[PATCH v2 0/2] Add configurable handler to execute a compound action

@@ -79,6 +79,8 @@ On all
 
 		echo t > /proc/sysrq-trigger
 
+The :kbd:`<command key>` is case sensitive.
+
 What are the 'command' keys?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

@@ -325,7 +325,7 @@ static void drm_fb_helper_sysrq(int dummy1)
 
 static const struct sysrq_key_op sysrq_drm_fb_helper_restore_op = {
 	.handler = drm_fb_helper_sysrq,
-	.help_msg = "force-fb(V)",
+	.help_msg = "force-fb(v)",
 	.action_msg = "Restore framebuffer console",
 };
 #else

@@ -19,6 +19,7 @@
 #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>

@@ -440,7 +441,7 @@ static const struct sysrq_key_op sysrq_unrt_op = {
 /* Key Operations table and lock */
 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 
-static const struct sysrq_key_op *sysrq_key_table[36] = {
+static const struct sysrq_key_op *sysrq_key_table[62] = {
 	&sysrq_loglevel_op,		/* 0 */
 	&sysrq_loglevel_op,		/* 1 */
 	&sysrq_loglevel_op,		/* 2 */

@@ -497,6 +498,32 @@ static const struct sysrq_key_op *sysrq_key_table[36] = {
 	/* 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 */
+	NULL,				/* R */
+	NULL,				/* S */
+	NULL,				/* T */
+	NULL,				/* U */
+	NULL,				/* V */
+	NULL,				/* W */
+	NULL,				/* X */
+	NULL,				/* Y */
+	NULL,				/* Z */
 };
 
 /* key2index calculation, -1 on invalid index */

@@ -508,6 +535,8 @@ static int sysrq_key_table_key2index(int key)
 		retval = key - '0';
 	else if ((key >= 'a') && (key <= 'z'))
 		retval = key + 10 - 'a';
+	else if ((key >= 'A') && (key <= 'Z'))
+		retval = key + 36 - 'A';
 	else
 		retval = -1;
 	return retval;

@@ -621,6 +650,8 @@ struct sysrq_state {
 	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;

@@ -805,10 +836,20 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 		}
 		break;
 
+	case KEY_LEFTSHIFT:
+	case KEY_RIGHTSHIFT:
+		if (!value)
+			sysrq->shift = KEY_RESERVED;
+		else if (value != 2)
+			sysrq->shift = code;
+		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.

@@ -831,8 +872,12 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 
 	default:
 		if (sysrq->active && value && value != 2) {
+			unsigned char c = sysrq_xlate[code];
+
 			sysrq->need_reinject = false;
-			__handle_sysrq(sysrq_xlate[code], true);
+			if (sysrq->shift_use != KEY_RESERVED)
+				c = toupper(c);
+			__handle_sysrq(c, true);
 		}
 		break;
 	}

@@ -32,6 +32,7 @@ to 1. Here is the list of possible values in /proc/sys/kernel/sysrq:
          64 =  0x40 - enable signalling of processes (term, kill, oom-kill)
         128 =  0x80 - allow reboot/poweroff
         256 = 0x100 - allow nicing of all RT tasks
+        512 = 0x200 - allow compound action
 
 You can set the value in the file by the following command::
 

@@ -148,6 +149,14 @@ Command	    Function
 
 ``z``	    Dump the ftrace buffer
 
+``C``	    Execute a predefined, compound action. The action is defined with
+	    sysrq.sysrq_compound_action module parameter, whose value contains known
+	    command keys (except ``C`` to prevent recursion). The command keys can
+	    be optionally followed by a colon and a number of milliseconds to wait
+	    after executing the last action. For example:
+
+	    sysrq.sysrq_compound_action=r:100eis:1000ub
+
 ``0``-``9`` Sets the console log level, controlling which kernel messages
             will be printed to your console. (``0``, for example would make
             it so that only emergency messages like PANICs or OOPSes would

@@ -20,6 +20,7 @@
 #include <linux/sched/debug.h>
 #include <linux/sched/task.h>
 #include <linux/ctype.h>
+#include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/mm.h>
 #include <linux/fs.h>

@@ -438,6 +439,15 @@ static const struct sysrq_key_op sysrq_unrt_op = {
 	.enable_mask	= SYSRQ_ENABLE_RTNICE,
 };
 
