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Commit f5bbfd64 authored by Bowgo Tsai's avatar Bowgo Tsai
Browse files

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
parent 37a0b318

fs_mgr/fs_mgr_avb_ops.cpp

+29 −24
Original line number Diff line number Diff line
@@ -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 @@ static AvbIOResult read_from_partition(AvbOps* ops ATTRIBUTE_UNUSED, const char* 
    // 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 @@ static AvbIOResult dummy_get_unique_guid_for_partition(AvbOps* ops ATTRIBUTE_UNU 
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) {