  static Expected<std::unique_ptr<MinidumpFile>> create(MemoryBufferRef Source);
+
+  static bool classof(const Binary *B) { return B->isMinidump(); }
+
+  /// Returns the contents of the minidump header.
+  const minidump::Header &header() const { return Header; }
+
+  /// Returns the list of streams (stream directory entries) in this file.
+  ArrayRef<minidump::Directory> streams() const { return Streams; }
+
+  /// Returns the raw contents of the stream given by the directory entry.
+  ArrayRef<uint8_t> getRawStream(const minidump::Directory &Stream) const {
+    return getData().slice(Stream.Location.RVA, Stream.Location.DataSize);
+  }
+
+  /// Returns the raw contents of the stream of the given type, or None if the
+  /// file does not contain a stream of this type.
+  Optional<ArrayRef<uint8_t>> getRawStream(minidump::StreamType Type) const;
+
+  /// Returns the raw contents of an object given by the LocationDescriptor. An
+  /// error is returned if the descriptor points outside of the minidump file.
+  Expected<ArrayRef<uint8_t>>
+  getRawData(minidump::LocationDescriptor Desc) const {
+    return getDataSlice(getData(), Desc.RVA, Desc.DataSize);
+  }
+
+  /// Returns the minidump string at the given offset. An error is returned if
+  /// we fail to parse the string, or the string is invalid UTF16.
+  Expected<std::string> getString(size_t Offset) const;
+
+  /// Returns the contents of the SystemInfo stream, cast to the appropriate
+  /// type. An error is returned if the file does not contain this stream, or
+  /// the stream is smaller than the size of the SystemInfo structure. The
+  /// internal consistency of the stream is not checked in any way.
+  Expected<const minidump::SystemInfo &> getSystemInfo() const {
+    return getStream<minidump::SystemInfo>(minidump::StreamType::SystemInfo);
+  }
+
+  /// Returns the module list embedded in the ModuleList stream. An error is
+  /// returned if the file does not contain this stream, or if the stream is
+  /// not large enough to contain the number of modules declared in the stream
+  /// header. The consistency of the Module entries themselves is not checked in
+  /// any way.
+  Expected<ArrayRef<minidump::Module>> getModuleList() const {
+    return getListStream<minidump::Module>(minidump::StreamType::ModuleList);
+  }
+
+  /// Returns the thread list embedded in the ThreadList stream. An error is
+  /// returned if the file does not contain this stream, or if the stream is
+  /// not large enough to contain the number of threads declared in the stream
+  /// header. The consistency of the Thread entries themselves is not checked in
+  /// any way.
+  Expected<ArrayRef<minidump::Thread>> getThreadList() const {
+    return getListStream<minidump::Thread>(minidump::StreamType::ThreadList);
+  }
+
+  /// Returns the contents of the Exception stream.  An error is returned if the
+  /// file does not contain this stream, or the stream is smaller than the size
+  /// of the ExceptionStream structure.  The internal consistency of the stream
+  /// is not checked in any way.
+  Expected<const minidump::ExceptionStream &> getExceptionStream() const {
+    return getStream<minidump::ExceptionStream>(
+        minidump::StreamType::Exception);
+  }
+
+  /// Returns the list of descriptors embedded in the MemoryList stream. The
+  /// descriptors provide the content of interesting regions of memory at the
+  /// time the minidump was taken. An error is returned if the file does not
+  /// contain this stream, or if the stream is not large enough to contain the
+  /// number of memory descriptors declared in the stream header. The
+  /// consistency of the MemoryDescriptor entries themselves is not checked in
+  /// any way.
