Input: sysrq - allow specifying alternate reset sequence
This patch adds keyreset functionality to the sysrq driver. It allows
certain button/key combinations to be used in order to trigger emergency
reboots.
Redefining the '__weak platform_sysrq_reset_seq' variable is required
to trigger the feature. Alternatively keys can be passed to the driver
via a module parameter.
This functionality comes from the keyreset driver submitted by
Arve Hjønnevåg in the Android kernel.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 16ee6ce..77fcad4 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -41,6 +41,7 @@
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/uaccess.h>
+#include <linux/moduleparam.h>
#include <asm/ptrace.h>
#include <asm/irq_regs.h>
@@ -576,8 +577,71 @@
bool active;
bool need_reinject;
bool reinjecting;
+
+ /* reset sequence handling */
+ bool reset_canceled;
+ unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
+ int reset_seq_len;
+ int reset_seq_cnt;
+ int reset_seq_version;
};
+#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 bool 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.
+ */
+ if (value && state->reset_seq_cnt)
+ state->reset_canceled = true;
+ } else if (value == 0) {
+ /* key release */
+ 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) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
static void sysrq_reinject_alt_sysrq(struct work_struct *work)
{
struct sysrq_state *sysrq =
@@ -604,11 +668,104 @@
}
}
+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);
+
+ if (sysrq_detect_reset_sequence(sysrq, code, value)) {
+ /* Force emergency reboot */
+ __handle_sysrq(sysrq_xlate[KEY_B], false);
+ }
+
+ } 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 was_active = sysrq->active;
bool suppress;
/*
@@ -625,79 +782,7 @@
break;
case EV_KEY:
- 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, 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) {
- /*
- * 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);
-
- } 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;
- }
+ suppress = sysrq_handle_keypress(sysrq, code, value);
break;
default:
@@ -785,7 +870,20 @@
static inline void sysrq_register_handler(void)
{
+ extern unsigned short platform_sysrq_reset_seq[] __weak;
+ unsigned short key;
int error;
+ int i;
+
+ if (platform_sysrq_reset_seq) {
+ for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
+ key = platform_sysrq_reset_seq[i];
+ if (key == KEY_RESERVED || key > KEY_MAX)
+ break;
+
+ sysrq_reset_seq[sysrq_reset_seq_len++] = key;
+ }
+ }
error = input_register_handler(&sysrq_handler);
if (error)
@@ -802,6 +900,36 @@
}
}
+static int sysrq_reset_seq_param_set(const char *buffer,
+ const struct kernel_param *kp)
+{
+ unsigned long val;
+ int error;
+
+ error = strict_strtoul(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 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)
+
+module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
+ &sysrq_reset_seq_len, 0644);
+
#else
static inline void sysrq_register_handler(void)