fs_mgr_avb_ops: stores the by-name prefix of /misc instead of fstab struct
fs_mgr_avb_ops->read_from_partition() relies on the by-name prefix to
get the device file when reading a partition. Previously we store the
fstab struct and use fs_mgr_get_entry_for_mount_point() for every read.
It's better to do that once and store the by-name prefix for later use.
Bug: 33254008
Test: test AVB on bullhead
Change-Id: Ie999851b529f984e29ccbf39fb52a8220056fe0c
(cherry picked from commit f5bbfd64a9d9f7dce24ce1505b8bf587dd949b92)
diff --git a/fs_mgr/fs_mgr_avb_ops.cpp b/fs_mgr/fs_mgr_avb_ops.cpp
index 2c14c9b..8e49663 100644
--- a/fs_mgr/fs_mgr_avb_ops.cpp
+++ b/fs_mgr/fs_mgr_avb_ops.cpp
@@ -39,7 +39,28 @@
#include "fs_mgr_avb_ops.h"
#include "fs_mgr_priv.h"
-static struct fstab* fs_mgr_fstab = nullptr;
+static std::string fstab_by_name_prefix;
+
+static std::string extract_by_name_prefix(struct fstab* fstab) {
+ // In AVB, we can assume that there's an entry for the /misc mount
+ // point in the fstab file and use that to get the device file for
+ // the misc partition. The device needs not to have an actual /misc
+ // partition. Then returns the prefix by removing the trailing "misc":
+ //
+ // - /dev/block/platform/soc.0/7824900.sdhci/by-name/misc ->
+ // - /dev/block/platform/soc.0/7824900.sdhci/by-name/
+
+ struct fstab_rec* fstab_entry = fs_mgr_get_entry_for_mount_point(fstab, "/misc");
+ if (fstab_entry == nullptr) {
+ LERROR << "/misc mount point not found in fstab";
+ return "";
+ }
+
+ std::string full_path(fstab_entry->blk_device);
+ size_t end_slash = full_path.find_last_of("/");
+
+ return full_path.substr(0, end_slash + 1);
+}
static AvbIOResult read_from_partition(AvbOps* ops ATTRIBUTE_UNUSED, const char* partition,
int64_t offset, size_t num_bytes, void* buffer,
@@ -49,30 +70,14 @@
// for partitions having 'slotselect' optin in fstab file, but it
// won't be appended to the mount point.
//
- // In AVB, we can assume that there's an entry for the /misc mount
- // point and use that to get the device file for the misc partition.
- // From there we'll assume that a by-name scheme is used
- // so we can just replace the trailing "misc" by the given
- // |partition|, e.g.
+ // Appends |partition| to the fstab_by_name_prefix, which is obtained
+ // by removing the trailing "misc" from the device file of /misc mount
+ // point. e.g.,
//
- // - /dev/block/platform/soc.0/7824900.sdhci/by-name/misc ->
+ // - /dev/block/platform/soc.0/7824900.sdhci/by-name/ ->
// - /dev/block/platform/soc.0/7824900.sdhci/by-name/system_a
- struct fstab_rec* fstab_entry = fs_mgr_get_entry_for_mount_point(fs_mgr_fstab, "/misc");
-
- if (fstab_entry == nullptr) {
- LERROR << "/misc mount point not found in fstab";
- return AVB_IO_RESULT_ERROR_IO;
- }
-
- std::string partition_name(partition);
- std::string path(fstab_entry->blk_device);
- // Replaces the last field of device file if it's not misc.
- if (!android::base::StartsWith(partition_name, "misc")) {
- size_t end_slash = path.find_last_of("/");
- std::string by_name_prefix(path.substr(0, end_slash + 1));
- path = by_name_prefix + partition_name;
- }
+ std::string path = fstab_by_name_prefix + partition;
// Ensures the device path (a symlink created by init) is ready to
// access. fs_mgr_test_access() will test a few iterations if the
@@ -168,8 +173,8 @@
AvbOps* fs_mgr_dummy_avb_ops_new(struct fstab* fstab) {
AvbOps* ops;
- // Assigns the fstab to the static variable for later use.
- fs_mgr_fstab = fstab;
+ fstab_by_name_prefix = extract_by_name_prefix(fstab);
+ if (fstab_by_name_prefix.empty()) return nullptr;
ops = (AvbOps*)calloc(1, sizeof(AvbOps));
if (ops == nullptr) {