[RFC] Input: implement sysrq as an input handler

Dmitry Torokhov
2010-03-17T06:20:05Z

Instead of keeping SysRq support inside of legacy keyboard driver split
it out into a separate input handler (filter). This stops most SysRq input
events from leaking into evdev clients (some events, such as first SysRq
scancode - not keycode - event, are still leaked into both legacy keyboard
and evdev).

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

drivers/char/keyboard.c | 40 +-------
drivers/char/sysrq.c | 222 +++++++++++++++++++++++++++++++++++++++++------
include/linux/sysrq.h | 23 +----
kernel/sysctl.c | 23 +++++
4 files changed, 224 insertions(+), 84 deletions(-)

diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
index ada25bb..50f6c01 100644
--- a/drivers/char/keyboard.c
+++ b/drivers/char/keyboard.c
@@ -38,7 +38,6 @@
#include <linux/kbd_kern.h>
#include <linux/kbd_diacr.h>
#include <linux/vt_kern.h>
-#include <linux/sysrq.h>
#include <linux/input.h>
#include <linux/reboot.h>
#include <linux/notifier.h>
@@ -82,8 +81,7 @@ void compute_shiftstate(void);
typedef void (k_handler_fn)(struct vc_data *vc, unsigned char value,
char up_flag);
static k_handler_fn K_HANDLERS;
-k_handler_fn *k_handler[16] = { K_HANDLERS };
-EXPORT_SYMBOL_GPL(k_handler);
+static k_handler_fn *k_handler[16] = { K_HANDLERS };

#define FN_HANDLERS\
fn_null, fn_enter, fn_show_ptregs, fn_show_mem,\
@@ -147,22 +145,6 @@ static struct ledptr {
unsigned char valid:1;
} ledptrs[3];

-/* Simple translation table for the SysRq keys */
-
-#ifdef CONFIG_MAGIC_SYSRQ
-unsigned char kbd_sysrq_xlate[KEY_MAX + 1] =
- "\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 */
-static int sysrq_down;
-static int sysrq_alt_use;
-#endif
-static int sysrq_alt;
-
/*
* Notifier list for console keyboard events
*/
@@ -1108,7 +1090,8 @@ static int emulate_raw(struct vc_data *vc, unsigned int keycode,
* pressing PrtSc/SysRq alone, but simply 0x54
* when pressing Alt+PrtSc/SysRq.
*/
- if (sysrq_alt) {
+ if (test_bit(KEY_LEFTALT, key_down) ||
+ test_bit(KEY_RIGHTALT, key_down)) {
put_queue(vc, 0x54 | up_flag);
} else {
put_queue(vc, 0xe0);
@@ -1176,8 +1159,6 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)

kbd = kbd_table + vc->vc_num;

- if (keycode == KEY_LEFTALT || keycode == KEY_RIGHTALT)
- sysrq_alt = down ? keycode : 0;
#ifdef CONFIG_SPARC
if (keycode == KEY_STOP)
sparc_l1_a_state = down;
@@ -1190,21 +1171,6 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
if (keycode < BTN_MISC && printk_ratelimit())
printk(KERN_WARNING "keyboard.c: can't emulate rawmode for keycode %d\n", keycode);

-#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */
- if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 && sysrq_alt))) {
- if (!sysrq_down) {
- sysrq_down = down;
- sysrq_alt_use = sysrq_alt;
- }
- return;
- }
- if (sysrq_down && !down && keycode == sysrq_alt_use)
- sysrq_down = 0;
- if (sysrq_down && down && !rep) {
- handle_sysrq(kbd_sysrq_xlate[keycode], tty);
- return;
- }
-#endif
#ifdef CONFIG_SPARC
if (keycode == KEY_A && sparc_l1_a_state) {
sparc_l1_a_state = 0;
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 1ae2de7..1883dd8 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -1,7 +1,4 @@
-/* -*- linux-c -*-
- *
- * $Id: sysrq.c,v 1.15 1998/08/23 14:56:41 mj Exp $
- *
+/*
* Linux Magic System Request Key Hacks
*
* (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
@@ -10,8 +7,13 @@
* (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.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
@@ -38,33 +40,34 @@
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
#include <linux/oom.h>
+#include <linux/input.h>

#include <asm/ptrace.h>
#include <asm/irq_regs.h>

/* Whether we react on sysrq keys or just ignore them */
-int __read_mostly __sysrq_enabled = 1;
+static int __read_mostly sysrq_enabled = 1;
+static bool __read_mostly sysrq_always_enabled;

-static int __read_mostly sysrq_always_enabled;
-
-int sysrq_on(void)
+static bool sysrq_on(void)
{
- return __sysrq_enabled || sysrq_always_enabled;
+ return sysrq_enabled || sysrq_always_enabled;
}

