Input: implement SysRq as a separate input handler

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).

[martinez.javier@gmail.com: fix compile error when CONFIG_MAGIC_SYSRQ is
 not defined]
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 213 insertions, 30 deletions

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 59de2525d303..193f9c214946 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>
@@ -39,33 +41,34 @@
 #include <linux/hrtimer.h>
 #include <linux/oom.h>
 #include <linux/slab.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_always_enabled;
+static int __read_mostly sysrq_enabled = 1;
+static bool __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;
 }
@@ -76,6 +79,7 @@ __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);
@@ -101,7 +105,7 @@ 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
@@ -119,7 +123,7 @@ 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)
@@ -195,7 +199,7 @@ 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
@@ -298,7 +302,7 @@ 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)
@@ -477,6 +481,7 @@ 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;
 }
 
@@ -488,11 +493,7 @@ 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;
@@ -544,10 +545,6 @@ 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())
@@ -555,10 +552,177 @@ void handle_sysrq(int key, struct tty_struct *tty)
 }
 EXPORT_SYMBOL(handle_sysrq);
 
+#ifdef CONFIG_INPUT
+
+/* 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)
+                        __handle_sysrq(sysrq_xlate[code], NULL, 1);
+                break;
+        }
+
+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,
+};
+
+static bool sysrq_handler_registered;
+
+static inline void sysrq_register_handler(void)
+{
+        int error;
+
+        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;
+        }
+}
+
+#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;
         unsigned long flags;
 
@@ -599,6 +763,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
                         return -EFAULT;
                 __handle_sysrq(c, NULL, 0);
         }
+
         return count;
 }
 
@@ -606,10 +771,28 @@ 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 /* CONFIG_PROC_FS */
+
 static int __init sysrq_init(void)
 {
-        proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
+        sysrq_init_procfs();
+
+        if (sysrq_on())
+                sysrq_register_handler();
+
         return 0;
 }
 module_init(sysrq_init);
-#endif