v4.19.13 snapshot.
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
new file mode 100644
index 0000000..06ed20d
--- /dev/null
+++ b/drivers/tty/sysrq.c
@@ -0,0 +1,1140 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Magic System Request Key Hacks
+ *
+ * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+ * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
+ *
+ * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
+ * overhauled to use key registration
+ * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
+ *
+ * Copyright (c) 2010 Dmitry Torokhov
+ * Input handler conversion
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/sched/signal.h>
+#include <linux/sched/rt.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task.h>
+#include <linux/interrupt.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/kdev_t.h>
+#include <linux/major.h>
+#include <linux/reboot.h>
+#include <linux/sysrq.h>
+#include <linux/kbd_kern.h>
+#include <linux/proc_fs.h>
+#include <linux/nmi.h>
+#include <linux/quotaops.h>
+#include <linux/perf_event.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/suspend.h>
+#include <linux/writeback.h>
+#include <linux/swap.h>
+#include <linux/spinlock.h>
+#include <linux/vt_kern.h>
+#include <linux/workqueue.h>
+#include <linux/hrtimer.h>
+#include <linux/oom.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/uaccess.h>
+#include <linux/moduleparam.h>
+#include <linux/jiffies.h>
+#include <linux/syscalls.h>
+#include <linux/of.h>
+#include <linux/rcupdate.h>
+
+#include <asm/ptrace.h>
+#include <asm/irq_regs.h>
+
+/* Whether we react on sysrq keys or just ignore them */
+static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
+static bool __read_mostly sysrq_always_enabled;
+
+static bool sysrq_on(void)
+{
+ return sysrq_enabled || sysrq_always_enabled;
+}
+
+/*
+ * A value of 1 means 'all', other nonzero values are an op mask:
+ */
+static bool sysrq_on_mask(int mask)
+{
+ return sysrq_always_enabled ||
+ sysrq_enabled == 1 ||
+ (sysrq_enabled & mask);
+}
+
+static int __init sysrq_always_enabled_setup(char *str)
+{
+ sysrq_always_enabled = true;
+ pr_info("sysrq always enabled.\n");
+
+ return 1;
+}
+
+__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
+
+
+static void sysrq_handle_loglevel(int key)
+{
+ int i;
+
+ i = key - '0';
+ console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
+ pr_info("Loglevel set to %d\n", i);
+ console_loglevel = i;
+}
+static struct sysrq_key_op sysrq_loglevel_op = {
+ .handler = sysrq_handle_loglevel,
+ .help_msg = "loglevel(0-9)",
+ .action_msg = "Changing Loglevel",
+ .enable_mask = SYSRQ_ENABLE_LOG,
+};
+
+#ifdef CONFIG_VT
+static void sysrq_handle_SAK(int key)
+{
+ struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
+ schedule_work(SAK_work);
+}
+static struct sysrq_key_op sysrq_SAK_op = {
+ .handler = sysrq_handle_SAK,
+ .help_msg = "sak(k)",
+ .action_msg = "SAK",
+ .enable_mask = SYSRQ_ENABLE_KEYBOARD,
+};
+#else
+#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
+#endif
+
+#ifdef CONFIG_VT
+static void sysrq_handle_unraw(int key)
+{
+ vt_reset_unicode(fg_console);
+}
+
+static struct sysrq_key_op sysrq_unraw_op = {
+ .handler = sysrq_handle_unraw,
+ .help_msg = "unraw(r)",
+ .action_msg = "Keyboard mode set to system default",
+ .enable_mask = SYSRQ_ENABLE_KEYBOARD,
+};
+#else
+#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
+#endif /* CONFIG_VT */
+
+static void sysrq_handle_crash(int key)
+{
+ char *killer = NULL;
+
+ /* we need to release the RCU read lock here,
+ * otherwise we get an annoying
+ * 'BUG: sleeping function called from invalid context'
+ * complaint from the kernel before the panic.
