diff options
Diffstat (limited to 'include/linux/console.h')
| -rw-r--r-- | include/linux/console.h | 414 |
1 files changed, 345 insertions, 69 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index 7de11c763eb3..eba367bf605d 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -16,8 +16,11 @@ #include <linux/atomic.h> #include <linux/bits.h> +#include <linux/irq_work.h> #include <linux/rculist.h> +#include <linux/rcuwait.h> #include <linux/types.h> +#include <linux/vesa.h> struct vc_data; struct console_font_op; @@ -36,63 +39,91 @@ enum vc_intensity; /** * struct consw - callbacks for consoles * + * @owner: the module to get references of when this console is used + * @con_startup: set up the console and return its name (like VGA, EGA, ...) + * @con_init: initialize the console on @vc. @init is true for the very first + * call on this @vc. + * @con_deinit: deinitialize the console from @vc. + * @con_clear: erase @count characters at [@x, @y] on @vc. @count >= 1. + * @con_putc: emit one character with attributes @ca to [@x, @y] on @vc. + * (optional -- @con_putcs would be called instead) + * @con_putcs: emit @count characters with attributes @s to [@x, @y] on @vc. + * @con_cursor: enable/disable cursor depending on @enable * @con_scroll: move lines from @top to @bottom in direction @dir by @lines. * Return true if no generic handling should be done. * Invoked by csi_M and printing to the console. - * @con_set_palette: sets the palette of the console to @table (optional) + * @con_switch: notifier about the console switch; it is supposed to return + * true if a redraw is needed. + * @con_blank: blank/unblank the console. The target mode is passed in @blank. + * @mode_switch is set if changing from/to text/graphics. The hook + * is supposed to return true if a redraw is needed. + * @con_font_set: set console @vc font to @font with height @vpitch. @flags can + * be %KD_FONT_FLAG_DONT_RECALC. (optional) + * @con_font_get: fetch the current font on @vc of height @vpitch into @font. + * (optional) + * @con_font_default: set default font on @vc. @name can be %NULL or font name + * to search for. @font can be filled back. (optional) + * @con_resize: resize the @vc console to @width x @height. @from_user is true + * when this change comes from the user space. + * @con_set_palette: sets the palette of the console @vc to @table (optional) * @con_scrolldelta: the contents of the console should be scrolled by @lines. * Invoked by user. (optional) + * @con_set_origin: set origin (see &vc_data::vc_origin) of the @vc. If not + * provided or returns false, the origin is set to + * @vc->vc_screenbuf. (optional) + * @con_save_screen: save screen content into @vc->vc_screenbuf. Called e.g. + * upon entering graphics. (optional) + * @con_build_attr: build attributes based on @color, @intensity and other + * parameters. The result is used for both normal and erase + * characters. (optional) + * @con_invert_region: invert a region of length @count on @vc starting at @p. + * (optional) + * @con_debug_enter: prepare the console for the debugger. This includes, but + * is not limited to, unblanking the console, loading an + * appropriate palette, and allowing debugger generated output. + * (optional) + * @con_debug_leave: restore the console to its pre-debug state as closely as + * possible. (optional) */ struct consw { struct module *owner; const char *(*con_startup)(void); - void (*con_init)(struct vc_data *vc, int init); + void (*con_init)(struct vc_data *vc, bool init); void (*con_deinit)(struct vc_data *vc); - void (*con_clear)(struct vc_data *vc, int sy, int sx, int height, - int width); - void (*con_putc)(struct vc_data *vc, int c, int ypos, int xpos); - void (*con_putcs)(struct vc_data *vc, const unsigned short *s, - int count, int ypos, int xpos); - void (*con_cursor)(struct vc_data *vc, int mode); + void (*con_clear)(struct vc_data *vc, unsigned int y, + unsigned int x, unsigned int count); + void (*con_putc)(struct vc_data *vc, u16 ca, unsigned int y, + unsigned int x); + void (*con_putcs)(struct vc_data *vc, const u16 *s, + unsigned int count, unsigned int ypos, + unsigned int xpos); + void (*con_cursor)(struct vc_data *vc, bool enable); bool (*con_scroll)(struct vc_data *vc, unsigned int top, unsigned int bottom, enum con_scroll dir, unsigned int lines); - int (*con_switch)(struct vc_data *vc); - int (*con_blank)(struct vc_data *vc, int blank, int mode_switch); - int (*con_font_set)(struct vc_data *vc, struct console_font *font, - unsigned int vpitch, unsigned int flags); + bool (*con_switch)(struct vc_data *vc); + bool (*con_blank)(struct vc_data *vc, enum vesa_blank_mode blank, + bool mode_switch); + int (*con_font_set)(struct vc_data *vc, + const struct console_font *font, + unsigned int vpitch, unsigned int flags); int (*con_font_get)(struct vc_data *vc, struct console_font *font, unsigned int vpitch); int (*con_font_default)(struct vc_data *vc, - struct console_font *font, char *name); + struct console_font *font, const char *name); int (*con_resize)(struct vc_data *vc, unsigned int width, - unsigned int height, unsigned int user); + unsigned int height, bool from_user); void (*con_set_palette)(struct vc_data *vc, const unsigned char *table); void (*con_scrolldelta)(struct vc_data *vc, int lines); - int (*con_set_origin)(struct vc_data *vc); + bool (*con_set_origin)(struct vc_data *vc); void (*con_save_screen)(struct vc_data *vc); u8 (*con_build_attr)(struct vc_data *vc, u8 color, enum vc_intensity intensity, bool blink, bool underline, bool reverse, bool italic); void (*con_invert_region)(struct vc_data *vc, u16 *p, int count); - u16 *(*con_screen_pos)(const struct vc_data *vc, int offset); - unsigned long (*con_getxy)(struct vc_data *vc, unsigned long position, - int *px, int *py); - /* - * Flush the video console driver's scrollback buffer - */ - void (*con_flush_scrollback)(struct vc_data *vc); - /* - * Prepare the console for the debugger. This includes, but is not - * limited to, unblanking the console, loading an appropriate - * palette, and allowing debugger generated output. - */ - int (*con_debug_enter)(struct vc_data *vc); - /* - * Restore the console to its pre-debug state as closely as possible. - */ - int (*con_debug_leave)(struct vc_data *vc); + void (*con_debug_enter)(struct vc_data *vc); + void (*con_debug_leave)(struct vc_data *vc); }; extern const struct consw *conswitchp; @@ -101,36 +132,32 @@ 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); void give_up_console(const struct consw *sw); -#ifdef CONFIG_HW_CONSOLE -int con_debug_enter(struct vc_data *vc); -int con_debug_leave(void); +#ifdef CONFIG_VT +void con_debug_enter(struct vc_data *vc); +void con_debug_leave(void); #else -static inline int con_debug_enter(struct vc_data *vc) -{ - return 0; -} -static inline int con_debug_leave(void) -{ - return 0; -} +static inline void con_debug_enter(struct vc_data *vc) { } +static inline void con_debug_leave(void) { } #endif -/* cursor */ -#define CM_DRAW (1) -#define CM_ERASE (2) -#define CM_MOVE (3) - /* * The interface for a console, or any other device that wants to capture * console messages (printer driver?) */ /** - * cons_flags - General console flags + * enum cons_flags - General console flags * @CON_PRINTBUFFER: Used by newly registered consoles to avoid duplicate * output of messages that were already shown by boot * consoles or read by userspace via syslog() syscall. @@ -156,6 +183,8 @@ 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), @@ -166,12 +195,117 @@ 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)); + +/** + * enum 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; }; /** * struct console - The console descriptor structure * @name: The name of the console driver - * @write: Write callback to output messages (Optional) + * @write: Legacy write callback to output messages (Optional) * @read: Read callback for console input (Optional) * @device: The underlying TTY device driver (Optional) * @unblank: Callback to unblank the console (Optional) @@ -187,6 +321,15 @@ enum cons_flags { * @dropped: Number of unreported dropped ringbuffer records * @data: Driver private data * @node: hlist node for the console list + * + * @nbcon_state: State for nbcon consoles + * @nbcon_seq: Sequence number of the next record for nbcon to print + * @nbcon_device_ctxt: Context available for non-printing operations + * @nbcon_prev_seq: Seq num the previous