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Commit 7b4801a9 authored by Jiyong Park's avatar Jiyong Park
Browse files

Don't bind-mount bionic files 

Bind-mounting of the bionic files on /bionic/* paths no longer required
as there are direct symlinks from bionic files in /system partition to
the corresponding bionic files in the runtime APEX. e.g.,

/system/lib/libc.so -> /apex/com.android.runtime/lib/bionic/libc.so

Bug: 125549215
Test: m; devices boots
Change-Id: I4a43101c3e3e2e14a81001d6d65a8a4b727df385
parent 9a00f596

init/builtins.cpp

+0 −9
Original line number Diff line number Diff line
@@ -1118,14 +1118,6 @@ static Result<Success> do_parse_apex_configs(const BuiltinArguments& args) { 
    }

}



static Result<Success> do_setup_runtime_bionic(const BuiltinArguments& args) {

    if (SetupRuntimeBionic()) {

        return Success();

    } else {

        return Error() << "Failed to setup runtime bionic";

    }

}



static Result<Success> do_enter_default_mount_ns(const BuiltinArguments& args) {

    if (SwitchToDefaultMountNamespace()) {

        return Success();
@@ -1181,7 +1173,6 @@ const BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const { 
        {"rmdir",                   {1,     1,    {true,   do_rmdir}}},

        {"setprop",                 {2,     2,    {true,   do_setprop}}},

        {"setrlimit",               {3,     3,    {false,  do_setrlimit}}},

        {"setup_runtime_bionic",    {0,     0,    {false,  do_setup_runtime_bionic}}},

        {"start",                   {1,     1,    {false,  do_start}}},

        {"stop",                    {1,     1,    {false,  do_stop}}},

        {"swapon_all",              {1,     1,    {false,  do_swapon_all}}},

init/mount_namespace.cpp

+5 −115
Original line number Diff line number Diff line
@@ -33,37 +33,6 @@ namespace android { 
namespace init {

namespace {



static constexpr const char* kLinkerMountPoint = "/bionic/bin/linker";

static constexpr const char* kBootstrapLinkerPath = "/system/bin/bootstrap/linker";

static constexpr const char* kRuntimeLinkerPath = "/apex/com.android.runtime/bin/linker";



static constexpr const char* kBionicLibsMountPointDir = "/bionic/lib/";

static constexpr const char* kBootstrapBionicLibsDir = "/system/lib/bootstrap/";

static constexpr const char* kRuntimeBionicLibsDir = "/apex/com.android.runtime/lib/bionic/";



static constexpr const char* kLinkerMountPoint64 = "/bionic/bin/linker64";

static constexpr const char* kBootstrapLinkerPath64 = "/system/bin/bootstrap/linker64";

static constexpr const char* kRuntimeLinkerPath64 = "/apex/com.android.runtime/bin/linker64";



static constexpr const char* kBionicLibsMountPointDir64 = "/bionic/lib64/";

static constexpr const char* kBootstrapBionicLibsDir64 = "/system/lib64/bootstrap/";

static constexpr const char* kRuntimeBionicLibsDir64 = "/apex/com.android.runtime/lib64/bionic/";



static const std::vector<std::string> kBionicLibFileNames = {"libc.so", "libm.so", "libdl.so"};



static bool BindMount(const std::string& source, const std::string& mount_point,

                      bool recursive = false) {

    unsigned long mountflags = MS_BIND;

    if (recursive) {

        mountflags |= MS_REC;

    }

    if (mount(source.c_str(), mount_point.c_str(), nullptr, mountflags, nullptr) == -1) {

        PLOG(ERROR) << "Could not bind-mount " << source << " to " << mount_point;

        return false;

    }

    return true;

}



static bool MakeShared(const std::string& mount_point, bool recursive = false) {

    unsigned long mountflags = MS_SHARED;

    if (recursive) {
@@ -105,34 +74,6 @@ static std::string GetMountNamespaceId() { 
    return ret;

}



static bool BindMountBionic(const std::string& linker_source, const std::string& lib_dir_source,

                            const std::string& linker_mount_point,

                            const std::string& lib_mount_dir) {

    if (access(linker_source.c_str(), F_OK) != 0) {

        PLOG(INFO) << linker_source << " does not exist. skipping mounting bionic there.";

        // This can happen for 64-bit bionic in 32-bit only device.

        // It is okay to skip mounting the 64-bit bionic.

        return true;

    }

    if (!BindMount(linker_source, linker_mount_point)) {

        return false;

    }

    if (!MakePrivate(linker_mount_point)) {

        return false;

    }

    for (const auto& libname : kBionicLibFileNames) {

        std::string mount_point = lib_mount_dir + libname;

        std::string source = lib_dir_source + libname;

        if (!BindMount(source, mount_point)) {

            return false;

        }

        if (!MakePrivate(mount_point)) {

            return false;

        }

    }

    return true;

}



static bool IsApexUpdatable() {

    static bool updatable = android::sysprop::ApexProperties::updatable().value_or(false);

    return updatable;
@@ -154,26 +95,7 @@ bool SetupMountNamespaces() { 
    // point to private.

    if (!MakeShared("/", true /*recursive*/)) return false;



    // Since different files (bootstrap or runtime APEX) should be mounted to

    // the same mount point paths (e.g. /bionic/bin/linker, /bionic/lib/libc.so,

    // etc.) across the two mount namespaces, we create a private mount point at

    // /bionic so that a mount event for the bootstrap bionic in the mount

    // namespace for pre-apexd processes is not propagated to the other mount

    // namespace for post-apexd process, and vice versa.

