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From:   John Ogness <john.ogness@linutronix.de>
To:     Petr Mladek <pmladek@suse.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        kexec@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH printk 2/3] printk: move dictionary keys to dev_printk_info
Date:   Thu, 17 Sep 2020 15:22:43 +0206
Message-Id: <20200917131644.25838-3-john.ogness@linutronix.de>
In-Reply-To: <20200917131644.25838-1-john.ogness@linutronix.de>
References: <20200917131644.25838-1-john.ogness@linutronix.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Dictionaries are only used for SUBSYSTEM and DEVICE properties. The
current implementation stores the property names each time they are
used. This requires more space than otherwise necessary. Also,
because the dictionary entries are currently considered optional,
it cannot be relied upon that they are always available, even if the
writer wanted to store them. These issues will increase should new
dictionary properties be introduced.

Rather than storing the subsystem and device properties in the
dict ring, introduce a struct dev_printk_info with separate fields
to store only the property values. Embed this struct within the
struct printk_info to provide guaranteed availability.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 Documentation/admin-guide/kdump/gdbmacros.txt |  73 ++++----
 drivers/base/core.c                           |  46 ++---
 include/linux/dev_printk.h                    |   8 +
 include/linux/printk.h                        |   6 +-
 kernel/printk/internal.h                      |   4 +-
 kernel/printk/printk.c                        | 161 +++++++++---------
 kernel/printk/printk_ringbuffer.h             |   3 +
 kernel/printk/printk_safe.c                   |   2 +-
 scripts/gdb/linux/dmesg.py                    |  16 +-
 9 files changed, 159 insertions(+), 160 deletions(-)

diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt
index 94fabb165abf..82aecdcae8a6 100644
--- a/Documentation/admin-guide/kdump/gdbmacros.txt
+++ b/Documentation/admin-guide/kdump/gdbmacros.txt
@@ -172,13 +172,13 @@ end
 
 define dump_record
 	set var $desc = $arg0
-	if ($argc > 1)
-		set var $prev_flags = $arg1
+	set var $info = $arg1
+	if ($argc > 2)
+		set var $prev_flags = $arg2
 	else
 		set var $prev_flags = 0
 	end
 
-	set var $info = &$desc->info
 	set var $prefix = 1
 	set var $newline = 1
 
@@ -237,44 +237,36 @@ define dump_record
 
 	# handle dictionary data
 
-	set var $begin = $desc->dict_blk_lpos.begin % (1U << prb->dict_data_ring.size_bits)
-	set var $next = $desc->dict_blk_lpos.next % (1U << prb->dict_data_ring.size_bits)
-
-	# handle data-less record
-	if ($begin & 1)
-		set var $dict_len = 0
-		set var $dict = ""
-	else
-		# handle wrapping data block
-		if ($begin > $next)
-			set var $begin = 0
-		end
-
-		# skip over descriptor id
-		set var $begin = $begin + sizeof(long)
-
-		# handle truncated message
-		if ($next - $begin < $info->dict_len)
-			set var $dict_len = $next - $begin
-		else
-			set var $dict_len = $info->dict_len
+	set var $dict = &$info->dev_info.subsystem[0]
+	set var $dict_len = sizeof($info->dev_info.subsystem)
+	if ($dict[0] != '\0')
+		printf " SUBSYSTEM="
+		set var $idx = 0
+		while ($idx < $dict_len)
+			set var $c = $dict[$idx]
+			if ($c == '\0')
+				loop_break
+			else
+				if ($c < ' ' || $c >= 127 || $c == '\\')
+					printf "\\x%02x", $c
+				else
+					printf "%c", $c
+				end
+			end
+			set var $idx = $idx + 1
 		end
-
-		set var $dict = &prb->dict_data_ring.data[$begin]
+		printf "\n"
 	end
 
