Merge tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Fix two more locations where printf formatting leaked pointers

 - Better log_buf_len parameter handling

 - Add prefix to messages from printk code

 - Do not miss messages on other consoles when the log is replayed on a
   new one

 - Reduce race between console registration and panic() when the log
   might get replayed on all consoles

 - Some cont buffer code clean up

 - Call console only when there is something to do (log vs cont buffer)

* tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  lib/vsprintf: Hash printed address for netdev bits fallback
  lib/vsprintf: Hash legacy clock addresses
  lib/vsprintf: Prepare for more general use of ptr_to_id()
  lib/vsprintf: Make ptr argument conts in ptr_to_id()
  printk: fix integer overflow in setup_log_buf()
  printk: do not preliminary split up cont buffer
  printk: lock/unlock console only for new logbuf entries
  printk: keep kernel cont support always enabled
  printk: Give error on attempt to set log buffer length to over 2G
  printk: Add KBUILD_MODNAME and remove a redundant print prefix
  printk: Correct wrong casting
  printk: Fix panic caused by passing log_buf_len to command line
  printk: CON_PRINTBUFFER console registration is a bit racy
  printk: Do not miss new messages when replaying the log

Documentation/core-api/printk-formats.rst

@@ -420,9 +420,8 @@ struct clk
 	%pC	pll1
 	%pCn	pll1
 
-For printing struct clk structures. %pC and %pCn print the name
-(Common Clock Framework) or address (legacy clock framework) of the
-structure.
+For printing struct clk structures. %pC and %pCn print the name of the clock
+(Common Clock Framework) or a unique 32-bit ID (legacy clock framework).
 
 Passed by reference.
 

kernel/printk/printk.c

@@ -16,6 +16,8 @@
  *	01Mar01 Andrew Morton
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/tty.h>
@@ -192,16 +194,7 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
 	return 0;
 }
 
-/*
- * Number of registered extended console drivers.
- *
- * If extended consoles are present, in-kernel cont reassembly is disabled
- * and each fragment is stored as a separate log entry with proper
- * continuation flag so that every emitted message has full metadata.  This
- * doesn't change the result for regular consoles or /proc/kmsg.  For
- * /dev/kmsg, as long as the reader concatenates messages according to
- * consecutive continuation flags, the end result should be the same too.
- */
+/* Number of registered extended console drivers. */
 static int nr_ext_console_drivers;
 
 /*
@@ -423,6 +416,7 @@ static u32 log_next_idx;
 /* the next printk record to write to the console */
 static u64 console_seq;
 static u32 console_idx;
+static u64 exclusive_console_stop_seq;
 
 /* the next printk record to read after the last 'clear' command */
 static u64 clear_seq;
@@ -437,6 +431,7 @@ static u32 clear_idx;
 /* record buffer */
 #define LOG_ALIGN __alignof__(struct printk_log)
 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
+#define LOG_BUF_LEN_MAX (u32)(1 << 31)
 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
 static u32 log_buf_len = __LOG_BUF_LEN;
@@ -1037,18 +1032,28 @@ void log_buf_vmcoreinfo_setup(void)
 static unsigned long __initdata new_log_buf_len;
 
 /* we practice scaling the ring buffer by powers of 2 */
-static void __init log_buf_len_update(unsigned size)
+static void __init log_buf_len_update(u64 size)
 {
+	if (size > (u64)LOG_BUF_LEN_MAX) {
+		size = (u64)LOG_BUF_LEN_MAX;
+		pr_err("log_buf over 2G is not supported.\n");
+	}
+
 	if (size)
 		size = roundup_pow_of_two(size);
 	if (size > log_buf_len)
-		new_log_buf_len = size;
+		new_log_buf_len = (unsigned long)size;
 }
 
 /* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
-	unsigned size = memparse(str, &str);
+	u64 size;
+
+	if (!str)
+		return -EINVAL;
+
+	size = memparse(str, &str);
 
 	log_buf_len_update(size);
 
@@ -1093,7 +1098,7 @@ void __init setup_log_buf(int early)
 {
 	unsigned long flags;
 	char *new_log_buf;
-	int free;
+	unsigned int free;
 
 	if (log_buf != __log_buf)
 		return;
@@ -1113,7 +1118,7 @@ void __init setup_log_buf(int early)
 	}
 
 	if (unlikely(!new_log_buf)) {
-		pr_err("log_buf_len: %ld bytes not available\n",
+		pr_err("log_buf_len: %lu bytes not available\n",
 			new_log_buf_len);
 		return;
 	}
@@ -1126,8 +1131,8 @@ void __init setup_log_buf(int early)
 	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
 	logbuf_unlock_irqrestore(flags);
 
