Commit d594d8f4 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'printk-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux 

Pull printk updates from Petr Mladek:
 "The big new thing is the fully lockless ringbuffer implementation,
  including the support for continuous lines. It will allow to store and
  read messages in any situation wihtout the risk of deadlocks and
  without the need of temporary per-CPU buffers.

  The access is still serialized by logbuf_lock. It synchronizes few
  more operations, for example, temporary buffer for formatting the
  message, syslog and kmsg_dump operations. The lock removal is being
  discussed and should be ready for the next release.

  The continuous lines are handled exactly the same way as before to
  avoid regressions in user space. It means that they are appended to
  the last message when the caller is the same. Only the last message
  can be extended.

  The data ring includes plain text of the messages. Except for an
  integer at the beginning of each message that points back to the
  descriptor ring with other metadata.

  The dictionary has to stay. journalctl uses it to filter the log. It
  allows to show messages related to a given device. The dictionary
  values are stored in the descriptor ring with the other metadata.

  This is the first part of the printk rework as discussed at Plumbers
  2019, see https://lore.kernel.org/r/87k1acz5rx.fsf@linutronix.de. The
  next big step will be handling consoles by kthreads during the normal
  system operation. It will require special handling of situations when
  the kthreads could not get scheduled, for example, early boot,
  suspend, panic.

  Other changes:

   - Add John Ogness as a reviewer for printk subsystem. He is author of
     the rework and is familiar with the code and history.

   - Fix locking in serial8250_do_startup() to prevent lockdep report.

   - Few code cleanups"

* tag 'printk-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (27 commits)
  printk: Use fallthrough pseudo-keyword
  printk: reduce setup_text_buf size to LOG_LINE_MAX
  printk: avoid and/or handle record truncation
  printk: remove dict ring
  printk: move dictionary keys to dev_printk_info
  printk: move printk_info into separate array
  printk: reimplement log_cont using record extension
  printk: ringbuffer: add finalization/extension support
  printk: ringbuffer: change representation of states
  printk: ringbuffer: clear initial reserved fields
  printk: ringbuffer: add BLK_DATALESS() macro
  printk: ringbuffer: relocate get_data()
  printk: ringbuffer: avoid memcpy() on state_var
  printk: ringbuffer: fix setting state in desc_read()
  kernel.h: Move oops_in_progress to printk.h
  scripts/gdb: update for lockless printk ringbuffer
  scripts/gdb: add utils.read_ulong()
  docs: vmcoreinfo: add lockless printk ringbuffer vmcoreinfo
  printk: reduce LOG_BUF_SHIFT range for H8300
  printk: ringbuffer: support dataless records
  ...
parents 029f56db 70333f4f

Documentation/admin-guide/kdump/gdbmacros.txt

+109 −50
Original line number Diff line number Diff line
@@ -170,57 +170,103 @@ document trapinfo 
	address the kernel panicked.

end



define dump_log_idx

	set $idx = $arg0

	if ($argc > 1)

		set $prev_flags = $arg1

define dump_record

	set var $desc = $arg0

	set var $info = $arg1

	if ($argc > 2)

		set var $prev_flags = $arg2

	else

		set $prev_flags = 0

		set var $prev_flags = 0

	end

	set $msg = ((struct printk_log *) (log_buf + $idx))

	set $prefix = 1

	set $newline = 1

	set $log = log_buf + $idx + sizeof(*$msg)



	# prev & LOG_CONT && !(msg->flags & LOG_PREIX)

	if (($prev_flags & 8) && !($msg->flags & 4))

		set $prefix = 0

	set var $prefix = 1

	set var $newline = 1



	set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)

	set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)



	# handle data-less record

	if ($begin & 1)

		set var $text_len = 0

		set var $log = ""

	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->text_len)

			set var $text_len = $next - $begin

		else

			set var $text_len = $info->text_len

		end



		set var $log = &prb->text_data_ring.data[$begin]

	end



	# prev & LOG_CONT && !(info->flags & LOG_PREIX)

	if (($prev_flags & 8) && !($info->flags & 4))

		set var $prefix = 0

	end



	# msg->flags & LOG_CONT

	if ($msg->flags & 8)

	# info->flags & LOG_CONT

	if ($info->flags & 8)