-	if ($dict_len > 0)
+	set var $dict = &$info->dev_info.device[0]
+	set var $dict_len = sizeof($info->dev_info.device)
+	if ($dict[0] != '\0')
+		printf " DEVICE="
 		set var $idx = 0
-		set var $line = 1
 		while ($idx < $dict_len)
-			if ($line)
-				printf " "
-				set var $line = 0
-			end
 			set var $c = $dict[$idx]
 			if ($c == '\0')
-				printf "\n"
-				set var $line = 1
+				loop_break
 			else
 				if ($c < ' ' || $c >= 127 || $c == '\\')
 					printf "\\x%02x", $c
@@ -288,10 +280,10 @@ define dump_record
 	end
 end
 document dump_record
-	Dump a single record. The first parameter is the descriptor
-	sequence number, the second is optional and specifies the
-	previous record's flags, used for properly formatting
-	continued lines.
+	Dump a single record. The first parameter is the descriptor,
+	the second parameter is the info, the third parameter is
+	optional and specifies the previous record's flags, used for
+	properly formatting continued lines.
 end
 
 define dmesg
@@ -311,12 +303,13 @@ define dmesg
 
 	while (1)
 		set var $desc = &prb->desc_ring.descs[$id % $desc_count]
+		set var $info = &prb->desc_ring.infos[$id % $desc_count]
 
 		# skip non-committed record
 		set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
 		if ($state == $desc_committed || $state == $desc_finalized)
-			dump_record $desc $prev_flags
-			set var $prev_flags = $desc->info.flags
+			dump_record $desc $info $prev_flags
+			set var $prev_flags = $info->flags
 		end
 
 		set var $id = ($id + 1) & $id_mask
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 67d39a90b45c..bdc5fcbd12e9 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3815,22 +3815,21 @@ void device_shutdown(void)
  */
 
 #ifdef CONFIG_PRINTK
-static int
-create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
+static void
+set_dev_info(const struct device *dev, struct dev_printk_info *dev_info)
 {
 	const char *subsys;
-	size_t pos = 0;
+
+	memset(dev_info, 0, sizeof(*dev_info));
 
 	if (dev->class)
 		subsys = dev->class->name;
 	else if (dev->bus)
 		subsys = dev->bus->name;
 	else
-		return 0;
+		return;
 
-	pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);
-	if (pos >= hdrlen)
-		goto overflow;
+	snprintf(dev_info->subsystem, sizeof(dev_info->subsystem), subsys);
 
 	/*
 	 * Add device identifier DEVICE=:
@@ -3846,41 +3845,28 @@ create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
 			c = 'b';
 		else
 			c = 'c';
-		pos++;
-		pos += snprintf(hdr + pos, hdrlen - pos,
-				"DEVICE=%c%u:%u",
-				c, MAJOR(dev->devt), MINOR(dev->devt));
+
+		snprintf(dev_info->device, sizeof(dev_info->device),
+			 "%c%u:%u", c, MAJOR(dev->devt), MINOR(dev->devt));
 	} else if (strcmp(subsys, "net") == 0) {
 		struct net_device *net = to_net_dev(dev);
 
-		pos++;
-		pos += snprintf(hdr + pos, hdrlen - pos,
-				"DEVICE=n%u", net->ifindex);
+		snprintf(dev_info->device, sizeof(dev_info->device),
+			 "n%u", net->ifindex);
 	} else {
-		pos++;
-		pos += snprintf(hdr + pos, hdrlen - pos,
-				"DEVICE=+%s:%s", subsys, dev_name(dev));
+		snprintf(dev_info->device, sizeof(dev_info->device),
+			 "+%s:%s", subsys, dev_name(dev));
 	}
-
-	if (pos >= hdrlen)
-		goto overflow;
-
-	return pos;
-
-overflow:
-	dev_WARN(dev, "device/subsystem name too long");
-	return 0;
 }
 
 int dev_vprintk_emit(int level, const struct device *dev,
 		     const char *fmt, va_list args)
 {
-	char hdr[128];
-	size_t hdrlen;
+	struct dev_printk_info dev_info;
 
-	hdrlen = create_syslog_header(dev, hdr, sizeof(hdr));
+	set_dev_info(dev, &dev_info);
 