-	pr_info("log_buf_len: %d bytes\n", log_buf_len);
-	pr_info("early log buf free: %d(%d%%)\n",
+	pr_info("log_buf_len: %u bytes\n", log_buf_len);
+	pr_info("early log buf free: %u(%u%%)\n",
 		free, (free * 100) / __LOG_BUF_LEN);
 }
 
@@ -1767,12 +1772,8 @@ static void cont_flush(void)
 
 static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
 {
-	/*
-	 * If ext consoles are present, flush and skip in-kernel
-	 * continuation.  See nr_ext_console_drivers definition.  Also, if
-	 * the line gets too long, split it up in separate records.
-	 */
-	if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
+	/* If the line gets too long, split it up in separate records. */
+	if (cont.len + len > sizeof(cont.buf)) {
 		cont_flush();
 		return false;
 	}
@@ -1795,9 +1796,6 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
 		cont_flush();
 	}
 
-	if (cont.len > (sizeof(cont.buf) * 80) / 100)
-		cont_flush();
-
 	return true;
 }
 
@@ -1889,8 +1887,9 @@ asmlinkage int vprintk_emit(int facility, int level,
 			    const char *fmt, va_list args)
 {
 	int printed_len;
-	bool in_sched = false;
+	bool in_sched = false, pending_output;
 	unsigned long flags;
+	u64 curr_log_seq;
 
 	if (level == LOGLEVEL_SCHED) {
 		level = LOGLEVEL_DEFAULT;
@@ -1902,11 +1901,13 @@ asmlinkage int vprintk_emit(int facility, int level,
 
 	/* This stops the holder of console_sem just where we want him */
 	logbuf_lock_irqsave(flags);
+	curr_log_seq = log_next_seq;
 	printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
+	pending_output = (curr_log_seq != log_next_seq);
 	logbuf_unlock_irqrestore(flags);
 
 	/* If called from the scheduler, we can not call up(). */
-	if (!in_sched) {
+	if (!in_sched && pending_output) {
 		/*
 		 * Disable preemption to avoid being preempted while holding
 		 * console_sem which would prevent anyone from printing to
@@ -1923,7 +1924,8 @@ asmlinkage int vprintk_emit(int facility, int level,
 		preempt_enable();
 	}
 
-	wake_up_klogd();
+	if (pending_output)
+		wake_up_klogd();
 	return printed_len;
 }
 EXPORT_SYMBOL(vprintk_emit);
@@ -2009,6 +2011,7 @@ static u64 syslog_seq;
 static u32 syslog_idx;
 static u64 console_seq;
 static u32 console_idx;
+static u64 exclusive_console_stop_seq;
 static u64 log_first_seq;
 static u32 log_first_idx;
 static u64 log_next_seq;
@@ -2351,8 +2354,9 @@ again:
 		printk_safe_enter_irqsave(flags);
 		raw_spin_lock(&logbuf_lock);
 		if (console_seq < log_first_seq) {
-			len = sprintf(text, "** %u printk messages dropped **\n",
-				      (unsigned)(log_first_seq - console_seq));
+			len = sprintf(text,
+				      "** %llu printk messages dropped **\n",
+				      log_first_seq - console_seq);
 
 			/* messages are gone, move to first one */
 			console_seq = log_first_seq;
@@ -2376,6 +2380,12 @@ skip:
 			goto skip;
 		}
 
+		/* Output to all consoles once old messages replayed. */
+		if (unlikely(exclusive_console &&
+			     console_seq >= exclusive_console_stop_seq)) {
+			exclusive_console = NULL;
+		}
+
 		len += msg_print_text(msg,
 				console_msg_format & MSG_FORMAT_SYSLOG,
 				text + len,
@@ -2418,10 +2428,6 @@ skip:
 
 	console_locked = 0;
 
-	/* Release the exclusive_console once it is used */
-	if (unlikely(exclusive_console))
-		exclusive_console = NULL;
-
 	raw_spin_unlock(&logbuf_lock);
 
 	up_console_sem();
@@ -2688,8 +2694,7 @@ 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");
+		nr_ext_console_drivers++;
 
