[Lldb-commits] [lldb] Read and store gnu build id from loaded core file (PR #92492)

[Pavel Labath via lldb-commits]

================
@@ -983,6 +1005,73 @@ llvm::Error ProcessElfCore::ParseThreadContextsFromNoteSegment(
   }
 }
 
+bool ProcessElfCore::IsElf(const lldb::addr_t address) {
+  uint8_t buf[4];
+  Status error;
+  size_t byte_read = ReadMemory(address, buf, 4, error);
+  if (byte_read != 4)
+    return false;
+  return elf::ELFHeader::MagicBytesMatch(buf);
+}
+
+std::optional<UUID> ProcessElfCore::FindNote(const lldb::addr_t address,
+                                             const uint32_t type) {
+  if (!IsElf(address))
+    return std::nullopt;
+  const uint32_t addr_size = GetAddressByteSize();
+  const lldb::offset_t ehdr_phoff_offset = ELFOFFSETOF(Ehdr, e_phoff);
+  const lldb::offset_t ehdr_phentsize_offset = ELFOFFSETOF(Ehdr, e_phentsize);
+  const lldb::offset_t ehdr_phnum_offset = ELFOFFSETOF(Ehdr, e_phnum);
+  const size_t elf_header_size = addr_size == 4 ? sizeof(llvm::ELF::Elf32_Ehdr)
+                                                : sizeof(llvm::ELF::Elf64_Ehdr);
+
+  unsigned char buf[4096];
+  Status error;
+  size_t byte_read = ReadMemory(address, buf, elf_header_size, error);
+  DataExtractor data(buf, 4096, GetByteOrder(), addr_size);
+  lldb::offset_t offset = ehdr_phoff_offset;
+  lldb::offset_t phoff = data.GetAddress(&offset);
+
+  offset = ehdr_phentsize_offset;
+  lldb::offset_t phentsize = data.GetU16(&offset);
+  offset = ehdr_phnum_offset;
+  lldb::offset_t phnum = data.GetU16(&offset);
+
+  Section_Note note;
+  const lldb::addr_t ph_addr = address + phoff;
+
+  for (unsigned int i = 0; i < phnum; ++i) {
+    byte_read = ReadMemory(ph_addr + i * phentsize, buf, phentsize, error);
+    if (byte_read != phentsize)
+      break;
+    offset = 0;
+    uint32_t p_type = data.GetU32(&offset);
+    if (p_type != llvm::ELF::PT_NOTE)
+      continue;
+    offset = ELFOFFSETOF(Phdr, p_vaddr);
+    lldb::addr_t p_vaddr = data.GetAddress(&offset);
+    offset = ELFOFFSETOF(Phdr, p_memsz);
+    lldb::addr_t p_memsz = data.GetAddress(&offset);
+
+    byte_read = ReadMemory(p_vaddr, buf, p_memsz, error);
+    if (byte_read != p_memsz)
+      continue;
+    offset = 0;
+    while (
+        offset < p_memsz &&
+        data.GetU32(&offset, &note, sizeof(Section_Note) / sizeof(uint32_t))) {
+      if (note.namesz == 4 && note.type == type) {
+        const char *name = data.GetCStr(&offset);
+        if (name && strcmp("GNU", name) == 0)
+          return UUID(
+              llvm::ArrayRef<uint8_t>(buf + offset, note.descsz /*byte size*/));
+      }
+      offset += note.namesz + note.descsz;
+    }
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labath wrote:

And `parseSegment` for this (despite the generic name, this is really for parsing note segments, maybe you could rename it while you're in here).

https://github.com/llvm/llvm-project/pull/92492