Object/Minidump: Add support for reading the ModuleList stream

Summary:
The ModuleList stream consists of an integer giving the number of
entries in the list, followed by the list itself. Each entry in the list
describes a module (dynamically loaded objects which were loaded in the
process when it crashed (or when the minidump was generated).

The code for reading the list is relatively straight-forward, with a
single gotcha. Some minidump writers are emitting padding after the
"count" field in order to align the subsequent list on 8 byte boundary
(this depends on how their ModuleList type was defined and the native
alignment of various types on their platform). Fortunately, the minidump
format contains enough redundancy (in the form of the stream length
field in the stream directory), which allows us to detect this situation
and correct it.

This patch just adds the ability to parse the stream. Code for
conversion to/from yaml will come in a follow-up patch.

Reviewers: zturner, amccarth, jhenderson, clayborg

Subscribers: jdoerfert, markmentovai, lldb-commits, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60121

llvm-svn: 357897

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/lib/Object/Minidump.cpp b/llvm/lib/Object/Minidump.cpp
index 1a22491ce3c..4b1abe52994 100644
--- a/llvm/lib/Object/Minidump.cpp
+++ b/llvm/lib/Object/Minidump.cpp
@@ -53,6 +53,27 @@ Expected<std::string> MinidumpFile::getString(size_t Offset) const {
   return Result;
 }
 
+Expected<ArrayRef<Module>> MinidumpFile::getModuleList() const {
+  auto OptionalStream = getRawStream(StreamType::ModuleList);
+  if (!OptionalStream)
+    return createError("No such stream");
+  auto ExpectedSize =
+      getDataSliceAs<support::ulittle32_t>(*OptionalStream, 0, 1);
+  if (!ExpectedSize)
+    return ExpectedSize.takeError();
+
+  size_t ListSize = ExpectedSize.get()[0];
+
+  size_t ListOffset = 4;
+  // Some producers insert additional padding bytes to align the module list to
+  // 8-byte boundary. Check for that by comparing the module list size with the
+  // overall stream size.
+  if (ListOffset + sizeof(Module) * ListSize < OptionalStream->size())
+    ListOffset = 8;
+
+  return getDataSliceAs<Module>(*OptionalStream, ListOffset, ListSize);
+}
+
 Expected<ArrayRef<uint8_t>>
 MinidumpFile::getDataSlice(ArrayRef<uint8_t> Data, size_t Offset, size_t Size) {
   // Check for overflow.