Commit b125d903 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'printk-for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 

Pull printk updates from Petr Mladek:

 - Different vendors have a different expectation about a console
   quietness. Make it configurable to reduce bike-shedding about the
   upstream default

 - Decide about the message visibility when the message is stored. It
   avoids races caused by a delayed console handling

 - Always store printk() messages into the per-CPU buffers again in NMI.
   The only exception is when flushing trace log in panic(). There the
   risk of loosing messages is worth an eventual reordering

 - Handle invalid %pO printf modifiers correctly

 - Better handle %p printf modifier tests before crng is initialized

 - Some clean up

* tag 'printk-for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  lib/vsprintf: Do not handle %pO[^F] as %px
  printk: Fix warning about unused suppress_message_printing
  printk/nmi: Prevent deadlock when accessing the main log buffer in NMI
  printk: Create helper function to queue deferred console handling
  printk: Split the code for storing a message into the log buffer
  printk: Clean up syslog_print_all()
  printk: Remove unnecessary kmalloc() from syslog during clear
  printk: Make CONSOLE_LOGLEVEL_QUIET configurable
  printk: make sure to print log on console.
  lib/test_printf.c: accept "ptrval" as valid result for plain 'p' tests
parents 8c326850 9f68cb57

include/linux/printk.h

+7 −3
Original line number Diff line number Diff line
@@ -50,15 +50,15 @@ static inline const char *printk_skip_headers(const char *buffer) 
/* We show everything that is MORE important than this.. */

#define CONSOLE_LOGLEVEL_SILENT  0 /* Mum's the word */

#define CONSOLE_LOGLEVEL_MIN	 1 /* Minimum loglevel we let people use */

#define CONSOLE_LOGLEVEL_QUIET	 4 /* Shhh ..., when booted with "quiet" */

#define CONSOLE_LOGLEVEL_DEBUG	10 /* issue debug messages */

#define CONSOLE_LOGLEVEL_MOTORMOUTH 15	/* You can't shut this one up */



/*

 * Default used to be hard-coded at 7, we're now allowing it to be set from

 * kernel config.

 * Default used to be hard-coded at 7, quiet used to be hardcoded at 4,

 * we're now allowing both to be set from kernel config.

 */

#define CONSOLE_LOGLEVEL_DEFAULT CONFIG_CONSOLE_LOGLEVEL_DEFAULT

#define CONSOLE_LOGLEVEL_QUIET	 CONFIG_CONSOLE_LOGLEVEL_QUIET



extern int console_printk[];
@@ -148,9 +148,13 @@ void early_printk(const char *s, ...) { } 
#ifdef CONFIG_PRINTK_NMI

extern void printk_nmi_enter(void);

extern void printk_nmi_exit(void);

extern void printk_nmi_direct_enter(void);

extern void printk_nmi_direct_exit(void);

#else

static inline void printk_nmi_enter(void) { }

static inline void printk_nmi_exit(void) { }

static inline void printk_nmi_direct_enter(void) { }

static inline void printk_nmi_direct_exit(void) { }

#endif /* PRINTK_NMI */



#ifdef CONFIG_PRINTK

kernel/printk/internal.h

+8 −1
Original line number Diff line number Diff line
@@ -19,11 +19,16 @@ 
#ifdef CONFIG_PRINTK



#define PRINTK_SAFE_CONTEXT_MASK	 0x3fffffff

#define PRINTK_NMI_DEFERRED_CONTEXT_MASK 0x40000000

#define PRINTK_NMI_DIRECT_CONTEXT_MASK	 0x40000000

#define PRINTK_NMI_CONTEXT_MASK		 0x80000000



extern raw_spinlock_t logbuf_lock;



__printf(5, 0)

int vprintk_store(int facility, int level,

		  const char *dict, size_t dictlen,

		  const char *fmt, va_list args);



__printf(1, 0) int vprintk_default(const char *fmt, va_list args);

__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);

__printf(1, 0) int vprintk_func(const char *fmt, va_list args);
@@ -54,6 +59,8 @@ void __printk_safe_exit(void); 
		local_irq_enable();		\