+ */
+ rcu_read_unlock();
+ panic_on_oops = 1; /* force panic */
+ wmb();
+ *killer = 1;
+}
+static struct sysrq_key_op sysrq_crash_op = {
+ .handler = sysrq_handle_crash,
+ .help_msg = "crash(c)",
+ .action_msg = "Trigger a crash",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+
+static void sysrq_handle_reboot(int key)
+{
+ lockdep_off();
+ local_irq_enable();
+ emergency_restart();
+}
+static struct sysrq_key_op sysrq_reboot_op = {
+ .handler = sysrq_handle_reboot,
+ .help_msg = "reboot(b)",
+ .action_msg = "Resetting",
+ .enable_mask = SYSRQ_ENABLE_BOOT,
+};
+
+static void sysrq_handle_sync(int key)
+{
+ emergency_sync();
+}
+static struct sysrq_key_op sysrq_sync_op = {
+ .handler = sysrq_handle_sync,
+ .help_msg = "sync(s)",
+ .action_msg = "Emergency Sync",
+ .enable_mask = SYSRQ_ENABLE_SYNC,
+};
+
+static void sysrq_handle_show_timers(int key)
+{
+ sysrq_timer_list_show();
+}
+
+static struct sysrq_key_op sysrq_show_timers_op = {
+ .handler = sysrq_handle_show_timers,
+ .help_msg = "show-all-timers(q)",
+ .action_msg = "Show clockevent devices & pending hrtimers (no others)",
+};
+
+static void sysrq_handle_mountro(int key)
+{
+ emergency_remount();
+}
+static struct sysrq_key_op sysrq_mountro_op = {
+ .handler = sysrq_handle_mountro,
+ .help_msg = "unmount(u)",
+ .action_msg = "Emergency Remount R/O",
+ .enable_mask = SYSRQ_ENABLE_REMOUNT,
+};
+
+#ifdef CONFIG_LOCKDEP
+static void sysrq_handle_showlocks(int key)
+{
+ debug_show_all_locks();
+}
+
+static struct sysrq_key_op sysrq_showlocks_op = {
+ .handler = sysrq_handle_showlocks,
+ .help_msg = "show-all-locks(d)",
+ .action_msg = "Show Locks Held",
+};
+#else
+#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
+#endif
+
+#ifdef CONFIG_SMP
+static DEFINE_SPINLOCK(show_lock);
+
+static void showacpu(void *dummy)
+{
+ unsigned long flags;
+
+ /* Idle CPUs have no interesting backtrace. */
+ if (idle_cpu(smp_processor_id()))
+ return;
+
+ spin_lock_irqsave(&show_lock, flags);
+ pr_info("CPU%d:\n", smp_processor_id());
+ show_stack(NULL, NULL);
+ spin_unlock_irqrestore(&show_lock, flags);
+}
+
+static void sysrq_showregs_othercpus(struct work_struct *dummy)
+{
+ smp_call_function(showacpu, NULL, 0);
+}
+
+static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
+
+static void sysrq_handle_showallcpus(int key)
+{
+ /*
+ * Fall back to the workqueue based printing if the
+ * backtrace printing did not succeed or the
+ * architecture has no support for it:
+ */
+ if (!trigger_all_cpu_backtrace()) {
+ struct pt_regs *regs = NULL;
+
+ if (in_irq())
+ regs = get_irq_regs();
+ if (regs) {
+ pr_info("CPU%d:\n", smp_processor_id());
+ show_regs(regs);
+ }
+ schedule_work(&sysrq_showallcpus);
+ }
+}
+
+static struct sysrq_key_op sysrq_showallcpus_op = {
+ .handler = sysrq_handle_showallcpus,
+ .help_msg = "show-backtrace-all-active-cpus(l)",
+ .action_msg = "Show backtrace of all active CPUs",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+#endif
+
+static void sysrq_handle_showregs(int key)
+{
+ struct pt_regs *regs = NULL;
+
+ if (in_irq())
