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0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  *  Linux Magic System Request Key Hacks
0004  *
0005  *  (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
0006  *  based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
0007  *
0008  *  (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
0009  *  overhauled to use key registration
0010  *  based upon discusions in irc://irc.openprojects.net/#kernelnewbies
0011  *
0012  *  Copyright (c) 2010 Dmitry Torokhov
0013  *  Input handler conversion
0014  */
0015 
0016 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0017 
0018 #include <linux/sched/signal.h>
0019 #include <linux/sched/rt.h>
0020 #include <linux/sched/debug.h>
0021 #include <linux/sched/task.h>
0022 #include <linux/ctype.h>
0023 #include <linux/interrupt.h>
0024 #include <linux/mm.h>
0025 #include <linux/fs.h>
0026 #include <linux/mount.h>
0027 #include <linux/kdev_t.h>
0028 #include <linux/major.h>
0029 #include <linux/reboot.h>
0030 #include <linux/sysrq.h>
0031 #include <linux/kbd_kern.h>
0032 #include <linux/proc_fs.h>
0033 #include <linux/nmi.h>
0034 #include <linux/quotaops.h>
0035 #include <linux/perf_event.h>
0036 #include <linux/kernel.h>
0037 #include <linux/module.h>
0038 #include <linux/suspend.h>
0039 #include <linux/writeback.h>
0040 #include <linux/swap.h>
0041 #include <linux/spinlock.h>
0042 #include <linux/vt_kern.h>
0043 #include <linux/workqueue.h>
0044 #include <linux/hrtimer.h>
0045 #include <linux/oom.h>
0046 #include <linux/slab.h>
0047 #include <linux/input.h>
0048 #include <linux/uaccess.h>
0049 #include <linux/moduleparam.h>
0050 #include <linux/jiffies.h>
0051 #include <linux/syscalls.h>
0052 #include <linux/of.h>
0053 #include <linux/rcupdate.h>
0054 
0055 #include <asm/ptrace.h>
0056 #include <asm/irq_regs.h>
0057 
0058 /* Whether we react on sysrq keys or just ignore them */
0059 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
0060 static bool __read_mostly sysrq_always_enabled;
0061 
0062 static bool sysrq_on(void)
0063 {
0064     return sysrq_enabled || sysrq_always_enabled;
0065 }
0066 
0067 /**
0068  * sysrq_mask - Getter for sysrq_enabled mask.
0069  *
0070  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
0071  */
0072 int sysrq_mask(void)
0073 {
0074     if (sysrq_always_enabled)
0075         return 1;
0076     return sysrq_enabled;
0077 }
0078 EXPORT_SYMBOL_GPL(sysrq_mask);
0079 
0080 /*
0081  * A value of 1 means 'all', other nonzero values are an op mask:
0082  */
0083 static bool sysrq_on_mask(int mask)
0084 {
0085     return sysrq_always_enabled ||
0086            sysrq_enabled == 1 ||
0087            (sysrq_enabled & mask);
0088 }
0089 
0090 static int __init sysrq_always_enabled_setup(char *str)
0091 {
0092     sysrq_always_enabled = true;
0093     pr_info("sysrq always enabled.\n");
0094 
0095     return 1;
0096 }
0097 
0098 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
0099 
0100 
0101 static void sysrq_handle_loglevel(int key)
0102 {
0103     int i;
0104 
0105     i = key - '0';
0106     console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
0107     pr_info("Loglevel set to %d\n", i);
0108     console_loglevel = i;
0109 }
0110 static const struct sysrq_key_op sysrq_loglevel_op = {
0111     .handler    = sysrq_handle_loglevel,
0112     .help_msg   = "loglevel(0-9)",
0113     .action_msg = "Changing Loglevel",
0114     .enable_mask    = SYSRQ_ENABLE_LOG,
0115 };
0116 
0117 #ifdef CONFIG_VT
0118 static void sysrq_handle_SAK(int key)
0119 {
0120     struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
0121 
0122     schedule_work(SAK_work);
0123 }
0124 static const struct sysrq_key_op sysrq_SAK_op = {
0125     .handler    = sysrq_handle_SAK,
0126     .help_msg   = "sak(k)",
0127     .action_msg = "SAK",
0128     .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
0129 };
0130 #else
0131 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
0132 #endif
0133 
0134 #ifdef CONFIG_VT
0135 static void sysrq_handle_unraw(int key)
0136 {
0137     vt_reset_unicode(fg_console);
0138 }
0139 
0140 static const struct sysrq_key_op sysrq_unraw_op = {
0141     .handler    = sysrq_handle_unraw,
0142     .help_msg   = "unraw(r)",
0143     .action_msg = "Keyboard mode set to system default",
0144     .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
0145 };
0146 #else
