printk: implement extended console support

index 9b30871..58b1fec 100644
@@ -30,6 +30,8 @@ static inline const char *printk_skip_level(const char *buffer)
 	return buffer;
 }
 
+#define CONSOLE_EXT_LOG_MAX	8192
+
 /* printk's without a loglevel use this.. */
 #define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
 

index c099b08..a115490 100644
@@ -505,6 +505,11 @@ int check_syslog_permissions(int type, bool from_file)
 	return security_syslog(type);
 }
 
+static void append_char(char **pp, char *e, char c)
+{
+	if (*pp < e)
+		*(*pp)++ = c;
+}
 
 /* /dev/kmsg - userspace message inject/listen interface */
 struct devkmsg_user {

@@ -512,7 +517,7 @@ struct devkmsg_user {
 	u32 idx;
 	enum log_flags prev;
 	struct mutex lock;
-	char buf[8192];
+	char buf[CONSOLE_EXT_LOG_MAX];
 };
 
 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)

@@ -570,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 {
 	struct devkmsg_user *user = file->private_data;
 	struct printk_log *msg;
+	char *p, *e;
 	u64 ts_usec;
 	size_t i;
 	char cont = '-';

@@ -579,6 +585,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	if (!user)
 		return -EBADF;
 
+	p = user->buf;
+	e = user->buf + sizeof(user->buf);
+
 	ret = mutex_lock_interruptible(&user->lock);
 	if (ret)
 		return ret;

@@ -625,9 +634,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
 		cont = '+';
 
-	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
-		      (msg->facility << 3) | msg->level,
-		      user->seq, ts_usec, cont);
+	p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
+		       (msg->facility << 3) | msg->level,
+		       user->seq, ts_usec, cont);
 	user->prev = msg->flags;
 
 	/* escape non-printable characters */

@@ -635,11 +644,11 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		unsigned char c = log_text(msg)[i];
 
 		if (c < ' ' || c >= 127 || c == '\\')
-			len += sprintf(user->buf + len, "\\x%02x", c);
+			p += scnprintf(p, e - p, "\\x%02x", c);
 		else
-			user->buf[len++] = c;
+			append_char(&p, e, c);
 	}
-	user->buf[len++] = '\n';
+	append_char(&p, e, '\n');
 
 	if (msg->dict_len) {
 		bool line = true;

@@ -648,30 +657,31 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 			unsigned char c = log_dict(msg)[i];
 
 			if (line) {
-				user->buf[len++] = ' ';
+				append_char(&p, e, ' ');
 				line = false;
 			}
 
 			if (c == '\0') {
-				user->buf[len++] = '\n';
+				append_char(&p, e, '\n');
 				line = true;
 				continue;
 			}
 
 			if (c < ' ' || c >= 127 || c == '\\') {
-				len += sprintf(user->buf + len, "\\x%02x", c);
+				p += scnprintf(p, e - p, "\\x%02x", c);
 				continue;
 			}
 
-			user->buf[len++] = c;
+			append_char(&p, e, c);
 		}
-		user->buf[len++] = '\n';
+		append_char(&p, e, '\n');
 	}
 
 	user->idx = log_next(user->idx);
 	user->seq++;
 	raw_spin_unlock_irq(&logbuf_lock);
 
+	len = p - user->buf;
 	if (len > count) {
 		ret = -EINVAL;
 		goto out;

index a115490..51ce4f1 100644
@@ -511,6 +511,81 @@ static void append_char(char **pp, char *e, char c)
 		*(*pp)++ = c;
 }
 
