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Finit bringup: add optional fallback shell

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This patch adds an `--enable-fallback-shell` option to confiugre.
When enabled Finit will start `/bin/sh` on the console, but only
if there are no active TTYs running in the current runlevel.

With this it will be easier to do board bringup with Finit, but it also
enables using the fallback shell in a rescue mode (runlevel) where no
TTYs are allowed to run.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson
2016-09-18 10:27:03 +02:00
parent d373ebfdd7
commit ee901b018c
2 changed files with 55 additions and 2 deletions
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configure.ac
+6
View File
@@ -41,6 +41,9 @@ AC_ARG_ENABLE(emergency_shell,
AS_HELP_STRING([--enable-emergency-shell], [Experimental emergency fallback at boot.
Only use this for debugging very early boot problems with Finit.]))
AC_ARG_ENABLE(fallback_shell,
AS_HELP_STRING([--enable-fallback-shell], [Start a shell if no TTYs can start.]))
AC_ARG_ENABLE(rw-rootfs,
AS_HELP_STRING([--enable-rw-rootfs], [Remount / R/W at boot, usually not for embedded]))
@@ -120,6 +123,9 @@ AC_ARG_WITH(random-seed,
AS_IF([test "x$enable_emergency_shell" = "xyes"], [
AC_DEFINE(EMERGENCY_SHELL, 1, [Fork off init and let PID 1 wait and start /bin/sh if init crashes.])])
AS_IF([test "x$enable_fallback_shell" = "xyes"], [
AC_DEFINE(FALLBACK_SHELL, 1, [Start /bin/sh on console if no TTYs.])])
AS_IF([test "x$enable_rw_rootfs" = "xyes"], [
AC_DEFINE(REMOUNT_ROOTFS, 1, [Remount / as rw at boot])])
tty.c
+49 -2
View File
@@ -23,6 +23,8 @@
*/
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <lite/lite.h>
@@ -34,6 +36,7 @@
#include "utmp-api.h"
LIST_HEAD(, tty_node) tty_list = LIST_HEAD_INITIALIZER();
static pid_t fallback = 0;
/* tty [!1-9,S] <DEV> [BAUD[,BAUD,...]] [TERM] */
@@ -208,13 +211,54 @@ int tty_enabled(finit_tty_t *tty, int runlevel)
return 0;
}
/* TTY monitor, called by service_monitor() */
/*
* Fallback shell if no TTYs are active
*/
int tty_fallback(pid_t lost)
{
#ifdef FALLBACK_SHELL
if (lost == 1) {
if (fallback) {
_d("Stopping fallback shell");
kill(fallback, SIGKILL);
fallback = 0;
}
return 0;
}
if (fallback != lost || tty_num_active()) {
_d("Not starting fallback (%d) shell, lost pid %d", fallback, lost);
return 0;
}
_d("Starting fallback shell");
fallback = fork();
if (fallback)
return 1;
/*
* Become session leader and set controlling TTY
* to enable Ctrl-C and job control in shell.
*/
setsid();
ioctl(STDIN_FILENO, TIOCSCTTY, 1);
_exit(execl(_PATH_BSHELL, _PATH_BSHELL, NULL));
#endif /* FALLBACK_SHELL */
return 0;
}
/*
* TTY monitor, called by service_monitor()
*/
int tty_respawn(pid_t pid)
{
tty_node_t *entry = tty_find_by_pid(pid);
if (!entry)
return 0;
return tty_fallback(pid);
/* Set DEAD_PROCESS UTMP entry */
utmp_set_dead(pid);
@@ -241,6 +285,9 @@ void tty_runlevel(int runlevel)
else
tty_start(&entry->data);
}
/* Start fallback shell if enabled && no TTYs */
tty_fallback(tty_num_active() > 0 ? 1 : 0);
}
/**