/*
* A value of 1 means 'all', other nonzero values are an op mask:
*/
-static inline int sysrq_on_mask(int mask)
+static bool sysrq_on_mask(int mask)
{
- return sysrq_always_enabled || __sysrq_enabled == 1 ||
- (__sysrq_enabled & mask);
+ return sysrq_always_enabled ||
+ sysrq_enabled == 1 ||
+ (sysrq_enabled & mask);
}

static int __init sysrq_always_enabled_setup(char *str)
{
- sysrq_always_enabled = 1;
- printk(KERN_INFO "debug: sysrq always enabled.\n");
+ sysrq_always_enabled = true;
+ pr_info("sysrq always enabled.\n");

return 1;
}
@@ -75,6 +78,7 @@ __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
{
int i;
+
i = key - '0';
console_loglevel = 7;
printk("Loglevel set to %d\n", i);
@@ -100,7 +104,7 @@ static struct sysrq_key_op sysrq_SAK_op = {
.enable_mask = SYSRQ_ENABLE_KEYBOARD,
};
#else
-#define sysrq_SAK_op (*(struct sysrq_key_op *)0)
+#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
#endif

#ifdef CONFIG_VT
@@ -118,7 +122,7 @@ static struct sysrq_key_op sysrq_unraw_op = {
.enable_mask = SYSRQ_ENABLE_KEYBOARD,
};
#else
-#define sysrq_unraw_op (*(struct sysrq_key_op *)0)
+#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
#endif /* CONFIG_VT */

static void sysrq_handle_crash(int key, struct tty_struct *tty)
@@ -194,7 +198,7 @@ static struct sysrq_key_op sysrq_showlocks_op = {
.action_msg = "Show Locks Held",
};
#else
-#define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
+#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
#endif

#ifdef CONFIG_SMP
@@ -297,7 +301,7 @@ static struct sysrq_key_op sysrq_ftrace_dump_op = {
.enable_mask = SYSRQ_ENABLE_DUMP,
};
#else
-#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
+#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
#endif

static void sysrq_handle_showmem(int key, struct tty_struct *tty)
@@ -476,6 +480,7 @@ struct sysrq_key_op *__sysrq_get_key_op(int key)
i = sysrq_key_table_key2index(key);
if (i != -1)
op_p = sysrq_key_table[i];
+
return op_p;
}

@@ -487,11 +492,7 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
sysrq_key_table[i] = op_p;
}

-/*
- * This is the non-locking version of handle_sysrq. It must/can only be called
- * by sysrq key handlers, as they are inside of the lock
- */
-void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
+static void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
{
struct sysrq_key_op *op_p;
int orig_log_level;
@@ -543,10 +544,6 @@ void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
}

-/*
- * This function is called by the keyboard handler when SysRq is pressed
- * and any other keycode arrives.
- */
void handle_sysrq(int key, struct tty_struct *tty)
{
if (sysrq_on())
@@ -554,6 +551,148 @@ void handle_sysrq(int key, struct tty_struct *tty)
}
EXPORT_SYMBOL(handle_sysrq);

