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Index: sbin/reboot/reboot.8
===================================================================
--- sbin/reboot/reboot.8
+++ sbin/reboot/reboot.8
@@ -28,7 +28,7 @@
.\" @(#)reboot.8 8.1 (Berkeley) 6/9/93
.\" $FreeBSD$
.\"
-.Dd October 11, 2010
+.Dd May 22, 2015
.Dt REBOOT 8
.Os
.Sh NAME
@@ -42,7 +42,7 @@
.Op Fl lnpq
.Op Fl k Ar kernel
.Nm
-.Op Fl dlnpq
+.Op Fl dlnpqr
.Op Fl k Ar kernel
.Nm fasthalt
.Op Fl lnpq
@@ -111,6 +111,13 @@
.Fl n
option is not specified).
This option should probably not be used.
+.It Fl r
+The system will kill all processes, unmount all filesystems, mount the new
+root filesystem, and start
+.Xr init 8 .
+It can be used after updating the vfs.root.mountfrom using
+.Xr kenv 8 ,
+to change the root filesystem while preserving kernel state.
.El
.Pp
The
Index: sbin/reboot/reboot.c
===================================================================
--- sbin/reboot/reboot.c
+++ sbin/reboot/reboot.c
@@ -77,7 +77,7 @@
} else
howto = 0;
lflag = nflag = qflag = 0;
- while ((ch = getopt(argc, argv, "dk:lnpq")) != -1)
+ while ((ch = getopt(argc, argv, "dk:lnpqr")) != -1)
switch(ch) {
case 'd':
howto |= RB_DUMP;
@@ -98,6 +98,9 @@
case 'q':
qflag = 1;
break;
+ case 'r':
+ howto |= RB_REROOT;
+ break;
case '?':
default:
usage();
@@ -107,6 +110,8 @@
if ((howto & (RB_DUMP | RB_HALT)) == (RB_DUMP | RB_HALT))
errx(1, "cannot dump (-d) when halting; must reboot instead");
+ if ((howto & RB_REROOT) != 0 && (howto & RB_REROOT) != RB_REROOT)
+ errx(1, "-r flag is mutually exclusive with -d, -n, and -p");
if (geteuid()) {
errno = EPERM;
err(1, NULL);
Index: sys/kern/init_main.c
===================================================================
--- sys/kern/init_main.c
+++ sys/kern/init_main.c
@@ -816,13 +816,13 @@
* Note special case - do not make it runnable yet. Other work
* in progress will change this more.
*/
-static void
+void
create_init(const void *udata __unused)
{
struct ucred *newcred, *oldcred;
int error;
- error = fork1(&thread0, RFFDG | RFPROC | RFSTOPPED, 0, &initproc,
+ error = fork1(&thread0, RFFDG | RFPID1 | RFPROC | RFSTOPPED, 0, &initproc,
NULL, 0);
if (error)
panic("cannot fork init: %d\n", error);
@@ -854,7 +854,7 @@
/*
* Make it runnable now.
*/
-static void
+void
kick_init(const void *udata __unused)
{
struct thread *td;
Index: sys/kern/kern_fork.c
===================================================================
--- sys/kern/kern_fork.c
+++ sys/kern/kern_fork.c
@@ -234,7 +234,9 @@
* low-numbered pids.
*/
trypid = lastpid + 1;
- if (flags & RFHIGHPID) {
+ if (flags & RFPID1) {
+ trypid = 1;
+ } else if (flags & RFHIGHPID) {
if (trypid < 10)
trypid = 10;
} else {
Index: sys/kern/kern_shutdown.c
===================================================================
--- sys/kern/kern_shutdown.c
+++ sys/kern/kern_shutdown.c
@@ -50,6 +50,7 @@
#include <sys/conf.h>
#include <sys/cons.h>
#include <sys/eventhandler.h>
+#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
@@ -67,6 +68,7 @@
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
+#include <sys/sx.h>
#include <sys/vnode.h>
#include <sys/watchdog.h>
@@ -154,6 +156,7 @@
static void shutdown_halt(void *junk, int howto);
static void shutdown_panic(void *junk, int howto);
static void shutdown_reset(void *junk, int howto);
+static void kern_reroot(void);
/* register various local shutdown events */
static void
@@ -173,6 +176,47 @@
SYSINIT(shutdown_conf, SI_SUB_INTRINSIC, SI_ORDER_ANY, shutdown_conf, NULL);
/*
+ * XXX: The whole point of this is to avoid 'vm_object_unwire: missing page'
+ * panic for random processes surviving the procedure. It's also racy.