+  Expected<ArrayRef<minidump::MemoryDescriptor>> getMemoryList() const {
+    return getListStream<minidump::MemoryDescriptor>(
+        minidump::StreamType::MemoryList);
+  }
+
+  class MemoryInfoIterator
+      : public iterator_facade_base<MemoryInfoIterator,
+                                    std::forward_iterator_tag,
+                                    minidump::MemoryInfo> {
+  public:
+    MemoryInfoIterator(ArrayRef<uint8_t> Storage, size_t Stride)
+        : Storage(Storage), Stride(Stride) {
+      assert(Storage.size() % Stride == 0);
+    }
+
+    bool operator==(const MemoryInfoIterator &R) const {
+      return Storage.size() == R.Storage.size();
+    }
+
+    const minidump::MemoryInfo &operator*() const {
+      assert(Storage.size() >= sizeof(minidump::MemoryInfo));
+      return *reinterpret_cast<const minidump::MemoryInfo *>(Storage.data());
+    }
+
+    MemoryInfoIterator &operator++() {
+      Storage = Storage.drop_front(Stride);
+      return *this;
+    }
+
+  private:
+    ArrayRef<uint8_t> Storage;
+    size_t Stride;
+  };
+
+  /// Returns the list of descriptors embedded in the MemoryInfoList stream. The
+  /// descriptors provide properties (e.g. permissions) of interesting regions
+  /// of memory at the time the minidump was taken. An error is returned if the
+  /// file does not contain this stream, or if the stream is not large enough to
+  /// contain the number of memory descriptors declared in the stream header.
+  /// The consistency of the MemoryInfoList entries themselves is not checked
+  /// in any way.
+  Expected<iterator_range<MemoryInfoIterator>> getMemoryInfoList() const;
+
+private:
+  static Error createError(StringRef Str) {
+    return make_error<GenericBinaryError>(Str, object_error::parse_failed);
+  }
+
+  static Error createEOFError() {
+    return make_error<GenericBinaryError>("Unexpected EOF",
+                                          object_error::unexpected_eof);
+  }
+
+  /// Return a slice of the given data array, with bounds checking.
+  static Expected<ArrayRef<uint8_t>> getDataSlice(ArrayRef<uint8_t> Data,
+                                                  size_t Offset, size_t Size);
+
+  /// Return the slice of the given data array as an array of objects of the
+  /// given type. The function checks that the input array is large enough to
+  /// contain the correct number of objects of the given type.
+  template <typename T>
+  static Expected<ArrayRef<T>> getDataSliceAs(ArrayRef<uint8_t> Data,
+                                              size_t Offset, size_t Count);
+
+  MinidumpFile(MemoryBufferRef Source, const minidump::Header &Header,
+               ArrayRef<minidump::Directory> Streams,
+               DenseMap<minidump::StreamType, std::size_t> StreamMap)
+      : Binary(ID_Minidump, Source), Header(Header), Streams(Streams),
+        StreamMap(std::move(StreamMap)) {}
+
+  ArrayRef<uint8_t> getData() const {
+    return arrayRefFromStringRef(Data.getBuffer());
+  }
+
+  /// Return the stream of the given type, cast to the appropriate type. Checks
+  /// that the stream is large enough to hold an object of this type.
+  template <typename T>
+  Expected<const T &> getStream(minidump::StreamType Stream) const;
+
+  /// Return the contents of a stream which contains a list of fixed-size items,
+  /// prefixed by the list size.
+  template <typename T>
+  Expected<ArrayRef<T>> getListStream(minidump::StreamType Stream) const;
+
+  const minidump::Header &Header;
+  ArrayRef<minidump::Directory> Streams;
+  DenseMap<minidump::StreamType, std::size_t> StreamMap;
+};
+
+template <typename T>
+Expected<const T &> MinidumpFile::getStream(minidump::StreamType Type) const {
+  if (Optional<ArrayRef<uint8_t>> Stream = getRawStream(Type)) {
+    if (Stream->size() >= sizeof(T))
+      return *reinterpret_cast<const T *>(Stream->data());
+    return createEOFError();
+  }
+  return createError("No such stream");
+}
+
+template <typename T>
+Expected<ArrayRef<T>> MinidumpFile::getDataSliceAs(ArrayRef<uint8_t> Data,
+                                                   size_t Offset,
+                                                   size_t Count) {
+  // Check for overflow.
+  if (Count > std::numeric_limits<size_t>::max() / sizeof(T))
+    return createEOFError();
+  Expected<ArrayRef<uint8_t>> Slice =
+      getDataSlice(Data, Offset, sizeof(T) * Count);
+  if (!Slice)
+    return Slice.takeError();
+  return ArrayRef<T>(reinterpret_cast<const T *>(Slice->data()), Count);
+}
+
+} // end namespace object
+} // end namespace llvm
+
+#endif // LLVM_OBJECT_MINIDUMP_H