// SPDX-License-Identifier: GPL-1.0+/* * n_tty.c --- implements the N_TTY line discipline. * * This code used to be in tty_io.c, but things are getting hairy * enough that it made sense to split things off. (The N_TTY * processing has changed so much that it's hardly recognizable, * anyway...) * * Note that the open routine for N_TTY is guaranteed never to return * an error. This is because Linux will fall back to setting a line * to N_TTY if it can not switch to any other line discipline. * * Written by Theodore Ts'o, Copyright 1994. * * This file also contains code originally written by Linus Torvalds, * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994. * * Reduced memory usage for older ARM systems - Russell King. * * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu> * who actually finally proved there really was a race. * * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to * waiting writing processes-Sapan Bhatia <sapan@corewars.org>. * Also fixed a bug in BLOCKING mode where n_tty_write returns * EAGAIN */ #include <linux/bitmap.h>#include <linux/bitops.h>#include <linux/ctype.h>#include <linux/errno.h>#include <linux/export.h>#include <linux/fcntl.h>#include <linux/file.h>#include <linux/jiffies.h>#include <linux/math.h>#include <linux/poll.h>#include <linux/ratelimit.h>#include <linux/sched.h>#include <linux/signal.h>#include <linux/slab.h>#include <linux/string.h>#include <linux/tty.h>#include <linux/types.h>#include <linux/uaccess.h>#include <linux/vmalloc.h> #include "tty.h" /* * Until this number of characters is queued in the xmit buffer, select will * return "we have room for writes". */#define WAKEUP_CHARS 256 #define N_TTY_BUF_SIZE 4096 /* * This defines the low- and high-watermarks for throttling and * unthrottling the TTY driver. These watermarks are used for * controlling the space in the read buffer. */#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */#define TTY_THRESHOLD_UNTHROTTLE 128 /* * Special byte codes used in the echo buffer to represent operations * or special handling of characters. Bytes in the echo buffer that * are not part of such special blocks are treated as normal character * codes. */#define ECHO_OP_START 0xff#define ECHO_OP_MOVE_BACK_COL 0x80#define ECHO_OP_SET_CANON_COL 0x81#define ECHO_OP_ERASE_TAB 0x82 #define ECHO_COMMIT_WATERMARK 256#define ECHO_BLOCK 256#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32) struct n_tty_data { /* producer-published */ size_t read_head; size_t commit_head; size_t canon_head; size_t echo_head; size_t echo_commit; size_t echo_mark; DECLARE_BITMAP(char_map, 256); /* private to n_tty_receive_overrun (single-threaded) */ unsigned long overrun_time; unsigned int num_overrun; /* non-atomic */ bool no_room; /* must hold exclusive termios_rwsem to reset these */ unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1; unsigned char push:1; /* shared by producer and consumer */ u8 read_buf[N_TTY_BUF_SIZE]; DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE); u8 echo_buf[N_TTY_BUF_SIZE]; /* consumer-published */ size_t read_tail; size_t line_start; /* # of chars looked ahead (to find software flow control chars) */ size_t lookahead_count; /* protected by output lock */ unsigned int column; unsigned int canon_column; size_t echo_tail; struct mutex atomic_read_lock; struct mutex output_lock;}; #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1)) static inline size_t read_cnt(struct n_tty_data *ldata){ return ldata->read_head - ldata->read_tail;} static inline u8 read_buf(struct n_tty_data *ldata, size_t i){ return ldata->read_buf[MASK(i)];} static inline u8 *read_buf_addr(struct n_tty_data *ldata, size_t i){ return &ldata->read_buf[MASK(i)];} static inline u8 echo_buf(struct n_tty_data *ldata, size_t i){ smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */ return ldata->echo_buf[MASK(i)];} static inline u8 *echo_buf_addr(struct n_tty_data *ldata, size_t i){ return &ldata->echo_buf[MASK(i)];} /* If we are not echoing the data, perhaps this is a secret so erase it */static void zero_buffer(const struct tty_struct *tty, u8 *buffer, size_t size){ if (L_ICANON(tty) && !L_ECHO(tty)) memset(buffer, 0, size);} static void tty_copy(const