Printk changes for 5.8

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Merge tag 'printk-for-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Benjamin Herrenschmidt solved a problem with non-matched console
   aliases by first checking consoles defined on the command line. It is
   a more conservative approach than the previous attempts.

 - Benjamin also made sure that the console accessible via /dev/console
   always has CON_CONSDEV flag.

 - Andy Shevchenko added the %ptT modifier for printing struct time64_t.
   It extends the existing %ptR handling for struct rtc_time.

 - Bruno Meneguele fixed /dev/kmsg error value returned by unsupported
   SEEK_CUR.

 - Tetsuo Handa removed unused pr_cont_once().

... and a few small fixes.

* tag 'printk-for-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: Remove pr_cont_once()
  printk: handle blank console arguments passed in.
  kernel/printk: add kmsg SEEK_CUR handling
  printk: Fix a typo in comment "interator"->"iterator"
  usb: pulse8-cec: Switch to use %ptT
  ARM: bcm2835: Switch to use %ptT
  lib/vsprintf: Print time64_t in human readable format
  lib/vsprintf: update comment about simple_strto<foo>() functions
  printk: Correctly set CON_CONSDEV even when preferred console was not registered
  printk: Fix preferred console selection with multiple matches
  printk: Move console matching logic into a separate function
  printk: Convert a use of sprintf to snprintf in console_unlock

Documentation/ABI/testing/dev-kmsg

@@ -56,6 +56,11 @@ Description:	The /dev/kmsg character device node provides userspace access
 		  seek after the last record available at the time
 		  the last SYSLOG_ACTION_CLEAR was issued.
 
+		Due to the record nature of this interface with a "read all"
+		behavior and the specific positions each seek operation sets,
+		SEEK_CUR is not supported, returning -ESPIPE (invalid seek) to
+		errno whenever requested.
+
 		The output format consists of a prefix carrying the syslog
 		prefix including priority and facility, the 64 bit message
 		sequence number and the monotonic timestamp in microseconds,

Documentation/core-api/printk-formats.rst

@@ -482,21 +482,23 @@ Examples (OF)::
 	%pfwf	/ocp@68000000/i2c@48072000/camera@10/port/endpoint - Full name
 	%pfwP	endpoint				- Node name
 
-Time and date (struct rtc_time)
+Time and date
--------------------------------
+-------------
 
 ::
 
-	%ptR		YYYY-mm-ddTHH:MM:SS
+	%pt[RT]			YYYY-mm-ddTHH:MM:SS
-	%ptRd		YYYY-mm-dd
+	%pt[RT]d		YYYY-mm-dd
-	%ptRt		HH:MM:SS
+	%pt[RT]t		HH:MM:SS
-	%ptR[dt][r]
+	%pt[RT][dt][r]
 
-For printing date and time as represented by struct rtc_time structure in
+For printing date and time as represented by
-human readable format.
+	R  struct rtc_time structure
+	T  time64_t type
+in human readable format.
 
-By default year will be incremented by 1900 and month by 1. Use %ptRr (raw)
+By default year will be incremented by 1900 and month by 1.
-to suppress this behaviour.
+Use %pt[RT]r (raw) to suppress this behaviour.
 
 Passed by reference.
 

drivers/firmware/raspberrypi.c

@@ -182,16 +182,10 @@ rpi_firmware_print_firmware_revision(struct rpi_firmware *fw)
 					RPI_FIRMWARE_GET_FIRMWARE_REVISION,
 					&packet, sizeof(packet));
 
-	if (ret == 0) {
+	if (ret)
-		struct tm tm;
+		return;
 
