Merge branch 'rework/nbcon-base' into for-linus (2966bd36) · Commits · git / linux-net

include/linux/console.h

+129 −0

Original line number	Diff line number	Diff line
		@@ -156,6 +156,8 @@ static inline int con_debug_leave(void)
		* /dev/kmesg which requires a larger output buffer.
		* @CON_SUSPENDED: Indicates if a console is suspended. If true, the
		* printing callbacks must not be called.
		* @CON_NBCON: Console can operate outside of the legacy style console_lock
		* constraints.
		*/
		enum cons_flags {
		CON_PRINTBUFFER = BIT(0),
		@@ -166,6 +168,111 @@ enum cons_flags {
		CON_BRL = BIT(5),
		CON_EXTENDED = BIT(6),
		CON_SUSPENDED = BIT(7),
		CON_NBCON = BIT(8),
		};

		/**
		* struct nbcon_state - console state for nbcon consoles
		* @atom: Compound of the state fields for atomic operations
		*
		* @req_prio: The priority of a handover request
		* @prio: The priority of the current owner
		* @unsafe: Console is busy in a non takeover region
		* @unsafe_takeover: A hostile takeover in an unsafe state happened in the
		* past. The console cannot be safe until re-initialized.
		* @cpu: The CPU on which the owner runs
		*
		* To be used for reading and preparing of the value stored in the nbcon
		* state variable @console::nbcon_state.
		*
		* The @prio and @req_prio fields are particularly important to allow
		* spin-waiting to timeout and give up without the risk of a waiter being
		* assigned the lock after giving up.
		*/
		struct nbcon_state {
		union {
		unsigned int atom;
		struct {
		unsigned int prio : 2;
		unsigned int req_prio : 2;
		unsigned int unsafe : 1;
		unsigned int unsafe_takeover : 1;
		unsigned int cpu : 24;
		};
		};
		};

		/*
		* The nbcon_state struct is used to easily create and interpret values that
		* are stored in the @console::nbcon_state variable. Ensure this struct stays
		* within the size boundaries of the atomic variable's underlying type in
		* order to avoid any accidental truncation.
		*/
		static_assert(sizeof(struct nbcon_state) <= sizeof(int));

		/**
		* nbcon_prio - console owner priority for nbcon consoles
		* @NBCON_PRIO_NONE: Unused
		* @NBCON_PRIO_NORMAL: Normal (non-emergency) usage
		* @NBCON_PRIO_EMERGENCY: Emergency output (WARN/OOPS...)
		* @NBCON_PRIO_PANIC: Panic output
		* @NBCON_PRIO_MAX: The number of priority levels
		*
		* A higher priority context can takeover the console when it is
		* in the safe state. The final attempt to flush consoles in panic()
		* can be allowed to do so even in an unsafe state (Hope and pray).
		*/
		enum nbcon_prio {
		NBCON_PRIO_NONE = 0,
		NBCON_PRIO_NORMAL,
		NBCON_PRIO_EMERGENCY,
		NBCON_PRIO_PANIC,
		NBCON_PRIO_MAX,
		};

		struct console;
		struct printk_buffers;

		/**
		* struct nbcon_context - Context for console acquire/release
		* @console: The associated console
		* @spinwait_max_us: Limit for spin-wait acquire
		* @prio: Priority of the context
		* @allow_unsafe_takeover: Allow performing takeover even if unsafe. Can
		* be used only with NBCON_PRIO_PANIC @prio. It
		* might cause a system freeze when the console
		* is used later.
		* @backlog: Ringbuffer has pending records
		* @pbufs: Pointer to the text buffer for this context
		* @seq: The sequence number to print for this context
		*/
		struct nbcon_context {
		/* members set by caller */
		struct console *console;
		unsigned int spinwait_max_us;
		enum nbcon_prio prio;
		unsigned int allow_unsafe_takeover : 1;

		/* members set by emit */
		unsigned int backlog : 1;

		/* members set by acquire */
		struct printk_buffers *pbufs;
		u64 seq;
		};

		/**
		* struct nbcon_write_context - Context handed to the nbcon write callbacks
		* @ctxt: The core console context
		* @outbuf: Pointer to the text buffer for output
		* @len: Length to write
		* @unsafe_takeover: If a hostile takeover in an unsafe state has occurred
		*/
		struct nbcon_write_context {
		struct nbcon_context __private ctxt;
		char *outbuf;
		unsigned int len;
		bool unsafe_takeover;
		};

