Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1259 insertions, 0 deletions

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
new file mode 100644
index 000000000..c2e4b31b6
--- /dev/null
+++ b/drivers/tty/sysrq.c
@@ -0,0 +1,1259 @@
+// 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/ctype.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;
+}
+
+/**
+ * sysrq_mask - Getter for sysrq_enabled mask.
+ *
+ * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
+ */
+int sysrq_mask(void)
+{
+	if (sysrq_always_enabled)
+		return 1;
+	return sysrq_enabled;
+}
+EXPORT_SYMBOL_GPL(sysrq_mask);
+
+/*
+ * 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(u8 key)
+{
+	u8 loglevel = key - '0';
+
+	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
+	pr_info("Loglevel set to %u\n", loglevel);
+	console_loglevel = loglevel;
+}
+static const 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(u8 key)
+{
+	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
+
+	schedule_work(SAK_work);
+}
+static const 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 (*(const struct sysrq_key_op *)NULL)
+#endif
+
+#ifdef CONFIG_VT
+static void sysrq_handle_unraw(u8 key)
+{
+	vt_reset_unicode(fg_console);
+}
+
+static const 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 (*(const struct sysrq_key_op *)NULL)
+#endif /* CONFIG_VT */
+
+static void sysrq_handle_crash(u8 key)
+{
+	/* release the RCU read lock before crashing */
+	rcu_read_unlock();
+
+	panic("sysrq triggered crash\n");
+}
+static const 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(u8 key)
+{
+	lockdep_off();
+	local_irq_enable();
+	emergency_restart();
+}
+static const struct sysrq_key_op sysrq_reboot_op = {
+	.handler	= sysrq_handle_reboot,
+	.help_msg	= "reboot(b)",
+	.action_msg	= "Resetting",
+	.enable_mask	= SYSRQ_ENABLE_BOOT,
+};
+
+const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
+
+static void sysrq_handle_sync(u8 key)
+{
+	emergency_sync();
+}
+static const 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(u8 key)
+{
+	sysrq_timer_list_show();
+}
+
+static const 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(u8 key)
+{
+	emergency_remount();
+}
+static const 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(u8 key)
+{
+	debug_show_all_locks();
+}
+
+static const 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 (*(const struct sysrq_key_op *)NULL)
+#endif
+
+#ifdef CONFIG_SMP
+static DEFINE_RAW_SPINLOCK(show_lock);
+
+static void showacpu(void *dummy)
+{
+	unsigned long flags;
+
+	/* Idle CPUs have no interesting backtrace. */
+	if (idle_cpu(smp_processor_id())) {
+		pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
+		return;
+	}
+
+	raw_spin_lock_irqsave(&show_lock, flags);
+	pr_info("CPU%d:\n", smp_processor_id());
+	show_stack(NULL, NULL, KERN_INFO);
+	raw_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(u8 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_hardirq())
+			regs = get_irq_regs();
+
+		pr_info("CPU%d:\n", get_cpu());
+		if (regs)
+			show_regs(regs);
+		else
+			show_stack(NULL, NULL, KERN_INFO);
+
+		schedule_work(&sysrq_showallcpus);
+		put_cpu();
+	}
+}
+
+static const 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,
+};
+#else
+#define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
+#endif
+
+static void sysrq_handle_showregs(u8 key)
+{
+	struct pt_regs *regs = NULL;
+
+	if (in_hardirq())
+		regs = get_irq_regs();
+	if (regs)
+		show_regs(regs);
+	perf_event_print_debug();
+}
+static const 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(u8 key)
+{
+	show_state();
+	show_all_workqueues();
+}
+static const 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(u8 key)
+{
+	show_state_filter(TASK_UNINTERRUPTIBLE);
+}
+static const 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(u8 key)
+{
+	ftrace_dump(DUMP_ALL);
+}
+static const 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 (*(const struct sysrq_key_op *)NULL)
+#endif
+
+static void sysrq_handle_showmem(u8 key)
+{
+	show_mem();
+}
+static const 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_PRIV, p, PIDTYPE_MAX);
+	}
+	read_unlock(&tasklist_lock);
+}
+
+static void sysrq_handle_term(u8 key)
+{
+	send_sig_all(SIGTERM);
+	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+}
+static const 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(u8 key)
+{
+	schedule_work(&moom_work);
+}
+static const 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(u8 key)
+{
+	emergency_thaw_all();
+}
+static const 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,
+};
+#else
+#define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
+#endif
+
+static void sysrq_handle_kill(u8 key)
+{
+	send_sig_all(SIGKILL);
+	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+}
+static const 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(u8 key)
+{
+	normalize_rt_tasks();
+}
+static const 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,
+};
+
+static void sysrq_handle_replay_logs(u8 key)
+{
+	console_try_replay_all();
+}
+static struct sysrq_key_op sysrq_replay_logs_op = {
+	.handler        = sysrq_handle_replay_logs,
+	.help_msg       = "replay-kernel-logs(R)",
+	.action_msg     = "Replay kernel logs on consoles",
+	.enable_mask    = SYSRQ_ENABLE_DUMP,
+};
+
+/* Key Operations table and lock */
+static DEFINE_SPINLOCK(sysrq_key_table_lock);
+
+static const struct sysrq_key_op *sysrq_key_table[62] = {
+	&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 */
+	&sysrq_thaw_op,			/* j */
+	&sysrq_SAK_op,			/* k */
+	&sysrq_showallcpus_op,		/* l */
+	&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 */
+	NULL,				/* A */
+	NULL,				/* B */
+	NULL,				/* C */
+	NULL,				/* D */
+	NULL,				/* E */
+	NULL,				/* F */
+	NULL,				/* G */
+	NULL,				/* H */
+	NULL,				/* I */
+	NULL,				/* J */
+	NULL,				/* K */
+	NULL,				/* L */
+	NULL,				/* M */
+	NULL,				/* N */
+	NULL,				/* O */
+	NULL,				/* P */
+	NULL,				/* Q */
+	&sysrq_replay_logs_op,		/* R */
+	/* S: May be registered by sched_ext for resetting */
+	NULL,				/* S */
+	NULL,				/* T */
+	NULL,				/* U */
+	NULL,				/* V */
+	NULL,				/* W */
+	NULL,				/* X */
+	NULL,				/* Y */
+	NULL,				/* Z */
+};
+
+/* key2index calculation, -1 on invalid index */
+static int sysrq_key_table_key2index(u8 key)
+{
+	switch (key) {
+	case '0' ... '9':
+		return key - '0';
+	case 'a' ... 'z':
+		return key - 'a' + 10;
+	case 'A' ... 'Z':
+		return key - 'A' + 10 + 26;
+	default:
+		return -1;
+	}
+}
+
+/*
+ * get and put functions for the table, exposed to modules.
