[lldb] Fix loading UUIDs from ELF headers. (llvm#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.

All processes map the ELF header + program headers + some program header
contents into memory. The program header for the `PT_NOTE` entries are
mapped, but the p_vaddr doesn't get relocated and is relative to the
load address of the ELF header. So we take a "p_vaddr" (file address)
and convert it into a load address in the process so we can load the
correct bytes that contain the `PT_NOTE` contents.

Author: clayborg

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 &&