1 files changed, 227 insertions, 101 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 53d9a9e..da8ca81 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -53,7 +53,7 @@ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
 #define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)
 
 /* printk's without a loglevel use this.. */
-#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
+#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
 
 /* We show everything that is MORE important than this.. */
 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
@@ -97,7 +97,7 @@ static int console_locked, console_suspended;
 /*
  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  * It is also used in interesting ways to provide interlocking in
- * release_console_sem().
+ * console_unlock();.
  */
 static DEFINE_SPINLOCK(logbuf_lock);
 
@@ -113,6 +113,11 @@ static unsigned con_start;	/* Index into log_buf: next char to be sent to consol
 static unsigned log_end;	/* Index into log_buf: most-recently-written-char + 1 */
 
 /*
+ * If exclusive_console is non-NULL then only this console is to be printed to.
+ */
+static struct console *exclusive_console;
+
+/*
  *	Array of consoles built from command line options (console=)
  */
 struct console_cmdline
@@ -262,25 +267,47 @@ int dmesg_restrict = 1;
 int dmesg_restrict;
 #endif
 
+static int syslog_action_restricted(int type)
+{
+	if (dmesg_restrict)
+		return 1;
+	/* Unless restricted, we allow "read all" and "get buffer size" for everybody */
+	return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
+}
+
+static int check_syslog_permissions(int type, bool from_file)
+{
+	/*
+	 * If this is from /proc/kmsg and we've already opened it, then we've
+	 * already done the capabilities checks at open time.
+	 */
+	if (from_file && type != SYSLOG_ACTION_OPEN)
+		return 0;
+
+	if (syslog_action_restricted(type)) {
+		if (capable(CAP_SYSLOG))
+			return 0;
+		/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
+		if (capable(CAP_SYS_ADMIN)) {
+			WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
+				 "but no CAP_SYSLOG (deprecated).\n");
+			return 0;
+		}
+		return -EPERM;
+	}
+	return 0;
+}
+
 int do_syslog(int type, char __user *buf, int len, bool from_file)
 {
 	unsigned i, j, limit, count;
 	int do_clear = 0;
 	char c;
-	int error = 0;
+	int error;
 
-	/*
-	 * If this is from /proc/kmsg we only do the capabilities checks
-	 * at open time.
-	 */
-	if (type == SYSLOG_ACTION_OPEN || !from_file) {
-		if (dmesg_restrict && !capable(CAP_SYSLOG))
-			goto warn; /* switch to return -EPERM after 2.6.39 */
-		if ((type != SYSLOG_ACTION_READ_ALL &&
-		     type != SYSLOG_ACTION_SIZE_BUFFER) &&
-		    !capable(CAP_SYSLOG))
-			goto warn; /* switch to return -EPERM after 2.6.39 */
-	}
+	error = check_syslog_permissions(type, from_file);
+	if (error)
+		goto out;
 
 	error = security_syslog(type);
 	if (error)
@@ -423,12 +450,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 	}
 out:
 	return error;
-warn:
-	/* remove after 2.6.39 */
-	if (capable(CAP_SYS_ADMIN))
-		WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
-		  "but no CAP_SYSLOG (deprecated and denied).\n");
-	return -EPERM;
 }
 
 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
@@ -460,6 +481,8 @@ static void __call_console_drivers(unsigned start, unsigned end)
 	struct console *con;
 
 	for_each_console(con) {
+		if (exclusive_console && con != exclusive_console)
+			continue;
 		if ((con->flags & CON_ENABLED) && con->write &&
 				(cpu_online(smp_processor_id()) ||
 				(con->flags & CON_ANYTIME)))
@@ -499,9 +522,74 @@ static void _call_console_drivers(unsigned start,
 }
 
