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Commit 9f97f479 authored by Luis Hector Chavez's avatar Luis Hector Chavez
Browse files

init: Allow clean system shutdown upon SIGTERM 

This allows Android to cleanly shutdown when running in a PID namespace
in a way that does not rely on adbd running. This is useful to allow
Android to be running in a container and its lifetime managed by an
OCI-compliant tool.

Bug: 65415372
Test: `kill -TERM 1` as root is correctly dropped.
Test: `kill -TERM 1` from the init PID namespace causes init to cleanly shutdown.
Change-Id: Ia66ebdb436221919081bc4723337c0c7f1e53b09
parent 61395923

init/Android.bp

+1 −1
Original line number Diff line number Diff line
@@ -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

+1 −1
Original line number Diff line number Diff line
@@ -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

+0 −1
Original line number Diff line number Diff line
@@ -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

+45 −2
Original line number Diff line number Diff line
@@ -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

+2 −4
Original line number Diff line number Diff line
@@ -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;