[Lldb-commits] [lldb] Fix loading UUIDs from ELF headers. (PR #117028)

[Greg Clayton via lldb-commits]

https://github.com/clayborg created https://github.com/llvm/llvm-project/pull/117028

A previous patch added the ability to load UUID from ELF headers using the program header and finding PT_NOTE entries. The fix would attempt to read the data for the PT_NOTE from memory, but it didn't slide the address so it ended up only working for the main executable if it wasn't moved in memory. This patch slides the address and adds logging.

>From 37eccb509ea6468879cf530c6952aab7adec4001 Mon Sep 17 00:00:00 2001
From: Greg Clayton <clayborg at gmail.com>
Date: Wed, 20 Nov 2024 10:55:12 -0800
Subject: [PATCH] Fix loading UUIDs from ELF headers.

A previous patch added the ability to load UUID from ELF headers using the program header and finding PT_NOTE entries. The fix would attempt to read the data for the PT_NOTE from memory, but it didn't slide the address so it ended up only working for the main executable if it wasn't moved in memory. This patch slides the address and adds logging.
---
 .../Process/elf-core/ProcessElfCore.cpp       | 20 ++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
index 7955594bf5d94c..e58c06b9bd333c 100644
--- a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
+++ b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
@@ -224,7 +224,7 @@ Status ProcessElfCore::DoLoadCore() {
   ArchSpec core_arch(m_core_module_sp->GetArchitecture());
   target_arch.MergeFrom(core_arch);
   GetTarget().SetArchitecture(target_arch);
- 
+
   SetUnixSignals(UnixSignals::Create(GetArchitecture()));
 
   // Ensure we found at least one thread that was stopped on a signal.
@@ -276,8 +276,13 @@ Status ProcessElfCore::DoLoadCore() {
 }
 
 void ProcessElfCore::UpdateBuildIdForNTFileEntries() {
+  Log *log = GetLog(LLDBLog::Process);
   for (NT_FILE_Entry &entry : m_nt_file_entries) {
     entry.uuid = FindBuidIdInCoreMemory(entry.start);
+    if (log && entry.uuid.IsValid())
+      LLDB_LOGF(log, "%s found UUID @ %16.16" PRIx64 ": %s \"%s\"",
+                __FUNCTION__, entry.start, entry.uuid.GetAsString().c_str(),
+                entry.path.c_str());
   }
 }
 
@@ -875,7 +880,7 @@ llvm::Error ProcessElfCore::parseOpenBSDNotes(llvm::ArrayRef<CoreNote> notes) {
 /// - NT_SIGINFO - Information about the signal that terminated the process
 /// - NT_AUXV - Process auxiliary vector
 /// - NT_FILE - Files mapped into memory
-/// 
+///
 /// Additionally, for each thread in the process the core file will contain at
 /// least the NT_PRSTATUS note, containing the thread id and general purpose
 /// registers. It may include additional notes for other register sets (floating
@@ -1034,15 +1039,20 @@ UUID ProcessElfCore::FindBuidIdInCoreMemory(lldb::addr_t address) {
     std::vector<uint8_t> note_bytes;
     note_bytes.resize(program_header.p_memsz);
 
-    byte_read = ReadMemory(program_header.p_vaddr, note_bytes.data(),
-                           program_header.p_memsz, error);
+    // We need to slide the address of the p_vaddr as these values don't get
+    // relocated in memory.
+    const lldb::addr_t vaddr = program_header.p_vaddr + address;
+    byte_read = ReadMemory(vaddr, note_bytes.data(), program_header.p_memsz,
+                           error);
     if (byte_read != program_header.p_memsz)
       continue;
     DataExtractor segment_data(note_bytes.data(), note_bytes.size(),
                                GetByteOrder(), addr_size);
     auto notes_or_error = parseSegment(segment_data);
-    if (!notes_or_error)
+    if (!notes_or_error) {
+      llvm::consumeError(notes_or_error.takeError());
       return invalid_uuid;
+    }
     for (const CoreNote &note : *notes_or_error) {
       if (note.info.n_namesz == 4 &&
           note.info.n_type == llvm::ELF::NT_GNU_BUILD_ID &&