 /*
+ * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
+ * lower 3 bit are the log level, the rest are the log facility. In case
+ * userspace passes usual userspace syslog messages to /dev/kmsg or
+ * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
+ * to extract the correct log level for in-kernel processing, and not mangle
+ * the original value.
+ *
+ * If a prefix is found, the length of the prefix is returned. If 'level' is
+ * passed, it will be filled in with the log level without a possible facility
+ * value. If 'special' is passed, the special printk prefix chars are accepted
+ * and returned. If no valid header is found, 0 is returned and the passed
+ * variables are not touched.
+ */
+static size_t log_prefix(const char *p, unsigned int *level, char *special)
+{
+	unsigned int lev = 0;
+	char sp = '\0';
+	size_t len;
+
+	if (p[0] != '<' || !p[1])
+		return 0;
+	if (p[2] == '>') {
+		/* usual single digit level number or special char */
+		switch (p[1]) {
+		case '0' ... '7':
+			lev = p[1] - '0';
+			break;
+		case 'c': /* KERN_CONT */
+		case 'd': /* KERN_DEFAULT */
+			sp = p[1];
+			break;
+		default:
+			return 0;
+		}
+		len = 3;
+	} else {
+		/* multi digit including the level and facility number */
+		char *endp = NULL;
+
+		if (p[1] < '0' && p[1] > '9')
+			return 0;
+
+		lev = (simple_strtoul(&p[1], &endp, 10) & 7);
+		if (endp == NULL || endp[0] != '>')
+			return 0;
+		len = (endp + 1) - p;
+	}
+
+	/* do not accept special char if not asked for */
+	if (sp && !special)
+		return 0;
+
+	if (special) {
+		*special = sp;
+		/* return special char, do not touch level */
+		if (sp)
+			return len;
+	}
+
+	if (level)
+		*level = lev;
+	return len;
+}
+
+/*
  * Call the console drivers, asking them to write out
  * log_buf[start] to log_buf[end - 1].
- * The console_sem must be held.
+ * The console_lock must be held.
  */
 static void call_console_drivers(unsigned start, unsigned end)
 {
@@ -513,13 +601,9 @@ static void call_console_drivers(unsigned start, unsigned end)
 	cur_index = start;
 	start_print = start;
 	while (cur_index != end) {
-		if (msg_level < 0 && ((end - cur_index) > 2) &&
-				LOG_BUF(cur_index + 0) == '<' &&
-				LOG_BUF(cur_index + 1) >= '0' &&
-				LOG_BUF(cur_index + 1) <= '7' &&
-				LOG_BUF(cur_index + 2) == '>') {
-			msg_level = LOG_BUF(cur_index + 1) - '0';
-			cur_index += 3;
+		if (msg_level < 0 && ((end - cur_index) > 2)) {
+			/* strip log prefix */
+			cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
 			start_print = cur_index;
 		}
 		while (cur_index != end) {
@@ -604,11 +688,11 @@ static int have_callable_console(void)
  *
  * This is printk().  It can be called from any context.  We want it to work.
  *
- * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
+ * We try to grab the console_lock.  If we succeed, it's easy - we log the output and
  * call the console drivers.  If we fail to get the semaphore we place the output
  * into the log buffer and return.  The current holder of the console_sem will
- * notice the new output in release_console_sem() and will send it to the
- * consoles before releasing the semaphore.
+ * notice the new output in console_unlock(); and will send it to the
+ * consoles before releasing the lock.
  *
  * One effect of this deferred printing is that code which calls printk() and
  * then changes console_loglevel may break. This is because console_loglevel
@@ -659,19 +743,19 @@ static inline int can_use_console(unsigned int cpu)
 /*
  * Try to get console ownership to actually show the kernel
  * messages from a 'printk'. Return true (and with the
- * console_semaphore held, and 'console_locked' set) if it
+ * console_lock held, and 'console_locked' set) if it
  * is successful, false otherwise.
  *
  * This gets called with the 'logbuf_lock' spinlock held and
  * interrupts disabled. It should return with 'lockbuf_lock'
  * released but interrupts still disabled.
  */
-static int acquire_console_semaphore_for_printk(unsigned int cpu)
+static int console_trylock_for_printk(unsigned int cpu)
 	__releases(&logbuf_lock)
 {
 	int retval = 0;
 
