commit 152a89138de5ce7c3e785374c211e273e6d9d111
author Bowgo Tsai <bowgotsai@google.com> Mon Jun 11 17:08:01 2018 +0800
committer Bowgo Tsai <bowgotsai@google.com> Mon Jun 11 22:08:45 2018 +0800
tree 2490fe4249e2d0bcd384bb1d55104f84e7ede0d2
parent f93a22d5edf99a67290a0007c1a9a7eed0f76f2d

fs_mg: allow getting VBMeta Digest from device-tree

fs_mgr gets androidboot.vbmeta.{size, hash_alg, digest} from kernel
cmdline to assure the integrity of all vbmeta structs. This CL Allows
fs_mgr to get those parameters from device tree because they're only
consumed by userland instead of kernel.

  https://android.googlesource.com/platform/external/avb/+/master#The-VBMeta-Digest

Bootloader could construct a device tree overlay at run time then merge
it into main device tree. e.g.,

    firmware {
        android {
            vbmeta.size = "5245";
            vbmeta.hash_alg = "sha256";
            vbmeta.digest = "0c51233ca3ecaa...63c6d912e79b709";
        };
    };

Bug: 80168311
Test: boot a device using AVB

Change-Id: I6cf151713af04e6cf554d593e9f0b43e9e214d8c

fs_mgr/fs_mgr_avb.cpp

diff --git a/fs_mgr/fs_mgr_avb.cpp b/fs_mgr/fs_mgr_avb.cpp
index 5d688e1..2020fa6 100644
--- a/fs_mgr/fs_mgr_avb.cpp
+++ b/fs_mgr/fs_mgr_avb.cpp
@@ -146,7 +146,7 @@
     }
 
     std::string value;
-    if (!fs_mgr_get_boot_config_from_kernel_cmdline("vbmeta.size", &value) ||
+    if (!fs_mgr_get_boot_config("vbmeta.size", &value) ||
         !android::base::ParseUint(value.c_str(), &avb_verifier->vbmeta_size_)) {
         LERROR << "Invalid hash size: " << value.c_str();
         return nullptr;
@@ -155,7 +155,7 @@
     // Reads hash algorithm.
     size_t expected_digest_size = 0;
     std::string hash_alg;
-    fs_mgr_get_boot_config_from_kernel_cmdline("vbmeta.hash_alg", &hash_alg);
+    fs_mgr_get_boot_config("vbmeta.hash_alg", &hash_alg);
     if (hash_alg == "sha256") {
         expected_digest_size = SHA256_DIGEST_LENGTH * 2;
         avb_verifier->hash_alg_ = kSHA256;
@@ -169,7 +169,7 @@
 
     // Reads digest.
     std::string digest;
-    fs_mgr_get_boot_config_from_kernel_cmdline("vbmeta.digest", &digest);
+    fs_mgr_get_boot_config("vbmeta.digest", &digest);
     if (digest.size() != expected_digest_size) {
         LERROR << "Unexpected digest size: " << digest.size()
                << " (expected: " << expected_digest_size << ")";