diff options
Diffstat (limited to 'drivers/tty/n_tty.cc')
| -rw-r--r-- | drivers/tty/n_tty.cc | 539 |
1 files changed, 539 insertions, 0 deletions
diff --git a/drivers/tty/n_tty.cc b/drivers/tty/n_tty.cc new file mode 100644 index 0000000..0e312b0 --- /dev/null +++ b/drivers/tty/n_tty.cc @@ -0,0 +1,539 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* Copyright (C) 2026 Richard Qin */ + +/* + * n_tty.cc — N_TTY line discipline + * + * Implements the standard terminal line discipline: + * + * Canonical mode (ICANON): + * Input is buffered until newline/EOF. Backspace (VERASE) and + * kill-line (VKILL) editing are supported. + * + * Raw mode (!ICANON): + * Characters are available immediately (subject to VMIN/VTIME). + * + * Signal generation (ISIG): + * VINTR → SIGINT, VQUIT → SIGQUIT, VSUSP → SIGTSTP + * + * Echo (ECHO): + * Typed characters are reflected to output. + * + * Input processing (c_iflag): + * ICRNL: CR → NL mapping + * INLCR: NL → CR mapping + * IGNCR: ignore CR + * ISTRIP: strip high bit + * + * Output processing (c_oflag): + * OPOST + ONLCR: NL → CR+NL on output + * + * Reference: Linux drivers/tty/n_tty.c + */ + +#include <lume/tty.h> +#include <lume/tty_ioctl.h> +#include <lume/signal.h> +#include <lume/signal_nr.h> +#include <lume/slab.h> +#include <lume/new.h> +#include <lume/errno.h> +#include <lume/task.h> +#include <lume/sched.h> + +#ifndef ENOIOCTLCMD +#define ENOIOCTLCMD 515 +#endif + +extern void schedule(); + +/* ================================================================== */ +/* N_TTY internal data */ +/* ================================================================== */ + +inline constexpr int N_TTY_BUF_SIZE = 4096; + +struct n_tty_data { + char read_buf[N_TTY_BUF_SIZE]; + int read_head; /* producer writes here (from receive_buf) */ + int read_tail; /* consumer reads from here (from read()) */ + int canon_head; /* in canonical mode: end of last complete line */ + bool eof_pending; /* Ctrl+D was pressed */ + Spinlock lock; +}; + +static inline int buf_count(const n_tty_data* d) +{ + return (d->read_head - d->read_tail + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; +} + +static inline int canon_count(const n_tty_data* d) +{ + return (d->canon_head - d->read_tail + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; +} + +static inline bool buf_full(const n_tty_data* d) +{ + return buf_count(d) >= N_TTY_BUF_SIZE - 1; +} + +static inline void buf_put(n_tty_data* d, char c) +{ + d->read_buf[d->read_head] = c; + d->read_head = (d->read_head + 1) % N_TTY_BUF_SIZE; +} + +static inline char buf_get(n_tty_data* d) +{ + char c = d->read_buf[d->read_tail]; + d->read_tail = (d->read_tail + 1) % N_TTY_BUF_SIZE; + return c; +} + +/* ================================================================== */ +/* Output helpers */ +/* ================================================================== */ + +static void tty_put_char(tty_struct* tty, char c) +{ + if (tty->driver && tty->driver->ops && tty->driver->ops->put_char) { + tty->driver->ops->put_char(tty, c); + } +} + +/* + * Process and output a single character, applying c_oflag transformations. + */ +static void tty_output_char(tty_struct* tty, char c) +{ + if (tty->termios_data.c_oflag & OPOST) { + if (c == '\n' && (tty->termios_data.c_oflag & ONLCR)) { + tty_put_char(tty, '\r'); + tty_put_char(tty, '\n'); + return; + } + if (c == '\r' && (tty->termios_data.c_oflag & OCRNL)) { + tty_put_char(tty, '\n'); + return; + } + } + tty_put_char(tty, c); +} + +/* + * Echo a character back to the terminal. + * Control characters are displayed as ^X. + */ +static void echo_char(tty_struct* tty, char c) +{ + if (!