struct tty_struct *tty, void *to, size_t tail, size_t n){ struct n_tty_data *ldata = tty->disc_data; size_t size = N_TTY_BUF_SIZE - tail; void *from = read_buf_addr(ldata, tail); if (n > size) { tty_audit_add_data(tty, from, size); memcpy(to, from, size); zero_buffer(tty, from, size); to += size; n -= size; from = ldata->read_buf; } tty_audit_add_data(tty, from, n); memcpy(to, from, n); zero_buffer(tty, from, n);} /** * n_tty_kick_worker - start input worker (if required) * @tty: terminal * * Re-schedules the flip buffer work if it may have stopped. * * Locking: * * Caller holds exclusive %termios_rwsem, or * * n_tty_read()/consumer path: * holds non-exclusive %termios_rwsem */static void n_tty_kick_worker(const struct tty_struct *tty){ struct n_tty_data *ldata = tty->disc_data; /* Did the input worker stop? Restart it */ if (unlikely(READ_ONCE(ldata->no_room))) { WRITE_ONCE(ldata->no_room, 0); WARN_RATELIMIT(tty->port->itty == NULL, "scheduling with invalid itty\n"); /* see if ldisc has been killed - if so, this means that * even though the ldisc has been halted and ->buf.work * cancelled, ->buf.work is about to be rescheduled */ WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags), "scheduling buffer work for halted ldisc\n"); tty_buffer_restart_work(tty->port); }} static ssize_t chars_in_buffer(const struct tty_struct *tty){ const struct n_tty_data *ldata = tty->disc_data; size_t head = ldata->icanon ? ldata->canon_head : ldata->commit_head; return head - ldata->read_tail;} /** * n_tty_write_wakeup - asynchronous I/O notifier * @tty: tty device * * Required for the ptys, serial driver etc. since processes that attach * themselves to the master and rely on ASYNC IO must be woken up. */static void n_tty_write_wakeup(struct tty_struct *tty){ clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); kill_fasync(&tty->fasync, SIGIO, POLL_OUT);} static void n_tty_check_throttle(struct tty_struct *tty){ struct n_tty_data *ldata = tty->disc_data; /* * Check the remaining room for the input canonicalization * mode. We don't want to throttle the driver if we're in * canonical mode and don't have a newline yet! */ if (ldata->icanon && ldata->canon_head == ldata->read_tail) return; do { tty_set_flow_change(tty, TTY_THROTTLE_SAFE); if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE) break; } while (!tty_throttle_safe(tty)); __tty_set_flow_change(tty, 0);} static void n_tty_check_unthrottle(struct tty_struct *tty){ if (tty->driver->type == TTY_DRIVER_TYPE_PTY) { if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) return; n_tty_kick_worker(tty); tty_wakeup(tty->link); return; } /* If there is enough space in the read buffer now, let the * low-level driver know. We use chars_in_buffer() to * check the buffer, as it now knows about canonical mode. * Otherwise, if the driver is throttled and the line is * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode, * we won't get any more characters. */ do { tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE); if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) break; n_tty_kick_worker(tty); } while (!tty_unthrottle_safe(tty)); __tty_set_flow_change(tty, 0);} /** * put_tty_queue - add character to tty * @c: character * @ldata: n_tty data * * Add a character to the tty read_buf queue. * * Locking: * * n_tty_receive_buf()/producer path: * caller holds non-exclusive %termios_rwsem */static inline void put_tty_queue(u8 c, struct n_tty_data *ldata){ *read_buf_addr(ldata, ldata->read_head) = c; ldata->read_head++;} /** * reset_buffer_flags - reset buffer state * @ldata: line disc data to reset * * Reset the read buffer counters and clear the flags. Called from * n_tty_open() and n_tty_flush_buffer(). * * Locking: * * caller holds exclusive %termios_rwsem, or * * (locking is not required) */static void reset_buffer_flags(struct n_tty_data *ldata){ ldata->read_head = ldata->canon_head = ldata->read_tail = 0; ldata->commit_head = 0; ldata->line_start = 0; ldata->erasing = 0; bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE); ldata->push = 0; ldata->lookahead_count = 0;} static void n_tty_packet_mode_flush(struct tty_struct *tty){ if (tty->link->ctrl.packet) { scoped_guard(spinlock_irqsave, &tty->ctrl.lock) tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD; wake_up_interruptible(&tty->link->read_wait); }} /** * n_tty_flush_buffer - clean input queue * @tty: terminal device * * Flush the input buffer. Called when the tty layer wants the buffer flushed * (eg at hangup) or when the %N_TTY line discipline internally has to clean * the pending queue (for example some signals). * * Holds %termios_rwsem to exclude producer/consumer while buffer indices are * reset. * * Locking: %ctrl.lock, exclusive %termios_rwsem */static void n_tty_flush_buffer(struct tty_struct *tty){ guard(rwsem_write)(&tty->termios_rwsem); reset_buffer_flags(tty->disc_data); n_tty_kick_worker(tty); if (tty->link) n_tty_packet_mode_flush(tty);} /** * is_utf8_continuation - utf8 multibyte check * @c: byte to check * * Returns: true if the utf8 character @c is a multibyte continuation * character. We use this to correctly compute the on-screen size of the * character when printing. */static inline int is_utf8_continuation(u8 c){ return (c & 0xc0) == 0x80;} /** * is_continuation - multibyte check * @c: byte to check * @tty: terminal device * * Returns: true if the utf8 character @c is a multibyte continuation character * and the terminal is in unicode mode. */static inline int is_continuation(u8 c, const struct tty_struct *tty){ return I_IUTF8(tty) && is_utf8_continuation(c);} /** * do_output_char - output one character * @c: character (or partial unicode symbol) * @tty: terminal device * @space: space available in tty driver write buffer * * This is a helper function that handles one output character (including * special characters like TAB, CR, LF, etc.), doing OPOST processing and * putting the results in the tty driver's write buffer. * * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY. * They simply aren't relevant in the world today. If you ever need them, add * them here. * * Returns: the number of bytes of buffer space used or -1 if no space left. * * Locking: should be called under the %output_lock to protect the column state * and space left in the buffer. */static int do_output_char(u8 c, struct tty_struct *tty, int space){ struct n_tty_data *ldata = tty->disc_data; int spaces; if (!space) return -1; switch (c) { case '\n': if (O_ONLRET(tty)) ldata->column = 0; if (O_ONLCR(tty)) { if (space < 2) return -1; ldata->canon_column = ldata->column = 0; tty->ops->write(tty, "\r\n", 2); return 2; } ldata->canon_column = ldata->column; break; case '\r': if (O_ONOCR(tty) && ldata->column == 0) return 0; if (O_OCRNL(tty)) { c = '\n'; if (O_ONLRET(tty)) ldata->canon_column = ldata->column = 0; break; } ldata->canon_column = ldata->column = 0; break; case '\t': spaces = 8 - (ldata->column & 7); if (O_TABDLY(tty) == XTABS) { if (space < spaces) return -1; ldata->column += spaces; tty->ops->write(tty, " ", spaces); return spaces; } ldata->column += spaces; break; case '\b': if (ldata->column > 0) ldata->column--; break; default: if (!iscntrl(c)) { if (O_OLCUC(tty)) c = toupper(c); if (!is_continuation(c, tty)) ldata->column++; } break; } tty_put_char(tty, c); return 1;} /** * process_output - output post processor * @c: character (or partial unicode symbol) * @tty: terminal device * * Output one character with OPOST processing. * * Returns: -1 when the output device is full and the character must be * retried. * * Locking: %output_lock to protect column state and space left (also, this is *called from n_tty_write() under the tty layer write lock). */static int process_output(u8 c, struct tty_struct *tty){ struct n_tty_data *ldata = tty->disc_data; guard(mutex)(&ldata->output_lock); if (do_output_char(c, tty, tty_write_room(tty)) < 0) return -1; return 0;} /** * process_output_block - block post processor * @tty: terminal device * @buf: character buffer * @nr: number of bytes to output * * Output a block of characters with OPOST processing. * * This path is used to speed up block console writes, among other things when * processing blocks of output data. It handles only the simple cases normally * found and helps to generate blocks of symbols for the console driver and * thus improve performance. *Lines 1–500 of 2535. Load more