-	return vprintk_emit(0, level, hdrlen ? hdr : NULL, hdrlen, fmt, args);
+	return vprintk_emit(0, level, &dev_info, fmt, args);
 }
 EXPORT_SYMBOL(dev_vprintk_emit);
 
diff --git a/include/linux/dev_printk.h b/include/linux/dev_printk.h
index 3028b644b4fb..6f009559ee54 100644
--- a/include/linux/dev_printk.h
+++ b/include/linux/dev_printk.h
@@ -21,6 +21,14 @@
 
 struct device;
 
+#define PRINTK_INFO_SUBSYSTEM_LEN	16
+#define PRINTK_INFO_DEVICE_LEN		48
+
+struct dev_printk_info {
+	char subsystem[PRINTK_INFO_SUBSYSTEM_LEN];
+	char device[PRINTK_INFO_DEVICE_LEN];
+};
+
 #ifdef CONFIG_PRINTK
 
 __printf(3, 0) __cold
diff --git a/include/linux/printk.h b/include/linux/printk.h
index fc8f03c54543..071500ee7281 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -158,10 +158,12 @@ static inline void printk_nmi_direct_enter(void) { }
 static inline void printk_nmi_direct_exit(void) { }
 #endif /* PRINTK_NMI */
 
+struct dev_printk_info;
+
 #ifdef CONFIG_PRINTK
-asmlinkage __printf(5, 0)
+asmlinkage __printf(4, 0)
 int vprintk_emit(int facility, int level,
-		 const char *dict, size_t dictlen,
+		 const struct dev_printk_info *dev_info,
 		 const char *fmt, va_list args);
 
 asmlinkage __printf(1, 0)
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 660f9a6bf73a..3a8fd491758c 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -14,9 +14,9 @@
 
 extern raw_spinlock_t logbuf_lock;
 
-__printf(5, 0)
+__printf(4, 0)
 int vprintk_store(int facility, int level,
-		  const char *dict, size_t dictlen,
+		  const struct dev_printk_info *dev_info,
 		  const char *fmt, va_list args);
 
 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7ad45d897277..b2e2bdd37028 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -296,8 +296,8 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
 
 /*
  * The printk log buffer consists of a sequenced collection of records, each
- * containing variable length message and dictionary text. Every record
- * also contains its own meta-data (@info).
+ * containing variable length message text. Every record also contains its
+ * own meta-data (@info).
  *
  * Every record meta-data carries the timestamp in microseconds, as well as
  * the standard userspace syslog level and syslog facility. The usual kernel
@@ -310,9 +310,7 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
  * terminated.
  *
  * Optionally, a record can carry a dictionary of properties (key/value
- * pairs), to provide userspace with a machine-readable message context. The
- * length of the dictionary is available in @dict_len. The dictionary is not
- * terminated.
+ * pairs), to provide userspace with a machine-readable message context.
  *
  * Examples for well-defined, commonly used property names are:
  *   DEVICE=b12:8               device identifier
@@ -322,21 +320,20 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
  *                                +sound:card0  subsystem:devname
  *   SUBSYSTEM=pci              driver-core subsystem name
  *
- * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
- * follows directly after a '=' character. Every property is terminated by
- * a '\0' character. The last property is not terminated.
+ * Valid characters in property names are [a-zA-Z0-9.-_]. Property names
+ * and values are terminated by a '\0' character.
  *
  * Example of record values:
- *   record.text_buf       = "it's a line" (unterminated)
- *   record.dict_buf       = "DEVICE=b8:2\0DRIVER=bug" (unterminated)
- *   record.info.seq       = 56
- *   record.info.ts_nsec   = 36863
- *   record.info.text_len  = 11
- *   record.info.dict_len  = 22
- *   record.info.facility  = 0 (LOG_KERN)
- *   record.info.flags     = 0
- *   record.info.level     = 3 (LOG_ERR)
- *   record.info.caller_id = 299 (task 299)
+ *   record.text_buf                = "it's a line" (unterminated)
+ *   record.info.seq                = 56
+ *   record.info.ts_nsec            = 36863
+ *   record.info.text_len           = 11
+ *   record.info.facility           = 0 (LOG_KERN)
+ *   record.info.flags              = 0
+ *   record.info.level              = 3 (LOG_ERR)
+ *   record.info.caller_id          = 299 (task 299)
+ *   record.info.dev_info.subsystem = "pci" (terminated)
+ *   record.info.dev_info.device    = "+pci:0000:00:01.0" (terminated)
  *
  * The 'struct printk_info' buffer must never be directly exported to
  * userspace, it is a kernel-private implementation detail that might
@@ -498,19 +495,19 @@ static void truncate_msg(u16 *text_len, u16 *trunc_msg_len)
 /* insert record into the buffer, discard old ones, update heads */
 static int log_store(u32 caller_id, int facility, int level,
 		     enum log_flags flags, u64 ts_nsec,
-		     const char *dict, u16 dict_len,
+		     const struct dev_printk_info *dev_info,
 		     const char *text, u16 text_len)
 {
 	struct prb_reserved_entry e;
 	struct printk_record r;
 	u16 trunc_msg_len = 0;
 