+ */
+static void
+exterminate(void)
+{
+ struct proc *p;
+
+ KASSERT(rebooting == 0, ("don't intend to kill system processes"));
+
+ sx_xlock(&allproc_lock);
+ FOREACH_PROC_IN_SYSTEM(p) {
+ if (p->p_pid == 11) {
+ /*
+ * XXX: Killing pid 11 (idle) wedges disk io.
+ */
+ continue;
+ }
+ PROC_LOCK(p);
+ kern_psignal(p, SIGKILL);
+ PROC_UNLOCK(p);
+ }
+ sx_xunlock(&allproc_lock);
+
+ pause("exterminate", hz);
+
+again:
+ sx_xlock(&proctree_lock);
+ sx_xlock(&allproc_lock);
+ while ((p = LIST_FIRST(&zombproc)) != NULL) {
+ PROC_LOCK(p);
+ sx_xunlock(&allproc_lock);
+ PROC_SLOCK(p);
+ proc_reap(&thread0, p, NULL, 0);
+ goto again;
+ }
+ sx_xunlock(&allproc_lock);
+ sx_xunlock(&proctree_lock);
+}
+
+/*
* The system call that results in a reboot.
*/
/* ARGSUSED */
@@ -188,8 +232,15 @@
if (error == 0)
error = priv_check(td, PRIV_REBOOT);
if (error == 0) {
- mtx_lock(&Giant);
- kern_reboot(uap->opt);
+ if (uap->opt & RB_REROOT) {
+ kern_reroot();
+ mtx_lock(&Giant);
+ } else {
+ mtx_lock(&Giant);
+ kern_reboot(uap->opt);
+ }
+ swapoff_all();
+ DELAY(100000); /* wait for console output to finish */
mtx_unlock(&Giant);
}
return (error);
@@ -453,6 +504,80 @@
/* NOTREACHED */
}
+static void
+kern_reroot(void)
+{
+ struct vnode *oldrootvnode;
+ struct proc *oldinitproc;
+ struct proc *p;
+
+ exterminate();
+
+ oldrootvnode = rootvnode;
+ oldinitproc = initproc;
+ initproc = NULL;
+
+ /*
+ * Undo something weird that happens in create_init().
+ * XXX: Why?
+ */
+ PROC_LOCK(oldinitproc);
+ LIST_REMOVE(&proc0, p_reapsibling);
+ PROC_UNLOCK(oldinitproc);
+
+ /*
+ * Kill init, so that we can reuse PID 1.
+ */
+ rebooting = 1;
+ PROC_LOCK(oldinitproc);
+ kern_psignal(oldinitproc, SIGKILL);
+ while (oldinitproc->p_state != PRS_ZOMBIE) {
+ PROC_UNLOCK(oldinitproc);
+ pause("killinit", hz);
+ PROC_LOCK(oldinitproc);
+ }
+ PROC_UNLOCK(oldinitproc);
+ rebooting = 0;
+
+ /*
+ * Unmount everything, including /dev and rootfs.
+ */
+ vfs_unmountall();
+
+ /*
+ * Start the new init; this includes mounting new
+ * rootfs and /dev. It's deferred to a kthread;
+ * wait until it completes.
+ */
+ create_init(NULL);
+ kick_init(NULL);
+ /*
+ * XXX: Without exterminate(), it dies at this point
+ * with 'vm_object_unwire: missing page'.
