Ensure oat checksum determinism across hosts and devices.

For Cloud Compilation, we need to enable hosts to generate a boot image
that has exactly the same checksum as generated on device. In other
words, we need to make the oat checksum deterministic across hosts and
devices.

To achieve that, when writing the oat header, the non-deterministic
fields are padded to their length limits and excluded from the oat
checksum computation.

Bug: 372868052
Test: m test-art-host-gtest
Test: Generate a boot image on host. See the checksum being identical to
  the one on device.
Change-Id: I9f73a28b349b673c25909b61a0c7ae8cf883c014

1 files changed, 25 insertions, 2 deletions

diff --git a/dex2oat/linker/oat_writer.h b/dex2oat/linker/oat_writer.h
index 5a775fa517..4f50b1a39c 100644
--- a/dex2oat/linker/oat_writer.h
+++ b/dex2oat/linker/oat_writer.h
@@ -70,6 +70,29 @@ enum class CopyOption {
   kOnlyIfCompressed
 };
 
+class OatKeyValueStore {
+ public:
+  // Puts a key value pair whose key is in `OatHeader::kNonDeterministicFieldsAndLengths`.
+  bool PutNonDeterministic(const std::string& k,
+                           const std::string& v,
+                           bool allow_truncation = false);
+
+  // Puts a key value pair whose key is in `OatHeader::kDeterministicFields`.
+  void Put(const std::string& k, const std::string& v);
+
+  // Puts a key value pair whose key is in `OatHeader::kDeterministicFields`.
+  void Put(const std::string& k, bool v);
+
+  // Makes sure calls with `const char*` falls into the overload for `std::string`, not the one for
+  // `bool`.
+  void Put(const std::string& k, const char* v) { Put(k, std::string(v)); }
+
+ private:
+  SafeMap<std::string, std::string> map_;
+
+  friend class OatWriter;
+};
+
 // OatHeader         variable length with count of D OatDexFiles
 //
 // TypeLookupTable[0] one descriptor to class def index hash table for each OatDexFile.
@@ -167,7 +190,7 @@ class OatWriter {
   // Start writing .rodata, including supporting data structures for dex files.
   bool StartRoData(const std::vector<const DexFile*>& dex_files,
                    OutputStream* oat_rodata,
-                   SafeMap<std::string, std::string>* key_value_store);
+                   OatKeyValueStore* key_value_store);
   // Initialize the writer with the given parameters.
   void Initialize(const CompilerDriver* compiler_driver,
                   const VerificationResults* verification_results,
@@ -291,7 +314,7 @@ class OatWriter {
   void WriteVerifierDeps(verifier::VerifierDeps* verifier_deps,
                          /*out*/std::vector<uint8_t>* buffer);
 
-  size_t InitOatHeader(uint32_t num_dex_files, SafeMap<std::string, std::string>* key_value_store);
+  size_t InitOatHeader(uint32_t num_dex_files, OatKeyValueStore* key_value_store);
   size_t InitClassOffsets(size_t offset);
   size_t InitOatClasses(size_t offset);
   size_t InitOatMaps(size_t offset);