+ regs = get_irq_regs();
+ if (regs)
+ show_regs(regs);
+ perf_event_print_debug();
+}
+static struct sysrq_key_op sysrq_showregs_op = {
+ .handler = sysrq_handle_showregs,
+ .help_msg = "show-registers(p)",
+ .action_msg = "Show Regs",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+
+static void sysrq_handle_showstate(int key)
+{
+ show_state();
+ show_workqueue_state();
+}
+static struct sysrq_key_op sysrq_showstate_op = {
+ .handler = sysrq_handle_showstate,
+ .help_msg = "show-task-states(t)",
+ .action_msg = "Show State",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+
+static void sysrq_handle_showstate_blocked(int key)
+{
+ show_state_filter(TASK_UNINTERRUPTIBLE);
+}
+static struct sysrq_key_op sysrq_showstate_blocked_op = {
+ .handler = sysrq_handle_showstate_blocked,
+ .help_msg = "show-blocked-tasks(w)",
+ .action_msg = "Show Blocked State",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+
+#ifdef CONFIG_TRACING
+#include <linux/ftrace.h>
+
+static void sysrq_ftrace_dump(int key)
+{
+ ftrace_dump(DUMP_ALL);
+}
+static struct sysrq_key_op sysrq_ftrace_dump_op = {
+ .handler = sysrq_ftrace_dump,
+ .help_msg = "dump-ftrace-buffer(z)",
+ .action_msg = "Dump ftrace buffer",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+#else
+#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
+#endif
+
+static void sysrq_handle_showmem(int key)
+{
+ show_mem(0, NULL);
+}
+static struct sysrq_key_op sysrq_showmem_op = {
+ .handler = sysrq_handle_showmem,
+ .help_msg = "show-memory-usage(m)",
+ .action_msg = "Show Memory",
+ .enable_mask = SYSRQ_ENABLE_DUMP,
+};
+
+/*
+ * Signal sysrq helper function. Sends a signal to all user processes.
+ */
+static void send_sig_all(int sig)
+{
+ struct task_struct *p;
+
+ read_lock(&tasklist_lock);
+ for_each_process(p) {
+ if (p->flags & PF_KTHREAD)
+ continue;
+ if (is_global_init(p))
+ continue;
+
+ do_send_sig_info(sig, SEND_SIG_FORCED, p, PIDTYPE_MAX);
+ }
+ read_unlock(&tasklist_lock);
+}
+
+static void sysrq_handle_term(int key)
+{
+ send_sig_all(SIGTERM);
+ console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+}
+static struct sysrq_key_op sysrq_term_op = {
+ .handler = sysrq_handle_term,
+ .help_msg = "terminate-all-tasks(e)",
+ .action_msg = "Terminate All Tasks",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
+};
+
+static void moom_callback(struct work_struct *ignored)
+{
+ const gfp_t gfp_mask = GFP_KERNEL;
+ struct oom_control oc = {
+ .zonelist = node_zonelist(first_memory_node, gfp_mask),
+ .nodemask = NULL,
+ .memcg = NULL,
+ .gfp_mask = gfp_mask,
+ .order = -1,
+ };
+
+ mutex_lock(&oom_lock);
+ if (!out_of_memory(&oc))
+ pr_info("OOM request ignored. No task eligible\n");
+ mutex_unlock(&oom_lock);
+}
+
+static DECLARE_WORK(moom_work, moom_callback);
+
+static void sysrq_handle_moom(int key)
+{
+ schedule_work(&moom_work);
+}
+static struct sysrq_key_op sysrq_moom_op = {
+ .handler = sysrq_handle_moom,
+ .help_msg = "memory-full-oom-kill(f)",
+ .action_msg = "Manual OOM execution",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