// SPDX-License-Identifier: GPL-1.0+ /* * n_tty.c --- implements the N_TTY line discipline. * * This code used to be in tty_io.c, but things are getting hairy * enough that it made sense to split things off. (The N_TTY * processing has changed so much that it's hardly recognizable, * anyway...) * * Note that the open routine for N_TTY is guaranteed never to return * an error. This is because Linux will fall back to setting a line * to N_TTY if it can not switch to any other line discipline. * * Written by Theodore Ts'o, Copyright 1994. * * This file also contains code originally written by Linus Torvalds, * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994. * * Reduced memory usage for older ARM systems - Russell King. * * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu> * who actually finally proved there really was a race. * * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to * waiting writing processes-Sapan Bhatia <sapan@corewars.org>. * Also fixed a bug in BLOCKING mode where n_tty_write returns * EAGAIN */ #include <linux/bitmap.h> #include <linux/bitops.h> #include <linux/ctype.h> #include <linux/errno.h> #include <linux/export.h> #include <linux/fcntl.h> #include <linux/file.h> #include <linux/jiffies.h> #include <linux/math.h> #include <linux/poll.h> #include <linux/ratelimit.h> #include <linux/sched.h> #include <linux/signal.h> #include <linux/slab.h> #include <linux/string.h> #include <linux/tty.h> #include <linux/types.h> #include <linux/uaccess.h> #include <linux/vmalloc.h> #include "tty.h" /* * Until this number of characters is queued in the xmit buffer, select will * return "we have room for writes". */ #define WAKEUP_CHARS 256 #define N_TTY_BUF_SIZE 4096 /* * This defines the low- and high-watermarks for throttling and * unthrottling the TTY driver. These watermarks are used for * controlling the space in the read buffer. */ #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */ #define TTY_THRESHOLD_UNTHROTTLE 128 /* * Special byte codes used in the echo buffer to represent operations * or special handling of characters. Bytes in the echo buffer that * are not part of such special blocks are treated as normal character * codes. */ #define ECHO_OP_START 0xff #define ECHO_OP_MOVE_BACK_COL 0x80 #define ECHO_OP_SET_CANON_COL 0x81 #define ECHO_OP_ERASE_TAB 0x82 #define ECHO_COMMIT_WATERMARK 256 #define ECHO_BLOCK 256 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32) struct n_tty_data { /* producer-published */ size_t read_head; size_t commit_head; size_t canon_head; size_t echo_head; size_t echo_commit; size_t echo_mark; DECLARE_BITMAP(char_map, 256); /* private to n_tty_receive_overrun (single-threaded) */ unsigned long overrun_time; unsigned int num_overrun; /* non-atomic */ bool no_room; /* must hold exclusive termios_rwsem to reset these */ unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1; unsigned char push:1; /* shared by producer and consumer */ u8 read_buf[N_TTY_BUF_SIZE]; DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE); u8 echo_buf[N_TTY_BUF_SIZE]; /* consumer-published */ size_t read_tail; size_t line_start; /* # of chars looked ahead (to find software flow control chars) */ size_t lookahead_count; /* protected by output lock */ unsigned int column; unsigned int canon_column; size_t echo_tail; struct mutex atomic_read_lock; struct mutex output_lock; }; #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1)) static inline size_t read_cnt(struct n_tty_data *ldata) { return ldata->read_head - ldata->read_tail; } static inline u8 read_buf(struct n_tty_data *ldata, size_t i) { return ldata->read_buf[MASK(i)]; } static inline u8 *read_buf_addr(struct n_tty_data *ldata, size_t i) { return &ldata->read_buf[MASK(i)]; } static inline u8 echo_buf(struct n_tty_data *ldata, size_t i) { smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */ return ldata->echo_buf[MASK(i)]; } static inline u8 *echo_buf_addr(struct n_tty_data *ldata, size_t i) { return &ldata->echo_buf[MASK(i)]; } /* If we are not echoing the data, perhaps this is a secret so erase it */ static void zero_buffer(const struct tty_struct *tty, u8 *buffer, size_t size) { if (L_ICANON(tty) && !L_ECHO(tty)) memset(buffer, 