-	if (!try_acquire_console_sem()) {
+	if (console_trylock()) {
 		retval = 1;
 
 		/*
@@ -717,6 +801,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	unsigned long flags;
 	int this_cpu;
 	char *p;
+	size_t plen;
+	char special;
 
 	boot_delay_msec();
 	printk_delay();
@@ -757,45 +843,52 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	printed_len += vscnprintf(printk_buf + printed_len,
 				  sizeof(printk_buf) - printed_len, fmt, args);
 
-
 	p = printk_buf;
 
-	/* Do we have a loglevel in the string? */
-	if (p[0] == '<') {
-		unsigned char c = p[1];
-		if (c && p[2] == '>') {
-			switch (c) {
-			case '0' ... '7': /* loglevel */
-				current_log_level = c - '0';
-			/* Fallthrough - make sure we're on a new line */
-			case 'd': /* KERN_DEFAULT */
-				if (!new_text_line) {
-					emit_log_char('\n');
-					new_text_line = 1;
-				}
-			/* Fallthrough - skip the loglevel */
-			case 'c': /* KERN_CONT */
-				p += 3;
-				break;
+	/* Read log level and handle special printk prefix */
+	plen = log_prefix(p, &current_log_level, &special);
+	if (plen) {
+		p += plen;
+
+		switch (special) {
+		case 'c': /* Strip <c> KERN_CONT, continue line */
+			plen = 0;
+			break;
+		case 'd': /* Strip <d> KERN_DEFAULT, start new line */
+			plen = 0;
+		default:
+			if (!new_text_line) {
+				emit_log_char('\n');
+				new_text_line = 1;
 			}
 		}
 	}
 
 	/*
-	 * Copy the output into log_buf.  If the caller didn't provide
-	 * appropriate log level tags, we insert them here
+	 * Copy the output into log_buf. If the caller didn't provide
+	 * the appropriate log prefix, we insert them here
 	 */
-	for ( ; *p; p++) {
+	for (; *p; p++) {
 		if (new_text_line) {
-			/* Always output the token */
-			emit_log_char('<');
-			emit_log_char(current_log_level + '0');
-			emit_log_char('>');
-			printed_len += 3;
 			new_text_line = 0;
 
+			if (plen) {
+				/* Copy original log prefix */
+				int i;
+
+				for (i = 0; i < plen; i++)
+					emit_log_char(printk_buf[i]);
+				printed_len += plen;
+			} else {
+				/* Add log prefix */
+				emit_log_char('<');
+				emit_log_char(current_log_level + '0');
+				emit_log_char('>');
+				printed_len += 3;
+			}
+
 			if (printk_time) {
-				/* Follow the token with the time */
+				/* Add the current time stamp */
 				char tbuf[50], *tp;
 				unsigned tlen;
 				unsigned long long t;
@@ -827,12 +920,12 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	 * actual magic (print out buffers, wake up klogd,
 	 * etc). 
 	 *
-	 * The acquire_console_semaphore_for_printk() function
+	 * The console_trylock_for_printk() function
 	 * will release 'logbuf_lock' regardless of whether it
 	 * actually gets the semaphore or not.
 	 */
-	if (acquire_console_semaphore_for_printk(this_cpu))
-		release_console_sem();
+	if (console_trylock_for_printk(this_cpu))
+		console_unlock();
 
 	lockdep_on();
 out_restore_irqs:
@@ -993,7 +1086,7 @@ void suspend_console(void)
 	if (!console_suspend_enabled)
 		return;
 	printk("Suspending console(s) (use no_console_suspend to debug)\n");
-	acquire_console_sem();
+	console_lock();
 	console_suspended = 1;
 	up(&console_sem);
 }
@@ -1004,7 +1097,7 @@ void resume_console(void)
 		return;
 	down(&console_sem);
 	console_suspended = 0;
-	release_console_sem();
+	console_unlock();
 }
 