+};
+
+#ifdef CONFIG_BLOCK
+static void sysrq_handle_thaw(int key)
+{
+ emergency_thaw_all();
+}
+static struct sysrq_key_op sysrq_thaw_op = {
+ .handler = sysrq_handle_thaw,
+ .help_msg = "thaw-filesystems(j)",
+ .action_msg = "Emergency Thaw of all frozen filesystems",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
+};
+#endif
+
+static void sysrq_handle_kill(int key)
+{
+ send_sig_all(SIGKILL);
+ console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+}
+static struct sysrq_key_op sysrq_kill_op = {
+ .handler = sysrq_handle_kill,
+ .help_msg = "kill-all-tasks(i)",
+ .action_msg = "Kill All Tasks",
+ .enable_mask = SYSRQ_ENABLE_SIGNAL,
+};
+
+static void sysrq_handle_unrt(int key)
+{
+ normalize_rt_tasks();
+}
+static struct sysrq_key_op sysrq_unrt_op = {
+ .handler = sysrq_handle_unrt,
+ .help_msg = "nice-all-RT-tasks(n)",
+ .action_msg = "Nice All RT Tasks",
+ .enable_mask = SYSRQ_ENABLE_RTNICE,
+};
+
+/* Key Operations table and lock */
+static DEFINE_SPINLOCK(sysrq_key_table_lock);
+
+static struct sysrq_key_op *sysrq_key_table[36] = {
+ &sysrq_loglevel_op, /* 0 */
+ &sysrq_loglevel_op, /* 1 */
+ &sysrq_loglevel_op, /* 2 */
+ &sysrq_loglevel_op, /* 3 */
+ &sysrq_loglevel_op, /* 4 */
+ &sysrq_loglevel_op, /* 5 */
+ &sysrq_loglevel_op, /* 6 */
+ &sysrq_loglevel_op, /* 7 */
+ &sysrq_loglevel_op, /* 8 */
+ &sysrq_loglevel_op, /* 9 */
+
+ /*
+ * a: Don't use for system provided sysrqs, it is handled specially on
+ * sparc and will never arrive.
+ */
+ NULL, /* a */
+ &sysrq_reboot_op, /* b */
+ &sysrq_crash_op, /* c */
+ &sysrq_showlocks_op, /* d */
+ &sysrq_term_op, /* e */
+ &sysrq_moom_op, /* f */
+ /* g: May be registered for the kernel debugger */
+ NULL, /* g */
+ NULL, /* h - reserved for help */
+ &sysrq_kill_op, /* i */
+#ifdef CONFIG_BLOCK
+ &sysrq_thaw_op, /* j */
+#else
+ NULL, /* j */
+#endif
+ &sysrq_SAK_op, /* k */
+#ifdef CONFIG_SMP
+ &sysrq_showallcpus_op, /* l */
+#else
+ NULL, /* l */
+#endif
+ &sysrq_showmem_op, /* m */
+ &sysrq_unrt_op, /* n */
+ /* o: This will often be registered as 'Off' at init time */
+ NULL, /* o */
+ &sysrq_showregs_op, /* p */
+ &sysrq_show_timers_op, /* q */
+ &sysrq_unraw_op, /* r */
+ &sysrq_sync_op, /* s */
+ &sysrq_showstate_op, /* t */
+ &sysrq_mountro_op, /* u */
+ /* v: May be registered for frame buffer console restore */
+ NULL, /* v */
+ &sysrq_showstate_blocked_op, /* w */
+ /* x: May be registered on mips for TLB dump */
+ /* x: May be registered on ppc/powerpc for xmon */
+ /* x: May be registered on sparc64 for global PMU dump */
+ NULL, /* x */
+ /* y: May be registered on sparc64 for global register dump */
+ NULL, /* y */
+ &sysrq_ftrace_dump_op, /* z */
+};
+
+/* key2index calculation, -1 on invalid index */
+static int sysrq_key_table_key2index(int key)
+{
+ int retval;
+
+ if ((key >= '0') && (key <= '9'))
+ retval = key - '0';
+ else if ((key >= 'a') && (key <= 'z'))
+ retval = key + 10 - 'a';
+ else
+ retval = -1;
+ return retval;
+}
+
+/*
+ * get and put functions for the table, exposed to modules.