-	prb_rec_init_wr(&r, text_len, dict_len);
+	prb_rec_init_wr(&r, text_len, 0);
 
 	if (!prb_reserve(&e, prb, &r)) {
 		/* truncate the message if it is too long for empty buffer */
 		truncate_msg(&text_len, &trunc_msg_len);
-		prb_rec_init_wr(&r, text_len + trunc_msg_len, dict_len);
+		prb_rec_init_wr(&r, text_len + trunc_msg_len, 0);
 		/* survive when the log buffer is too small for trunc_msg */
 		if (!prb_reserve(&e, prb, &r))
 			return 0;
@@ -521,10 +518,6 @@ static int log_store(u32 caller_id, int facility, int level,
 	if (trunc_msg_len)
 		memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
 	r.info->text_len = text_len + trunc_msg_len;
-	if (r.dict_buf) {
-		memcpy(&r.dict_buf[0], dict, dict_len);
-		r.info->dict_len = dict_len;
-	}
 	r.info->facility = facility;
 	r.info->level = level & 7;
 	r.info->flags = flags & 0x1f;
@@ -533,6 +526,8 @@ static int log_store(u32 caller_id, int facility, int level,
 	else
 		r.info->ts_nsec = local_clock();
 	r.info->caller_id = caller_id;
+	if (dev_info)
+		memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
 
 	/* insert message */
 	if ((flags & LOG_CONT) || !(flags & LOG_NEWLINE))
@@ -613,9 +608,9 @@ static ssize_t info_print_ext_header(char *buf, size_t size,
 			 ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller);
 }
 
-static ssize_t msg_print_ext_body(char *buf, size_t size,
-				  char *dict, size_t dict_len,
-				  char *text, size_t text_len)
+static ssize_t msg_add_ext_text(char *buf, size_t size,
+				const char *text, size_t text_len,
+				unsigned char endc)
 {
 	char *p = buf, *e = buf + size;
 	size_t i;
@@ -629,36 +624,43 @@ static ssize_t msg_print_ext_body(char *buf, size_t size,
 		else
 			append_char(&p, e, c);
 	}
-	append_char(&p, e, '\n');
+	append_char(&p, e, endc);
 
-	if (dict_len) {
-		bool line = true;
+	return p - buf;
+}
 
-		for (i = 0; i < dict_len; i++) {
-			unsigned char c = dict[i];
+static ssize_t msg_add_dict_text(char *buf, size_t size,
+				 const char *key, const char *val)
+{
+	size_t val_len = strlen(val);
+	ssize_t len;
 
-			if (line) {
-				append_char(&p, e, ' ');
-				line = false;
-			}
+	if (!val_len)
+		return 0;
 
-			if (c == '\0') {
-				append_char(&p, e, '\n');
-				line = true;
-				continue;
-			}
+	len = msg_add_ext_text(buf, size, key, strlen(key), '=');
+	len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n');
 
-			if (c < ' ' || c >= 127 || c == '\\') {
-				p += scnprintf(p, e - p, "\\x%02x", c);
-				continue;
-			}
+	return len;
+}
 