0147 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
0148 #endif /* CONFIG_VT */
0149 
0150 static void sysrq_handle_crash(int key)
0151 {
0152     /* release the RCU read lock before crashing */
0153     rcu_read_unlock();
0154 
0155     panic("sysrq triggered crash\n");
0156 }
0157 static const struct sysrq_key_op sysrq_crash_op = {
0158     .handler    = sysrq_handle_crash,
0159     .help_msg   = "crash(c)",
0160     .action_msg = "Trigger a crash",
0161     .enable_mask    = SYSRQ_ENABLE_DUMP,
0162 };
0163 
0164 static void sysrq_handle_reboot(int key)
0165 {
0166     lockdep_off();
0167     local_irq_enable();
0168     emergency_restart();
0169 }
0170 static const struct sysrq_key_op sysrq_reboot_op = {
0171     .handler    = sysrq_handle_reboot,
0172     .help_msg   = "reboot(b)",
0173     .action_msg = "Resetting",
0174     .enable_mask    = SYSRQ_ENABLE_BOOT,
0175 };
0176 
0177 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
0178 
0179 static void sysrq_handle_sync(int key)
0180 {
0181     emergency_sync();
0182 }
0183 static const struct sysrq_key_op sysrq_sync_op = {
0184     .handler    = sysrq_handle_sync,
0185     .help_msg   = "sync(s)",
0186     .action_msg = "Emergency Sync",
0187     .enable_mask    = SYSRQ_ENABLE_SYNC,
0188 };
0189 
0190 static void sysrq_handle_show_timers(int key)
0191 {
0192     sysrq_timer_list_show();
0193 }
0194 
0195 static const struct sysrq_key_op sysrq_show_timers_op = {
0196     .handler    = sysrq_handle_show_timers,
0197     .help_msg   = "show-all-timers(q)",
0198     .action_msg = "Show clockevent devices & pending hrtimers (no others)",
0199 };
0200 
0201 static void sysrq_handle_mountro(int key)
0202 {
0203     emergency_remount();
0204 }
0205 static const struct sysrq_key_op sysrq_mountro_op = {
0206     .handler    = sysrq_handle_mountro,
0207     .help_msg   = "unmount(u)",
0208     .action_msg = "Emergency Remount R/O",
0209     .enable_mask    = SYSRQ_ENABLE_REMOUNT,
0210 };
0211 
0212 #ifdef CONFIG_LOCKDEP
0213 static void sysrq_handle_showlocks(int key)
0214 {
0215     debug_show_all_locks();
0216 }
0217 
0218 static const struct sysrq_key_op sysrq_showlocks_op = {
0219     .handler    = sysrq_handle_showlocks,
0220     .help_msg   = "show-all-locks(d)",
0221     .action_msg = "Show Locks Held",
0222 };
0223 #else
0224 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
0225 #endif
0226 
0227 #ifdef CONFIG_SMP
0228 static DEFINE_RAW_SPINLOCK(show_lock);
0229 
0230 static void showacpu(void *dummy)
0231 {
0232     unsigned long flags;
0233 
0234     /* Idle CPUs have no interesting backtrace. */
0235     if (idle_cpu(smp_processor_id())) {
0236         pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
0237         return;
0238     }
0239 
0240     raw_spin_lock_irqsave(&show_lock, flags);
0241     pr_info("CPU%d:\n", smp_processor_id());
0242     show_stack(NULL, NULL, KERN_INFO);
0243     raw_spin_unlock_irqrestore(&show_lock, flags);
0244 }
0245 
0246 static void sysrq_showregs_othercpus(struct work_struct *dummy)
0247 {
0248     smp_call_function(showacpu, NULL, 0);
0249 }
0250 
0251 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
0252 
0253 static void sysrq_handle_showallcpus(int key)
0254 {
0255     /*
0256      * Fall back to the workqueue based printing if the
0257      * backtrace printing did not succeed or the
0258      * architecture has no support for it:
0259      */
0260     if (!trigger_all_cpu_backtrace()) {
0261         struct pt_regs *regs = NULL;
0262 
0263         if (in_hardirq())
0264             regs = get_irq_regs();
0265 
0266         pr_info("CPU%d:\n", smp_processor_id());
0267         if (regs)
0268             show_regs(regs);
0269         else
0270             show_stack(NULL, NULL, KERN_INFO);
0271 
0272         schedule_work(&sysrq_showallcpus);
0273     }
0274 }
0275 
0276 static const struct sysrq_key_op sysrq_showallcpus_op = {
0277     .handler    = sysrq_handle_showallcpus,
0278     .help_msg   = "show-backtrace-all-active-cpus(l)",
0279     .action_msg = "Show backtrace of all active CPUs",
0280     .enable_mask    = SYSRQ_ENABLE_DUMP,
0281 };
0282 #else
0283 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
0284 #endif
0285 
0286 static void sysrq_handle_showregs(int key)
0287 {
0288     struct pt_regs *regs = NULL;
0289 
0290     if (in_hardirq())
0291         regs = get_irq_regs();
