diff options
Diffstat (limited to 'include/linux/console.h')
| -rw-r--r-- | include/linux/console.h | 138 |
1 files changed, 137 insertions, 1 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index 7de11c763eb3..779d388af8a0 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -101,6 +101,13 @@ extern const struct consw dummy_con; /* dummy console buffer */ extern const struct consw vga_con; /* VGA text console */ extern const struct consw newport_con; /* SGI Newport console */ +struct screen_info; +#ifdef CONFIG_VGA_CONSOLE +void vgacon_register_screen(struct screen_info *si); +#else +static inline void vgacon_register_screen(struct screen_info *si) { } +#endif + int con_is_bound(const struct consw *csw); int do_unregister_con_driver(const struct consw *csw); int do_take_over_console(const struct consw *sw, int first, int last, int deflt); @@ -156,6 +163,8 @@ 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 +175,111 @@ 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 +301,11 @@ 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 +325,13 @@ 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 +458,16 @@ 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; @@ -340,7 +476,7 @@ enum con_flush_mode { CONSOLE_REPLAY_ALL, }; -extern int add_preferred_console(char *name, int idx, char *options); +extern int add_preferred_console(const char *name, const short idx, char *options); extern void console_force_preferred_locked(struct console *con); extern void register_console(struct console *); extern int unregister_console(struct console *); |