		/**
		@@ -187,6 +294,11 @@ enum cons_flags {
		* @dropped: Number of unreported dropped ringbuffer records
		* @data: Driver private data
		* @node: hlist node for the console list
		*
		* @write_atomic: Write callback for atomic context
		* @nbcon_state: State for nbcon consoles
		* @nbcon_seq: Sequence number of the next record for nbcon to print
		* @pbufs: Pointer to nbcon private buffer
		*/
		struct console {
		char name[16];
		@@ -206,6 +318,13 @@ struct console {
		unsigned long dropped;
		void *data;
		struct hlist_node node;

		/* nbcon console specific members */
		bool (write_atomic)(struct console con,
		struct nbcon_write_context *wctxt);
		atomic_t __private nbcon_state;
		atomic_long_t __private nbcon_seq;
		struct printk_buffers *pbufs;
		};

		#ifdef CONFIG_LOCKDEP
		@@ -332,6 +451,16 @@ static inline bool console_is_registered(const struct console *con)
		lockdep_assert_console_list_lock_held(); \
		hlist_for_each_entry(con, &console_list, node)

		#ifdef CONFIG_PRINTK
		extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
		extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
		extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
		#else
		static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
		static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
		static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
		#endif

		extern int console_set_on_cmdline;
		extern struct console *early_console;

kernel/printk/Makefile

+1 −1

Original line number	Diff line number	Diff line
		# SPDX-License-Identifier: GPL-2.0-only
		obj-y = printk.o
		obj-$(CONFIG_PRINTK) += printk_safe.o
		obj-$(CONFIG_PRINTK) += printk_safe.o nbcon.o
		obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o
		obj-$(CONFIG_PRINTK_INDEX) += index.o

kernel/printk/internal.h

+31 −0

Original line number	Diff line number	Diff line
		@@ -3,6 +3,8 @@
		* internal.h - printk internal definitions
		*/
		#include <linux/percpu.h>
		#include <linux/console.h>
		#include "printk_ringbuffer.h"

		#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
		void __init printk_sysctl_init(void);
		@@ -12,6 +14,12 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
		#define printk_sysctl_init() do { } while (0)
		#endif

		#define con_printk(lvl, con, fmt, ...) \
		printk(lvl pr_fmt("%s%sconsole [%s%d] " fmt), \
		(con->flags & CON_NBCON) ? "" : "legacy ", \
		(con->flags & CON_BOOT) ? "boot" : "", \
		con->name, con->index, ##__VA_ARGS__)

		#ifdef CONFIG_PRINTK

		#ifdef CONFIG_PRINTK_CALLER
		@@ -35,6 +43,8 @@ enum printk_info_flags {
		LOG_CONT = 8, /* text is a fragment of a continuation line */
		};

		extern struct printk_ringbuffer *prb;

		__printf(4, 0)
		int vprintk_store(int facility, int level,
		const struct dev_printk_info *dev_info,
		@@ -61,6 +71,13 @@ void defer_console_output(void);

		u16 printk_parse_prefix(const char text, int level,
		enum printk_info_flags *flags);

		u64 nbcon_seq_read(struct console *con);
		void nbcon_seq_force(struct console *con, u64 seq);
		bool nbcon_alloc(struct console *con);
		void nbcon_init(struct console *con);
		void nbcon_free(struct console *con);

		#else

		#define PRINTK_PREFIX_MAX 0
		@@ -76,8 +93,16 @@ u16 printk_parse_prefix(const char text, int level,
		#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)

		static inline bool printk_percpu_data_ready(void) { return false; }
		static inline u64 nbcon_seq_read(struct console *con) { return 0; }
		static inline void nbcon_seq_force(struct console *con, u64 seq) { }
		static inline bool nbcon_alloc(struct console *con) { return false; }
		static inline void nbcon_init(struct console *con) { }
		static inline void nbcon_free(struct console *con) { }

		#endif /* CONFIG_PRINTK */

		extern struct printk_buffers printk_shared_pbufs;

		/**
		* struct printk_buffers - Buffers to read/format/output printk messages.
		* @outbuf: After formatting, contains text to output.
		@@ -105,3 +130,9 @@ struct printk_message {
		};

		bool other_cpu_in_panic(void);
		bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		bool is_extended, bool may_supress);

		#ifdef CONFIG_PRINTK
		void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
		#endif

kernel/printk/nbcon.c

0 → 100644

+1029 −0

File added.