-		time64_to_tm(packet, 0, &tm);
+	dev_info(fw->cl.dev, "Attached to firmware from %ptT\n", &packet);
-
-		dev_info(fw->cl.dev,
-			 "Attached to firmware from %04ld-%02d-%02d %02d:%02d\n",
-			 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
-			 tm.tm_hour, tm.tm_min);
-	}
 }
 
 static void

drivers/media/usb/pulse8-cec/pulse8-cec.c

@@ -661,7 +661,6 @@ static int pulse8_setup(struct pulse8 *pulse8, struct serio *serio,
 	u8 *data = pulse8->data + 1;
 	u8 cmd[2];
 	int err;
-	struct tm tm;
 	time64_t date;
 
 	pulse8->vers = 0;
@@ -682,10 +681,7 @@ static int pulse8_setup(struct pulse8 *pulse8, struct serio *serio,
 	if (err)
 		return err;
 	date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
-	time64_to_tm(date, 0, &tm);
+	dev_info(pulse8->dev, "Firmware build date %ptT\n", &date);
-	dev_info(pulse8->dev, "Firmware build date %04ld.%02d.%02d %02d:%02d:%02d\n",
-		 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
-		 tm.tm_hour, tm.tm_min, tm.tm_sec);
 
 	dev_dbg(pulse8->dev, "Persistent config:\n");
 	cmd[0] = MSGCODE_GET_AUTO_ENABLED;

include/linux/console.h

@@ -134,7 +134,7 @@ static inline int con_debug_leave(void)
  */
 
 #define CON_PRINTBUFFER	(1)
-#define CON_CONSDEV	(2) /* Last on the command line */
+#define CON_CONSDEV	(2) /* Preferred console, /dev/console */
 #define CON_ENABLED	(4)
 #define CON_BOOT	(8)
 #define CON_ANYTIME	(16) /* Safe to call when cpu is offline */

include/linux/printk.h

@@ -384,8 +384,7 @@ extern int kptr_restrict;
 	printk_once(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
 #define pr_info_once(fmt, ...)					\
 	printk_once(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
-#define pr_cont_once(fmt, ...)					\
+/* no pr_cont_once, don't do that... */
-	printk_once(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
 
 #if defined(DEBUG)
 #define pr_devel_once(fmt, ...)					\

kernel/printk/console_cmdline.h

@@ -6,6 +6,7 @@ struct console_cmdline
 {
 	char	name[16];			/* Name of the driver	    */
 	int	index;				/* Minor dev. to use	    */
+	bool	user_specified;			/* Specified by command line vs. platform */
 	char	*options;			/* Options for the driver   */
 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 	char	*brl_options;			/* Options for braille driver */

kernel/printk/printk.c

@@ -280,6 +280,7 @@ static struct console *exclusive_console;
 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 
 static int preferred_console = -1;
+static bool has_preferred_console;
 int console_set_on_cmdline;
 EXPORT_SYMBOL(console_set_on_cmdline);
 
@@ -974,6 +975,16 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
 		user->idx = log_next_idx;
 		user->seq = log_next_seq;
 		break;
+	case SEEK_CUR:
+		/*
+		 * It isn't supported due to the record nature of this
+		 * interface: _SET _DATA and _END point to very specific
+		 * record positions, while _CUR would be more useful in case
+		 * of a byte-based log. Because of that, return the default
+		 * errno value for invalid seek operation.
+		 */
+		ret = -ESPIPE;
+		break;
 	default:
 		ret = -EINVAL;
 	}
@@ -2140,7 +2151,7 @@ asmlinkage __visible void early_printk(const char *fmt, ...)
 #endif
 
 static int __add_preferred_console(char *name, int idx, char *options,
-				   char *brl_options)
+				   char *brl_options, bool user_specified)
 {
 	struct console_cmdline *c;
 	int i;
@@ -2155,6 +2166,8 @@ static int __add_preferred_console(char *name, int idx, char *options,
 		if (strcmp(c->name, name) == 0 && c->index == idx) {
 			if (!brl_options)
 				preferred_console = i;
+			if (user_specified)
+				c->user_specified = true;
 			return 0;
 		}
 	}
@@ -2164,6 +2177,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
 		preferred_console = i;
 	strlcpy(c->name, name, sizeof(c->name));
 	c->options = options;
+	c->user_specified = user_specified;
 	braille_set_options(c, brl_options);
 
 	c->index = idx;
@@ -2190,6 +2204,9 @@ static int __init console_setup(char *str)
 	char *s, *options, *brl_options = NULL;
 	int idx;
 
+	if (str[0] == 0)
+		return 1;
+
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
@@ -2218,7 +2235,7 @@ static int __init console_setup(char *str)
 	idx = simple_strtoul(s, NULL, 10);
 	*s = 0;
 