0292     if (regs)
0293         show_regs(regs);
0294     perf_event_print_debug();
0295 }
0296 static const struct sysrq_key_op sysrq_showregs_op = {
0297     .handler    = sysrq_handle_showregs,
0298     .help_msg   = "show-registers(p)",
0299     .action_msg = "Show Regs",
0300     .enable_mask    = SYSRQ_ENABLE_DUMP,
0301 };
0302 
0303 static void sysrq_handle_showstate(int key)
0304 {
0305     show_state();
0306     show_all_workqueues();
0307 }
0308 static const struct sysrq_key_op sysrq_showstate_op = {
0309     .handler    = sysrq_handle_showstate,
0310     .help_msg   = "show-task-states(t)",
0311     .action_msg = "Show State",
0312     .enable_mask    = SYSRQ_ENABLE_DUMP,
0313 };
0314 
0315 static void sysrq_handle_showstate_blocked(int key)
0316 {
0317     show_state_filter(TASK_UNINTERRUPTIBLE);
0318 }
0319 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
0320     .handler    = sysrq_handle_showstate_blocked,
0321     .help_msg   = "show-blocked-tasks(w)",
0322     .action_msg = "Show Blocked State",
0323     .enable_mask    = SYSRQ_ENABLE_DUMP,
0324 };
0325 
0326 #ifdef CONFIG_TRACING
0327 #include <linux/ftrace.h>
0328 
0329 static void sysrq_ftrace_dump(int key)
0330 {
0331     ftrace_dump(DUMP_ALL);
0332 }
0333 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
0334     .handler    = sysrq_ftrace_dump,
0335     .help_msg   = "dump-ftrace-buffer(z)",
0336     .action_msg = "Dump ftrace buffer",
0337     .enable_mask    = SYSRQ_ENABLE_DUMP,
0338 };
0339 #else
0340 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
0341 #endif
0342 
0343 static void sysrq_handle_showmem(int key)
0344 {
0345     show_mem(0, NULL);
0346 }
0347 static const struct sysrq_key_op sysrq_showmem_op = {
0348     .handler    = sysrq_handle_showmem,
0349     .help_msg   = "show-memory-usage(m)",
0350     .action_msg = "Show Memory",
0351     .enable_mask    = SYSRQ_ENABLE_DUMP,
0352 };
0353 
0354 /*
0355  * Signal sysrq helper function.  Sends a signal to all user processes.
0356  */
0357 static void send_sig_all(int sig)
0358 {
0359     struct task_struct *p;
0360 
0361     read_lock(&tasklist_lock);
0362     for_each_process(p) {
0363         if (p->flags & PF_KTHREAD)
0364             continue;
0365         if (is_global_init(p))
0366             continue;
0367 
0368         do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
0369     }
0370     read_unlock(&tasklist_lock);
0371 }
0372 
0373 static void sysrq_handle_term(int key)
0374 {
0375     send_sig_all(SIGTERM);
0376     console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
0377 }
0378 static const struct sysrq_key_op sysrq_term_op = {
0379     .handler    = sysrq_handle_term,
0380     .help_msg   = "terminate-all-tasks(e)",
0381     .action_msg = "Terminate All Tasks",
0382     .enable_mask    = SYSRQ_ENABLE_SIGNAL,
0383 };
0384 
0385 static void moom_callback(struct work_struct *ignored)
0386 {
0387     const gfp_t gfp_mask = GFP_KERNEL;
0388     struct oom_control oc = {
0389         .zonelist = node_zonelist(first_memory_node, gfp_mask),
0390         .nodemask = NULL,
0391         .memcg = NULL,
0392         .gfp_mask = gfp_mask,
0393         .order = -1,
0394     };
0395 
0396     mutex_lock(&oom_lock);
0397     if (!out_of_memory(&oc))
0398         pr_info("OOM request ignored. No task eligible\n");
0399     mutex_unlock(&oom_lock);
0400 }
0401 
0402 static DECLARE_WORK(moom_work, moom_callback);
0403 
0404 static void sysrq_handle_moom(int key)
0405 {
0406     schedule_work(&moom_work);
0407 }
0408 static const struct sysrq_key_op sysrq_moom_op = {
0409     .handler    = sysrq_handle_moom,
0410     .help_msg   = "memory-full-oom-kill(f)",
0411     .action_msg = "Manual OOM execution",
0412     .enable_mask    = SYSRQ_ENABLE_SIGNAL,
0413 };
0414 
0415 #ifdef CONFIG_BLOCK
0416 static void sysrq_handle_thaw(int key)
0417 {
0418     emergency_thaw_all();
0419 }
0420 static const struct sysrq_key_op sysrq_thaw_op = {
0421     .handler    = sysrq_handle_thaw,
0422     .help_msg   = "thaw-filesystems(j)",
0423     .action_msg = "Emergency Thaw of all frozen filesystems",
0424     .enable_mask    = SYSRQ_ENABLE_SIGNAL,
0425 };
0426 #else
0427 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
0428 #endif
0429 
0430 static void sysrq_handle_kill(int key)
0431 {
0432     send_sig_all(SIGKILL);
0433     console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