+ */
+struct sysrq_key_op *__sysrq_get_key_op(int key)
+{
+ struct sysrq_key_op *op_p = NULL;
+ int i;
+
+ i = sysrq_key_table_key2index(key);
+ if (i != -1)
+ op_p = sysrq_key_table[i];
+
+ return op_p;
+}
+
+static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
+{
+ int i = sysrq_key_table_key2index(key);
+
+ if (i != -1)
+ sysrq_key_table[i] = op_p;
+}
+
+void __handle_sysrq(int key, bool check_mask)
+{
+ struct sysrq_key_op *op_p;
+ int orig_log_level;
+ int i;
+
+ rcu_sysrq_start();
+ rcu_read_lock();
+ /*
+ * Raise the apparent loglevel to maximum so that the sysrq header
+ * is shown to provide the user with positive feedback. We do not
+ * simply emit this at KERN_EMERG as that would change message
+ * routing in the consumers of /proc/kmsg.
+ */
+ orig_log_level = console_loglevel;
+ console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
+ pr_info("SysRq : ");
+
+ op_p = __sysrq_get_key_op(key);
+ if (op_p) {
+ /*
+ * Should we check for enabled operations (/proc/sysrq-trigger
+ * should not) and is the invoked operation enabled?
+ */
+ if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
+ pr_cont("%s\n", op_p->action_msg);
+ console_loglevel = orig_log_level;
+ op_p->handler(key);
+ } else {
+ pr_cont("This sysrq operation is disabled.\n");
+ }
+ } else {
+ pr_cont("HELP : ");
+ /* Only print the help msg once per handler */
+ for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
+ if (sysrq_key_table[i]) {
+ int j;
+
+ for (j = 0; sysrq_key_table[i] !=
+ sysrq_key_table[j]; j++)
+ ;
+ if (j != i)
+ continue;
+ pr_cont("%s ", sysrq_key_table[i]->help_msg);
+ }
+ }
+ pr_cont("\n");
+ console_loglevel = orig_log_level;
+ }
+ rcu_read_unlock();
+ rcu_sysrq_end();
+}
+
+void handle_sysrq(int key)
+{
+ if (sysrq_on())
+ __handle_sysrq(key, true);
+}
+EXPORT_SYMBOL(handle_sysrq);
+
+#ifdef CONFIG_INPUT
+static int sysrq_reset_downtime_ms;
+
+/* Simple translation table for the SysRq keys */
+static const unsigned char sysrq_xlate[KEY_CNT] =
+ "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
+ "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
+ "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
+ "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
+ "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
+ "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
+ "\r\000/"; /* 0x60 - 0x6f */
+
+struct sysrq_state {
+ struct input_handle handle;
+ struct work_struct reinject_work;
+ unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
+ unsigned int alt;
+ unsigned int alt_use;
+ bool active;
+ bool need_reinject;
+ bool reinjecting;
+
+ /* reset sequence handling */
+ bool reset_canceled;
+ bool reset_requested;
+ unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
+ int reset_seq_len;
+ int reset_seq_cnt;
+ int reset_seq_version;
+ struct timer_list keyreset_timer;
+};
+
+#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
+static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
+static unsigned int sysrq_reset_seq_len;
+static unsigned int sysrq_reset_seq_version = 1;
+
+static void sysrq_parse_reset_sequence(struct sysrq_state *state)
+{
+ int i;
+ unsigned short key;
+
+ state->reset_seq_cnt = 0;
+
+ for (i = 0; i < sysrq_reset_seq_len; i++) {
+ key = sysrq_reset_seq[i];
+
+ if (key == KEY_RESERVED || key > KEY_MAX)
+ break;
+
+ __set_bit(key, state->reset_keybit);
+ state->reset_seq_len++;
+
+ if (test_bit(key, state->key_down))
+ state->reset_seq_cnt++;
+ }
+
+ /* Disable reset until old keys are not released */
+ state->reset_canceled = state->reset_seq_cnt != 0;
+
+ state->reset_seq_version = sysrq_reset_seq_version;
+}
+
+static void sysrq_do_reset(struct timer_list *t)
+{
+ struct sysrq_state *state = from_timer(state, t, keyreset_timer);
+
+ state->reset_requested = true;
+
+ ksys_sync();
+ kernel_restart(NULL);
+}
+
+static void sysrq_handle_reset_request(struct sysrq_state *state)
+{
+ if (state->reset_requested)
+ __handle_sysrq(sysrq_xlate[KEY_B], false);
+
+ if (sysrq_reset_downtime_ms)
+ mod_timer(&state->keyreset_timer,
+ jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
+ else
+ sysrq_do_reset(&state->keyreset_timer);
+}
+
+static void sysrq_detect_reset_sequence(struct sysrq_state *state,
+ unsigned int code, int value)
+{
+ if (!test_bit(code, state->reset_keybit)) {
+ /*
+ * Pressing any key _not_ in reset sequence cancels
+ * the reset sequence. Also cancelling the timer in
+ * case additional keys were pressed after a reset
+ * has been requested.