Preview size limit exceeded, changes collapsed.

kernel/printk/printk.c

+73 −49

Original line number	Diff line number	Diff line
		@@ -102,12 +102,6 @@ DEFINE_STATIC_SRCU(console_srcu);
		*/
		int __read_mostly suppress_printk;

		/*
		* During panic, heavy printk by other CPUs can delay the
		* panic and risk deadlock on console resources.
		*/
		static int __read_mostly suppress_panic_printk;

		#ifdef CONFIG_LOCKDEP
		static struct lockdep_map console_lock_dep_map = {
		.name = "console_lock"
		@@ -445,6 +439,12 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
		static DEFINE_MUTEX(syslog_lock);

		#ifdef CONFIG_PRINTK
		/*
		* During panic, heavy printk by other CPUs can delay the
		* panic and risk deadlock on console resources.
		*/
		static int __read_mostly suppress_panic_printk;

		DECLARE_WAIT_QUEUE_HEAD(log_wait);
		/* All 3 protected by @syslog_lock. */
		/* the next printk record to read by syslog(READ) or /proc/kmsg */
		@@ -494,7 +494,7 @@ _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,

		static struct printk_ringbuffer printk_rb_dynamic;

		static struct printk_ringbuffer *prb = &printk_rb_static;
		struct printk_ringbuffer *prb = &printk_rb_static;

		/*
		* We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
		@@ -698,9 +698,6 @@ static ssize_t msg_print_ext_body(char *buf, size_t size,
		return len;
		}

		static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		bool is_extended, bool may_supress);

		/* /dev/kmsg - userspace message inject/listen interface */
		struct devkmsg_user {
		atomic64_t seq;
		@@ -2348,22 +2345,6 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre

		static u64 syslog_seq;

		static size_t record_print_text(const struct printk_record *r,
		bool syslog, bool time)
		{
		return 0;
		}
		static ssize_t info_print_ext_header(char *buf, size_t size,
		struct printk_info *info)
		{
		return 0;
		}
		static ssize_t msg_print_ext_body(char *buf, size_t size,
		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(int cookie) { return 0; }
		static bool suppress_message_printing(int level) { return false; }
		static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
		static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }

		@@ -2717,6 +2698,8 @@ static void __console_unlock(void)
		up_console_sem();
		}

		#ifdef CONFIG_PRINTK

		/*
		* Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This
		* is achieved by shifting the existing message over and inserting the dropped
		@@ -2731,8 +2714,7 @@ static void __console_unlock(void)
		*
		* If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
		*/
		#ifdef CONFIG_PRINTK
		static void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
		void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
		{
		struct printk_buffers *pbufs = pmsg->pbufs;
		const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
		@@ -2763,9 +2745,6 @@ static void console_prepend_dropped(struct printk_message *pmsg, unsigned long d
		memcpy(outbuf, scratchbuf, len);
		pmsg->outbuf_len += len;
		}
		#else
		#define console_prepend_dropped(pmsg, dropped)
		#endif /* CONFIG_PRINTK */

		/*
		* Read and format the specified record (or a later record if the specified
		@@ -2786,7 +2765,7 @@ static void console_prepend_dropped(struct printk_message *pmsg, unsigned long d
		* of @pmsg are valid. (See the documentation of struct printk_message
		* for information about the @pmsg fields.)
		*/
		static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		bool is_extended, bool may_suppress)
		{
		static int panic_console_dropped;
		@@ -2845,6 +2824,13 @@ static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		return true;
		}

		/*
		* Used as the printk buffers for non-panic, serialized console printing.
		* This is for legacy (!CON_NBCON) as well as all boot (CON_BOOT) consoles.
		* Its usage requires the console_lock held.
		*/
		struct printk_buffers printk_shared_pbufs;

		/*
		* Print one record for the given console. The record printed is whatever
		* record is the next available record for the given console.
		@@ -2862,12 +2848,10 @@ static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
		*/
		static bool console_emit_next_record(struct console con, bool handover, int cookie)
		{
		static struct printk_buffers pbufs;

		bool is_extended = console_srcu_read_flags(con) & CON_EXTENDED;
		char *outbuf = &pbufs.outbuf[0];
		char *outbuf = &printk_shared_pbufs.outbuf[0];
		struct printk_message pmsg = {
		.pbufs = &pbufs,
		.pbufs = &printk_shared_pbufs,
		};
		unsigned long flags;