 /**
@@ -1027,21 +1120,21 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self,
 	case CPU_DYING:
 	case CPU_DOWN_FAILED:
 	case CPU_UP_CANCELED:
-		acquire_console_sem();
-		release_console_sem();
+		console_lock();
+		console_unlock();
 	}
 	return NOTIFY_OK;
 }
 
 /**
- * acquire_console_sem - lock the console system for exclusive use.
+ * console_lock - lock the console system for exclusive use.
  *
- * Acquires a semaphore which guarantees that the caller has
+ * Acquires a lock which guarantees that the caller has
  * exclusive access to the console system and the console_drivers list.
  *
  * Can sleep, returns nothing.
  */
-void acquire_console_sem(void)
+void console_lock(void)
 {
 	BUG_ON(in_interrupt());
 	down(&console_sem);
@@ -1050,21 +1143,29 @@ void acquire_console_sem(void)
 	console_locked = 1;
 	console_may_schedule = 1;
 }
-EXPORT_SYMBOL(acquire_console_sem);
+EXPORT_SYMBOL(console_lock);
 
-int try_acquire_console_sem(void)
+/**
+ * console_trylock - try to lock the console system for exclusive use.
+ *
+ * Tried to acquire a lock which guarantees that the caller has
+ * exclusive access to the console system and the console_drivers list.
+ *
+ * returns 1 on success, and 0 on failure to acquire the lock.
+ */
+int console_trylock(void)
 {
 	if (down_trylock(&console_sem))
-		return -1;
+		return 0;
 	if (console_suspended) {
 		up(&console_sem);
-		return -1;
+		return 0;
 	}
 	console_locked = 1;
 	console_may_schedule = 0;
-	return 0;
+	return 1;
 }
-EXPORT_SYMBOL(try_acquire_console_sem);
+EXPORT_SYMBOL(console_trylock);
 
 int is_console_locked(void)
 {
@@ -1095,20 +1196,20 @@ void wake_up_klogd(void)
 }
 
 /**
- * release_console_sem - unlock the console system
+ * console_unlock - unlock the console system
  *
- * Releases the semaphore which the caller holds on the console system
+ * Releases the console_lock which the caller holds on the console system
  * and the console driver list.
  *
- * While the semaphore was held, console output may have been buffered
- * by printk().  If this is the case, release_console_sem() emits
- * the output prior to releasing the semaphore.
+ * While the console_lock was held, console output may have been buffered
+ * by printk().  If this is the case, console_unlock(); emits
+ * the output prior to releasing the lock.
  *
  * If there is output waiting for klogd, we wake it up.
  *
- * release_console_sem() may be called from any context.
+ * console_unlock(); may be called from any context.
  */
-void release_console_sem(void)
+void console_unlock(void)
 {
 	unsigned long flags;
 	unsigned _con_start, _log_end;
@@ -1136,12 +1237,17 @@ void release_console_sem(void)
 		local_irq_restore(flags);
 	}
 	console_locked = 0;
+
+	/* Release the exclusive_console once it is used */
+	if (unlikely(exclusive_console))
+		exclusive_console = NULL;
+
 	up(&console_sem);
 	spin_unlock_irqrestore(&logbuf_lock, flags);
 	if (wake_klogd)
 		wake_up_klogd();
 }
-EXPORT_SYMBOL(release_console_sem);
+EXPORT_SYMBOL(console_unlock);
 