nbcon owner was assigned to print + * @pbufs: Pointer to nbcon private buffer + * @kthread: Printer kthread for this console + * @rcuwait: RCU-safe wait object for @kthread waking + * @irq_work: Defer @kthread waking to IRQ work context */ struct console { char name[16]; @@ -206,6 +349,123 @@ struct console { unsigned long dropped; void *data; struct hlist_node node; + + /* nbcon console specific members */ + + /** + * @write_atomic: + * + * NBCON callback to write out text in any context. (Optional) + * + * This callback is called with the console already acquired. However, + * a higher priority context is allowed to take it over by default. + * + * The callback must call nbcon_enter_unsafe() and nbcon_exit_unsafe() + * around any code where the takeover is not safe, for example, when + * manipulating the serial port registers. + * + * nbcon_enter_unsafe() will fail if the context has lost the console + * ownership in the meantime. In this case, the callback is no longer + * allowed to go forward. It must back out immediately and carefully. + * The buffer content is also no longer trusted since it no longer + * belongs to the context. + * + * The callback should allow the takeover whenever it is safe. It + * increases the chance to see messages when the system is in trouble. + * If the driver must reacquire ownership in order to finalize or + * revert hardware changes, nbcon_reacquire_nobuf() can be used. + * However, on reacquire the buffer content is no longer available. A + * reacquire cannot be used to resume printing. + * + * The callback can be called from any context (including NMI). + * Therefore it must avoid usage of any locking and instead rely + * on the console ownership for synchronization. + */ + void (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt); + + /** + * @write_thread: + * + * NBCON callback to write out text in task context. + * + * This callback must be called only in task context with both + * device_lock() and the nbcon console acquired with + * NBCON_PRIO_NORMAL. + * + * The same rules for console ownership verification and unsafe + * sections handling applies as with write_atomic(). + * + * The console ownership handling is necessary for synchronization + * against write_atomic() which is synchronized only via the context. + * + * The device_lock() provides the primary serialization for operations + * on the device. It might be as relaxed (mutex)[*] or as tight + * (disabled preemption and interrupts) as needed. It allows + * the kthread to operate in the least restrictive mode[**]. + * + * [*] Standalone nbcon_context_try_acquire() is not safe with + * the preemption enabled, see nbcon_owner_matches(). But it + * can be safe when always called in the preemptive context + * under the device_lock(). + * + * [**] The device_lock() makes sure that nbcon_context_try_acquire() + * would never need to spin which is important especially with + * PREEMPT_RT. + */ + void (*write_thread)(struct console *con, struct nbcon_write_context *wctxt); + + /** + * @device_lock: + * + * NBCON callback to begin synchronization with driver code. + * + * Console drivers typically must deal with access to the hardware + * via user input/output (such as an interactive login shell) and + * output of kernel messages via printk() calls. This callback is + * called by the printk-subsystem whenever it needs to synchronize + * with hardware access by the driver. It should be implemented to + * use whatever synchronization mechanism the driver is using for + * itself (for example, the port lock for uart serial consoles). + * + * The callback is always called from task context. It may use any + * synchronization method required by the driver. + * + * IMPORTANT: The callback MUST disable migration. The console driver + * may be using a synchronization mechanism that already takes + * care of this (such as spinlocks). Otherwise this function must + * explicitly call migrate_disable(). + * + * The flags argument is provided as a convenience to the driver. It + * will be passed again to device_unlock(). It can be ignored if the + * driver does not need it. + */ + void (*device_lock)(struct console *con, unsigned long *flags); + + /** + * @device_unlock: + * + * NBCON callback to finish synchronization with driver code. + * + * It is the counterpart to device_lock(). + * + * This callback is always called from task context. It must + * appropriately re-enable migration (depending on how device_lock() + * disabled migration). + * + * The flags argument is the value of the same variable that was + * passed to device_lock(). + */ + void (*device_unlock)(struct console *con, unsigned long flags); + + atomic_t __private nbcon_state; + atomic_long_t __private nbcon_seq; + struct nbcon_context __private nbcon_device_ctxt; + atomic_long_t __private nbcon_prev_seq; + + struct printk_buffers *pbufs; + struct task_struct *kthread; + struct rcuwait rcuwait; + struct irq_work irq_work; }; #ifdef CONFIG_LOCKDEP @@ -234,28 +494,34 @@ extern void console_list_unlock(void) __releases(console_mutex); extern struct hlist_head console_list; /** - * console_srcu_read_flags - Locklessly read the console flags + * console_srcu_read_flags - Locklessly read flags of a possibly registered + * console * @con: struct console pointer of console to read flags from * - * This function provides the necessary READ_ONCE() and data_race() - * notation for locklessly reading the console flags. The READ_ONCE() - * in this function matches the WRITE_ONCE() when @flags are modified - * for registered consoles with console_srcu_write_flags(). + * Locklessly reading @con->flags provides a consistent read value because + * there is at most one CPU modifying @con->flags and that CPU is using only + * read-modify-write operations to do so. + * + * Requires console_srcu_read_lock to be held, which implies that @con might + * be a registered console. The purpose of holding console_srcu_read_lock is + * to guarantee that the console state is valid (CON_SUSPENDED/CON_ENABLED) + * and that no exit/cleanup routines will run if the console is currently + * undergoing unregistration. * - * Only use this function to read console flags when locklessly - * iterating the console list via srcu. + * If the caller is holding the console_list_lock or it is _certain_ that + * @con is not and will not become registered, the caller may read + * @con->flags directly instead. * * Context: Any context. + * Return: The current value of the @con->flags field. */ static inline short console_srcu_read_flags(const struct console *con) { WARN_ON_ONCE(!console_srcu_read_lock_is_held()); /* - * Locklessly reading console->flags provides a consistent - * read value because there is at most one CPU modifying - * console->flags and that CPU is using only read-modify-write - * operations to do so. + * The READ_ONCE() matches the WRITE_ONCE() when @flags are modified + * for registered consoles with console_srcu_write_flags(). */ return data_race(READ_ONCE(con->flags)); } @@ -324,7 +590,7 @@ static inline bool console_is_registered(const struct console *con) * for_each_console() - Iterator over registered consoles * @con: struct console pointer used as loop cursor * - * The console list and the console->flags are immutable while iterating. + * The console list and the &console.flags are immutable while iterating. * * Requires console_list_lock to be held. */ @@ -332,6 +598,22 @@ 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 void nbcon_cpu_emergency_enter(void); +extern void nbcon_cpu_emergency_exit(void); +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); +extern void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt); +#else +static inline void nbcon_cpu_emergency_enter(void) { } +static inline void nbcon_cpu_emergency_exit(void) { } +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; } +static inline void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { } +#endif + extern int console_set_on_cmdline; extern struct console *early_console; @@ -340,7 +622,7 @@ 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 *); @@ -384,12 +666,6 @@ void vcs_remove_sysfs(int index); */ extern atomic_t ignore_console_lock_warning; -/* VESA Blanking Levels */ -#define VESA_NO_BLANKING 0 -#define VESA_VSYNC_SUSPEND 1 -#define VESA_HSYNC_SUSPEND 2 -#define VESA_POWERDOWN 3 - extern void console_init(void); /* For deferred console takeover */ |