UUID: Add support for arbitrary-sized module IDs

Summary:
The data structure is optimized for the case where the UUID size is <=
20 bytes (standard length emitted by the GNU linkers), but larger sizes
are also possible.

I've modified the string conversion function to support the new sizes as
well. For standard UUIDs it maintains the traditional formatting
(4-2-2-2-6). If a UUID is shorter, we just cut this sequence short, and
for longer UUIDs it will just repeat the last 6-byte block as long as
necessary.

I've also modified ObjectFileELF to take advantage of the new UUIDs and
avoid manually padding the UUID to 16 bytes. While there, I also made
sure the computed UUID does not depend on host endianness.

Reviewers: clayborg, lemo, sas, davide, espindola

Subscribers: emaste, arichardson, lldb-commits

Differential Revision: https://reviews.llvm.org/D48633

llvm-svn: 335963

1 files changed, 17 insertions, 17 deletions

diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index de7b391a3b4..8701908378f 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -730,16 +730,17 @@ size_t ObjectFileELF::GetModuleSpecifications(
                     data.GetDataStart(), data.GetByteSize());
               }
             }
+            using u32le = llvm::support::ulittle32_t;
             if (gnu_debuglink_crc) {
               // Use 4 bytes of crc from the .gnu_debuglink section.
-              uint32_t uuidt[4] = {gnu_debuglink_crc, 0, 0, 0};
-              uuid = UUID::fromData(uuidt, sizeof(uuidt));
+              u32le data(gnu_debuglink_crc);
+              uuid = UUID::fromData(&data, sizeof(data));
             } else if (core_notes_crc) {
               // Use 8 bytes - first 4 bytes for *magic* prefix, mainly to make
               // it look different form .gnu_debuglink crc followed by 4 bytes
               // of note segments crc.
-              uint32_t uuidt[4] = {g_core_uuid_magic, core_notes_crc, 0, 0};
-              uuid = UUID::fromData(uuidt, sizeof(uuidt));
+              u32le data[] = {u32le(g_core_uuid_magic), u32le(core_notes_crc)};
+              uuid = UUID::fromData(data, sizeof(data));
             }
           }
 
@@ -909,6 +910,7 @@ bool ObjectFileELF::GetUUID(lldb_private::UUID *uuid) {
   if (!ParseSectionHeaders() && GetType() != ObjectFile::eTypeCoreFile)
     return false;
 
+  using u32le = llvm::support::ulittle32_t;
   if (m_uuid.IsValid()) {
     // We have the full build id uuid.
     *uuid = m_uuid;
@@ -925,8 +927,8 @@ bool ObjectFileELF::GetUUID(lldb_private::UUID *uuid) {
       // Use 8 bytes - first 4 bytes for *magic* prefix, mainly to make it look
       // different form .gnu_debuglink crc - followed by 4 bytes of note
       // segments crc.
-      uint32_t uuidt[4] = {g_core_uuid_magic, core_notes_crc, 0, 0};
-      m_uuid = UUID::fromData(uuidt, sizeof(uuidt));
+      u32le data[] = {u32le(g_core_uuid_magic), u32le(core_notes_crc)};
+      m_uuid = UUID::fromData(data, sizeof(data));
     }
   } else {
     if (!m_gnu_debuglink_crc)
@@ -934,8 +936,8 @@ bool ObjectFileELF::GetUUID(lldb_private::UUID *uuid) {
           calc_gnu_debuglink_crc32(m_data.GetDataStart(), m_data.GetByteSize());
     if (m_gnu_debuglink_crc) {
       // Use 4 bytes of crc from the .gnu_debuglink section.
-      uint32_t uuidt[4] = {m_gnu_debuglink_crc, 0, 0, 0};
-      m_uuid = UUID::fromData(uuidt, sizeof(uuidt));
+      u32le data(m_gnu_debuglink_crc);
+      m_uuid = UUID::fromData(&data, sizeof(data));
     }
   }
 
@@ -1273,18 +1275,16 @@ ObjectFileELF::RefineModuleDetailsFromNote(lldb_private::DataExtractor &data,
         // Only bother processing this if we don't already have the uuid set.
         if (!uuid.IsValid()) {
           // 16 bytes is UUID|MD5, 20 bytes is SHA1. Other linkers may produce a
-          // build-id of a different
-          // length. Accept it as long as it's at least 4 bytes as it will be
-          // better than our own crc32.
-          if (note.n_descsz >= 4 && note.n_descsz <= 20) {
-            uint8_t uuidbuf[20];
-            if (data.GetU8(&offset, &uuidbuf, note.n_descsz) == nullptr) {
+          // build-id of a different length. Accept it as long as it's at least
+          // 4 bytes as it will be better than our own crc32.
+          if (note.n_descsz >= 4) {
+            if (const uint8_t *buf = data.PeekData(offset, note.n_descsz)) {
+              // Save the build id as the UUID for the module.
+              uuid = UUID::fromData(buf, note.n_descsz);
+            } else {
               error.SetErrorString("failed to read GNU_BUILD_ID note payload");
               return error;
             }
-
-            // Save the build id as the UUID for the module.
-            uuid = UUID::fromData(uuidbuf, note.n_descsz);
           }
         }
         break;