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*
@@ -2699,13 +2704,18 @@ void register_console(struct console *newcon)
 		logbuf_lock_irqsave(flags);
 		console_seq = syslog_seq;
 		console_idx = syslog_idx;
-		logbuf_unlock_irqrestore(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.
+		 *
+		 * Set exclusive_console with disabled interrupts to reduce
+		 * race window with eventual console_flush_on_panic() that
+		 * ignores console_lock.
 		 */
 		exclusive_console = newcon;
+		exclusive_console_stop_seq = console_seq;
+		logbuf_unlock_irqrestore(flags);
 	}
 	console_unlock();
 	console_sysfs_notify();

lib/vsprintf.c

@@ -612,6 +612,109 @@ char *string(char *buf, char *end, const char *s, struct printf_spec spec)
 	return widen_string(buf, len, end, spec);
 }
 
+static noinline_for_stack
+char *pointer_string(char *buf, char *end, const void *ptr,
+		     struct printf_spec spec)
+{
+	spec.base = 16;
+	spec.flags |= SMALL;
+	if (spec.field_width == -1) {
+		spec.field_width = 2 * sizeof(ptr);
+		spec.flags |= ZEROPAD;
+	}
+
+	return number(buf, end, (unsigned long int)ptr, spec);
+}
+
+/* Make pointers available for printing early in the boot sequence. */
+static int debug_boot_weak_hash __ro_after_init;
+
+static int __init debug_boot_weak_hash_enable(char *str)
+{
+	debug_boot_weak_hash = 1;
+	pr_info("debug_boot_weak_hash enabled\n");
+	return 0;
+}
+early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
+
+static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
+static siphash_key_t ptr_key __read_mostly;
+
+static void enable_ptr_key_workfn(struct work_struct *work)
+{
+	get_random_bytes(&ptr_key, sizeof(ptr_key));
+	/* Needs to run from preemptible context */
+	static_branch_disable(&not_filled_random_ptr_key);
+}
+
+static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
+
+static void fill_random_ptr_key(struct random_ready_callback *unused)
+{
+	/* This may be in an interrupt handler. */
+	queue_work(system_unbound_wq, &enable_ptr_key_work);
+}
+
+static struct random_ready_callback random_ready = {
+	.func = fill_random_ptr_key
+};
+
+static int __init initialize_ptr_random(void)
+{
+	int key_size = sizeof(ptr_key);
+	int ret;
+
+	/* Use hw RNG if available. */
+	if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
+		static_branch_disable(&not_filled_random_ptr_key);
+		return 0;
+	}
+
+	ret = add_random_ready_callback(&random_ready);
+	if (!ret) {
+		return 0;
+	} else if (ret == -EALREADY) {
+		/* This is in preemptible context */
+		enable_ptr_key_workfn(&enable_ptr_key_work);
+		return 0;
+	}
+
+	return ret;
+}
+early_initcall(initialize_ptr_random);
+
+/* Maps a pointer to a 32 bit unique identifier. */
+static char *ptr_to_id(char *buf, char *end, const void *ptr,
+		       struct printf_spec spec)
+{
+	const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
+	unsigned long hashval;
+
+	/* When debugging early boot use non-cryptographically secure hash. */
+	if (unlikely(debug_boot_weak_hash)) {
+		hashval = hash_long((unsigned long)ptr, 32);
+		return pointer_string(buf, end, (const void *)hashval, spec);
+	}
+
+	if (static_branch_unlikely(&not_filled_random_ptr_key)) {
+		spec.field_width = 2 * sizeof(ptr);
+		/* string length must be less than default_width */
+		return string(buf, end, str, spec);
+	}
+
+#ifdef CONFIG_64BIT
+	hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
+	/*
+	 * Mask off the first 32 bits, this makes explicit that we have
+	 * modified the address (and 32 bits is plenty for a unique ID).
+	 */
+	hashval = hashval & 0xffffffff;
+#else
+	hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key);
+#endif
+	return pointer_string(buf, end, (const void *)hashval, spec);
+}
+
 static noinline_for_stack
 char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_spec spec,
 		  const char *fmt)
@@ -1357,20 +1460,6 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
 	return string(buf, end, uuid, spec);
 }
 