+static ssize_t msg_print_ext_header(char *buf, size_t size,
+				    struct printk_log *msg, u64 seq,
+				    enum log_flags prev_flags)
+{
+	u64 ts_usec = msg->ts_nsec;
+	char cont = '-';
+
+	do_div(ts_usec, 1000);
+
+	/*
+	 * If we couldn't merge continuation line fragments during the print,
+	 * export the stored flags to allow an optional external merge of the
+	 * records. Merging the records isn't always neccessarily correct, like
+	 * when we hit a race during printing. In most cases though, it produces
+	 * better readable output. 'c' in the record flags mark the first
+	 * fragment of a line, '+' the following.
+	 */
+	if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
+		cont = 'c';
+	else if ((msg->flags & LOG_CONT) ||
+		 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
+		cont = '+';
+
+	return scnprintf(buf, size, "%u,%llu,%llu,%c;",
+		       (msg->facility << 3) | msg->level, seq, ts_usec, cont);
+}
+
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+				  char *dict, size_t dict_len,
+				  char *text, size_t text_len)
+{
+	char *p = buf, *e = buf + size;
+	size_t i;
+
+	/* escape non-printable characters */
+	for (i = 0; i < text_len; i++) {
+		unsigned char c = text[i];
+
+		if (c < ' ' || c >= 127 || c == '\\')
+			p += scnprintf(p, e - p, "\\x%02x", c);
+		else
+			append_char(&p, e, c);
+	}
+	append_char(&p, e, '\n');
+
+	if (dict_len) {
+		bool line = true;
+
+		for (i = 0; i < dict_len; i++) {
+			unsigned char c = dict[i];
+
+			if (line) {
+				append_char(&p, e, ' ');
+				line = false;
+			}
+
+			if (c == '\0') {
+				append_char(&p, e, '\n');
+				line = true;
+				continue;
+			}
+
+			if (c < ' ' || c >= 127 || c == '\\') {
+				p += scnprintf(p, e - p, "\\x%02x", c);
+				continue;
+			}
+
+			append_char(&p, e, c);
+		}
+		append_char(&p, e, '\n');
+	}
+
+	return p - buf;
+}
+
 /* /dev/kmsg - userspace message inject/listen interface */
 struct devkmsg_user {
 	u64 seq;

@@ -575,19 +650,12 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 {
 	struct devkmsg_user *user = file->private_data;
 	struct printk_log *msg;
-	char *p, *e;
-	u64 ts_usec;
-	size_t i;
-	char cont = '-';
 	size_t len;
 	ssize_t ret;
 
 	if (!user)
 		return -EBADF;
 
-	p = user->buf;
-	e = user->buf + sizeof(user->buf);
-
 	ret = mutex_lock_interruptible(&user->lock);
 	if (ret)
 		return ret;

@@ -617,71 +685,17 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	}
 
 	msg = log_from_idx(user->idx);
-	ts_usec = msg->ts_nsec;
-	do_div(ts_usec, 1000);
+	len = msg_print_ext_header(user->buf, sizeof(user->buf),
+				   msg, user->seq, user->prev);
+	len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
+				  log_dict(msg), msg->dict_len,
+				  log_text(msg), msg->text_len);
 
-	/*
-	 * If we couldn't merge continuation line fragments during the print,
-	 * export the stored flags to allow an optional external merge of the
-	 * records. Merging the records isn't always neccessarily correct, like
-	 * when we hit a race during printing. In most cases though, it produces
-	 * better readable output. 'c' in the record flags mark the first
-	 * fragment of a line, '+' the following.
-	 */
-	if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
-		cont = 'c';
-	else if ((msg->flags & LOG_CONT) ||
-		 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
-		cont = '+';
-
-	p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
-		       (msg->facility << 3) | msg->level,
-		       user->seq, ts_usec, cont);
 	user->prev = msg->flags;
-
-	/* escape non-printable characters */
-	for (i = 0; i < msg->text_len; i++) {
-		unsigned char c = log_text(msg)[i];
-
-		if (c < ' ' || c >= 127 || c == '\\')
-			p += scnprintf(p, e - p, "\\x%02x", c);
-		else
-			append_char(&p, e, c);
-	}
-	append_char(&p, e, '\n');
-
-	if (msg->dict_len) {
-		bool line = true;
-
-		for (i = 0; i < msg->dict_len; i++) {
-			unsigned char c = log_dict(msg)[i];
-
-			if (line) {
-				append_char(&p, e, ' ');
-				line = false;
-			}
-
-			if (c == '\0') {
-				append_char(&p, e, '\n');
-				line = true;
-				continue;
-			}
-
-			if (c < ' ' || c >= 127 || c == '\\') {
-				p += scnprintf(p, e - p, "\\x%02x", c);
-				continue;
-			}
-
-			append_char(&p, e, c);
-		}
-		append_char(&p, e, '\n');
-	}
-
 	user->idx = log_next(user->idx);
 	user->seq++;
 	raw_spin_unlock_irq(&logbuf_lock);
 