0434 }
0435 static const struct sysrq_key_op sysrq_kill_op = {
0436     .handler    = sysrq_handle_kill,
0437     .help_msg   = "kill-all-tasks(i)",
0438     .action_msg = "Kill All Tasks",
0439     .enable_mask    = SYSRQ_ENABLE_SIGNAL,
0440 };
0441 
0442 static void sysrq_handle_unrt(int key)
0443 {
0444     normalize_rt_tasks();
0445 }
0446 static const struct sysrq_key_op sysrq_unrt_op = {
0447     .handler    = sysrq_handle_unrt,
0448     .help_msg   = "nice-all-RT-tasks(n)",
0449     .action_msg = "Nice All RT Tasks",
0450     .enable_mask    = SYSRQ_ENABLE_RTNICE,
0451 };
0452 
0453 /* Key Operations table and lock */
0454 static DEFINE_SPINLOCK(sysrq_key_table_lock);
0455 
0456 static const struct sysrq_key_op *sysrq_key_table[62] = {
0457     &sysrq_loglevel_op,     /* 0 */
0458     &sysrq_loglevel_op,     /* 1 */
0459     &sysrq_loglevel_op,     /* 2 */
0460     &sysrq_loglevel_op,     /* 3 */
0461     &sysrq_loglevel_op,     /* 4 */
0462     &sysrq_loglevel_op,     /* 5 */
0463     &sysrq_loglevel_op,     /* 6 */
0464     &sysrq_loglevel_op,     /* 7 */
0465     &sysrq_loglevel_op,     /* 8 */
0466     &sysrq_loglevel_op,     /* 9 */
0467 
0468     /*
0469      * a: Don't use for system provided sysrqs, it is handled specially on
0470      * sparc and will never arrive.
0471      */
0472     NULL,               /* a */
0473     &sysrq_reboot_op,       /* b */
0474     &sysrq_crash_op,        /* c */
0475     &sysrq_showlocks_op,        /* d */
0476     &sysrq_term_op,         /* e */
0477     &sysrq_moom_op,         /* f */
0478     /* g: May be registered for the kernel debugger */
0479     NULL,               /* g */
0480     NULL,               /* h - reserved for help */
0481     &sysrq_kill_op,         /* i */
0482     &sysrq_thaw_op,         /* j */
0483     &sysrq_SAK_op,          /* k */
0484     &sysrq_showallcpus_op,      /* l */
0485     &sysrq_showmem_op,      /* m */
0486     &sysrq_unrt_op,         /* n */
0487     /* o: This will often be registered as 'Off' at init time */
0488     NULL,               /* o */
0489     &sysrq_showregs_op,     /* p */
0490     &sysrq_show_timers_op,      /* q */
0491     &sysrq_unraw_op,        /* r */
0492     &sysrq_sync_op,         /* s */
0493     &sysrq_showstate_op,        /* t */
0494     &sysrq_mountro_op,      /* u */
0495     /* v: May be registered for frame buffer console restore */
0496     NULL,               /* v */
0497     &sysrq_showstate_blocked_op,    /* w */
0498     /* x: May be registered on mips for TLB dump */
0499     /* x: May be registered on ppc/powerpc for xmon */
0500     /* x: May be registered on sparc64 for global PMU dump */
0501     NULL,               /* x */
0502     /* y: May be registered on sparc64 for global register dump */
0503     NULL,               /* y */
0504     &sysrq_ftrace_dump_op,      /* z */
0505     NULL,               /* A */
0506     NULL,               /* B */
0507     NULL,               /* C */
0508     NULL,               /* D */
0509     NULL,               /* E */
0510     NULL,               /* F */
0511     NULL,               /* G */
0512     NULL,               /* H */
0513     NULL,               /* I */
0514     NULL,               /* J */
0515     NULL,               /* K */
0516     NULL,               /* L */
0517     NULL,               /* M */
0518     NULL,               /* N */
0519     NULL,               /* O */
0520     NULL,               /* P */
0521     NULL,               /* Q */
0522     NULL,               /* R */
0523     NULL,               /* S */
0524     NULL,               /* T */
0525     NULL,               /* U */
0526     NULL,               /* V */
0527     NULL,               /* W */
0528     NULL,               /* X */
0529     NULL,               /* Y */
0530     NULL,               /* Z */
0531 };
0532 
0533 /* key2index calculation, -1 on invalid index */
0534 static int sysrq_key_table_key2index(int key)
0535 {
0536     int retval;
0537 
0538     if ((key >= '0') && (key <= '9'))
0539         retval = key - '0';
0540     else if ((key >= 'a') && (key <= 'z'))
0541         retval = key + 10 - 'a';
0542     else if ((key >= 'A') && (key <= 'Z'))
0543         retval = key + 36 - 'A';
0544     else
0545         retval = -1;
0546     return retval;
0547 }
0548 
0549 /*
0550  * get and put functions for the table, exposed to modules.