-			append_char(&p, e, c);
-		}
-		append_char(&p, e, '\n');
-	}
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+				  char *text, size_t text_len,
+				  struct dev_printk_info *dev_info)
+{
+	ssize_t len;
 
-	return p - buf;
+	len = msg_add_ext_text(buf, size, text, text_len, '\n');
+
+	if (!dev_info)
+		goto out;
+
+	len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM",
+				 dev_info->subsystem);
+	len += msg_add_dict_text(buf + len, size - len, "DEVICE",
+				 dev_info->device);
+out:
+	return len;
 }
 
 /* /dev/kmsg - userspace message inject/listen interface */
@@ -670,7 +672,6 @@ struct devkmsg_user {
 
 	struct printk_info info;
 	char text_buf[CONSOLE_EXT_LOG_MAX];
-	char dict_buf[CONSOLE_EXT_LOG_MAX];
 	struct printk_record record;
 };
 
@@ -681,7 +682,7 @@ int devkmsg_emit(int facility, int level, const char *fmt, ...)
 	int r;
 
 	va_start(args, fmt);
-	r = vprintk_emit(facility, level, NULL, 0, fmt, args);
+	r = vprintk_emit(facility, level, NULL, fmt, args);
 	va_end(args);
 
 	return r;
@@ -791,8 +792,8 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 
 	len = info_print_ext_header(user->buf, sizeof(user->buf), r->info);
 	len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
-				  &r->dict_buf[0], r->info->dict_len,
-				  &r->text_buf[0], r->info->text_len);
+				  &r->text_buf[0], r->info->text_len,
+				  &r->info->dev_info);
 
 	user->seq = r->info->seq + 1;
 	logbuf_unlock_irq();
@@ -897,7 +898,7 @@ static int devkmsg_open(struct inode *inode, struct file *file)
 
 	prb_rec_init_rd(&user->record, &user->info,
 			&user->text_buf[0], sizeof(user->text_buf),
-			&user->dict_buf[0], sizeof(user->dict_buf));
+			NULL, 0);
 
 	logbuf_lock_irq();
 	user->seq = prb_first_valid_seq(prb);
@@ -978,6 +979,11 @@ void log_buf_vmcoreinfo_setup(void)
 	VMCOREINFO_OFFSET(printk_info, text_len);
 	VMCOREINFO_OFFSET(printk_info, dict_len);
 	VMCOREINFO_OFFSET(printk_info, caller_id);
+	VMCOREINFO_OFFSET(printk_info, dev_info);
+
+	VMCOREINFO_STRUCT_SIZE(dev_printk_info);
+	VMCOREINFO_OFFSET(dev_printk_info, subsystem);
+	VMCOREINFO_OFFSET(dev_printk_info, device);
 
 	VMCOREINFO_STRUCT_SIZE(prb_data_ring);
 	VMCOREINFO_OFFSET(prb_data_ring, size_bits);
@@ -1070,22 +1076,19 @@ static unsigned int __init add_to_rb(struct printk_ringbuffer *rb,
 	struct prb_reserved_entry e;
 	struct printk_record dest_r;
 
-	prb_rec_init_wr(&dest_r, r->info->text_len, r->info->dict_len);
+	prb_rec_init_wr(&dest_r, r->info->text_len, 0);
 
 	if (!prb_reserve(&e, rb, &dest_r))
 		return 0;
 
 	memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len);
 	dest_r.info->text_len = r->info->text_len;
-	if (dest_r.dict_buf) {
-		memcpy(&dest_r.dict_buf[0], &r->dict_buf[0], r->info->dict_len);
-		dest_r.info->dict_len = r->info->dict_len;
-	}
 	dest_r.info->facility = r->info->facility;
 	dest_r.info->level = r->info->level;
 	dest_r.info->flags = r->info->flags;
 	dest_r.info->ts_nsec = r->info->ts_nsec;
 	dest_r.info->caller_id = r->info->caller_id;
+	memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info));
 
 	prb_final_commit(&e);
 
