Restructure the minidump loading path and add early & explicit consistency checks

Corrupted minidumps was leading to unpredictable behavior.

This change adds explicit consistency checks for the minidump early on. The
checks are not comprehensive but they should catch obvious structural violations:

streams with type == 0
duplicate streams (same type)
overlapping streams
truncated minidumps

Another early check is to make sure we actually support the minidump architecture
instead of crashing at a random place deep inside LLDB.

Differential Revision: https://reviews.llvm.org/D49202

llvm-svn: 336918
diff --git a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
index 8149f95..b43f223 100644
--- a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
+++ b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
@@ -105,7 +105,7 @@
   if (!DataPtr)
     return nullptr;
 
-  assert(DataPtr->GetByteSize() == header_size);
+  lldbassert(DataPtr->GetByteSize() == header_size);
 
   // first, only try to parse the header, beacuse we need to be fast
   llvm::ArrayRef<uint8_t> HeaderBytes = DataPtr->GetData();
@@ -164,10 +164,29 @@
 Status ProcessMinidump::DoLoadCore() {
   Status error;
 
+  // Minidump parser initialization & consistency checks
+  error = m_minidump_parser.Initialize();
+  if (error.Fail())
+    return error;
+
+  // Do we support the minidump's architecture?
+  ArchSpec arch = GetArchitecture();
+  switch (arch.GetMachine()) {
+  case llvm::Triple::x86:
+  case llvm::Triple::x86_64:
+    // supported
+    break;
+
+  default:
+    error.SetErrorStringWithFormat("unsupported minidump architecture: %s",
+                                   arch.GetArchitectureName());
+    return error;
+  }
+
   m_thread_list = m_minidump_parser.GetThreads();
   m_active_exception = m_minidump_parser.GetExceptionStream();
   ReadModuleList();
-  GetTarget().SetArchitecture(GetArchitecture());
+  GetTarget().SetArchitecture(arch);
 
   llvm::Optional<lldb::pid_t> pid = m_minidump_parser.GetPid();
   if (!pid) {