0551  */
0552 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
0553 {
0554     const struct sysrq_key_op *op_p = NULL;
0555     int i;
0556 
0557     i = sysrq_key_table_key2index(key);
0558     if (i != -1)
0559         op_p = sysrq_key_table[i];
0560 
0561     return op_p;
0562 }
0563 
0564 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
0565 {
0566     int i = sysrq_key_table_key2index(key);
0567 
0568     if (i != -1)
0569         sysrq_key_table[i] = op_p;
0570 }
0571 
0572 void __handle_sysrq(int key, bool check_mask)
0573 {
0574     const struct sysrq_key_op *op_p;
0575     int orig_log_level;
0576     int orig_suppress_printk;
0577     int i;
0578 
0579     orig_suppress_printk = suppress_printk;
0580     suppress_printk = 0;
0581 
0582     rcu_sysrq_start();
0583     rcu_read_lock();
0584     /*
0585      * Raise the apparent loglevel to maximum so that the sysrq header
0586      * is shown to provide the user with positive feedback.  We do not
0587      * simply emit this at KERN_EMERG as that would change message
0588      * routing in the consumers of /proc/kmsg.
0589      */
0590     orig_log_level = console_loglevel;
0591     console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
0592 
0593     op_p = __sysrq_get_key_op(key);
0594     if (op_p) {
0595         /*
0596          * Should we check for enabled operations (/proc/sysrq-trigger
0597          * should not) and is the invoked operation enabled?
0598          */
0599         if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
0600             pr_info("%s\n", op_p->action_msg);
0601             console_loglevel = orig_log_level;
0602             op_p->handler(key);
0603         } else {
0604             pr_info("This sysrq operation is disabled.\n");
0605             console_loglevel = orig_log_level;
0606         }
0607     } else {
0608         pr_info("HELP : ");
0609         /* Only print the help msg once per handler */
0610         for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
0611             if (sysrq_key_table[i]) {
0612                 int j;
0613 
0614                 for (j = 0; sysrq_key_table[i] !=
0615                         sysrq_key_table[j]; j++)
0616                     ;
0617                 if (j != i)
0618                     continue;
0619                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
0620             }
0621         }
0622         pr_cont("\n");
0623         console_loglevel = orig_log_level;
0624     }
0625     rcu_read_unlock();
0626     rcu_sysrq_end();
0627 
0628     suppress_printk = orig_suppress_printk;
0629 }
0630 
0631 void handle_sysrq(int key)
0632 {
0633     if (sysrq_on())
0634         __handle_sysrq(key, true);
0635 }
0636 EXPORT_SYMBOL(handle_sysrq);
0637 
0638 #ifdef CONFIG_INPUT
0639 static int sysrq_reset_downtime_ms;
0640 
0641 /* Simple translation table for the SysRq keys */
0642 static const unsigned char sysrq_xlate[KEY_CNT] =
0643     "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
0644     "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
0645     "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
0646     "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
0647     "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
0648     "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
0649     "\r\000/";                                      /* 0x60 - 0x6f */
0650 
0651 struct sysrq_state {
0652     struct input_handle handle;
0653     struct work_struct reinject_work;
0654     unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
0655     unsigned int alt;
0656     unsigned int alt_use;
0657     unsigned int shift;
0658     unsigned int shift_use;
0659     bool active;
0660     bool need_reinject;
0661     bool reinjecting;
0662 
0663     /* reset sequence handling */
0664     bool reset_canceled;
0665     bool reset_requested;
0666     unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
0667     int reset_seq_len;
0668     int reset_seq_cnt;
0669     int reset_seq_version;
0670     struct timer_list keyreset_timer;
0671 };
0672 
0673 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
0674 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
0675 static unsigned int sysrq_reset_seq_len;
0676 static unsigned int sysrq_reset_seq_version = 1;
0677 
0678 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
0679 {
0680     int i;
0681     unsigned short key;
0682 
0683     state->reset_seq_cnt = 0;
0684 
0685     for (i = 0; i < sysrq_reset_seq_len; i++) {
0686         key = sysrq_reset_seq[i];
0687 
0688         if (key == KEY_RESERVED || key > KEY_MAX)
0689             break;
0690 
0691         __set_bit(key, state->reset_keybit);
0692         state->reset_seq_len++;
0693 
0694         if (test_bit(key, state->key_down))
0695             state->reset_seq_cnt++;
0696     }
0697 
0698     /* Disable reset until old keys are not released */
0699     state->reset_canceled = state->reset_seq_cnt != 0;
0700 
0701     state->reset_seq_version = sysrq_reset_seq_version;
0702 }
0703 
0704 static void sysrq_do_reset(struct timer_list *t)
0705 {
0706     struct sysrq_state *state = from_timer(state, t, keyreset_timer);
0707 
0708     state->reset_requested = true;
0709 
0710     orderly_reboot();
0711 }
0712 
0713 static void sysrq_handle_reset_request(struct sysrq_state *state)
0714 {
0715     if (state->reset_requested)
0716         __handle_sysrq(sysrq_xlate[KEY_B], false);
0717 
0718     if (sysrq_reset_downtime_ms)
0719         mod_timer(&state->keyreset_timer,
0720             jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
0721     else
0722         sysrq_do_reset(&state->keyreset_timer);
0723 }
0724 
0725 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
0726                     unsigned int code, int value)
0727 {
0728     if (!test_bit(code, state->reset_keybit)) {
0729         /*
0730          * Pressing any key _not_ in reset sequence cancels
0731          * the reset sequence.  Also cancelling the timer in
0732          * case additional keys were pressed after a reset
0733          * has been requested.