		# (prev & LOG_CONT && !(prev & LOG_NEWLINE))

		if (($prev_flags & 8) && !($prev_flags & 2))

			set $prefix = 0

			set var $prefix = 0

		end

		# (!(msg->flags & LOG_NEWLINE))

		if (!($msg->flags & 2))

			set $newline = 0

		# (!(info->flags & LOG_NEWLINE))

		if (!($info->flags & 2))

			set var $newline = 0

		end

	end



	if ($prefix)

		printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000

		printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000

	end

	if ($msg->text_len != 0)

		eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len

	if ($text_len)

		eval "printf \"%%%d.%ds\", $log", $text_len, $text_len

	end

	if ($newline)

		printf "\n"

	end

	if ($msg->dict_len > 0)

		set $dict = $log + $msg->text_len

		set $idx = 0

		set $line = 1

		while ($idx < $msg->dict_len)

			if ($line)

				printf " "

				set $line = 0

			end

			set $c = $dict[$idx]



	# handle dictionary data



	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

		printf "\n"

				set $line = 1

	end



	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

		while ($idx < $dict_len)

			set var $c = $dict[$idx]

			if ($c == '\0')

				loop_break

			else

				if ($c < ' ' || $c >= 127 || $c == '\\')

					printf "\\x%02x", $c
@@ -228,33 +274,46 @@ define dump_log_idx 
					printf "%c", $c

				end

			end

			set $idx = $idx + 1

			set var $idx = $idx + 1

		end

		printf "\n"

	end

end

document dump_log_idx

	Dump a single log given its index in the log buffer.  The first

	parameter is the index into log_buf, the second is optional and

	specified the previous log buffer's flags, used for properly

	formatting continued lines.

document dump_record

	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

	set $i = log_first_idx

	set $end_idx = log_first_idx

	set $prev_flags = 0

	# definitions from kernel/printk/printk_ringbuffer.h

	set var $desc_committed = 1

	set var $desc_finalized = 2

	set var $desc_sv_bits = sizeof(long) * 8

	set var $desc_flags_shift = $desc_sv_bits - 2

	set var $desc_flags_mask = 3 << $desc_flags_shift

	set var $id_mask = ~$desc_flags_mask



	set var $desc_count = 1U << prb->desc_ring.count_bits

	set var $prev_flags = 0



	set var $id = prb->desc_ring.tail_id.counter

	set var $end_id = prb->desc_ring.head_id.counter



	while (1)

		set $msg = ((struct printk_log *) (log_buf + $i))

		if ($msg->len == 0)

			set $i = 0

		else

			dump_log_idx $i $prev_flags

			set $i = $i + $msg->len

			set $prev_flags = $msg->flags

		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 $info $prev_flags

			set var $prev_flags = $info->flags

		end

		if ($i == $end_idx)



		set var $id = ($id + 1) & $id_mask

		if ($id == $end_id)

			loop_break

		end

	end

Documentation/admin-guide/kdump/vmcoreinfo.rst

+102 −29
Original line number Diff line number Diff line
@@ -189,50 +189,123 @@ from this. 
Free areas descriptor. User-space tools use this value to iterate the

free_area ranges. MAX_ORDER is used by the zone buddy allocator.



log_first_idx

prb

---



A pointer to the printk ringbuffer (struct printk_ringbuffer). This

may be pointing to the static boot ringbuffer or the dynamically

allocated ringbuffer, depending on when the the core dump occurred.

Used by user-space tools to read the active kernel log buffer.



printk_rb_static

----------------



A pointer to the static boot printk ringbuffer. If @prb has a

different value, this is useful for viewing the initial boot messages,

which may have been overwritten in the dynamically allocated

ringbuffer.



clear_seq

---------



The sequence number of the printk() record after the last clear

command. It indicates the first record after the last

SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space

tools to dump a subset of the dmesg log.



printk_ringbuffer

-----------------



The size of a printk_ringbuffer structure. This structure contains all

information required for accessing the various components of the

kernel log buffer.



(printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail)

-----------------------------------------------------------------



Offsets for the various components of the printk ringbuffer. Used by

user-space tools to view the kernel log buffer without requiring the

declaration of the structure.



prb_desc_ring

-------------



Index of the first record stored in the buffer log_buf. Used by

user-space tools to read the strings in the log_buf.