+/* Simple translation table for the SysRq keys */
+static const unsigned char sysrq_xlate[KEY_MAX + 1] =
+ "\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 */
+
+static bool sysrq_down;
+static int sysrq_alt_use;
+static int sysrq_alt;
+
+static bool sysrq_filter(struct input_handle *handle, unsigned int type,
+ unsigned int code, int value)
+{
+
+ if (type != EV_KEY)
+ goto out;
+
+ switch (code) {
+
+ case KEY_LEFTALT:
+ case KEY_RIGHTALT:
+ if (value)
+ sysrq_alt = code;
+ else if (sysrq_down && code == sysrq_alt_use)
+ sysrq_down = false;
+ break;
+
+ case KEY_SYSRQ:
+ if (value == 1 && sysrq_alt) {
+ sysrq_down = true;
+ sysrq_alt_use = sysrq_alt;
+ }
+
+ break;
+
+ default:
+ if (sysrq_down && value && value != 2) {
+ struct vc_data *vc = vc_cons[fg_console].d;
+
+ __handle_sysrq(sysrq_xlate[code], vc->vc_tty, 1);
+ }
+ }
+
+out:
+ return sysrq_down;
+}
+
+static int sysrq_connect(struct input_handler *handler,
+ struct input_dev *dev,
+ const struct input_device_id *id)
+{
+ struct input_handle *handle;
+ int error;
+
+ sysrq_down = false;
+ sysrq_alt = 0;
+
+ handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL);
+ if (!handle)
+ return -ENOMEM;
+
+ handle->dev = dev;
+ handle->handler = handler;
+ handle->name = "sysrq";
+
+ error = input_register_handle(handle);
+ if (error) {
+ pr_err("Failed to register input sysrq handler, error %d\n",
+ error);
+ goto err_free;
+ }
+
+ error = input_open_device(handle);
+ if (error) {
+ pr_err("Failed to open input device, error %d\n", error);
+ goto err_unregister;
+ }
+
+ return 0;
+
+ err_unregister:
+ input_unregister_handle(handle);
+ err_free:
+ kfree(handle);
+ return error;
+}
+
+static void sysrq_disconnect(struct input_handle *handle)
+{
+ input_close_device(handle);
+ input_unregister_handle(handle);
+ kfree(handle);
+}
+
+/*
+ * We are matching on KEY_LEFTALT insteard of KEY_SYSRQ because not all
+ * keyboards have SysRq ikey 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_MASK(EV_KEY) },
+ .keybit = { 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,
+};
+
+int sysrq_toggle_support(int enable_mask)
+{
+ bool was_enabled = sysrq_on();
+ int error;
+
+ sysrq_enabled = enable_mask;
+
+ if (was_enabled != sysrq_on()) {
+ if (sysrq_on()) {
+ error = input_register_handler(&sysrq_handler);
+ if (error)
+ pr_err("Failed to register input handler, error %d",
+ error);
+
+ } else
+ input_unregister_handler(&sysrq_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)
{
@@ -598,6 +737,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
return -EFAULT;
__handle_sysrq(c, NULL, 0);
}
+
return count;
}

@@ -605,10 +745,34 @@ static const struct file_operations proc_sysrq_trigger_operations = {
.write = write_sysrq_trigger,
};

+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
+
static int __init sysrq_init(void)
{
- proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
+ int error;
+
+ sysrq_init_procfs();
+
+ if (sysrq_on()) {
+ error = input_register_handler(&sysrq_handler);
+ if (error)
+ pr_err("Failed to register input handler, error %d",
+ error);
+ }
+
return 0;
}
module_init(sysrq_init);
-#endif
diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h
index 99adcdc..5f2bdef 100644
--- a/include/linux/sysrq.h
+++ b/include/linux/sysrq.h
@@ -39,41 +39,30 @@ struct sysrq_key_op {

#ifdef CONFIG_MAGIC_SYSRQ

-extern int sysrq_on(void);
-
-/*
- * Do not use this one directly:
- */
-extern int __sysrq_enabled;
-
/* Generic SysRq interface -- you may call it from any device driver, supplying
* ASCII code of the key, pointer to registers and kbd/tty structs (if they
* are available -- else NULL's).
*/

void handle_sysrq(int key, struct tty_struct *tty);
-void __handle_sysrq(int key, struct tty_struct *tty, int check_mask);
int register_sysrq_key(int key, struct sysrq_key_op *op);
int unregister_sysrq_key(int key, struct sysrq_key_op *op);
struct sysrq_key_op *__sysrq_get_key_op(int key);

+int sysrq_toggle_support(int enable_mask);
+
#else

-static inline int sysrq_on(void)
-{
- return 0;
-}
-static inline int __reterr(void)
+static inline int register_sysrq_key(int key, struct sysrq_key_op *op)
{
return -EINVAL;
}
-static inline void handle_sysrq(int key, struct tty_struct *tty)
+
+static inline int unregister_sysrq_key(int key, struct sysrq_key_op *op)
{
+ return -EINVAL;
}

-#define register_sysrq_key(ig,nore) __reterr()
-#define unregister_sysrq_key(ig,nore) __reterr()
-
#endif

#endif /* _LINUX_SYSRQ_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8686b0f..ce724a0 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -163,6 +163,27 @@ static int proc_taint(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
#endif

+#ifdef CONFIG_MAGIC_SYSRQ
+static int __sysrq_enabled; /* Note: sysrq code ises it's own private copy */
+
+static int sysrq_sysctl_handler(ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int error;
+
+ error = proc_dointvec(table, write, buffer, lenp, ppos);
+ if (error)
+ return error;
+
+ if (write)
+ sysrq_toggle_support(__sysrq_enabled);
+
+ return 0;
+}
+
+#endif
+
static struct ctl_table root_table[];
static struct ctl_table_root sysctl_table_root;
static struct ctl_table_header root_table_header = {
@@ -567,7 +588,7 @@ static struct ctl_table kern_table[] = {
.data = &__sysrq_enabled,
.maxlen = sizeof (int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sysrq_sysctl_handler,
},
#endif
#ifdef CONFIG_PROC_SYSCTL

--
Dmitry