	} while (0)



void defer_console_output(void);



#else



__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }

kernel/printk/printk.c

+100 −81
Original line number Diff line number Diff line
@@ -349,7 +349,7 @@ static int console_msg_format = MSG_FORMAT_DEFAULT; 
 */



enum log_flags {

	LOG_NOCONS	= 1,	/* already flushed, do not print to console */

	LOG_NOCONS	= 1,	/* suppress print, do not print to console */

	LOG_NEWLINE	= 2,	/* text ended with a newline */

	LOG_PREFIX	= 4,	/* text started with a prefix */

	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
@@ -1352,17 +1352,15 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
{

	char *text;

	int len = 0;

	u64 next_seq;

	u64 seq;

	u32 idx;



	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);

	if (!text)

		return -ENOMEM;



	logbuf_lock_irq();

	if (buf) {

		u64 next_seq;

		u64 seq;

		u32 idx;



	/*

	 * Find first record that fits, including all following records,

	 * into the user-provided buffer for this dump.
@@ -1418,7 +1416,6 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
			idx = log_first_idx;

		}

	}

	}



	if (clear) {

		clear_seq = log_next_seq;
@@ -1430,6 +1427,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
	return len;

}



static void syslog_clear(void)

{

	logbuf_lock_irq();

	clear_seq = log_next_seq;

	clear_idx = log_next_idx;

	logbuf_unlock_irq();

}



int do_syslog(int type, char __user *buf, int len, int source)

{

	bool clear = false;
@@ -1474,7 +1479,7 @@ int do_syslog(int type, char __user *buf, int len, int source) 
		break;

	/* Clear ring buffer */

	case SYSLOG_ACTION_CLEAR:

		syslog_print_all(NULL, 0, true);

		syslog_clear();

		break;

	/* Disable logging to console */

	case SYSLOG_ACTION_CONSOLE_OFF:
@@ -1824,7 +1829,8 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c 
	return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);

}



asmlinkage int vprintk_emit(int facility, int level,

/* Must be called under logbuf_lock. */

int vprintk_store(int facility, int level,

		  const char *dict, size_t dictlen,

		  const char *fmt, va_list args)

{
@@ -1832,20 +1838,7 @@ asmlinkage int vprintk_emit(int facility, int level, 
	char *text = textbuf;

	size_t text_len;

	enum log_flags lflags = 0;

	unsigned long flags;

	int printed_len;

	bool in_sched = false;



	if (level == LOGLEVEL_SCHED) {

		level = LOGLEVEL_DEFAULT;

		in_sched = true;

	}



	boot_delay_msec(level);

	printk_delay();



	/* This stops the holder of console_sem just where we want him */

	logbuf_lock_irqsave(flags);

	/*

	 * The printf needs to come first; we need the syslog

	 * prefix which might be passed-in as a parameter.
@@ -1886,8 +1879,32 @@ asmlinkage int vprintk_emit(int facility, int level, 
	if (dict)

		lflags |= LOG_PREFIX|LOG_NEWLINE;



	printed_len = log_output(facility, level, lflags, dict, dictlen, text, text_len);

	if (suppress_message_printing(level))

		lflags |= LOG_NOCONS;



	return log_output(facility, level, lflags,

			  dict, dictlen, text, text_len);

}



asmlinkage int vprintk_emit(int facility, int level,

			    const char *dict, size_t dictlen,

			    const char *fmt, va_list args)

{

	int printed_len;

	bool in_sched = false;

	unsigned long flags;



	if (level == LOGLEVEL_SCHED) {

		level = LOGLEVEL_DEFAULT;

		in_sched = true;

	}



	boot_delay_msec(level);

	printk_delay();



	/* 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);

	logbuf_unlock_irqrestore(flags);



	/* If called from the scheduler, we can not call up(). */
@@ -2013,7 +2030,6 @@ static void call_console_drivers(const char *ext_text, size_t ext_len, 
				 const char *text, size_t len) {}

static size_t msg_print_text(const struct printk_log *msg,

			     bool syslog, char *buf, size_t size) { return 0; }

static bool suppress_message_printing(int level) { return false; }



#endif /* CONFIG_PRINTK */
@@ -2349,11 +2365,10 @@ skip: 
			break;



		msg = log_from_idx(console_idx);

		if (suppress_message_printing(msg->level)) {

		if (msg->flags & LOG_NOCONS) {

			/*

			 * Skip record we have buffered and already printed

			 * directly to the console when we received it, and

			 * record that has level above the console loglevel.