    //

    // Other mount points other than /bionic, however, are all still shared.

    if (!BindMount("/bionic", "/bionic", true /*recursive*/)) return false;

    if (!MakePrivate("/bionic")) return false;



    // Bind-mount bootstrap bionic.

    if (!BindMountBionic(kBootstrapLinkerPath, kBootstrapBionicLibsDir, kLinkerMountPoint,

                         kBionicLibsMountPointDir))

        return false;

    if (!BindMountBionic(kBootstrapLinkerPath64, kBootstrapBionicLibsDir64, kLinkerMountPoint64,

                         kBionicLibsMountPointDir64))

        return false;



    // /apex is also a private mountpoint to give different sets of APEXes for

    // /apex is a private mountpoint to give different sets of APEXes for

    // the bootstrap and default mount namespaces. The processes running with

    // the bootstrap namespace get APEXes from the read-only partition.

    if (!(MakePrivate("/apex"))) return false;
@@ -181,12 +103,11 @@ bool SetupMountNamespaces() { 
    bootstrap_ns_fd.reset(OpenMountNamespace());

    bootstrap_ns_id = GetMountNamespaceId();



    // When bionic is updatable via the runtime APEX, we create separate mount

    // When APEXes are updatable (e.g. not-flattened), we create separate mount

    // namespaces for processes that are started before and after the APEX is

    // activated by apexd. In the namespace for pre-apexd processes, the bionic

    // from the /system partition (that we call bootstrap bionic) is

    // bind-mounted. In the namespace for post-apexd processes, the bionic from

    // the runtime APEX is bind-mounted.

    // activated by apexd. In the namespace for pre-apexd processes, small

    // number of essential APEXes (e.g. com.android.runtime) are activated.

    // In the namespace for post-apexd processes, all APEXes are activated.

    bool success = true;

    if (IsApexUpdatable() && !IsRecoveryMode()) {

        // Creating a new namespace by cloning, saving, and switching back to
@@ -198,15 +119,6 @@ bool SetupMountNamespaces() { 
        default_ns_fd.reset(OpenMountNamespace());

        default_ns_id = GetMountNamespaceId();



        // By this unmount, the bootstrap bionic are not mounted in the default

        // mount namespace.

        if (umount2("/bionic", MNT_DETACH) == -1) {

            PLOG(ERROR) << "Cannot unmount /bionic";

            // Don't return here. We have to switch back to the bootstrap

            // namespace.

            success = false;

        }



        if (setns(bootstrap_ns_fd.get(), CLONE_NEWNS) == -1) {

            PLOG(ERROR) << "Cannot switch back to bootstrap mount namespace";

            return false;
@@ -237,28 +149,6 @@ bool SwitchToDefaultMountNamespace() { 
    return true;

}



// TODO(jiyong): remove this when /system/lib/libc.so becomes

// a symlink to /apex/com.android.runtime/lib/bionic/libc.so

bool SetupRuntimeBionic() {

    if (IsRecoveryMode()) {

        // We don't have multiple namespaces in recovery mode

        return true;

    }

    // Bind-mount bionic from the runtime APEX since it is now available. Note

    // that in case of IsApexUpdatable() == false, these mounts are over the

    // existing existing bind mounts for the bootstrap bionic, which effectively

    // becomes hidden.

    if (!BindMountBionic(kRuntimeLinkerPath, kRuntimeBionicLibsDir, kLinkerMountPoint,

                         kBionicLibsMountPointDir))

        return false;

    if (!BindMountBionic(kRuntimeLinkerPath64, kRuntimeBionicLibsDir64, kLinkerMountPoint64,

                         kBionicLibsMountPointDir64))

        return false;



    LOG(INFO) << "Runtime bionic is set up";

    return true;

}



bool SwitchToBootstrapMountNamespaceIfNeeded() {

    if (IsRecoveryMode()) {

        // we don't have multiple namespaces in recovery mode

init/mount_namespace.h

+0 −1
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ namespace android { 
namespace init {



bool SetupMountNamespaces();

bool SetupRuntimeBionic();

bool SwitchToDefaultMountNamespace();

bool SwitchToBootstrapMountNamespaceIfNeeded();

rootdir/etc/ld.config.txt

+2 −2
Original line number Diff line number Diff line
@@ -83,7 +83,7 @@ namespace.default.permitted.paths += /%PRODUCT_SERVICES%/app 
namespace.default.permitted.paths += /%PRODUCT_SERVICES%/priv-app

namespace.default.permitted.paths += /data

namespace.default.permitted.paths += /mnt/expand

namespace.default.permitted.paths += /bionic/${LIB}

namespace.default.permitted.paths += /apex/com.android.runtime/${LIB}/bionic

namespace.default.permitted.paths += /system/${LIB}/bootstrap



namespace.default.asan.search.paths  = /data/asan/system/${LIB}
@@ -119,7 +119,7 @@ namespace.default.asan.permitted.paths += /%PRODUCT_SERVICES%/framework 
namespace.default.asan.permitted.paths += /%PRODUCT_SERVICES%/app

namespace.default.asan.permitted.paths += /%PRODUCT_SERVICES%/priv-app

namespace.default.asan.permitted.paths += /mnt/expand

namespace.default.asan.permitted.paths += /bionic/${LIB}

namespace.default.asan.permitted.paths += /apex/com.android.runtime/${LIB}/bionic

namespace.default.asan.permitted.paths += /system/${LIB}/bootstrap



# Keep in sync with ld.config.txt in the com.android.runtime APEX.

rootdir/init.rc

+0 −2
Original line number Diff line number Diff line
@@ -578,8 +578,6 @@ on post-fs-data 


    # Wait for apexd to finish activating APEXes before starting more processes.

    wait_for_prop apexd.status ready

    # TODO(jiyong): remove setup_runtime_bionic

    setup_runtime_bionic

    parse_apex_configs



    init_user0