The size of the prb_desc_ring structure. This structure contains

information about the set of record descriptors.



log_buf

-------

(prb_desc_ring, count_bits|descs|head_id|tail_id)

-------------------------------------------------



Offsets for the fields describing the set of record descriptors. Used

by user-space tools to be able to traverse the descriptors without

requiring the declaration of the structure.



prb_desc

--------



The size of the prb_desc structure. This structure contains

information about a single record descriptor.



(prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos)

------------------------------------------------------



Offsets for the fields describing a record descriptors. Used by

user-space tools to be able to read descriptors without requiring

the declaration of the structure.



prb_data_blk_lpos

-----------------



The size of the prb_data_blk_lpos structure. This structure contains

information about where the text or dictionary data (data block) is

located within the respective data ring.



(prb_data_blk_lpos, begin|next)

-------------------------------



Console output is written to the ring buffer log_buf at index

log_first_idx. Used to get the kernel log.

Offsets for the fields describing the location of a data block. Used

by user-space tools to be able to locate data blocks without

requiring the declaration of the structure.



log_buf_len

printk_info

-----------



log_buf's length.

The size of the printk_info structure. This structure contains all

the meta-data for a record.



clear_idx

---------

(printk_info, seq|ts_nsec|text_len|dict_len|caller_id)

------------------------------------------------------



The index that the next printk() record to read after the last clear

command. It indicates the first record after the last SYSLOG_ACTION

_CLEAR, like issued by 'dmesg -c'. Used by user-space tools to dump

the dmesg log.

Offsets for the fields providing the meta-data for a record. Used by

user-space tools to be able to read the information without requiring

the declaration of the structure.



log_next_idx

------------

prb_data_ring

-------------



The index of the next record to store in the buffer log_buf. Used to

compute the index of the current buffer position.

The size of the prb_data_ring structure. This structure contains

information about a set of data blocks.



printk_log

----------

(prb_data_ring, size_bits|data|head_lpos|tail_lpos)

---------------------------------------------------



The size of a structure printk_log. Used to compute the size of

messages, and extract dmesg log. It encapsulates header information for

log_buf, such as timestamp, syslog level, etc.

Offsets for the fields describing a set of data blocks. Used by

user-space tools to be able to access the data blocks without

requiring the declaration of the structure.



(printk_log, ts_nsec|len|text_len|dict_len)

-------------------------------------------

atomic_long_t

-------------



The size of the atomic_long_t structure. Used by user-space tools to

be able to copy the full structure, regardless of its

architecture-specific implementation.



(atomic_long_t, counter)

------------------------



It represents field offsets in struct printk_log. User space tools

parse it and check whether the values of printk_log's members have been

changed.

Offset for the long value of an atomic_long_t variable. Used by

user-space tools to access the long value without requiring the

architecture-specific declaration.



(free_area.free_list, MIGRATE_TYPES)

------------------------------------

MAINTAINERS

+1 −0
Original line number Diff line number Diff line
@@ -13970,6 +13970,7 @@ PRINTK 
M:	Petr Mladek <pmladek@suse.com>

M:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

R:	Steven Rostedt <rostedt@goodmis.org>

R:	John Ogness <john.ogness@linutronix.de>

S:	Maintained

F:	include/linux/printk.h

F:	kernel/printk/

drivers/base/core.c

+16 −30
Original line number Diff line number Diff line
@@ -4061,22 +4061,21 @@ 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;

	strscpy(dev_info->subsystem, subsys, sizeof(dev_info->subsystem));



	/*

	 * Add device identifier DEVICE=:
@@ -4092,41 +4091,28 @@ 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);

include/linux/crash_core.h

+3 −0
Original line number Diff line number Diff line
@@ -55,6 +55,9 @@ phys_addr_t paddr_vmcoreinfo_note(void); 
#define VMCOREINFO_OFFSET(name, field) \

	vmcoreinfo_append_str("OFFSET(%s.%s)=%lu\n", #name, #field, \

			      (unsigned long)offsetof(struct name, field))

#define VMCOREINFO_TYPE_OFFSET(name, field) \

	vmcoreinfo_append_str("OFFSET(%s.%s)=%lu\n", #name, #field, \

			      (unsigned long)offsetof(name, field))

#define VMCOREINFO_LENGTH(name, value) \

	vmcoreinfo_append_str("LENGTH(%s)=%lu\n", #name, (unsigned long)value)

#define VMCOREINFO_NUMBER(name) \

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