0734          */
0735         if (value && state->reset_seq_cnt) {
0736             state->reset_canceled = true;
0737             del_timer(&state->keyreset_timer);
0738         }
0739     } else if (value == 0) {
0740         /*
0741          * Key release - all keys in the reset sequence need
0742          * to be pressed and held for the reset timeout
0743          * to hold.
0744          */
0745         del_timer(&state->keyreset_timer);
0746 
0747         if (--state->reset_seq_cnt == 0)
0748             state->reset_canceled = false;
0749     } else if (value == 1) {
0750         /* key press, not autorepeat */
0751         if (++state->reset_seq_cnt == state->reset_seq_len &&
0752             !state->reset_canceled) {
0753             sysrq_handle_reset_request(state);
0754         }
0755     }
0756 }
0757 
0758 #ifdef CONFIG_OF
0759 static void sysrq_of_get_keyreset_config(void)
0760 {
0761     u32 key;
0762     struct device_node *np;
0763     struct property *prop;
0764     const __be32 *p;
0765 
0766     np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
0767     if (!np) {
0768         pr_debug("No sysrq node found");
0769         return;
0770     }
0771 
0772     /* Reset in case a __weak definition was present */
0773     sysrq_reset_seq_len = 0;
0774 
0775     of_property_for_each_u32(np, "keyset", prop, p, key) {
0776         if (key == KEY_RESERVED || key > KEY_MAX ||
0777             sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
0778             break;
0779 
0780         sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
0781     }
0782 
0783     /* Get reset timeout if any. */
0784     of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
0785 
0786     of_node_put(np);
0787 }
0788 #else
0789 static void sysrq_of_get_keyreset_config(void)
0790 {
0791 }
0792 #endif
0793 
0794 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
0795 {
0796     struct sysrq_state *sysrq =
0797             container_of(work, struct sysrq_state, reinject_work);
0798     struct input_handle *handle = &sysrq->handle;
0799     unsigned int alt_code = sysrq->alt_use;
0800 
0801     if (sysrq->need_reinject) {
0802         /* we do not want the assignment to be reordered */
0803         sysrq->reinjecting = true;
0804         mb();
0805 
0806         /* Simulate press and release of Alt + SysRq */
0807         input_inject_event(handle, EV_KEY, alt_code, 1);
0808         input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
0809         input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
0810 
0811         input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
0812         input_inject_event(handle, EV_KEY, alt_code, 0);
0813         input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
0814 
0815         mb();
0816         sysrq->reinjecting = false;
0817     }
0818 }
0819 
0820 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
0821                   unsigned int code, int value)
0822 {
0823     bool was_active = sysrq->active;
0824     bool suppress;
0825 
0826     switch (code) {
0827 
0828     case KEY_LEFTALT:
0829     case KEY_RIGHTALT:
0830         if (!value) {
0831             /* One of ALTs is being released */
0832             if (sysrq->active && code == sysrq->alt_use)
0833                 sysrq->active = false;
0834 
0835             sysrq->alt = KEY_RESERVED;
0836 
0837         } else if (value != 2) {
0838             sysrq->alt = code;
0839             sysrq->need_reinject = false;
0840         }
0841         break;
0842 
0843     case KEY_LEFTSHIFT:
0844     case KEY_RIGHTSHIFT:
0845         if (!value)
0846             sysrq->shift = KEY_RESERVED;
0847         else if (value != 2)
0848             sysrq->shift = code;
0849         if (sysrq->active)
0850             sysrq->shift_use = sysrq->shift;
0851         break;
0852 
0853     case KEY_SYSRQ:
0854         if (value == 1 && sysrq->alt != KEY_RESERVED) {
0855             sysrq->active = true;
0856             sysrq->alt_use = sysrq->alt;
0857             /* either RESERVED (for released) or actual code */
0858             sysrq->shift_use = sysrq->shift;
0859             /*
0860              * If nothing else will be pressed we'll need
0861              * to re-inject Alt-SysRq keysroke.