-	__add_preferred_console(buf, idx, options, brl_options);
+	__add_preferred_console(buf, idx, options, brl_options, true);
 	console_set_on_cmdline = 1;
 	return 1;
 }
@@ -2239,7 +2256,7 @@ __setup("console=", console_setup);
  */
 int add_preferred_console(char *name, int idx, char *options)
 {
-	return __add_preferred_console(name, idx, options, NULL);
+	return __add_preferred_console(name, idx, options, NULL, false);
 }
 
 bool console_suspend_enabled = true;
@@ -2438,9 +2455,9 @@ again:
 		printk_safe_enter_irqsave(flags);
 		raw_spin_lock(&logbuf_lock);
 		if (console_seq < log_first_seq) {
-			len = sprintf(text,
+			len = snprintf(text, sizeof(text),
-				      "** %llu printk messages dropped **\n",
+				       "** %llu printk messages dropped **\n",
-				      log_first_seq - console_seq);
+				       log_first_seq - console_seq);
 
 			/* messages are gone, move to first one */
 			console_seq = log_first_seq;
@@ -2651,6 +2668,63 @@ static int __init keep_bootcon_setup(char *str)
 
 early_param("keep_bootcon", keep_bootcon_setup);
 
+/*
+ * This is called by register_console() to try to match
+ * the newly registered console with any of the ones selected
+ * by either the command line or add_preferred_console() and
+ * setup/enable it.
+ *
+ * Care need to be taken with consoles that are statically
+ * enabled such as netconsole
+ */
+static int try_enable_new_console(struct console *newcon, bool user_specified)
+{
+	struct console_cmdline *c;
+	int i;
+
+	for (i = 0, c = console_cmdline;
+	     i < MAX_CMDLINECONSOLES && c->name[0];
+	     i++, c++) {
+		if (c->user_specified != user_specified)
+			continue;
+		if (!newcon->match ||
+		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
+			/* default matching */
+			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
+			if (strcmp(c->name, newcon->name) != 0)
+				continue;
+			if (newcon->index >= 0 &&
+			    newcon->index != c->index)
+				continue;
+			if (newcon->index < 0)
+				newcon->index = c->index;
+
+			if (_braille_register_console(newcon, c))
+				return 0;
+
+			if (newcon->setup &&
+			    newcon->setup(newcon, c->options) != 0)
+				return -EIO;
+		}
+		newcon->flags |= CON_ENABLED;
+		if (i == preferred_console) {
+			newcon->flags |= CON_CONSDEV;
+			has_preferred_console = true;
+		}
+		return 0;
+	}
+
+	/*
+	 * Some consoles, such as pstore and netconsole, can be enabled even
+	 * without matching. Accept the pre-enabled consoles only when match()
+	 * and setup() had a change to be called.
+	 */
+	if (newcon->flags & CON_ENABLED && c->user_specified ==	user_specified)
+		return 0;
+
+	return -ENOENT;
+}
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -2672,11 +2746,9 @@ early_param("keep_bootcon", keep_bootcon_setup);
  */
 void register_console(struct console *newcon)
 {
-	int i;
 	unsigned long flags;
 	struct console *bcon = NULL;
-	struct console_cmdline *c;
+	int err;
-	static bool has_preferred;
 
 	for_each_console(bcon) {
 		if (WARN(bcon == newcon, "console '%s%d' already registered\n",
@@ -2701,15 +2773,15 @@ void register_console(struct console *newcon)
 	if (console_drivers && console_drivers->flags & CON_BOOT)
 		bcon = console_drivers;
 
-	if (!has_preferred || bcon || !console_drivers)
+	if (!has_preferred_console || bcon || !console_drivers)
-		has_preferred = preferred_console >= 0;
+		has_preferred_console = preferred_console >= 0;
 
 	/*
 	 *	See if we want to use this console driver. If we
 	 *	didn't select a console we take the first one
 	 *	that registers here.
 	 */
-	if (!has_preferred) {
+	if (!has_preferred_console) {
 		if (newcon->index < 0)
 			newcon->index = 0;
 		if (newcon->setup == NULL ||
@@ -2717,47 +2789,20 @@ void register_console(struct console *newcon)
 			newcon->flags |= CON_ENABLED;
 			if (newcon->device) {
 				newcon->flags |= CON_CONSDEV;
-				has_preferred = true;
+				has_preferred_console = true;
 			}
 		}
 	}
 
-	/*
+	/* See if this console matches one we selected on the command line */
-	 *	See if this console matches one we selected on
+	err = try_enable_new_console(newcon, true);
-	 *	the command line.
-	 */
-	for (i = 0, c = console_cmdline;
-	     i < MAX_CMDLINECONSOLES && c->name[0];
-	     i++, c++) {
-		if (!newcon->match ||
-		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
-			/* default matching */
-			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
-			if (strcmp(c->name, newcon->name) != 0)
-				continue;
-			if (newcon->index >= 0 &&
-			    newcon->index != c->index)
-				continue;
-			if (newcon->index < 0)
-				newcon->index = c->index;
 
-			if (_braille_register_console(newcon, c))
+	/* If not, try to match against the platform default(s) */
-				return;
+	if (err == -ENOENT)
+		err = try_enable_new_console(newcon, false);
 
-			if (newcon->setup &&
+	/* printk() messages are not printed to the Braille console. */
-			    newcon->setup(newcon, c->options) != 0)
+	if (err || newcon->flags & CON_BRL)
-				break;
-		}
-
-		newcon->flags |= CON_ENABLED;
-		if (i == preferred_console) {
-			newcon->flags |= CON_CONSDEV;
-			has_preferred = true;
-		}
-		break;
-	}
-
-	if (!(newcon->flags & CON_ENABLED))
 		return;
 
 	/*
@@ -2779,6 +2824,8 @@ void register_console(struct console *newcon)
 		console_drivers = newcon;
 		if (newcon->next)
 			newcon->next->flags &= ~CON_CONSDEV;
+		/* Ensure this flag is always set for the head of the list */
+		newcon->flags |= CON_CONSDEV;
 	} else {
 		newcon->next = console_drivers->next;
 		console_drivers->next = newcon;
@@ -3384,7 +3431,7 @@ out:
 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
 
 /**
- * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
+ * kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
  * @dumper: registered kmsg dumper
  *
  * Reset the dumper's iterator so that kmsg_dump_get_line() and
@@ -3402,7 +3449,7 @@ void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
 }
 
 /**
- * kmsg_dump_rewind - reset the interator
+ * kmsg_dump_rewind - reset the iterator
  * @dumper: registered kmsg dumper
  *
  * Reset the dumper's iterator so that kmsg_dump_get_line() and

lib/test_printf.c

@@ -494,7 +494,7 @@ struct_va_format(void)
 }
 
 static void __init
-struct_rtc_time(void)
+time_and_date(void)
 {
 	/* 1543210543 */
 	const struct rtc_time tm = {
@@ -505,14 +505,21 @@ struct_rtc_time(void)
 		.tm_mon = 10,
 		.tm_year = 118,
 	};
+	/* 2019-01-04T15:32:23 */
+	time64_t t = 1546615943;
 
-	test("(%ptR?)", "%pt", &tm);
+	test("(%pt?)", "%pt", &tm);
 	test("2018-11-26T05:35:43", "%ptR", &tm);
 	test("0118-10-26T05:35:43", "%ptRr", &tm);
 	test("05:35:43|2018-11-26", "%ptRt|%ptRd", &tm, &tm);
 	test("05:35:43|0118-10-26", "%ptRtr|%ptRdr", &tm, &tm);
 	test("05:35:43|2018-11-26", "%ptRttr|%ptRdtr", &tm, &tm);
 	test("05:35:43 tr|2018-11-26 tr", "%ptRt tr|%ptRd tr", &tm, &tm);
+
+	test("2019-01-04T15:32:23", "%ptT", &t);
+	test("0119-00-04T15:32:23", "%ptTr", &t);
+	test("15:32:23|2019-01-04", "%ptTt|%ptTd", &t, &t);
+	test("15:32:23|0119-00-04", "%ptTtr|%ptTdr", &t, &t);
 }
 
 static void __init
@@ -678,7 +685,7 @@ test_pointer(void)
 	uuid();
 	dentry();
 	struct_va_format();
-	struct_rtc_time();
+	time_and_date();
 	struct_clk();
 	bitmap();
 	netdev_features();

lib/vsprintf.c

@@ -34,6 +34,7 @@
 #include <linux/dcache.h>
 #include <linux/cred.h>
 #include <linux/rtc.h>
+#include <linux/time.h>
 #include <linux/uuid.h>
 #include <linux/of.h>
 #include <net/addrconf.h>
@@ -58,7 +59,7 @@
  * @endp: A pointer to the end of the parsed string will be placed here
  * @base: The number base to use
  *
- * This function is obsolete. Please use kstrtoull instead.
+ * This function has caveats. Please use kstrtoull instead.
  */
 unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
 {
@@ -83,7 +84,7 @@ EXPORT_SYMBOL(simple_strtoull);
  * @endp: A pointer to the end of the parsed string will be placed here
  * @base: The number base to use
  *
- * This function is obsolete. Please use kstrtoul instead.
+ * This function has caveats. Please use kstrtoul instead.
  */
 unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base)
 {
@@ -97,7 +98,7 @@ EXPORT_SYMBOL(simple_strtoul);
  * @endp: A pointer to the end of the parsed string will be placed here
  * @base: The number base to use
  *
- * This function is obsolete. Please use kstrtol instead.
+ * This function has caveats. Please use kstrtol instead.
  */
 long simple_strtol(const char *cp, char **endp, unsigned int base)
 {
@@ -114,7 +115,7 @@ EXPORT_SYMBOL(simple_strtol);
  * @endp: A pointer to the end of the parsed string will be placed here
  * @base: The number base to use
  *
- * This function is obsolete. Please use kstrtoll instead.
+ * This function has caveats. Please use kstrtoll instead.
  */
 long long simple_strtoll(const char *cp, char **endp, unsigned int base)
 {
@@ -1826,6 +1827,29 @@ char *rtc_str(char *buf, char *end, const struct rtc_time *tm,
 	return buf;
 }
 
+static noinline_for_stack
+char *time64_str(char *buf, char *end, const time64_t time,
+		 struct printf_spec spec, const char *fmt)
+{
+	struct rtc_time rtc_time;
+	struct tm tm;
+
+	time64_to_tm(time, 0, &tm);
+
+	rtc_time.tm_sec = tm.tm_sec;
+	rtc_time.tm_min = tm.tm_min;
+	rtc_time.tm_hour = tm.tm_hour;
+	rtc_time.tm_mday = tm.tm_mday;
+	rtc_time.tm_mon = tm.tm_mon;
+	rtc_time.tm_year = tm.tm_year;
+	rtc_time.tm_wday = tm.tm_wday;
+	rtc_time.tm_yday = tm.tm_yday;
+
+	rtc_time.tm_isdst = 0;
+
+	return rtc_str(buf, end, &rtc_time, spec, fmt);
+}
+
 static noinline_for_stack
 char *time_and_date(char *buf, char *end, void *ptr, struct printf_spec spec,
 		    const char *fmt)
@@ -1833,8 +1857,10 @@ char *time_and_date(char *buf, char *end, void *ptr, struct printf_spec spec,
 	switch (fmt[1]) {
 	case 'R':
 		return rtc_str(buf, end, (const struct rtc_time *)ptr, spec, fmt);
+	case 'T':
+		return time64_str(buf, end, *(const time64_t *)ptr, spec, fmt);
 	default:
-		return error_string(buf, end, "(%ptR?)", spec);
+		return error_string(buf, end, "(%pt?)", spec);
 	}
 }
 
@@ -2150,8 +2176,9 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
  * - 'd[234]' For a dentry name (optionally 2-4 last components)
  * - 'D[234]' Same as 'd' but for a struct file
  * - 'g' For block_device name (gendisk + partition number)
- * - 't[R][dt][r]' For time and date as represented:
+ * - 't[RT][dt][r]' For time and date as represented by:
  *      R    struct rtc_time
+ *      T    time64_t
  * - 'C' For a clock, it prints the name (Common Clock Framework) or address
  *       (legacy clock framework) of the clock
  * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address