+ */
+ if (value && state->reset_seq_cnt) {
+ state->reset_canceled = true;
+ del_timer(&state->keyreset_timer);
+ }
+ } else if (value == 0) {
+ /*
+ * Key release - all keys in the reset sequence need
+ * to be pressed and held for the reset timeout
+ * to hold.
+ */
+ del_timer(&state->keyreset_timer);
+
+ if (--state->reset_seq_cnt == 0)
+ state->reset_canceled = false;
+ } else if (value == 1) {
+ /* key press, not autorepeat */
+ if (++state->reset_seq_cnt == state->reset_seq_len &&
+ !state->reset_canceled) {
+ sysrq_handle_reset_request(state);
+ }
+ }
+}
+
+#ifdef CONFIG_OF
+static void sysrq_of_get_keyreset_config(void)
+{
+ u32 key;
+ struct device_node *np;
+ struct property *prop;
+ const __be32 *p;
+
+ np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
+ if (!np) {
+ pr_debug("No sysrq node found");
+ return;
+ }
+
+ /* Reset in case a __weak definition was present */
+ sysrq_reset_seq_len = 0;
+
+ of_property_for_each_u32(np, "keyset", prop, p, key) {
+ if (key == KEY_RESERVED || key > KEY_MAX ||
+ sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
+ break;
+
+ sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
+ }
+
+ /* Get reset timeout if any. */
+ of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
+}
+#else
+static void sysrq_of_get_keyreset_config(void)
+{
+}
+#endif
+
+static void sysrq_reinject_alt_sysrq(struct work_struct *work)
+{
+ struct sysrq_state *sysrq =
+ container_of(work, struct sysrq_state, reinject_work);
+ struct input_handle *handle = &sysrq->handle;
+ unsigned int alt_code = sysrq->alt_use;
+
+ if (sysrq->need_reinject) {
+ /* we do not want the assignment to be reordered */
+ sysrq->reinjecting = true;
+ mb();
+
+ /* Simulate press and release of Alt + SysRq */
+ input_inject_event(handle, EV_KEY, alt_code, 1);
+ input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
+ input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
+
+ input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
+ input_inject_event(handle, EV_KEY, alt_code, 0);
+ input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
+
+ mb();
+ sysrq->reinjecting = false;
+ }
+}
+
+static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
+ unsigned int code, int value)
+{
+ bool was_active = sysrq->active;
+ bool suppress;
+
+ switch (code) {
+
+ case KEY_LEFTALT:
+ case KEY_RIGHTALT:
+ if (!value) {
+ /* One of ALTs is being released */
+ if (sysrq->active && code == sysrq->alt_use)
+ sysrq->active = false;
+
+ sysrq->alt = KEY_RESERVED;
+
+ } else if (value != 2) {
+ sysrq->alt = code;
+ sysrq->need_reinject = false;
+ }
+ break;
+
+ case KEY_SYSRQ:
+ if (value == 1 && sysrq->alt != KEY_RESERVED) {
+ sysrq->active = true;
+ sysrq->alt_use = sysrq->alt;
+ /*
+ * If nothing else will be pressed we'll need
+ * to re-inject Alt-SysRq keysroke.
+ */
+ sysrq->need_reinject = true;
+ }
+
+ /*
+ * Pretend that sysrq was never pressed at all. This
+ * is needed to properly handle KGDB which will try
+ * to release all keys after exiting debugger. If we
+ * do not clear key bit it KGDB will end up sending
+ * release events for Alt and SysRq, potentially
+ * triggering print screen function.