			 * Skip record if !ignore_loglevel, and

			 * record has level above the console loglevel.

			 */

			console_idx = log_next(console_idx);

			console_seq++;
@@ -2878,16 +2893,20 @@ void wake_up_klogd(void) 
	preempt_enable();

}



int vprintk_deferred(const char *fmt, va_list args)

void defer_console_output(void)

{

	int r;



	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);



	preempt_disable();

	__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);

	irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));

	preempt_enable();

}



int vprintk_deferred(const char *fmt, va_list args)

{

	int r;



	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);

	defer_console_output();



	return r;

}

kernel/printk/printk_safe.c

+37 −21
Original line number Diff line number Diff line
@@ -308,24 +308,33 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args) 


void printk_nmi_enter(void)

{

	/*

	 * The size of the extra per-CPU buffer is limited. Use it only when

	 * the main one is locked. If this CPU is not in the safe context,

	 * the lock must be taken on another CPU and we could wait for it.

	 */

	if ((this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) &&

	    raw_spin_is_locked(&logbuf_lock)) {

	this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);

	} else {

		this_cpu_or(printk_context, PRINTK_NMI_DEFERRED_CONTEXT_MASK);

	}

}



void printk_nmi_exit(void)

{

	this_cpu_and(printk_context,

		     ~(PRINTK_NMI_CONTEXT_MASK |

		       PRINTK_NMI_DEFERRED_CONTEXT_MASK));

	this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);

}



/*

 * Marks a code that might produce many messages in NMI context

 * and the risk of losing them is more critical than eventual

 * reordering.

 *

 * It has effect only when called in NMI context. Then printk()

 * will try to store the messages into the main logbuf directly

 * and use the per-CPU buffers only as a fallback when the lock

 * is not available.

 */

void printk_nmi_direct_enter(void)

{

	if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)

		this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);

}



void printk_nmi_direct_exit(void)

{

	this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);

}



#else
@@ -363,6 +372,20 @@ void __printk_safe_exit(void) 


__printf(1, 0) int vprintk_func(const char *fmt, va_list args)

{

	/*

	 * Try to use the main logbuf even in NMI. But avoid calling console

	 * drivers that might have their own locks.

	 */

	if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&

	    raw_spin_trylock(&logbuf_lock)) {

		int len;



		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);

		raw_spin_unlock(&logbuf_lock);

		defer_console_output();

		return len;

	}



	/* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */

	if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)

		return vprintk_nmi(fmt, args);
@@ -371,13 +394,6 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args) 
	if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK)

		return vprintk_safe(fmt, args);



	/*

	 * Use the main logbuf when logbuf_lock is available in NMI.

	 * But avoid calling console drivers that might have their own locks.

	 */

	if (this_cpu_read(printk_context) & PRINTK_NMI_DEFERRED_CONTEXT_MASK)

		return vprintk_deferred(fmt, args);



	/* No obstacles. */

	return vprintk_default(fmt, args);

}

kernel/trace/trace.c

+3 −1
Original line number Diff line number Diff line
@@ -8288,6 +8288,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) 
	tracing_off();



	local_irq_save(flags);

	printk_nmi_direct_enter();



	/* Simulate the iterator */

	trace_init_global_iter(&iter);
@@ -8368,6 +8369,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) 
		atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);

	}

	atomic_dec(&dump_running);

	printk_nmi_direct_exit();

	local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(ftrace_dump);

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