0862              */
0863             sysrq->need_reinject = true;
0864         }
0865 
0866         /*
0867          * Pretend that sysrq was never pressed at all. This
0868          * is needed to properly handle KGDB which will try
0869          * to release all keys after exiting debugger. If we
0870          * do not clear key bit it KGDB will end up sending
0871          * release events for Alt and SysRq, potentially
0872          * triggering print screen function.
0873          */
0874         if (sysrq->active)
0875             clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
0876 
0877         break;
0878 
0879     default:
0880         if (sysrq->active && value && value != 2) {
0881             unsigned char c = sysrq_xlate[code];
0882 
0883             sysrq->need_reinject = false;
0884             if (sysrq->shift_use != KEY_RESERVED)
0885                 c = toupper(c);
0886             __handle_sysrq(c, true);
0887         }
0888         break;
0889     }
0890 
0891     suppress = sysrq->active;
0892 
0893     if (!sysrq->active) {
0894 
0895         /*
0896          * See if reset sequence has changed since the last time.
0897          */
0898         if (sysrq->reset_seq_version != sysrq_reset_seq_version)
0899             sysrq_parse_reset_sequence(sysrq);
0900 
0901         /*
0902          * If we are not suppressing key presses keep track of
0903          * keyboard state so we can release keys that have been
0904          * pressed before entering SysRq mode.
0905          */
0906         if (value)
0907             set_bit(code, sysrq->key_down);
0908         else
0909             clear_bit(code, sysrq->key_down);
0910 
0911         if (was_active)
0912             schedule_work(&sysrq->reinject_work);
0913 
0914         /* Check for reset sequence */
0915         sysrq_detect_reset_sequence(sysrq, code, value);
0916 
0917     } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
0918         /*
0919          * Pass on release events for keys that was pressed before
0920          * entering SysRq mode.
0921          */
0922         suppress = false;
0923     }
0924 
0925     return suppress;
0926 }
0927 
0928 static bool sysrq_filter(struct input_handle *handle,
0929              unsigned int type, unsigned int code, int value)
0930 {
0931     struct sysrq_state *sysrq = handle->private;
0932     bool suppress;
0933 
0934     /*
0935      * Do not filter anything if we are in the process of re-injecting
0936      * Alt+SysRq combination.
0937      */
0938     if (sysrq->reinjecting)
0939         return false;
0940 
0941     switch (type) {
0942 
0943     case EV_SYN:
0944         suppress = false;
0945         break;
0946 
0947     case EV_KEY:
0948         suppress = sysrq_handle_keypress(sysrq, code, value);
0949         break;
0950 
0951     default:
0952         suppress = sysrq->active;
0953         break;
0954     }
0955 
0956     return suppress;
0957 }
0958 
0959 static int sysrq_connect(struct input_handler *handler,
0960              struct input_dev *dev,
0961              const struct input_device_id *id)
0962 {
0963     struct sysrq_state *sysrq;
0964     int error;
0965 
0966     sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
0967     if (!sysrq)
0968         return -ENOMEM;
0969 
0970     INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
0971 
0972     sysrq->handle.dev = dev;
0973     sysrq->handle.handler = handler;
0974     sysrq->handle.name = "sysrq";
0975     sysrq->handle.private = sysrq;
0976     timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
0977 
0978     error = input_register_handle(&sysrq->handle);
0979     if (error) {
0980         pr_err("Failed to register input sysrq handler, error %d\n",
0981             error);
0982         goto err_free;
0983     }
0984 
0985     error = input_open_device(&sysrq->handle);
0986     if (error) {
0987         pr_err("Failed to open input device, error %d\n", error);
0988         goto err_unregister;
0989     }
0990 
0991     return 0;
0992 
0993  err_unregister:
0994     input_unregister_handle(&sysrq->handle);
0995  err_free:
0996     kfree(sysrq);
0997     return error;
0998 }
0999 
1000 static void sysrq_disconnect(struct input_handle *handle)
1001 {
1002     struct sysrq_state *sysrq = handle->private;
1003 
1004     input_close_device(handle);
1005     cancel_work_sync(&sysrq->reinject_work);
1006     del_timer_sync(&sysrq->keyreset_timer);
1007     input_unregister_handle(handle);
1008     kfree(sysrq);
1009 }
1010 
1011 /*
1012  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1013  * keyboards have SysRq key predefined and so user may add it to keymap
1014  * later, but we expect all such keyboards to have left alt.