+ */
+ if (sysrq->active)
+ clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
+
+ break;
+
+ default:
+ if (sysrq->active && value && value != 2) {
+ sysrq->need_reinject = false;
+ __handle_sysrq(sysrq_xlate[code], true);
+ }
+ break;
+ }
+
+ suppress = sysrq->active;
+
+ if (!sysrq->active) {
+
+ /*
+ * See if reset sequence has changed since the last time.
+ */
+ if (sysrq->reset_seq_version != sysrq_reset_seq_version)
+ sysrq_parse_reset_sequence(sysrq);
+
+ /*
+ * If we are not suppressing key presses keep track of
+ * keyboard state so we can release keys that have been
+ * pressed before entering SysRq mode.
+ */
+ if (value)
+ set_bit(code, sysrq->key_down);
+ else
+ clear_bit(code, sysrq->key_down);
+
+ if (was_active)
+ schedule_work(&sysrq->reinject_work);
+
+ /* Check for reset sequence */
+ sysrq_detect_reset_sequence(sysrq, code, value);
+
+ } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
+ /*
+ * Pass on release events for keys that was pressed before
+ * entering SysRq mode.
+ */
+ suppress = false;
+ }
+
+ return suppress;
+}
+
+static bool sysrq_filter(struct input_handle *handle,
+ unsigned int type, unsigned int code, int value)
+{
+ struct sysrq_state *sysrq = handle->private;
+ bool suppress;
+
+ /*
+ * Do not filter anything if we are in the process of re-injecting
+ * Alt+SysRq combination.
+ */
+ if (sysrq->reinjecting)
+ return false;
+
+ switch (type) {
+
+ case EV_SYN:
+ suppress = false;
+ break;
+
+ case EV_KEY:
+ suppress = sysrq_handle_keypress(sysrq, code, value);
+ break;
+
+ default:
+ suppress = sysrq->active;
+ break;
+ }
+
+ return suppress;
+}
+
+static int sysrq_connect(struct input_handler *handler,
+ struct input_dev *dev,
+ const struct input_device_id *id)
+{
+ struct sysrq_state *sysrq;
+ int error;
+
+ sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
+ if (!sysrq)
+ return -ENOMEM;
+
+ INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
+
+ sysrq->handle.dev = dev;
+ sysrq->handle.handler = handler;
+ sysrq->handle.name = "sysrq";
+ sysrq->handle.private = sysrq;
+ timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
+
+ error = input_register_handle(&sysrq->handle);
+ if (error) {
+ pr_err("Failed to register input sysrq handler, error %d\n",
+ error);
+ goto err_free;
+ }
+
+ error = input_open_device(&sysrq->handle);
+ if (error) {
+ pr_err("Failed to open input device, error %d\n", error);
+ goto err_unregister;
+ }
+
+ return 0;
+
+ err_unregister:
+ input_unregister_handle(&sysrq->handle);
+ err_free:
+ kfree(sysrq);
+ return error;
+}
+
+static void sysrq_disconnect(struct input_handle *handle)
+{
+ struct sysrq_state *sysrq = handle->private;
+
+ input_close_device(handle);
+ cancel_work_sync(&sysrq->reinject_work);
+ del_timer_sync(&sysrq->keyreset_timer);
+ input_unregister_handle(handle);
+ kfree(sysrq);
+}
+
+/*
+ * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
+ * keyboards have SysRq key predefined and so user may add it to keymap
+ * later, but we expect all such keyboards to have left alt.