+static void sysrq_action_compound(int key);
+
+static struct sysrq_key_op sysrq_action_compound_op = {
+	.handler	= sysrq_action_compound,
+	.help_msg	= "execute-compound-action(C)",
+	.action_msg	= "Execute compound action",
+	.enable_mask	= SYSRQ_ENABLE_COMPOUND,
+};
+
 /* Key Operations table and lock */
 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 

@@ -500,7 +510,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = {
 	&sysrq_ftrace_dump_op,		/* z */
 	NULL,				/* A */
 	NULL,				/* B */
-	NULL,				/* C */
+	&sysrq_action_compound_op,	/* C */
 	NULL,				/* D */
 	NULL,				/* E */
 	NULL,				/* F */

@@ -633,6 +643,7 @@ EXPORT_SYMBOL(handle_sysrq);
 
 #ifdef CONFIG_INPUT
 static int sysrq_reset_downtime_ms;
+static char *sysrq_compound_action;
 
 /* Simple translation table for the SysRq keys */
 static const unsigned char sysrq_xlate[KEY_CNT] =

@@ -786,6 +797,62 @@ static void sysrq_of_get_keyreset_config(void)
 {
 }
 #endif
+#define SYSRQ_COMPOUND_ACTION_VALIDATE	0
+#define SYSRQ_COMPOUND_ACTION_RUN	1
+
+static int sysrq_process_compound_action(int pass)
+{
+	const char *action = sysrq_compound_action;
+	const struct sysrq_key_op *op_p;
+	int ret;
+	unsigned int delay;
+
+	while (*action) {
+		op_p = __sysrq_get_key_op(*action);
+		if (!op_p)
+			return -EINVAL;
+
+		/* Don't allow calling ourselves recursively */
+		if (op_p == &sysrq_action_compound_op)
+			return -EINVAL;
+
+		if (pass == SYSRQ_COMPOUND_ACTION_RUN)
+			__handle_sysrq(*action, false);
+
+		if (*++action == ':') {
+			ret = sscanf(action++, ":%u", &delay);
+			if (ret < 1) /* we want at least ":[0-9]" => 1 item */
+				return -EINVAL;
+
+			while (*action >= '0' && *action <= '9')
+				++action;
+			if (pass == SYSRQ_COMPOUND_ACTION_RUN)
+				mdelay(delay);
+		}
+	}
+
+	return 0;
+}
+
+static void sysrq_action_compound(int key)
+{
+	if (!sysrq_compound_action) {
+		pr_err("Unconfigured compound action for %s\n",
+		       sysrq_action_compound_op.help_msg);
+
+		return;
+	}
+
+	if (sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_VALIDATE)) {
+		pr_err("Incorrect compound action %s for %s\n",
+		       sysrq_compound_action,
+		       sysrq_action_compound_op.help_msg);
+
+		return;
+	}
+
+	sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_RUN);
+}
 
 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 {

@@ -1077,8 +1144,21 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
 
 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
 
+module_param(sysrq_compound_action, charp, 0644);
+MODULE_PARM_DESC(sysrq_compound_action,
+	"\tCompound sysrq action to be executed on Alt-Shift-SysRq-C\n"
+	"\tThe compound action definition consists of known SysRq action letters except 'C',\n"
+	"\teach letter can be optionally followed by a colon and a number of milliseconds to wait\n"
+	"\tafter executing the last action.\n"
+	"\tExample:\n"
+	"\tTo unRaw, wait 100ms, tErminate, kIll, Sync, wait 1000ms, Unmount, Boot\n"
+	"\tsysrq.sysrq_compound_action=r:100eis:1000ub");
 #else
 
+{
+}
+
+static void sysrq_action_compound(int key)
 static inline void sysrq_register_handler(void)
 {
 }

@@ -28,6 +28,7 @@
 #define SYSRQ_ENABLE_SIGNAL	0x0040
 #define SYSRQ_ENABLE_BOOT	0x0080
 #define SYSRQ_ENABLE_RTNICE	0x0100
+#define SYSRQ_ENABLE_COMPOUND	0x0200
 
 struct sysrq_key_op {
 	void (* const handler)(int);