Activate system APEXes early
Summary: Boot sequence around apexd is changed to make it possible for
pre-apexd processes to use libraries from APEXes. They no longer need to
wait for the apexd to finish activating APEXes, which again can be
done only after /data/ is mounted. This improves overall boot
performance.
Detail: This change fixes the problem that processes that are started
before apexd (so called pre-apexd processes) can't access libraries
that are provided only by the APEXes but are not found in the system
partition (e.g. libdexfile_external.so, etc.). Main idea is to activate
system APEXes (/system/apex/*.apex) before /data is mounted and then
activate the updated APEXes (/data/apex/*.apex) after the /data mount.
Detailed boot sequence is as follows.
1) init prepares the bootstrap and default mount namespaces. A tmpfs is
mounted on /apex and the propagation type of the mountpoint is set to
private.
2) before any other process is started, apexd is started in bootstrap
mode. When executed in the mode, apexd only activates APEXes under
/system/apex. Note that APEXes activated in this phase are mounted in
the bootstrap mount namespace only.
3) other pre-apexd processes are started. They are in the bootstrap
mount namespace and thus are provided with the libraries from the system
APEXes.
4) /data is mounted. init switches into the default mount namespace and
starts apexd as a daemon as usual.
5) apexd scans both /data/apex and /system/apex, and activate latest
APEXes from the directories. Note that APEXes activated in this phase
are mounted in the default namespaces only and thus are not visible to
the pre-apexd processes.
Bug: 125549215
Test: m; device boots
Change-Id: I21c60d0ebe188fa4f24d6e6861f85ca204843069
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 538ed00..6511d29 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1119,13 +1119,21 @@
}
static Result<Success> do_setup_runtime_bionic(const BuiltinArguments& args) {
- if (SwitchToDefaultMountNamespace()) {
+ 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();
+ } else {
+ return Error() << "Failed to enter into default mount namespace";
+ }
+}
+
// Builtin-function-map start
const BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
constexpr std::size_t kMax = std::numeric_limits<std::size_t>::max();
@@ -1177,6 +1185,7 @@
{"start", {1, 1, {false, do_start}}},
{"stop", {1, 1, {false, do_stop}}},
{"swapon_all", {1, 1, {false, do_swapon_all}}},
+ {"enter_default_mount_ns", {0, 0, {false, do_enter_default_mount_ns}}},
{"symlink", {2, 2, {true, do_symlink}}},
{"sysclktz", {1, 1, {false, do_sysclktz}}},
{"trigger", {1, 1, {false, do_trigger}}},
diff --git a/init/mount_namespace.cpp b/init/mount_namespace.cpp
index 413fe8f..327446a 100644
--- a/init/mount_namespace.cpp
+++ b/init/mount_namespace.cpp
@@ -172,6 +172,11 @@
kBionicLibsMountPointDir64))
return false;
+ // /apex is also 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;
+
bootstrap_ns_fd.reset(OpenMountNamespace());
bootstrap_ns_id = GetMountNamespaceId();
@@ -227,6 +232,17 @@
}
}
+ LOG(INFO) << "Switched to default mount namespace";
+ 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 IsBionicUpdatable() == false, these mounts are over the
// existing existing bind mounts for the bootstrap bionic, which effectively
@@ -238,7 +254,7 @@
kBionicLibsMountPointDir64))
return false;
- LOG(INFO) << "Switched to default mount namespace";
+ LOG(INFO) << "Runtime bionic is set up";
return true;
}
diff --git a/init/mount_namespace.h b/init/mount_namespace.h
index c41a449..4eef785 100644
--- a/init/mount_namespace.h
+++ b/init/mount_namespace.h
@@ -20,6 +20,7 @@
namespace init {
bool SetupMountNamespaces();
+bool SetupRuntimeBionic();
bool SwitchToDefaultMountNamespace();
bool SwitchToBootstrapMountNamespaceIfNeeded();