-static noinline_for_stack
-char *pointer_string(char *buf, char *end, const void *ptr,
-		     struct printf_spec spec)
-{
-	spec.base = 16;
-	spec.flags |= SMALL;
-	if (spec.field_width == -1) {
-		spec.field_width = 2 * sizeof(ptr);
-		spec.flags |= ZEROPAD;
-	}
-
-	return number(buf, end, (unsigned long int)ptr, spec);
-}
-
 int kptr_restrict __read_mostly;
 
 static noinline_for_stack
@@ -1421,7 +1510,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
 }
 
 static noinline_for_stack
-char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
+char *netdev_bits(char *buf, char *end, const void *addr,
+		  struct printf_spec spec,  const char *fmt)
 {
 	unsigned long long num;
 	int size;
@@ -1432,9 +1522,7 @@ char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
 		size = sizeof(netdev_features_t);
 		break;
 	default:
-		num = (unsigned long)addr;
-		size = sizeof(unsigned long);
-		break;
+		return ptr_to_id(buf, end, addr, spec);
 	}
 
 	return special_hex_number(buf, end, num, size);
@@ -1474,7 +1562,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
 #ifdef CONFIG_COMMON_CLK
 		return string(buf, end, __clk_get_name(clk), spec);
 #else
-		return special_hex_number(buf, end, (unsigned long)clk, sizeof(unsigned long));
+		return ptr_to_id(buf, end, clk, spec);
 #endif
 	}
 }
@@ -1651,94 +1739,6 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
 	return widen_string(buf, buf - buf_start, end, spec);
 }
 
-/* Make pointers available for printing early in the boot sequence. */
-static int debug_boot_weak_hash __ro_after_init;
-
-static int __init debug_boot_weak_hash_enable(char *str)
-{
-	debug_boot_weak_hash = 1;
-	pr_info("debug_boot_weak_hash enabled\n");
-	return 0;
-}
-early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
-
-static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
-static siphash_key_t ptr_key __read_mostly;
-
-static void enable_ptr_key_workfn(struct work_struct *work)
-{
-	get_random_bytes(&ptr_key, sizeof(ptr_key));
-	/* Needs to run from preemptible context */
-	static_branch_disable(&not_filled_random_ptr_key);
-}
-
-static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
-
-static void fill_random_ptr_key(struct random_ready_callback *unused)
-{
-	/* This may be in an interrupt handler. */
-	queue_work(system_unbound_wq, &enable_ptr_key_work);
-}
-
-static struct random_ready_callback random_ready = {
-	.func = fill_random_ptr_key
-};
-
-static int __init initialize_ptr_random(void)
-{
-	int key_size = sizeof(ptr_key);
-	int ret;
-
-	/* Use hw RNG if available. */
-	if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
-		static_branch_disable(&not_filled_random_ptr_key);
-		return 0;
-	}
-
-	ret = add_random_ready_callback(&random_ready);
-	if (!ret) {
-		return 0;
-	} else if (ret == -EALREADY) {
-		/* This is in preemptible context */
-		enable_ptr_key_workfn(&enable_ptr_key_work);
-		return 0;
-	}
-
-	return ret;
-}
-early_initcall(initialize_ptr_random);
-
-/* Maps a pointer to a 32 bit unique identifier. */
-static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
-{
-	const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
-	unsigned long hashval;
-
-	/* When debugging early boot use non-cryptographically secure hash. */
-	if (unlikely(debug_boot_weak_hash)) {
-		hashval = hash_long((unsigned long)ptr, 32);
-		return pointer_string(buf, end, (const void *)hashval, spec);
-	}
-
-	if (static_branch_unlikely(&not_filled_random_ptr_key)) {
-		spec.field_width = 2 * sizeof(ptr);
-		/* string length must be less than default_width */
-		return string(buf, end, str, spec);
-	}
-
-#ifdef CONFIG_64BIT
-	hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
-	/*
-	 * Mask off the first 32 bits, this makes explicit that we have
-	 * modified the address (and 32 bits is plenty for a unique ID).
-	 */
-	hashval = hashval & 0xffffffff;
-#else
-	hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key);
-#endif
-	return pointer_string(buf, end, (const void *)hashval, spec);
-}
-
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -1942,7 +1942,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 			break;
 		return restricted_pointer(buf, end, ptr, spec);
 	case 'N':
-		return netdev_bits(buf, end, ptr, fmt);
+		return netdev_bits(buf, end, ptr, spec, fmt);
 	case 'a':
 		return address_val(buf, end, ptr, fmt);
 	case 'd':