@@ -1093,7 +1096,6 @@ static unsigned int __init add_to_rb(struct printk_ringbuffer *rb,
 }
 
 static char setup_text_buf[CONSOLE_EXT_LOG_MAX] __initdata;
-static char setup_dict_buf[CONSOLE_EXT_LOG_MAX] __initdata;
 
 void __init setup_log_buf(int early)
 {
@@ -1170,7 +1172,7 @@ void __init setup_log_buf(int early)
 
 	prb_rec_init_rd(&r, &info,
 			&setup_text_buf[0], sizeof(setup_text_buf),
-			&setup_dict_buf[0], sizeof(setup_dict_buf));
+			NULL, 0);
 
 	prb_init(&printk_rb_dynamic,
 		 new_log_buf, ilog2(new_log_buf_len),
@@ -1900,7 +1902,9 @@ static inline u32 printk_caller_id(void)
 		0x80000000 + raw_smp_processor_id();
 }
 
-static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
+static size_t log_output(int facility, int level, enum log_flags lflags,
+			 const struct dev_printk_info *dev_info,
+			 char *text, size_t text_len)
 {
 	const u32 caller_id = printk_caller_id();
 
@@ -1924,12 +1928,12 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
 
 	/* Store it in the record log */
 	return log_store(caller_id, facility, level, lflags, 0,
-			 dict, dictlen, text, text_len);
+			 dev_info, text, text_len);
 }
 
 /* Must be called under logbuf_lock. */
 int vprintk_store(int facility, int level,
-		  const char *dict, size_t dictlen,
+		  const struct dev_printk_info *dev_info,
 		  const char *fmt, va_list args)
 {
 	static char textbuf[LOG_LINE_MAX];
@@ -1971,15 +1975,14 @@ int vprintk_store(int facility, int level,
 	if (level == LOGLEVEL_DEFAULT)
 		level = default_message_loglevel;
 
-	if (dict)
+	if (dev_info)
 		lflags |= LOG_NEWLINE;
 
-	return log_output(facility, level, lflags,
-			  dict, dictlen, text, text_len);
+	return log_output(facility, level, lflags, dev_info, text, text_len);
 }
 
 asmlinkage int vprintk_emit(int facility, int level,
-			    const char *dict, size_t dictlen,
+			    const struct dev_printk_info *dev_info,
 			    const char *fmt, va_list args)
 {
 	int printed_len;
@@ -2000,7 +2003,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 
 	/* This stops the holder of console_sem just where we want him */
 	logbuf_lock_irqsave(flags);
-	printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
+	printed_len = vprintk_store(facility, level, dev_info, fmt, args);
 	logbuf_unlock_irqrestore(flags);
 
 	/* If called from the scheduler, we can not call up(). */
@@ -2034,7 +2037,7 @@ EXPORT_SYMBOL(vprintk);
 
 int vprintk_default(const char *fmt, va_list args)
 {
-	return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
+	return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
 }
 EXPORT_SYMBOL_GPL(vprintk_default);
 
@@ -2097,8 +2100,8 @@ static ssize_t info_print_ext_header(char *buf, size_t size,
 	return 0;
 }
 static ssize_t msg_print_ext_body(char *buf, size_t size,
-				  char *dict, size_t dict_len,
-				  char *text, size_t text_len) { return 0; }
+				  char *text, size_t text_len,
+				  struct dev_printk_info *dev_info) { return 0; }
 static void console_lock_spinning_enable(void) { }
 static int console_lock_spinning_disable_and_check(void) { return 0; }
 static void call_console_drivers(const char *ext_text, size_t ext_len,
@@ -2387,7 +2390,6 @@ void console_unlock(void)
 {
 	static char ext_text[CONSOLE_EXT_LOG_MAX];
 	static char text[LOG_LINE_MAX + PREFIX_MAX];
-	static char dict[LOG_LINE_MAX];
 	unsigned long flags;
 	bool do_cond_resched, retry;
 	struct printk_info info;
@@ -2398,7 +2400,7 @@ void console_unlock(void)
 		return;
 	}
 
-	prb_rec_init_rd(&r, &info, text, sizeof(text), dict, sizeof(dict));
+	prb_rec_init_rd(&r, &info, text, sizeof(text), NULL, 0);
 