+ */
+static const struct input_device_id sysrq_ids[] = {
+ {
+ .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+ INPUT_DEVICE_ID_MATCH_KEYBIT,
+ .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
+ .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
+ },
+ { },
+};
+
+static struct input_handler sysrq_handler = {
+ .filter = sysrq_filter,
+ .connect = sysrq_connect,
+ .disconnect = sysrq_disconnect,
+ .name = "sysrq",
+ .id_table = sysrq_ids,
+};
+
+static bool sysrq_handler_registered;
+
+static inline void sysrq_register_handler(void)
+{
+ int error;
+
+ sysrq_of_get_keyreset_config();
+
+ error = input_register_handler(&sysrq_handler);
+ if (error)
+ pr_err("Failed to register input handler, error %d", error);
+ else
+ sysrq_handler_registered = true;
+}
+
+static inline void sysrq_unregister_handler(void)
+{
+ if (sysrq_handler_registered) {
+ input_unregister_handler(&sysrq_handler);
+ sysrq_handler_registered = false;
+ }
+}
+
+static int sysrq_reset_seq_param_set(const char *buffer,
+ const struct kernel_param *kp)
+{
+ unsigned long val;
+ int error;
+
+ error = kstrtoul(buffer, 0, &val);
+ if (error < 0)
+ return error;
+
+ if (val > KEY_MAX)
+ return -EINVAL;
+
+ *((unsigned short *)kp->arg) = val;
+ sysrq_reset_seq_version++;
+
+ return 0;
+}
+
+static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
+ .get = param_get_ushort,
+ .set = sysrq_reset_seq_param_set,
+};
+
+#define param_check_sysrq_reset_seq(name, p) \
+ __param_check(name, p, unsigned short)
+
+/*
+ * not really modular, but the easiest way to keep compat with existing
+ * bootargs behaviour is to continue using module_param here.
+ */
+module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
+ &sysrq_reset_seq_len, 0644);
+
+module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
+
+#else
+
+static inline void sysrq_register_handler(void)
+{
+}
+
+static inline void sysrq_unregister_handler(void)
+{
+}
+
+#endif /* CONFIG_INPUT */
+
+int sysrq_toggle_support(int enable_mask)
+{
+ bool was_enabled = sysrq_on();
+
+ sysrq_enabled = enable_mask;
+
+ if (was_enabled != sysrq_on()) {
+ if (sysrq_on())
+ sysrq_register_handler();
+ else
+ sysrq_unregister_handler();
+ }
+
+ return 0;
+}
+
+static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
+ struct sysrq_key_op *remove_op_p)
+{
+ int retval;
+
+ spin_lock(&sysrq_key_table_lock);
+ if (__sysrq_get_key_op(key) == remove_op_p) {
+ __sysrq_put_key_op(key, insert_op_p);
+ retval = 0;
+ } else {
+ retval = -1;
+ }
+ spin_unlock(&sysrq_key_table_lock);
+
+ /*
+ * A concurrent __handle_sysrq either got the old op or the new op.
+ * Wait for it to go away before returning, so the code for an old
+ * op is not freed (eg. on module unload) while it is in use.
+ */
+ synchronize_rcu();
+
+ return retval;
+}
+
+int register_sysrq_key(int key, struct sysrq_key_op *op_p)
+{
+ return __sysrq_swap_key_ops(key, op_p, NULL);
+}
+EXPORT_SYMBOL(register_sysrq_key);
+
+int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
+{
+ return __sysrq_swap_key_ops(key, NULL, op_p);
+}
+EXPORT_SYMBOL(unregister_sysrq_key);
+
+#ifdef CONFIG_PROC_FS
+/*
+ * writing 'C' to /proc/sysrq-trigger is like sysrq-C
+ */
+static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ if (count) {
+ char c;
+
+ if (get_user(c, buf))
+ return -EFAULT;
+ __handle_sysrq(c, false);
+ }
+
+ return count;
+}
+
+static const struct file_operations proc_sysrq_trigger_operations = {
+ .write = write_sysrq_trigger,
+ .llseek = noop_llseek,
+};
+
+static void sysrq_init_procfs(void)
+{
+ if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
+ &proc_sysrq_trigger_operations))
+ pr_err("Failed to register proc interface\n");
+}
+
+#else
+
+static inline void sysrq_init_procfs(void)
+{
+}
+
+#endif /* CONFIG_PROC_FS */
+
+static int __init sysrq_init(void)
+{
+ sysrq_init_procfs();
+
+ if (sysrq_on())
+ sysrq_register_handler();
+
+ return 0;
+}
+device_initcall(sysrq_init);