4 files changed, 65 insertions, 12 deletions
diff --git a/bootloader_message/bootloader_message.cpp b/bootloader_message/bootloader_message.cpp
index 9a5671843..b873d3dc3 100644
--- a/bootloader_message/bootloader_message.cpp
+++ b/bootloader_message/bootloader_message.cpp
@@ -176,6 +176,27 @@ bool write_bootloader_message(const std::vector<std::string>& options, std::stri
   return write_bootloader_message(boot, err);
 }
 
+bool update_bootloader_message(const std::vector<std::string>& options, std::string* err) {
+  bootloader_message boot;
+  if (!read_bootloader_message(&boot, err)) {
+    return false;
+  }
+
+  // Zero out the entire fields.
+  memset(boot.command, 0, sizeof(boot.command));
+  memset(boot.recovery, 0, sizeof(boot.recovery));
+
+  strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
+  strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
+  for (const auto& s : options) {
+    strlcat(boot.recovery, s.c_str(), sizeof(boot.recovery));
+    if (s.back() != '\n') {
+      strlcat(boot.recovery, "\n", sizeof(boot.recovery));
+    }
+  }
+  return write_bootloader_message(boot, err);
+}
+
 bool write_reboot_bootloader(std::string* err) {
   bootloader_message boot;
   if (!read_bootloader_message(&boot, err)) {
diff --git a/bootloader_message/include/bootloader_message/bootloader_message.h b/bootloader_message/include/bootloader_message/bootloader_message.h
index ec47facf6..bc5104ddf 100644
--- a/bootloader_message/include/bootloader_message/bootloader_message.h
+++ b/bootloader_message/include/bootloader_message/bootloader_message.h
@@ -194,9 +194,14 @@ bool write_bootloader_message(const bootloader_message& boot, std::string* err);
 bool write_bootloader_message_to(const bootloader_message& boot,
                                  const std::string& misc_blk_device, std::string* err);
 
-// Write bootloader message (boots into recovery with the options) to BCB.
+// Write bootloader message (boots into recovery with the options) to BCB. Will
+// set the command and recovery fields, and reset the rest.
 bool write_bootloader_message(const std::vector<std::string>& options, std::string* err);
 
+// Update bootloader message (boots into recovery with the options) to BCB. Will
+// only update the command and recovery fields.
+bool update_bootloader_message(const std::vector<std::string>& options, std::string* err);
+
 // Clear BCB.
 bool clear_bootloader_message(std::string* err);
 
diff --git a/recovery.cpp b/recovery.cpp
index 0fdc31cb4..0da3946bb 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -354,20 +354,21 @@ static std::vector<std::string> get_args(const int argc, char** const argv) {
   // bootloader control block. So the device will always boot into recovery to
   // finish the pending work, until finish_recovery() is called.
   std::vector<std::string> options(args.cbegin() + 1, args.cend());
-  if (!write_bootloader_message(options, &err)) {
-    LOG(ERROR) << err;
+  if (!update_bootloader_message(options, &err)) {
+    LOG(ERROR) << "Failed to set BCB message: " << err;
   }
 
   return args;
 }
 
-static void
-set_sdcard_update_bootloader_message() {
-    std::vector<std::string> options;
-    std::string err;
-    if (!write_bootloader_message(options, &err)) {
-        LOG(ERROR) << err;
-    }
+// Set the BCB to reboot back into recovery (it won't resume the install from
+// sdcard though).
+static void set_sdcard_update_bootloader_message() {
+  std::vector<std::string> options;
+  std::string err;
+  if (!update_bootloader_message(options, &err)) {
+    LOG(ERROR) << "Failed to set BCB message: " << err;
+  }
 }
 
 // Read from kernel log into buffer and write out to file.
@@ -485,7 +486,7 @@ static void finish_recovery() {
     // Reset to normal system boot so recovery won't cycle indefinitely.
     std::string err;
     if (!clear_bootloader_message(&err)) {
-        LOG(ERROR) << err;
+        LOG(ERROR) << "Failed to clear BCB message: " << err;
     }
 
     // Remove the command file, so recovery won't repeat indefinitely.
@@ -1323,7 +1324,7 @@ static void set_retry_bootloader_message(int retry_count, int argc, char** argv)
     // Increment the retry counter by 1.
     options.push_back(android::base::StringPrintf("--retry_count=%d", retry_count+1));
     std::string err;
-    if (!write_bootloader_message(options, &err)) {
+    if (!update_bootloader_message(options, &err)) {
         LOG(ERROR) << err;
     }
 }
diff --git a/tests/component/bootloader_message_test.cpp b/tests/component/bootloader_message_test.cpp
index cff129cfc..dbcaf619e 100644
--- a/tests/component/bootloader_message_test.cpp
+++ b/tests/component/bootloader_message_test.cpp
@@ -137,3 +137,29 @@ TEST_F(BootloaderMessageTest, write_bootloader_message_options_long) {
   ASSERT_EQ(std::string(sizeof(boot.reserved), '\0'),
             std::string(boot.reserved, sizeof(boot.reserved)));
 }
+
+TEST_F(BootloaderMessageTest, update_bootloader_message) {
+  // Inject some bytes into boot, which should be not overwritten later.
+  bootloader_message boot;
+  strlcpy(boot.recovery, "random message", sizeof(boot.recovery));
+  strlcpy(boot.reserved, "reserved bytes", sizeof(boot.reserved));
+  std::string err;
+  ASSERT_TRUE(write_bootloader_message(boot, &err)) << "Failed to write BCB: " << err;
+
+  // Update the BCB message.
+  std::vector<std::string> options = { "option1", "option2" };
+  ASSERT_TRUE(update_bootloader_message(options, &err)) << "Failed to update BCB: " << err;
+
+  bootloader_message boot_verify;
+  ASSERT_TRUE(read_bootloader_message(&boot_verify, &err)) << "Failed to read BCB: " << err;
+
+  // Verify that command and recovery fields should be set.
+  ASSERT_EQ("boot-recovery", std::string(boot_verify.command));
+  std::string expected = "recovery\n" + android::base::Join(options, "\n") + "\n";
+  ASSERT_EQ(expected, std::string(boot_verify.recovery));
+
+  // The rest should be intact.
+  ASSERT_EQ(std::string(boot.status), std::string(boot_verify.status));
+  ASSERT_EQ(std::string(boot.stage), std::string(boot_verify.stage));
+  ASSERT_EQ(std::string(boot.reserved), std::string(boot_verify.reserved));
+}