printk: move dictionary keys to dev_printk_info

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>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/87mu1jl6ne.fsf@jogness.linutronix.de

4 files changed, 92 insertions, 83 deletions

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 25cfe4fe48af..f1e243cc284a 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 +624,44 @@ 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, "", 0, ' ');	/* dict prefix */
+	len += msg_add_ext_text(buf + len, size - len, 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 +673,6 @@ 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 +683,7 @@ 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 +793,8 @@ 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 +899,7 @@ 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);
@@ -941,6 +943,8 @@ const struct file_operations kmsg_fops = {
  */
 void log_buf_vmcoreinfo_setup(void)
 {
+	struct dev_printk_info *dev_info = NULL;
+
 	VMCOREINFO_SYMBOL(prb);
 	VMCOREINFO_SYMBOL(printk_rb_static);
 	VMCOREINFO_SYMBOL(clear_seq);
@@ -978,6 +982,13 @@ 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_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem));
+	VMCOREINFO_OFFSET(dev_printk_info, device);
+	VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device));
 
 	VMCOREINFO_STRUCT_SIZE(prb_data_ring);
 	VMCOREINFO_OFFSET(prb_data_ring, size_bits);
@@ -1070,22 +1081,19 @@ 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 +1101,6 @@ 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)
 {
@@ -1165,7 +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),
@@ -1903,7 +1910,9 @@ 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();
 
@@ -1927,12 +1936,12 @@ 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];
@@ -1974,15 +1983,14 @@ 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;
@@ -2003,7 +2011,7 @@ 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(). */
@@ -2037,7 +2045,7 @@ 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);
 
@@ -2100,8 +2108,8 @@ 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,
@@ -2390,7 +2398,6 @@ 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;
@@ -2401,7 +2408,7 @@ 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
@@ -2473,10 +2480,9 @@ skip:
 						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,
@@ -3055,7 +3061,7 @@ 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;