+ */
+ while (rootvnode == NULL)
+ pause("rootvnode", 1);
+
+ /*
+ * Update all references to the old rootvnode.
+ */
+ mountcheckdirs(oldrootvnode, rootvnode);
+
+ /*
+ * Reparent old zombies to the new init,
+ * so that they can be properly reaped.
+ */
+ sx_xlock(&proctree_lock);
+ sx_xlock(&allproc_lock);
+ LIST_FOREACH(p, &zombproc, p_list) {
+ PROC_LOCK(p);
+ proc_reparent(p, initproc);
+ PROC_UNLOCK(p);
+ }
+ sx_xunlock(&allproc_lock);
+ sx_xunlock(&proctree_lock);
+}
+
/*
* If the shutdown was a clean halt, behave accordingly.
*/
Index: sys/kern/kern_sig.c
===================================================================
--- sys/kern/kern_sig.c
+++ sys/kern/kern_sig.c
@@ -2735,9 +2735,12 @@
case (intptr_t)SIG_DFL:
/*
- * Don't take default actions on system processes.
+ * Don't take default actions on system processes,
+ * but make sure to allow killing init(8)
+ * when rebooting.
*/
- if (p->p_pid <= 1) {
+ if (p->p_pid < 1 ||
+ (p->p_pid == 1 && rebooting == 0)) {
#ifdef DIAGNOSTIC
/*
* Are you sure you want to ignore SIGSEGV
Index: sys/sys/kernel.h
===================================================================
--- sys/sys/kernel.h
+++ sys/sys/kernel.h
@@ -64,6 +64,7 @@
extern int profhz; /* profiling clock's frequency */
extern int profprocs; /* number of process's profiling */
extern volatile int ticks;
+struct thread;
#endif /* _KERNEL */
@@ -374,4 +375,7 @@
int config_intrhook_establish(struct intr_config_hook *hook);
void config_intrhook_disestablish(struct intr_config_hook *hook);
+void create_init(const void *udata __unused);
+void kick_init(const void *udata __unused);
+
#endif /* !_SYS_KERNEL_H_*/
Index: sys/sys/reboot.h
===================================================================
--- sys/sys/reboot.h
+++ sys/sys/reboot.h
@@ -59,6 +59,7 @@
#define RB_RESERVED1 0x40000 /* reserved for internal use of boot blocks */
#define RB_RESERVED2 0x80000 /* reserved for internal use of boot blocks */
#define RB_PAUSE 0x100000 /* pause after each output line during probe */
+#define RB_REROOT 0x200000 /* unmount the rootfs and mount it again */
#define RB_MULTIPLE 0x20000000 /* use multiple consoles */
#define RB_BOOTINFO 0x80000000 /* have `struct bootinfo *' arg */
Index: sys/sys/unistd.h
===================================================================
--- sys/sys/unistd.h
+++ sys/sys/unistd.h
@@ -186,11 +186,12 @@
#define RFTSIGNUM(flags) (((flags) >> RFTSIGSHIFT) & RFTSIGMASK)
#define RFTSIGFLAGS(signum) ((signum) << RFTSIGSHIFT)
#define RFPROCDESC (1<<28) /* return a process descriptor */
+#define RFPID1 (1<<29) /* try to allocate pid 1 */
#define RFPPWAIT (1<<31) /* parent sleeps until child exits (vfork) */
#define RFFLAGS (RFFDG | RFPROC | RFMEM | RFNOWAIT | RFCFDG | \
RFTHREAD | RFSIGSHARE | RFLINUXTHPN | RFSTOPPED | RFHIGHPID | RFTSIGZMB | \
- RFPROCDESC | RFPPWAIT)
-#define RFKERNELONLY (RFSTOPPED | RFHIGHPID | RFPPWAIT | RFPROCDESC)
+ RFPROCDESC | RFPID1 | RFPPWAIT)
+#define RFKERNELONLY (RFSTOPPED | RFHIGHPID | RFPPWAIT | RFPROCDESC | RFPID1)
#endif /* __BSD_VISIBLE */

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