-	len = p - user->buf;
 	if (len > count) {
 		ret = -EINVAL;
 		goto out;

index 9f50fb4..bd19434 100644
@@ -115,6 +115,7 @@ static inline int con_debug_leave(void)
 #define CON_BOOT	(8)
 #define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
 #define CON_BRL		(32) /* Used for a braille device */
+#define CON_EXTENDED	(64) /* Use the extended output format a la /dev/kmsg */
 
 struct console {
 	char	name[16];

145 lines not on this page · raw message

index 9f50fb4..bd19434 100644
@@ -115,6 +115,7 @@ static inline int con_debug_leave(void)
 #define CON_BOOT	(8)
 #define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
 #define CON_BRL		(32) /* Used for a braille device */
+#define CON_EXTENDED	(64) /* Use the extended output format a la /dev/kmsg */
 
 struct console {
 	char	name[16];

146 lines not on this page · raw message

@@ -84,6 +84,10 @@ static struct lockdep_map console_lock_d
 };
 #endif
 
+#ifdef CONFIG_PRINTK_CON_EXTENDED
+
+#define CONSOLE_EXT_LOG_BUF_LEN		CONSOLE_EXT_LOG_MAX
+
 /*
  * Number of registered extended console drivers.
  *

@@ -96,6 +100,25 @@ static struct lockdep_map console_lock_d
  */
 static int nr_ext_console_drivers;
 
+static void inc_nr_ext_console_drivers(void)
+{
+	nr_ext_console_drivers++;
+}
+
+static void dec_nr_ext_console_drivers(void)
+{
+	nr_ext_console_drivers--;
+}
+
+#else	/* CONFIG_PRINTK_CON_EXTENDED */
+
+#define CONSOLE_EXT_LOG_BUF_LEN		0
+#define nr_ext_console_drivers		0
+static void inc_nr_ext_console_drivers(void) { }
+static void dec_nr_ext_console_drivers(void) { }
+
+#endif	/* CONFIG_PRINTK_CON_EXTENDED */
+
 /*
  * Helper macros to handle lockdep when locking/unlocking console_sem. We use
  * macros instead of functions so that _RET_IP_ contains useful information.

@@ -2224,7 +2247,7 @@ out:
  */
 void console_unlock(void)
 {
-	static char ext_text[CONSOLE_EXT_LOG_MAX];
+	static char ext_text[CONSOLE_EXT_LOG_BUF_LEN];
 	static char text[LOG_LINE_MAX + PREFIX_MAX];
 	static u64 seen_seq;
 	unsigned long flags;

@@ -2561,9 +2584,11 @@ void register_console(struct console *ne
 		console_drivers->next = newcon;
 	}
 
-	if (newcon->flags & CON_EXTENDED)
-		if (!nr_ext_console_drivers++)
+	if (newcon->flags & CON_EXTENDED) {
+		if (!nr_ext_console_drivers)
 			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+		inc_nr_ext_console_drivers();
+	}
 
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*

@@ -2638,7 +2663,7 @@ int unregister_console(struct console *c
 	}
 
 	if (!res && (console->flags & CON_EXTENDED))
-		nr_ext_console_drivers--;
+		dec_nr_ext_console_drivers();
 
 	/*
 	 * If this isn't the last console and it has CON_CONSDEV set, we

index cf8c242..f719118 100644
@@ -84,6 +84,10 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+#ifdef CONFIG_PRINTK_CON_EXTENDED
+
+#define CONSOLE_EXT_LOG_BUF_LEN		CONSOLE_EXT_LOG_MAX
+
 /*
  * Number of registered extended console drivers.
  *

@@ -96,6 +100,32 @@ static struct lockdep_map console_lock_dep_map = {
  */
 static int nr_ext_console_drivers;
 
+static void inc_nr_ext_console_drivers(void)
+{
+	nr_ext_console_drivers++;
+}
+
+static void dec_nr_ext_console_drivers(void)
+{
+	nr_ext_console_drivers--;
+}
+
+#else	/* CONFIG_PRINTK_CON_EXTENDED */
+
+#define CONSOLE_EXT_LOG_BUF_LEN		0
+#define nr_ext_console_drivers		0
+
+static void inc_nr_ext_console_drivers(void)
+{
+	WARN_ONCE(true, "printk: CON_EXTENDED requested when !CONFIG_PRINTK_CON_EXTENDED\n");
+}
+
+static void dec_nr_ext_console_drivers(void)
+{
+}
+
+#endif	/* CONFIG_PRINTK_CON_EXTENDED */
+
 /*
  * Helper macros to handle lockdep when locking/unlocking console_sem. We use
  * macros instead of functions so that _RET_IP_ contains useful information.

