Support additional argument in reboot

reboot syscall can be performed with an additional argument. In some
systems this functionality can be useful to modify the mode of the
next boot performed by the bootloader.

4 files changed, 48 insertions, 11 deletions

diff --git a/man/systemctl.xml b/man/systemctl.xml
index c7313edcc2..7f1e98f5c5 100644
--- a/man/systemctl.xml
+++ b/man/systemctl.xml
@@ -1179,7 +1179,7 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
           </listitem>
         </varlistentry>
         <varlistentry>
-          <term><command>reboot</command></term>
+          <term><command>reboot <optional><replaceable>arg</replaceable></optional></command></term>
 
           <listitem>
             <para>Shut down and reboot the system. This is mostly
@@ -1192,6 +1192,16 @@ kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
             specified twice, the operation is immediately executed
             without terminating any processes or unmounting any file
             systems. This may result in data loss.</para>
+
+            <para>If the optional argument
+            <replaceable>arg</replaceable> is given, it will be passed
+            as the optional argument to the
+            <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+            system call. The value is architecture and firmware
+            specific. As an example, <literal>recovery</literal> might
+            be used to trigger system recovery, and
+            <literal>fota</literal> might be used to trigger a
+            <quote>firmware over the air</quote> update.</para>
           </listitem>
         </varlistentry>
         <varlistentry>
diff --git a/src/core/shutdown.c b/src/core/shutdown.c
index aa9548e2a4..377c1971a3 100644
--- a/src/core/shutdown.c
+++ b/src/core/shutdown.c
@@ -47,6 +47,7 @@
 #include "watchdog.h"
 #include "killall.h"
 #include "cgroup-util.h"
+#include "def.h"
 
 #define FINALIZE_ATTEMPTS 50
 
@@ -134,7 +135,7 @@ static int pivot_to_new_root(void) {
 int main(int argc, char *argv[]) {
         bool need_umount = true, need_swapoff = true, need_loop_detach = true, need_dm_detach = true;
         bool in_container, use_watchdog = false;
-        _cleanup_free_ char *line = NULL, *cgroup = NULL;
+        _cleanup_free_ char *line = NULL, *cgroup = NULL, *param = NULL;
         char *arguments[3];
         unsigned retries;
         int cmd, r;
@@ -173,9 +174,11 @@ int main(int argc, char *argv[]) {
 
         in_container = detect_container(NULL) > 0;
 
-        if (streq(argv[1], "reboot"))
+        if (streq(argv[1], "reboot")) {
                 cmd = RB_AUTOBOOT;
-        else if (streq(argv[1], "poweroff"))
+                /* if this fails, that's OK */
+                read_one_line_file(REBOOT_PARAM_FILE, &param);
+        } else if (streq(argv[1], "poweroff"))
                 cmd = RB_POWER_OFF;
         else if (streq(argv[1], "halt"))
                 cmd = RB_HALT_SYSTEM;
@@ -337,7 +340,11 @@ int main(int argc, char *argv[]) {
                 cmd = RB_AUTOBOOT;
         }
 
-        reboot(cmd);
+        if (param)
+                syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
+                        LINUX_REBOOT_CMD_RESTART2, param);
+        else
+                reboot(cmd);
 
         if (errno == EPERM && in_container) {
                 /* If we are in a container, and we lacked
diff --git a/src/shared/def.h b/src/shared/def.h
index edd0bcf7a4..46b88a8a49 100644
--- a/src/shared/def.h
+++ b/src/shared/def.h
@@ -38,3 +38,5 @@
 #define LOWERCASE_LETTERS "abcdefghijklmnopqrstuvwxyz"
 #define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 #define LETTERS LOWERCASE_LETTERS UPPERCASE_LETTERS
+
+#define REBOOT_PARAM_FILE "/run/systemd/reboot-param"
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 9d22aad287..6170cc93d5 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -20,6 +20,8 @@
 ***/
 
 #include <sys/reboot.h>
+#include <linux/reboot.h>
+#include <sys/syscall.h>
 #include <stdio.h>
 #include <getopt.h>
 #include <locale.h>
@@ -4804,7 +4806,7 @@ static int systemctl_help(void) {
                "  emergency                       Enter system emergency mode\n"
                "  halt                            Shut down and halt the system\n"
                "  poweroff                        Shut down and power-off the system\n"
-               "  reboot                          Shut down and reboot the system\n"
+               "  reboot [ARG]                    Shut down and reboot the system\n"
                "  kexec                           Shut down and reboot the system with kexec\n"
                "  exit                            Request user instance exit\n"
                "  switch-root [ROOT] [INIT]       Change to a different root file system\n"
@@ -4818,7 +4820,7 @@ static int systemctl_help(void) {
 
 static int halt_help(void) {
 
-        printf("%s [OPTIONS...]\n\n"
+        printf("%s [OPTIONS...]%s\n\n"
                "%s the system.\n\n"
                "     --help      Show this help\n"
                "     --halt      Halt the machine\n"
@@ -4829,6 +4831,7 @@ static int halt_help(void) {
                "  -d --no-wtmp   Don't write wtmp record\n"
                "     --no-wall   Don't send wall message before halt/power-off/reboot\n",
                program_invocation_short_name,
+               arg_action == ACTION_REBOOT   ? " [ARG]" : "",
                arg_action == ACTION_REBOOT   ? "Reboot" :
                arg_action == ACTION_POWEROFF ? "Power off" :
                                                "Halt");
@@ -5253,7 +5256,7 @@ static int halt_parse_argv(int argc, char *argv[]) {
                 {}
         };
 
-        int c, runlevel;
+        int c, r, runlevel;
 
         assert(argc >= 0);
         assert(argv);
@@ -5311,7 +5314,14 @@ static int halt_parse_argv(int argc, char *argv[]) {
                 }
         }
 
-        if (optind < argc) {
+        if (arg_action == ACTION_REBOOT && argc == optind + 1) {
+                r = write_string_file(REBOOT_PARAM_FILE, argv[optind]);
+                if (r < 0) {
+                        log_error("Failed to write reboot param to "
+                                  REBOOT_PARAM_FILE": %s", strerror(-r));
+                        return r;
+                }
+        } else if (optind < argc) {
                 log_error("Too many arguments.");
                 return -EINVAL;
         }
@@ -5944,6 +5954,8 @@ done:
 
 static _noreturn_ void halt_now(enum action a) {
 
+        _cleanup_free_ char *param = NULL;
+
        /* Make sure C-A-D is handled by the kernel from this
          * point on... */
         reboot(RB_ENABLE_CAD);
@@ -5961,8 +5973,14 @@ static _noreturn_ void halt_now(enum action a) {
                 break;
 
         case ACTION_REBOOT:
-                log_info("Rebooting.");
-                reboot(RB_AUTOBOOT);
+                if (read_one_line_file(REBOOT_PARAM_FILE, &param) == 0) {
+                        log_info("Rebooting with arg '%s'.", param);
+                        syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
+                                LINUX_REBOOT_CMD_RESTART2, param);
+                } else {
+                        log_info("Rebooting.");
+                        reboot(RB_AUTOBOOT);
+                }
                 break;
 
         default: