printk changes for 6.13

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Merge tag 'printk-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Print more precise information about the printk log buffer memory
   usage.

 - Make sure that the sysrq title is shown on the console even when
   deferred.

 - Do not enable earlycon by `console=` which is meant to disable the
   default console.

* tag 'printk-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: add dummy printk_force_console_enter/exit helpers
  tty: sysrq: Use printk_force_console context on __handle_sysrq
  printk: Introduce FORCE_CON flag
  printk: Improve memory usage logging during boot
  init: Don't proxy `console=` to earlycon

drivers/tty/serial/earlycon.c

@@ -248,6 +248,29 @@ static int __init param_setup_earlycon(char *buf)
 }
 early_param("earlycon", param_setup_earlycon);
 
+/*
+ * The `console` parameter is overloaded. It's handled here as an early param
+ * and in `printk.c` as a late param. It's possible to specify an early
+ * `bootconsole` using `earlycon=uartXXXX` (handled above), or via
+ * the `console=uartXXX` alias. See the comment in `8250_early.c`.
+ */
+static int __init param_setup_earlycon_console_alias(char *buf)
+{
+	/*
+	 * A plain `console` parameter must not enable the SPCR `bootconsole`
+	 * like a plain `earlycon` does.
+	 *
+	 * A `console=` parameter that specifies an empty value is used to
+	 * disable the `console`, not the `earlycon` `bootconsole`. The
+	 * disabling of the `console` is handled by `printk.c`.
+	 */
+	if (!buf || !buf[0])
+		return 0;
+
+	return param_setup_earlycon(buf);
+}
+early_param("console", param_setup_earlycon_console_alias);
+
 #ifdef CONFIG_OF_EARLY_FLATTREE
 
 int __init of_setup_earlycon(const struct earlycon_id *match,

drivers/tty/sysrq.c

@@ -583,7 +583,6 @@ static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
 void __handle_sysrq(u8 key, bool check_mask)
 {
 	const struct sysrq_key_op *op_p;
-	int orig_log_level;
 	int orig_suppress_printk;
 	int i;
 
@@ -593,13 +592,12 @@ void __handle_sysrq(u8 key, bool check_mask)
 	rcu_sysrq_start();
 	rcu_read_lock();
 	/*
-	 * Raise the apparent loglevel to maximum so that the sysrq header
+	 * Enter in the force_console context so that sysrq header is shown to
-	 * is shown to provide the user with positive feedback.  We do not
+	 * provide the user with positive feedback.  We do not simply emit this
-	 * simply emit this at KERN_EMERG as that would change message
+	 * at KERN_EMERG as that would change message routing in the consumers
-	 * routing in the consumers of /proc/kmsg.
+	 * of /proc/kmsg.
 	 */
-	orig_log_level = console_loglevel;
+	printk_force_console_enter();
-	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 
 	op_p = __sysrq_get_key_op(key);
 	if (op_p) {
@@ -609,11 +607,11 @@ void __handle_sysrq(u8 key, bool check_mask)
 		 */
 		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 			pr_info("%s\n", op_p->action_msg);
-			console_loglevel = orig_log_level;
+			printk_force_console_exit();
 			op_p->handler(key);
 		} else {
 			pr_info("This sysrq operation is disabled.\n");
-			console_loglevel = orig_log_level;
+			printk_force_console_exit();
 		}
 	} else {
 		pr_info("HELP : ");
@@ -631,7 +629,7 @@ void __handle_sysrq(u8 key, bool check_mask)
 			}
 		}
 		pr_cont("\n");
-		console_loglevel = orig_log_level;
+		printk_force_console_exit();
 	}
 	rcu_read_unlock();
 	rcu_sysrq_end();

include/linux/printk.h

@@ -166,6 +166,9 @@ __printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);
 extern void __printk_deferred_enter(void);
 extern void __printk_deferred_exit(void);
 
+extern void printk_force_console_enter(void);
+extern void printk_force_console_exit(void);
+
 /*
  * The printk_deferred_enter/exit macros are available only as a hack for
  * some code paths that need to defer all printk console printing. Interrupts
@@ -229,6 +232,14 @@ static inline void printk_deferred_exit(void)
 {
 }
 
+static inline void printk_force_console_enter(void)
+{
+}
+
+static inline void printk_force_console_exit(void)
+{
+}
+
 static inline int printk_ratelimit(void)
 {
 	return 0;

init/main.c

@@ -754,10 +754,7 @@ static int __init do_early_param(char *param, char *val,
 	const struct obs_kernel_param *p;
 
 	for (p = __setup_start; p < __setup_end; p++) {
-		if ((p->early && parameq(param, p->str)) ||
+		if (p->early && parameq(param, p->str)) {
-		    (strcmp(param, "console") == 0 &&
-		     strcmp(p->str, "earlycon") == 0)
-		) {
 			if (p->setup_func(val) != 0)
 				pr_warn("Malformed early option '%s'\n", param);
 		}

kernel/printk/internal.h

@@ -53,6 +53,8 @@ int devkmsg_sysctl_set_loglvl(const struct ctl_table *table, int write,
 
 /* Flags for a single printk record. */
 enum printk_info_flags {
+	/* always show on console, ignore console_loglevel */
+	LOG_FORCE_CON	= 1,
 	LOG_NEWLINE	= 2,	/* text ended with a newline */
 	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
 };
@@ -90,6 +92,7 @@ bool printk_percpu_data_ready(void);
 
 void defer_console_output(void);
 bool is_printk_legacy_deferred(void);
+bool is_printk_force_console(void);
 
 u16 printk_parse_prefix(const char *text, int *level,
 			enum printk_info_flags *flags);

kernel/printk/printk.c

@@ -1157,6 +1157,17 @@ static unsigned int __init add_to_rb(struct printk_ringbuffer *rb,
 
 static char setup_text_buf[PRINTKRB_RECORD_MAX] __initdata;
 
+static void print_log_buf_usage_stats(void)
+{
+	unsigned int descs_count = log_buf_len >> PRB_AVGBITS;
+	size_t meta_data_size;
+
+	meta_data_size = descs_count * (sizeof(struct prb_desc) + sizeof(struct printk_info));
+
+	pr_info("log buffer data + meta data: %u + %zu = %zu bytes\n",
+		log_buf_len, meta_data_size, log_buf_len + meta_data_size);
+}
+
 void __init setup_log_buf(int early)
 {
 	struct printk_info *new_infos;
@@ -1186,20 +1197,25 @@ void __init setup_log_buf(int early)
 	if (!early && !new_log_buf_len)
 		log_buf_add_cpu();
 
-	if (!new_log_buf_len)
+	if (!new_log_buf_len) {
+		/* Show the memory stats only once. */
+		if (!early)
+			goto out;
+
 		return;
+	}
 
 	new_descs_count = new_log_buf_len >> PRB_AVGBITS;
 	if (new_descs_count == 0) {
 		pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len);
-		return;
+		goto out;
 	}
 
 	new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
 	if (unlikely(!new_log_buf)) {
 		pr_err("log_buf_len: %lu text bytes not available\n",
 		       new_log_buf_len);
-		return;
+		goto out;
 	}
 
 	new_descs_size = new_descs_count * sizeof(struct prb_desc);
@@ -1262,7 +1278,7 @@ void __init setup_log_buf(int early)
 		       prb_next_seq(&printk_rb_static) - seq);
 	}
 
-	pr_info("log_buf_len: %u bytes\n", log_buf_len);
+	print_log_buf_usage_stats();
 	pr_info("early log buf free: %u(%u%%)\n",
 		free, (free * 100) / __LOG_BUF_LEN);
 	return;
@@ -1271,6 +1287,8 @@ void __init setup_log_buf(int early)
 	memblock_free(new_descs, new_descs_size);
 err_free_log_buf:
 	memblock_free(new_log_buf, new_log_buf_len);
+out:
+	print_log_buf_usage_stats();
 }
 
 static bool __read_mostly ignore_loglevel;
@@ -1320,11 +1338,11 @@ static void boot_delay_msec(int level)
 {
 	unsigned long long k;
 	unsigned long timeout;
+	bool suppress = !is_printk_force_console() &&
+			suppress_message_printing(level);
 
-	if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
+	if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) || suppress)
-		|| suppress_message_printing(level)) {
 		return;
-	}
 
 	k = (unsigned long long)loops_per_msec * boot_delay;
 
@@ -2274,6 +2292,9 @@ int vprintk_store(int facility, int level,
 	if (dev_info)
 		flags |= LOG_NEWLINE;
 
+	if (is_printk_force_console())
+		flags |= LOG_FORCE_CON;
+
 	if (flags & LOG_CONT) {
 		prb_rec_init_wr(&r, reserve_size);
 		if (prb_reserve_in_last(&e, prb, &r, caller_id, PRINTKRB_RECORD_MAX)) {
@@ -2281,6 +2302,9 @@ int vprintk_store(int facility, int level,
 						 facility, &flags, fmt, args);
 			r.info->text_len += text_len;
 
+			if (flags & LOG_FORCE_CON)
+				r.info->flags |= LOG_FORCE_CON;
+
 			if (flags & LOG_NEWLINE) {
 				r.info->flags |= LOG_NEWLINE;
 				prb_final_commit(&e);
@@ -2948,6 +2972,7 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
 	struct printk_info info;
 	struct printk_record r;
 	size_t len = 0;
+	bool force_con;
 
 	/*
 	 * Formatting extended messages requires a separate buffer, so use the
@@ -2966,9 +2991,13 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
 
 	pmsg->seq = r.info->seq;
 	pmsg->dropped = r.info->seq - seq;
+	force_con = r.info->flags & LOG_FORCE_CON;
 
-	/* Skip record that has level above the console loglevel. */
+	/*
-	if (may_suppress && suppress_message_printing(r.info->level))
+	 * Skip records that are not forced to be printed on consoles and that
+	 * has level above the console loglevel.
+	 */
+	if (!force_con && may_suppress && suppress_message_printing(r.info->level))
 		goto out;
 
 	if (is_extended) {

kernel/printk/printk_safe.c

@@ -12,6 +12,24 @@
 
 #include "internal.h"
 
+/* Context where printk messages are never suppressed */
+static atomic_t force_con;
+
+void printk_force_console_enter(void)
+{
+	atomic_inc(&force_con);
+}
+
+void printk_force_console_exit(void)
+{
+	atomic_dec(&force_con);
+}
+
+bool is_printk_force_console(void)
+{
+	return atomic_read(&force_con);
+}
+
 static DEFINE_PER_CPU(int, printk_context);
 
 /* Can be preempted by NMI. */