@@ -2224,7 +2254,7 @@ static void console_cont_flush(char *text, size_t size)
  */
 void console_unlock(void)
 {
-	static char ext_text[CONSOLE_EXT_LOG_MAX];
+	static char ext_text[CONSOLE_EXT_LOG_BUF_LEN];
 	static char text[LOG_LINE_MAX + PREFIX_MAX];
 	static u64 seen_seq;
 	unsigned long flags;

@@ -2561,9 +2591,11 @@ void register_console(struct console *newcon)
 		console_drivers->next = newcon;
 	}
 
-	if (newcon->flags & CON_EXTENDED)
-		if (!nr_ext_console_drivers++)
+	if (newcon->flags & CON_EXTENDED) {
+		if (!nr_ext_console_drivers)
 			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+		inc_nr_ext_console_drivers();
+	}
 
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*

@@ -2638,7 +2670,7 @@ int unregister_console(struct console *console)
 	}
 
 	if (!res && (console->flags & CON_EXTENDED))
-		nr_ext_console_drivers--;
+		dec_nr_ext_console_drivers();
 
 	/*
 	 * If this isn't the last console and it has CON_CONSDEV set, we

index cf8c242..841ea4d 100644
@@ -84,6 +84,10 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+#ifdef CONFIG_PRINTK_CON_EXTENDED
+
+#define CONSOLE_EXT_LOG_BUF_LEN		CONSOLE_EXT_LOG_MAX
+
 /*
  * Number of registered extended console drivers.
  *

@@ -96,6 +100,33 @@ static struct lockdep_map console_lock_dep_map = {
  */
 static int nr_ext_console_drivers;
 
+static void inc_nr_ext_console_drivers(void)
+{
+	if (!nr_ext_console_drivers++)
+		pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+}
+
+static void dec_nr_ext_console_drivers(void)
+{
+	nr_ext_console_drivers--;
+}
+
+#else	/* CONFIG_PRINTK_CON_EXTENDED */
+
+#define CONSOLE_EXT_LOG_BUF_LEN		0
+#define nr_ext_console_drivers		0
+
+static void inc_nr_ext_console_drivers(void)
+{
+	WARN_ONCE(true, "printk: CON_EXTENDED requested when !CONFIG_PRINTK_CON_EXTENDED\n");
+}
+
+static void dec_nr_ext_console_drivers(void)
+{
+}
+
+#endif	/* CONFIG_PRINTK_CON_EXTENDED */
+
 /*
  * Helper macros to handle lockdep when locking/unlocking console_sem. We use
  * macros instead of functions so that _RET_IP_ contains useful information.

@@ -2224,7 +2255,7 @@ static void console_cont_flush(char *text, size_t size)
  */
 void console_unlock(void)
 {
-	static char ext_text[CONSOLE_EXT_LOG_MAX];
+	static char ext_text[CONSOLE_EXT_LOG_BUF_LEN];
 	static char text[LOG_LINE_MAX + PREFIX_MAX];
 	static u64 seen_seq;
 	unsigned long flags;

@@ -2562,8 +2593,7 @@ void register_console(struct console *newcon)
 	}
 
 	if (newcon->flags & CON_EXTENDED)
-		if (!nr_ext_console_drivers++)
-			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+		inc_nr_ext_console_drivers();
 
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*

@@ -2638,7 +2668,7 @@ int unregister_console(struct console *console)
 	}
 
 	if (!res && (console->flags & CON_EXTENDED))
-		nr_ext_console_drivers--;
+		dec_nr_ext_console_drivers();
 
 	/*
 	 * If this isn't the last console and it has CON_CONSDEV set, we