1015  */
1016 static const struct input_device_id sysrq_ids[] = {
1017     {
1018         .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1019                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1020         .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1021         .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1022     },
1023     { },
1024 };
1025 
1026 static struct input_handler sysrq_handler = {
1027     .filter     = sysrq_filter,
1028     .connect    = sysrq_connect,
1029     .disconnect = sysrq_disconnect,
1030     .name       = "sysrq",
1031     .id_table   = sysrq_ids,
1032 };
1033 
1034 static inline void sysrq_register_handler(void)
1035 {
1036     int error;
1037 
1038     sysrq_of_get_keyreset_config();
1039 
1040     error = input_register_handler(&sysrq_handler);
1041     if (error)
1042         pr_err("Failed to register input handler, error %d", error);
1043 }
1044 
1045 static inline void sysrq_unregister_handler(void)
1046 {
1047     input_unregister_handler(&sysrq_handler);
1048 }
1049 
1050 static int sysrq_reset_seq_param_set(const char *buffer,
1051                      const struct kernel_param *kp)
1052 {
1053     unsigned long val;
1054     int error;
1055 
1056     error = kstrtoul(buffer, 0, &val);
1057     if (error < 0)
1058         return error;
1059 
1060     if (val > KEY_MAX)
1061         return -EINVAL;
1062 
1063     *((unsigned short *)kp->arg) = val;
1064     sysrq_reset_seq_version++;
1065 
1066     return 0;
1067 }
1068 
1069 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1070     .get    = param_get_ushort,
1071     .set    = sysrq_reset_seq_param_set,
1072 };
1073 
1074 #define param_check_sysrq_reset_seq(name, p)    \
1075     __param_check(name, p, unsigned short)
1076 
1077 /*
1078  * not really modular, but the easiest way to keep compat with existing
1079  * bootargs behaviour is to continue using module_param here.
1080  */
1081 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1082              &sysrq_reset_seq_len, 0644);
1083 
1084 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1085 
1086 #else
1087 
1088 static inline void sysrq_register_handler(void)
1089 {
1090 }
1091 
1092 static inline void sysrq_unregister_handler(void)
1093 {
1094 }
1095 
1096 #endif /* CONFIG_INPUT */
1097 
1098 int sysrq_toggle_support(int enable_mask)
1099 {
1100     bool was_enabled = sysrq_on();
1101 
1102     sysrq_enabled = enable_mask;
1103 
1104     if (was_enabled != sysrq_on()) {
1105         if (sysrq_on())
1106             sysrq_register_handler();
1107         else
1108             sysrq_unregister_handler();
1109     }
1110 
1111     return 0;
1112 }
1113 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1114 
1115 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1116                 const struct sysrq_key_op *remove_op_p)
1117 {
1118     int retval;
1119 
1120     spin_lock(&sysrq_key_table_lock);
1121     if (__sysrq_get_key_op(key) == remove_op_p) {
1122         __sysrq_put_key_op(key, insert_op_p);
1123         retval = 0;
1124     } else {
1125         retval = -1;
1126     }
1127     spin_unlock(&sysrq_key_table_lock);
1128 
1129     /*
1130      * A concurrent __handle_sysrq either got the old op or the new op.
1131      * Wait for it to go away before returning, so the code for an old
1132      * op is not freed (eg. on module unload) while it is in use.
1133      */
1134     synchronize_rcu();
1135 
1136     return retval;
1137 }
1138 
1139 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1140 {
1141     return __sysrq_swap_key_ops(key, op_p, NULL);
1142 }
1143 EXPORT_SYMBOL(register_sysrq_key);
1144 
1145 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1146 {
1147     return __sysrq_swap_key_ops(key, NULL, op_p);
1148 }
1149 EXPORT_SYMBOL(unregister_sysrq_key);
1150 
1151 #ifdef CONFIG_PROC_FS
1152 /*
1153  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1154  */
1155 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1156                    size_t count, loff_t *ppos)
1157 {
1158     if (count) {
1159         char c;
1160 
1161         if (get_user(c, buf))
1162             return -EFAULT;
1163         __handle_sysrq(c, false);
1164     }
1165 
1166     return count;
1167 }
1168 
1169 static const struct proc_ops sysrq_trigger_proc_ops = {
1170     .proc_write = write_sysrq_trigger,
1171     .proc_lseek = noop_llseek,
1172 };
1173 
1174 static void sysrq_init_procfs(void)
1175 {
1176     if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1177              &sysrq_trigger_proc_ops))
1178         pr_err("Failed to register proc interface\n");
1179 }
1180 
1181 #else
1182 
1183 static inline void sysrq_init_procfs(void)
1184 {
1185 }
1186 
1187 #endif /* CONFIG_PROC_FS */
1188 
1189 static int __init sysrq_init(void)
1190 {
1191     sysrq_init_procfs();
1192 
1193     if (sysrq_on())
1194         sysrq_register_handler();
1195 
1196     return 0;
1197 }
1198 device_initcall(sysrq_init);
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