commit ab40c1108330caee9a01317628a28dac4c5a8bf1
author Alexey Alexandrov <aalexand@google.com> Mon Sep 19 09:33:49 2016 -0700
committer Alexey Alexandrov <aalexand@google.com> Wed Oct 05 19:20:14 2016 -0700
tree 0e03c80a8a74cc4bed3f8dba8f238ce6ba2f6f0a
parent 2f61867045ffbd0c38a4ecec5f59632004f7efff

Generate SHA-1 build ID for host-generated *.oat files (1/2).

For host-generated *.oat files, generate a SHA-1 build ID based on the
file content and write it to .note.gnu.build-id ELF section.  This
should allow various developer tools like profilers correlate the data
captured for files like boot.oat on the device with the corresponding
known version of the file during an offline analysis.

Test: Verified that boot.oat contains the build ID section now (with
      this change and https://android-review.googlesource.com/#/c/275630
      applied)
Test: Added ElfWriterTest::CheckBuildIdPresent test.
Test: make test-art-host
Bug: 31292208
Change-Id: Ie5e89da2ef87e34c27c0237ab34ddc7d2dc0aa3b

compiler/elf_writer_quick.cc

diff --git a/compiler/elf_writer_quick.cc b/compiler/elf_writer_quick.cc
index 36cd232..0d6575c 100644
--- a/compiler/elf_writer_quick.cc
+++ b/compiler/elf_writer_quick.cc
@@ -16,6 +16,7 @@
 
 #include "elf_writer_quick.h"
 
+#include <openssl/sha.h>
 #include <unordered_map>
 #include <unordered_set>
 
@@ -126,6 +127,8 @@
   std::unique_ptr<DebugInfoTask> debug_info_task_;
   std::unique_ptr<ThreadPool> debug_info_thread_pool_;
 
+  void ComputeFileBuildId(uint8_t (*build_id)[ElfBuilder<ElfTypes>::kBuildIdLen]);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(ElfWriterQuick);
 };
 
@@ -167,6 +170,9 @@
 template <typename ElfTypes>
 void ElfWriterQuick<ElfTypes>::Start() {
   builder_->Start();
+  if (compiler_options_->GetGenerateBuildId()) {
+    builder_->WriteBuildIdSection();
+  }
 }
 
 template <typename ElfTypes>
@@ -275,11 +281,36 @@
 template <typename ElfTypes>
 bool ElfWriterQuick<ElfTypes>::End() {
   builder_->End();
-
+  if (compiler_options_->GetGenerateBuildId()) {
+    uint8_t build_id[ElfBuilder<ElfTypes>::kBuildIdLen];
+    ComputeFileBuildId(&build_id);
+    builder_->WriteBuildId(build_id);
+  }
   return builder_->Good();
 }
 
 template <typename ElfTypes>
+void ElfWriterQuick<ElfTypes>::ComputeFileBuildId(
+    uint8_t (*build_id)[ElfBuilder<ElfTypes>::kBuildIdLen]) {
+  constexpr int kBufSize = 8192;
+  std::vector<char> buffer(kBufSize);
+  int64_t offset = 0;
+  SHA_CTX ctx;
+  SHA1_Init(&ctx);
+  while (true) {
+    int64_t bytes_read = elf_file_->Read(buffer.data(), kBufSize, offset);
+    CHECK_GE(bytes_read, 0);
+    if (bytes_read == 0) {
+      // End of file.
+      break;
+    }
+    SHA1_Update(&ctx, buffer.data(), bytes_read);
+    offset += bytes_read;
+  }
+  SHA1_Final(*build_id, &ctx);
+}
+
+template <typename ElfTypes>
 OutputStream* ElfWriterQuick<ElfTypes>::GetStream() {
   return builder_->GetStream();
 }