		@@ -2918,6 +2902,16 @@ static bool console_emit_next_record(struct console con, bool handover, int co
		return true;
		}

		#else

		static bool console_emit_next_record(struct console con, bool handover, int cookie)
		{
		*handover = false;
		return false;
		}

		#endif /* CONFIG_PRINTK */

		/*
		* Print out all remaining records to all consoles.
		*
		@@ -3162,6 +3156,7 @@ void console_flush_on_panic(enum con_flush_mode mode)

		if (mode == CONSOLE_REPLAY_ALL) {
		struct console *c;
		short flags;
		int cookie;
		u64 seq;

		@@ -3169,12 +3164,18 @@ void console_flush_on_panic(enum con_flush_mode mode)

		cookie = console_srcu_read_lock();
		for_each_console_srcu(c) {
		flags = console_srcu_read_flags(c);

		if (flags & CON_NBCON) {
		nbcon_seq_force(c, seq);
		} else {
		/*
		* This is an unsynchronized assignment, but the
		* kernel is in "hope and pray" mode anyway.
		* This is an unsynchronized assignment. On
		* panic legacy consoles are only best effort.
		*/
		c->seq = seq;
		}
		}
		console_srcu_read_unlock(cookie);
		}

		@@ -3325,11 +3326,6 @@ static void try_enable_default_console(struct console *newcon)
		newcon->flags \|= CON_CONSDEV;
		}

		#define con_printk(lvl, con, fmt, ...) \
		printk(lvl pr_fmt("%sconsole [%s%d] " fmt), \
		(con->flags & CON_BOOT) ? "boot" : "", \
		con->name, con->index, ##__VA_ARGS__)

		static void console_init_seq(struct console *newcon, bool bootcon_registered)
		{
		struct console *con;
		@@ -3443,6 +3439,15 @@ void register_console(struct console *newcon)
		goto unlock;
		}

		if (newcon->flags & CON_NBCON) {
		/*
		* Ensure the nbcon console buffers can be allocated
		* before modifying any global data.
		*/
		if (!nbcon_alloc(newcon))
		goto unlock;
		}

		/*
		* See if we want to enable this console driver by default.
		*
		@@ -3470,8 +3475,11 @@ void register_console(struct console *newcon)
		err = try_enable_preferred_console(newcon, false);

		/* printk() messages are not printed to the Braille console. */
		if (err \|\| newcon->flags & CON_BRL)
		if (err \|\| newcon->flags & CON_BRL) {
		if (newcon->flags & CON_NBCON)
		nbcon_free(newcon);
		goto unlock;
		}

		/*
		* If we have a bootconsole, and are switching to a real console,
		@@ -3487,6 +3495,9 @@ void register_console(struct console *newcon)
		newcon->dropped = 0;
		console_init_seq(newcon, bootcon_registered);

		if (newcon->flags & CON_NBCON)
		nbcon_init(newcon);

		/*
		* Put this console in the list - keep the
		* preferred driver at the head of the list.
		@@ -3578,6 +3589,9 @@ static int unregister_console_locked(struct console *console)
		*/
		synchronize_srcu(&console_srcu);

		if (console->flags & CON_NBCON)
		nbcon_free(console);

		console_sysfs_notify();

		if (console->exit)
		@@ -3732,6 +3746,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
		struct console *c;
		u64 last_diff = 0;
		u64 printk_seq;
		short flags;
		int cookie;
		u64 diff;
		u64 seq;
		@@ -3762,6 +3777,9 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
		for_each_console_srcu(c) {
		if (con && con != c)
		continue;

		flags = console_srcu_read_flags(c);

		/*
		* If consoles are not usable, it cannot be expected
		* that they make forward progress, so only increment
		@@ -3769,7 +3787,13 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
		*/
		if (!console_is_usable(c))
		continue;

		if (flags & CON_NBCON) {
		printk_seq = nbcon_seq_read(c);
		} else {
		printk_seq = c->seq;
		}

		if (printk_seq < seq)
		diff += seq - printk_seq;
		}