+ */
+static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
+{
+	const 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(u8 key, const 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(u8 key, bool check_mask)
+{
+	const struct sysrq_key_op *op_p;
+	int orig_suppress_printk;
+	int i;
+
+	orig_suppress_printk = suppress_printk;
+	suppress_printk = 0;
+
+	rcu_sysrq_start();
+	rcu_read_lock();
+	/*
+	 * Enter in the force_console context so that 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.
+	 */
+	printk_force_console_enter();
+
+	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_info("%s\n", op_p->action_msg);
+			printk_force_console_exit();
+			op_p->handler(key);
+		} else {
+			pr_info("This sysrq operation is disabled.\n");
+			printk_force_console_exit();
+		}
+	} else {
+		pr_info("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");
+		printk_force_console_exit();
+	}
+	rcu_read_unlock();
+	rcu_sysrq_end();
+
+	suppress_printk = orig_suppress_printk;
+}
+
+void handle_sysrq(u8 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;
+	unsigned int shift;
+	unsigned int shift_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 = timer_container_of(state, t,
+						       keyreset_timer);
+
+	state->reset_requested = true;
+
+	orderly_reboot();
+}
+
+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;
+			timer_delete(&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.
+		 */
+		timer_delete(&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;
+
+	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", 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);
+
+	of_node_put(np);
+}
+#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_LEFTSHIFT:
+	case KEY_RIGHTSHIFT:
+		if (!value)
+			sysrq->shift = KEY_RESERVED;
+		else if (value != 2)
+			sysrq->shift = code;
+		if (sysrq->active)
+			sysrq->shift_use = sysrq->shift;
+		break;
+
+	case KEY_SYSRQ:
+		if (value == 1 && sysrq->alt != KEY_RESERVED) {
+			sysrq->active = true;
+			sysrq->alt_use = sysrq->alt;
+			/* either RESERVED (for released) or actual code */
+			sysrq->shift_use = sysrq->shift;
+			/*
+			 * 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) {
+			unsigned char c = sysrq_xlate[code];
+
+			sysrq->need_reinject = false;
+			if (sysrq->shift_use != KEY_RESERVED)
+				c = toupper(c);
+			__handle_sysrq(c, 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_obj(struct sysrq_state);
+	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);
+	timer_shutdown_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 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);
+}
+
+static inline void sysrq_unregister_handler(void)
+{
+	input_unregister_handler(&sysrq_handler);
+}
+
+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;
+}
+EXPORT_SYMBOL_GPL(sysrq_toggle_support);
+
+static int sysrq_sysctl_handler(const struct ctl_table *table, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int tmp, ret;
+	struct ctl_table t = *table;
+
+	tmp = sysrq_mask();
+	t.data = &tmp;
+
+	/*
+	 * Behaves like do_proc_dointvec as t does not have min nor max.
+	 */
+	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+	if (ret)
+		return ret;
+
+	if (write)
+		sysrq_toggle_support(tmp);
+
+	return 0;
+}
+
+static const struct ctl_table sysrq_sysctl_table[] = {
+	{
+		.procname	= "sysrq",
+		.data		= NULL,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sysrq_sysctl_handler,
+	},
+};
+
+static int __init init_sysrq_sysctl(void)
+{
+	register_sysctl_init("kernel", sysrq_sysctl_table);
+	return 0;
+}
+
+subsys_initcall(init_sysrq_sysctl);
+
+static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
+				const 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(u8 key, const struct sysrq_key_op *op_p)
+{
+	return __sysrq_swap_key_ops(key, op_p, NULL);
+}
+EXPORT_SYMBOL(register_sysrq_key);
+
+int unregister_sysrq_key(u8 key, const 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
+ * Normally, only the first character written is processed.
+ * However, if the first character is an underscore,
+ * all characters are processed.
+ */
+static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	bool bulk = false;
+	size_t i;
+
+	for (i = 0; i < count; i++) {
+		char c;
+
+		if (get_user(c, buf + i))
+			return -EFAULT;
+
+		if (c == '_')
+			bulk = true;
+		else
+			__handle_sysrq(c, false);
+
+		if (!bulk)
+			break;
+	}
+
+	return count;
+}
+
+static const struct proc_ops sysrq_trigger_proc_ops = {
+	.proc_write	= write_sysrq_trigger,
+	.proc_lseek	= noop_llseek,
+};
+
+static void sysrq_init_procfs(void)
+{
+	if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
+			 &sysrq_trigger_proc_ops))
+		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);