From cb9a7c22ee6789569e28dde073e6827761b4d003 Mon Sep 17 00:00:00 2001
From: Zequan Wu <zequanwu@google.com>
Date: Mon, 5 Jun 2023 15:07:06 -0400
Subject: [PATCH] [LLDB][PDB] Fix age field in UUID in PDB file.

There are two age fields in a PDB file. One from the PDB Stream and another one
from the DBI stream.

According to https://randomascii.wordpress.com/2011/11/11/source-indexing-is-underused-awesomeness/#comment-34328,
The age in DBI stream is used to against the binary's age. `Pdbstr.exe` is used
to only increment the age from PDB stream without changing the DBI age. I
also verified this by manually changing the DBI age of a PDB file and let
`windbg.exe` to load it. It shows the following logs before and after changing:

Before:
```
SYMSRV:  BYINDEX: 0xA
         c:\symbols*https://msdl.microsoft.com/download/symbols
         nlaapi.pdb
         D72AA69CD5ABE5D28C74FADB17DE3F8C1
SYMSRV:  PATH: c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
SYMSRV:  RESULT: 0x00000000
*** WARNING: Unable to verify checksum for NLAapi.dll
DBGHELP: NLAapi - public symbols
        c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
...
```

After:
```
SYMSRV:  BYINDEX: 0xA
         c:\symbols*https://msdl.microsoft.com/download/symbols
         nlaapi.pdb
         D72AA69CD5ABE5D28C74FADB17DE3F8C1
SYMSRV:  PATH: c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
SYMSRV:  RESULT: 0x00000000
DBGHELP: c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb - mismatched pdb
SYMSRV:  BYINDEX: 0xB
         c:\symbols*https://chromium-browser-symsrv.commondatastorage.googleapis.com
         nlaapi.pdb
         D72AA69CD5ABE5D28C74FADB17DE3F8C1
SYMSRV:  PATH: c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
SYMSRV:  RESULT: 0x00000000
DBGHELP: c:\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb - mismatched pdb
SYMSRV:  BYINDEX: 0xC
         c:\src\symbols*https://msdl.microsoft.com/download/symbols
         nlaapi.pdb
         D72AA69CD5ABE5D28C74FADB17DE3F8C1
SYMSRV:  PATH: c:\src\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
SYMSRV:  RESULT: 0x00000000
*** WARNING: Unable to verify checksum for NLAapi.dll
DBGHELP: NLAapi - public symbols
        c:\src\symbols\nlaapi.pdb\D72AA69CD5ABE5D28C74FADB17DE3F8C1\nlaapi.pdb
```

So, `windbg.exe` uses the DBI age to detect mismatched pdb, but it still loads
the pdb even if the age mismatched. Probably lldb should do the same and give
some warnings.

This fixes a bug that lldb can't load some windows system pdbs due to mismatched
uuid.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D152189
---
 .../source/Plugins/ObjectFile/PDB/ObjectFilePDB.cpp | 13 +++++++++----
 lldb/test/Shell/ObjectFile/PDB/object.test          |  4 ++--
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/lldb/source/Plugins/ObjectFile/PDB/ObjectFilePDB.cpp b/lldb/source/Plugins/ObjectFile/PDB/ObjectFilePDB.cpp
index c62a67fa29f9..a3b91fc37dac 100644
--- a/lldb/source/Plugins/ObjectFile/PDB/ObjectFilePDB.cpp
+++ b/lldb/source/Plugins/ObjectFile/PDB/ObjectFilePDB.cpp
@@ -27,10 +27,10 @@ using namespace llvm::codeview;
 
 LLDB_PLUGIN_DEFINE(ObjectFilePDB)
 
-static UUID GetPDBUUID(InfoStream &IS) {
+static UUID GetPDBUUID(InfoStream &IS, DbiStream &DS) {
   UUID::CvRecordPdb70 debug_info;
   memcpy(&debug_info.Uuid, IS.getGuid().Guid, sizeof(debug_info.Uuid));
-  debug_info.Age = IS.getAge();
+  debug_info.Age = DS.getAge();
   return UUID(debug_info);
 }
 
@@ -82,7 +82,12 @@ bool ObjectFilePDB::initPDBFile() {
     llvm::consumeError(info_stream.takeError());
     return false;
   }
-  m_uuid = GetPDBUUID(*info_stream);
+  auto dbi_stream = m_file_up->getPDBDbiStream();
+  if (!dbi_stream) {
+    llvm::consumeError(dbi_stream.takeError());
+    return false;
+  }
+  m_uuid = GetPDBUUID(*info_stream, *dbi_stream);
   return true;
 }
 
@@ -126,7 +131,7 @@ size_t ObjectFilePDB::GetModuleSpecifications(
   }
 
   lldb_private::UUID &uuid = module_spec.GetUUID();
-  uuid = GetPDBUUID(*info_stream);
+  uuid = GetPDBUUID(*info_stream, *dbi_stream);
 
   ArchSpec &module_arch = module_spec.GetArchitecture();
   switch (dbi_stream->getMachineType()) {
diff --git a/lldb/test/Shell/ObjectFile/PDB/object.test b/lldb/test/Shell/ObjectFile/PDB/object.test
index 35373d52a393..62564243f054 100644
--- a/lldb/test/Shell/ObjectFile/PDB/object.test
+++ b/lldb/test/Shell/ObjectFile/PDB/object.test
@@ -3,7 +3,7 @@
 
 # CHECK: Plugin name: pdb
 # CHECK: Architecture: x86_64-pc-windows-msvc
-# CHECK: UUID: 61AF583F-29A8-7A6C-4C4C-44205044422E-00000001
+# CHECK: UUID: 61AF583F-29A8-7A6C-4C4C-44205044422E-00000003
 # CHECK: Executable: false
 # CHECK: Stripped: false
 # CHECK: Type: debug info
@@ -52,7 +52,7 @@ PdbStream:
   Version:         VC70
 DbiStream:
   VerHeader:       V70
-  Age:             1
+  Age:             3
   BuildNumber:     36363
   PdbDllVersion:   0
   PdbDllRbld:      0
-- 
2.34.1