 /**
  * console_conditional_schedule - yield the CPU if required
@@ -1150,7 +1256,7 @@ EXPORT_SYMBOL(release_console_sem);
  * if this CPU should yield the CPU to another task, do
  * so here.
  *
- * Must be called within acquire_console_sem().
+ * Must be called within console_lock();.
  */
 void __sched console_conditional_schedule(void)
 {
@@ -1171,14 +1277,14 @@ void console_unblank(void)
 		if (down_trylock(&console_sem) != 0)
 			return;
 	} else
-		acquire_console_sem();
+		console_lock();
 
 	console_locked = 1;
 	console_may_schedule = 0;
 	for_each_console(c)
 		if ((c->flags & CON_ENABLED) && c->unblank)
 			c->unblank();
-	release_console_sem();
+	console_unlock();
 }
 
 /*
@@ -1189,7 +1295,7 @@ struct tty_driver *console_device(int *index)
 	struct console *c;
 	struct tty_driver *driver = NULL;
 
-	acquire_console_sem();
+	console_lock();
 	for_each_console(c) {
 		if (!c->device)
 			continue;
@@ -1197,7 +1303,7 @@ struct tty_driver *console_device(int *index)
 		if (driver)
 			break;
 	}
-	release_console_sem();
+	console_unlock();
 	return driver;
 }
 
@@ -1208,20 +1314,32 @@ struct tty_driver *console_device(int *index)
  */
 void console_stop(struct console *console)
 {
-	acquire_console_sem();
+	console_lock();
 	console->flags &= ~CON_ENABLED;
-	release_console_sem();
+	console_unlock();
 }
 EXPORT_SYMBOL(console_stop);
 
 void console_start(struct console *console)
 {
-	acquire_console_sem();
+	console_lock();
 	console->flags |= CON_ENABLED;
-	release_console_sem();
+	console_unlock();
 }
 EXPORT_SYMBOL(console_start);
 
+static int __read_mostly keep_bootcon;
+
+static int __init keep_bootcon_setup(char *str)
+{
+	keep_bootcon = 1;
+	printk(KERN_INFO "debug: skip boot console de-registration.\n");
+
+	return 0;
+}
+
+early_param("keep_bootcon", keep_bootcon_setup);
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -1340,7 +1458,7 @@ void register_console(struct console *newcon)
 	 *	Put this console in the list - keep the
 	 *	preferred driver at the head of the list.
 	 */
-	acquire_console_sem();
+	console_lock();
 	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
 		newcon->next = console_drivers;
 		console_drivers = newcon;
@@ -1352,14 +1470,20 @@ void register_console(struct console *newcon)
 	}
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*
-		 * release_console_sem() will print out the buffered messages
+		 * console_unlock(); will print out the buffered messages
 		 * for us.
 		 */
 		spin_lock_irqsave(&logbuf_lock, flags);
 		con_start = log_start;
 		spin_unlock_irqrestore(&logbuf_lock, flags);
+		/*
+		 * We're about to replay the log buffer.  Only do this to the
+		 * just-registered console to avoid excessive message spam to
+		 * the already-registered consoles.
+		 */
+		exclusive_console = newcon;
 	}
-	release_console_sem();
+	console_unlock();
 	console_sysfs_notify();
 
 	/*
@@ -1369,7 +1493,9 @@ void register_console(struct console *newcon)
 	 * users know there might be something in the kernel's log buffer that
 	 * went to the bootconsole (that they do not see on the real console)
 	 */
-	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
+	if (bcon &&
+	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
+	    !keep_bootcon) {
 		/* we need to iterate through twice, to make sure we print
 		 * everything out, before we unregister the console(s)
 		 */
@@ -1396,7 +1522,7 @@ int unregister_console(struct console *console)
 		return braille_unregister_console(console);
 #endif
 
-	acquire_console_sem();
+	console_lock();
 	if (console_drivers == console) {
 		console_drivers=console->next;
 		res = 0;
@@ -1418,7 +1544,7 @@ int unregister_console(struct console *console)
 	if (console_drivers != NULL && console->flags & CON_CONSDEV)
 		console_drivers->flags |= CON_CONSDEV;
 
-	release_console_sem();
+	console_unlock();
 	console_sysfs_notify();
 	return res;
 }