 	/*
 	 * Console drivers are called with interrupts disabled, so
@@ -2470,10 +2472,9 @@ void console_unlock(void)
 						r.info);
 			ext_len += msg_print_ext_body(ext_text + ext_len,
 						sizeof(ext_text) - ext_len,
-						&r.dict_buf[0],
-						r.info->dict_len,
 						&r.text_buf[0],
-						r.info->text_len);
+						r.info->text_len,
+						&r.info->dev_info);
 		}
 		len = record_print_text(&r,
 				console_msg_format & MSG_FORMAT_SYSLOG,
@@ -3052,7 +3053,7 @@ int vprintk_deferred(const char *fmt, va_list args)
 {
 	int r;
 
-	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
+	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
 	defer_console_output();
 
 	return r;
diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 97c8561e74e0..480499ce3c6b 100644
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -4,6 +4,7 @@
 #define _KERNEL_PRINTK_RINGBUFFER_H
 
 #include <linux/atomic.h>
+#include <linux/dev_printk.h>
 
 /*
  * Meta information about each stored message.
@@ -21,6 +22,8 @@ struct printk_info {
 	u8	flags:5;	/* internal record flags */
 	u8	level:3;	/* syslog level */
 	u32	caller_id;	/* thread id or processor id */
+
+	struct dev_printk_info	dev_info;
 };
 
 /*
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 50aeae770434..5dbc40160990 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -375,7 +375,7 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
 	    raw_spin_trylock(&logbuf_lock)) {
 		int len;
 
-		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
+		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
 		raw_spin_unlock(&logbuf_lock);
 		defer_console_output();
 		return len;
diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
index bce14de5f610..a92c55bd8de5 100644
--- a/scripts/gdb/linux/dmesg.py
+++ b/scripts/gdb/linux/dmesg.py
@@ -52,6 +52,12 @@ class LxDmesg(gdb.Command):
         addr = utils.read_ulong(desc_ring, off)
         descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes()
 
+        # read in info array
+        info_sz = printk_info_type.get_type().sizeof
+        off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
+        addr = utils.read_ulong(desc_ring, off)
+        infos = utils.read_memoryview(inf, addr, info_sz * desc_ring_count).tobytes()
+
         # read in text data ring structure
         off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
         addr = prb_addr + off
@@ -73,9 +79,8 @@ class LxDmesg(gdb.Command):
         begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8)
         next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8)
 
-        off = prb_desc_type.get_type()['info'].bitpos // 8
-        ts_off = off + printk_info_type.get_type()['ts_nsec'].bitpos // 8
-        len_off = off + printk_info_type.get_type()['text_len'].bitpos // 8
+        ts_off = printk_info_type.get_type()['ts_nsec'].bitpos // 8
+        len_off = printk_info_type.get_type()['text_len'].bitpos // 8
 
         # definitions from kernel/printk/printk_ringbuffer.h
         desc_committed = 1
@@ -95,6 +100,7 @@ class LxDmesg(gdb.Command):
         while True:
             ind = did % desc_ring_count
             desc_off = desc_sz * ind
+            info_off = info_sz * ind
 
             # skip non-committed record
             state = 3 & (utils.read_u64(descs, desc_off + sv_off +
@@ -119,7 +125,7 @@ class LxDmesg(gdb.Command):
                 # skip over descriptor id
                 text_start = begin + utils.get_long_type().sizeof
 
-                text_len = utils.read_u16(descs, desc_off + len_off)
+                text_len = utils.read_u16(infos, info_off + len_off)
 
                 # handle truncated message
                 if end - text_start < text_len:
@@ -128,7 +134,7 @@ class LxDmesg(gdb.Command):
                 text = text_data[text_start:text_start + text_len].decode(
                     encoding='utf8', errors='replace')
 
-            time_stamp = utils.read_u64(descs, desc_off + ts_off)
+            time_stamp = utils.read_u64(infos, info_off + ts_off)
 
             for line in text.splitlines():
                 msg = u"[{time:12.6f}] {line}\n".format(
-- 
2.20.1