0, size); } static void tty_copy(const struct tty_struct *tty, void *to, size_t tail, size_t n) { struct n_tty_data *ldata = tty->disc_data; size_t size = N_TTY_BUF_SIZE - tail; void *from = read_buf_addr(ldata, tail); if (n > size) { tty_audit_add_data(tty, from, size); memcpy(to, from, size); zero_buffer(tty, from, size); to += size; n -= size; from = ldata->read_buf; } tty_audit_add_data(tty, from, n); memcpy(to, from, n); zero_buffer(tty, from, n); } /** * n_tty_kick_worker - start input worker (if required) * @tty: terminal * * Re-schedules the flip buffer work if it may have stopped. * * Locking: * * Caller holds exclusive %termios_rwsem, or * * n_tty_read()/consumer path: * holds non-exclusive %termios_rwsem */ static void n_tty_kick_worker(const struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; /* Did the input worker stop? Restart it */ if (unlikely(READ_ONCE(ldata->no_room))) { WRITE_ONCE(ldata->no_room, 0); WARN_RATELIMIT(tty->port->itty == NULL, "scheduling with invalid itty\n"); /* see if ldisc has been killed - if so, this means that * even though the ldisc has been halted and ->buf.work * cancelled, ->buf.work is about to be rescheduled */ WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags), "scheduling buffer work for halted ldisc\n"); tty_buffer_restart_work(tty->port); } } static ssize_t chars_in_buffer(const struct tty_struct *tty) { const struct n_tty_data *ldata = tty->disc_data; size_t head = ldata->icanon ? ldata->canon_head : ldata->commit_head; return head - ldata->read_tail; } /** * n_tty_write_wakeup - asynchronous I/O notifier * @tty: tty device * * Required for the ptys, serial driver etc. since processes that attach * themselves to the master and rely on ASYNC IO must be woken up. */ static void n_tty_write_wakeup(struct tty_struct *tty) { clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); kill_fasync(&tty->fasync, SIGIO, POLL_OUT); } static void n_tty_check_throttle(struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; /* * Check the remaining room for the input canonicalization * mode. We don't want to throttle the driver if we're in * canonical mode and don't have a newline yet! */ if (ldata->icanon && ldata->canon_head == ldata->read_tail) return; do { tty_set_flow_change(tty, TTY_THROTTLE_SAFE); if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE) break; } while (!tty_throttle_safe(tty)); __tty_set_flow_change(tty, 0); } static void n_tty_check_unthrottle(struct tty_struct *tty) { if (tty->driver->type == TTY_DRIVER_TYPE_PTY) { if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) return; n_tty_kick_worker(tty); tty_wakeup(tty->link); return; } /* If there is enough space in the read buffer now, let the * low-level driver know. We use chars_in_buffer() to * check the buffer, as it now knows about canonical mode. * Otherwise, if the driver is throttled and the line is * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode, * we won't get any more characters. */ do { tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE); if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) break; n_tty_kick_worker(tty); } while (!tty_unthrottle_safe(tty)); __tty_set_flow_change(tty, 0); } /** * put_tty_queue - add character to tty * @c: character * @ldata: n_tty data * * Add a character to the tty read_buf queue. * * Locking: * * n_tty_receive_buf()/producer path: * caller holds non-exclusive %termios_rwsem */ static inline void put_tty_queue(u8 c, struct n_tty_data *ldata) { *read_buf_addr(ldata, ldata->read_head) = c; ldata->read_head++; } /** * reset_buffer_flags - reset buffer state * @ldata: line disc data to reset * * Reset the read buffer counters and clear the flags. Called from * n_tty_open() and n_tty_flush_buffer(). * * Locking: * * caller holds exclusive %termios_rwsem, or * * (locking is not required) */ static void reset_buffer_flags(struct n_tty_data *ldata) { ldata->read_head = ldata->canon_head = ldata->read_tail = 0; ldata->commit_head = 0; ldata->line_start = 0; ldata->erasing = 0; bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE); ldata->push = 0; ldata->lookahead_count = 0; } static void n_tty_packet_mode_flush(struct tty_struct *tty) { if (tty->link->ctrl.packet) { scoped_guard(spinlock_irqsave, &tty->ctrl.lock) tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD; wake_up_interruptible(&tty->link->read_wait); } } /** * n_tty_flush_buffer - clean input queue * @tty: terminal device * * Flush the input buffer. Called when the tty layer wants the buffer flushed * (eg at hangup) or when the %N_TTY line discipline internally has to clean * the pending queue (for example some signals). * * Holds %termios_rwsem to exclude producer/consumer while buffer indices are * reset. * * Locking: %ctrl.lock, exclusive %termios_rwsem */ static void n_tty_flush_buffer(struct tty_struct *tty) { guard(rwsem_write)(&tty->termios_rwsem); reset_buffer_flags(tty->disc_data); n_tty_kick_worker(tty); if (tty->link) n_tty_packet_mode_flush(tty); } /** * is_utf8_continuation - utf8 multibyte check * @c: byte to check * * Returns: true if the utf8 character @c is a multibyte continuation * character. We use this to correctly compute the on-screen size of the * character when printing. */ static inline int is_utf8_continuation(u8 c) { return (c & 0xc0) == 0x80; } /** * is_continuation - multibyte check * @c: byte to check * @tty: terminal device * * Returns: true if the utf8 character @c is a multibyte continuation character * and the terminal is in unicode mode. */ static inline int is_continuation(u8 c, const struct tty_struct *tty) { return I_IUTF8(tty) && is_utf8_continuation(c); } /** * do_output_char - output one character * @c: character (or partial unicode symbol) * @tty: terminal device * @space: space available in tty driver write buffer * * This is a helper function that handles one output character (including * special characters like TAB, CR, LF, etc.), doing OPOST processing and * putting the results in the tty driver's write buffer. * * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY. * They simply aren't relevant in the world today. If you ever need them, add * them here. * * Returns: the number of bytes of buffer space used or -1 if no space left. * * Locking: should be called under the %output_lock to protect the column state * and space left in the buffer. */ static int do_output_char(u8 c, struct tty_struct *tty, int space) { struct n_tty_data *ldata = tty->disc_data; int spaces; if (!space) return -1; switch (c) { case '\n': if (O_ONLRET(tty)) ldata->column = 0; if (O_ONLCR(tty)) { if (space < 2) return -1; ldata->canon_column = ldata->column = 0; tty->ops->write(tty, "\r\n", 2); return 2; } ldata->canon_column = ldata->column; break; case '\r': if (O_ONOCR(tty) && ldata->column == 0) return 0; if (O_OCRNL(tty)) { c = '\n'; if (O_ONLRET(tty)) ldata->canon_column = ldata->column = 0; break; } ldata->canon_column = ldata->column = 0; break; case '\t': spaces = 8 - (ldata->column & 7); if (O_TABDLY(tty) == XTABS) { if (space < spaces) return -1; ldata->column += spaces; tty->ops->write(tty, " ", spaces); return spaces; } ldata->column += spaces; break; case '\b': if (ldata->column > 0) ldata->column--; break; default: if (!iscntrl(c)) { if (O_OLCUC(tty)) c = toupper(c); if (!is_continuation(c, tty)) ldata->column++; } break; } tty_put_char(tty, c); return 1; } /** * process_output - output post processor * @c: character (or partial unicode symbol) * @tty: terminal device * * Output one character with OPOST processing. * * Returns: -1 when the output device is full and the character must be * retried. * * Locking: %output_lock to protect column state and space left (also, this is *called from n_tty_write() under the tty layer write lock). */ static int process_output(u8 c, struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; guard(mutex)(&ldata->output_lock); if (do_output_char(c, tty, tty_write_room(tty)) < 0) return -1; return 0; } /** * process_output_block - block post processor * @tty: terminal device * @buf: character buffer * @nr: number of bytes to output * * Output a block of characters with OPOST processing. * * This path is used to speed up block console writes, among other things when * processing blocks of output data. It handles only the simple cases normally * found and helps to generate blocks of symbols for the console driver and * thus improve performance. *