Merge "init: Allow clean system shutdown upon SIGTERM"

am: 61cb88add2

Change-Id: If0a495fa067440f0b59969ac0dbc010b4687b52f

init/Android.bp

@@ -119,7 +119,7 @@ cc_binary {
         "init_first_stage.cpp",
         "keychords.cpp",
         "reboot.cpp",
-        "signal_handler.cpp",
+        "sigchld_handler.cpp",
         "ueventd.cpp",
         "watchdogd.cpp",
     ],

init/Android.mk

@@ -48,7 +48,7 @@ LOCAL_SRC_FILES:= \
     init_first_stage.cpp \
     keychords.cpp \
     reboot.cpp \
-    signal_handler.cpp \
+    sigchld_handler.cpp \
     ueventd.cpp \
     watchdogd.cpp \
 

init/builtins.cpp

@@ -66,7 +66,6 @@
 #include "reboot.h"
 #include "rlimit_parser.h"
 #include "service.h"
-#include "signal_handler.h"
 #include "util.h"
 
 using namespace std::literals::string_literals;

init/init.cpp

@@ -25,6 +25,7 @@
 #include <string.h>
 #include <sys/epoll.h>
 #include <sys/mount.h>
+#include <sys/signalfd.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ -51,7 +52,7 @@
 #include "reboot.h"
 #include "security.h"
 #include "selinux.h"
-#include "signal_handler.h"
+#include "sigchld_handler.h"
 #include "ueventd.h"
 #include "util.h"
 #include "watchdogd.h"
@@ -72,6 +73,7 @@ static char qemu[32];
 std::string default_console = "/dev/console";
 
 static int epoll_fd = -1;
+static int sigterm_signal_fd = -1;
 
 static std::unique_ptr<Timer> waiting_for_prop(nullptr);
 static std::string wait_prop_name;
@@ -392,6 +394,41 @@ static void InstallRebootSignalHandlers() {
     sigaction(SIGTRAP, &action, nullptr);
 }
 
+static void HandleSigtermSignal() {
+    signalfd_siginfo siginfo;
+    ssize_t bytes_read = TEMP_FAILURE_RETRY(read(sigterm_signal_fd, &siginfo, sizeof(siginfo)));
+    if (bytes_read != sizeof(siginfo)) {
+        PLOG(ERROR) << "Failed to read siginfo from sigterm_signal_fd";
+        return;
+    }
+
+    if (siginfo.ssi_pid != 0) {
+        // Drop any userspace SIGTERM requests.
+        LOG(DEBUG) << "Ignoring SIGTERM from pid " << siginfo.ssi_pid;
+        return;
+    }
+
+    LOG(INFO) << "Handling SIGTERM, shutting system down";
+    HandlePowerctlMessage("shutdown");
+}
+
+static void InstallSigtermHandler() {
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGTERM);
+
+    if (sigprocmask(SIG_BLOCK, &mask, nullptr) == -1) {
+        PLOG(FATAL) << "failed to block SIGTERM";
+    }
+
+    sigterm_signal_fd = signalfd(-1, &mask, SFD_CLOEXEC);
+    if (sigterm_signal_fd == -1) {
+        PLOG(FATAL) << "failed to create signalfd for SIGTERM";
+    }
+
+    register_epoll_handler(sigterm_signal_fd, HandleSigtermSignal);
+}
+
 int main(int argc, char** argv) {
     if (!strcmp(basename(argv[0]), "ueventd")) {
         return ueventd_main(argc, argv);
@@ -527,7 +564,13 @@ int main(int argc, char** argv) {
         exit(1);
     }
 
-    signal_handler_init();
+    sigchld_handler_init();
+
+    if (!IsRebootCapable()) {
+        // If init does not have the CAP_SYS_BOOT capability, it is running in a container.
+        // In that case, receiving SIGTERM will cause the system to shut down.
+        InstallSigtermHandler();
+    }
 
     property_load_boot_defaults();
     export_oem_lock_status();

init/reboot.cpp

@@ -54,7 +54,7 @@
 #include "init.h"
 #include "property_service.h"
 #include "service.h"
-#include "signal_handler.h"
+#include "sigchld_handler.h"
 
 using android::base::StringPrintf;
 using android::base::Timer;
@@ -169,9 +169,7 @@ static void LogShutdownTime(UmountStat stat, Timer* t) {
                  << stat;
 }
 
-// Determines whether the system is capable of rebooting. This is conservative,
-// so if any of the attempts to determine this fail, it will still return true.
-static bool IsRebootCapable() {
+bool IsRebootCapable() {
     if (!CAP_IS_SUPPORTED(CAP_SYS_BOOT)) {
         PLOG(WARNING) << "CAP_SYS_BOOT is not supported";
         return true;

init/reboot.h

@@ -38,6 +38,10 @@ void DoReboot(unsigned int cmd, const std::string& reason, const std::string& re
 // Parses and handles a setprop sys.powerctl message.
 bool HandlePowerctlMessage(const std::string& command);
 
+// Determines whether the system is capable of rebooting. This is conservative,
+// so if any of the attempts to determine this fail, it will still return true.
+bool IsRebootCapable();
+
 }  // namespace init
 }  // namespace android
 

init/sigchld_handler.cpp

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "signal_handler.h"
+#include "sigchld_handler.h"
 
 #include <signal.h>
 #include <string.h>
@@ -115,7 +115,7 @@ void ReapAnyOutstandingChildren() {
     }
 }
 
-void signal_handler_init() {
+void sigchld_handler_init() {
     // Create a signalling mechanism for SIGCHLD.
     int s[2];
     if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0, s) == -1) {

init/sigchld_handler.h

@@ -14,15 +14,15 @@
  * limitations under the License.
  */
 
-#ifndef _INIT_SIGNAL_HANDLER_H_
-#define _INIT_SIGNAL_HANDLER_H_
+#ifndef _INIT_SIGCHLD_HANDLER_H_
+#define _INIT_SIGCHLD_HANDLER_H_
 
 namespace android {
 namespace init {
 
 void ReapAnyOutstandingChildren();
 
-void signal_handler_init(void);
+void sigchld_handler_init(void);
 
 }  // namespace init
 }  // namespace android