(tty->termios_data.c_lflag & ECHO)) + return; + + if (c == '\n') { + tty_output_char(tty, '\n'); + return; + } + + if (c == '\t') { + tty_put_char(tty, '\t'); + return; + } + + /* Control characters: echo as ^X */ + if ((tty->termios_data.c_lflag & ECHOCTL) && c < 0x20 && c != '\t' && c != '\n') { + tty_put_char(tty, '^'); + tty_put_char(tty, c + '@'); + return; + } + + if (c == 0x7f) { /* DEL */ + tty_put_char(tty, '^'); + tty_put_char(tty, '?'); + return; + } + + tty_output_char(tty, c); +} + +/* + * Erase one character visually (backspace + space + backspace). + */ +static void erase_char(tty_struct* tty, char erased) +{ + if (!(tty->termios_data.c_lflag & ECHO)) + return; + + if ((tty->termios_data.c_lflag & ECHOE)) { + /* If the erased char was a control char displayed as ^X, erase 2 cols */ + if ((erased < 0x20 && erased != '\t' && erased != '\n') || erased == 0x7f) { + tty_put_char(tty, '\b'); + tty_put_char(tty, ' '); + tty_put_char(tty, '\b'); + tty_put_char(tty, '\b'); + tty_put_char(tty, ' '); + tty_put_char(tty, '\b'); + } else { + tty_put_char(tty, '\b'); + tty_put_char(tty, ' '); + tty_put_char(tty, '\b'); + } + } +} + +/* ================================================================== */ +/* Input processing — receive_buf (called from IRQ or driver) */ +/* ================================================================== */ + +static void n_tty_receive_buf(tty_struct* tty, const char* cp, int count) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (!d) return; + + const termios& t = tty->termios_data; + + LockGuard guard(d->lock); + + for (int i = 0; i < count; i++) { + char c = cp[i]; + + /* Strip high bit if requested */ + if (t.c_iflag & ISTRIP) + c &= 0x7f; + + /* Input CR/NL processing */ + if (c == '\r') { + if (t.c_iflag & IGNCR) + continue; + if (t.c_iflag & ICRNL) + c = '\n'; + } else if (c == '\n') { + if (t.c_iflag & INLCR) + c = '\r'; + } + + /* Signal generation */ + if (t.c_lflag & ISIG) { + if (c == t.c_cc[VINTR]) { + tty_signal_pgrp(tty, SIGINT); + echo_char(tty, c); + if (!(t.c_lflag & NOFLSH)) { + /* Flush input buffer */ + d->read_head = d->read_tail; + d->canon_head = d->read_tail; + } + continue; + } + if (c == t.c_cc[VQUIT]) { + tty_signal_pgrp(tty, SIGQUIT); + echo_char(tty, c); + if (!(t.c_lflag & NOFLSH)) { + d->read_head = d->read_tail; + d->canon_head = d->read_tail; + } + continue; + } + if (c == t.c_cc[VSUSP]) { + tty_signal_pgrp(tty, SIGTSTP); + echo_char(tty, c); + continue; + } + } + + /* Canonical mode processing */ + if (t.c_lflag & ICANON) { + /* EOF (Ctrl+D) */ + if (c == t.c_cc[VEOF]) { + d->eof_pending = true; + d->canon_head = d->read_head; + tty->read_wait.wake_all(); + continue; + } + + /* ERASE (backspace/DEL) */ + if (c == t.c_cc[VERASE]) { + if (d->read_head != d->canon_head && + d->read_head != d->read_tail) { + int prev = (d->read_head - 1 + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; + char erased = d->read_buf[prev]; + d->read_head = prev; + erase_char(tty, erased); + } + continue; + } + + /* KILL (Ctrl+U — erase entire line) */ + if (c == t.c_cc[VKILL]) { + while (d->read_head != d->canon_head && + d->read_head != d->read_tail) { + int prev = (d->read_head - 1 + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; + char erased = d->read_buf[prev]; + d->read_head = prev; + erase_char(tty, erased); + } + if (t.c_lflag & ECHOK) { + tty_output_char(tty, '\n'); + } + continue; + } + + /* WERASE (Ctrl+W — erase word) */ + if ((t.c_lflag & IEXTEN) && c == t.c_cc[VWERASE]) { + /* Skip trailing spaces */ + while (d->read_head != d->canon_head) { + int prev = (d->read_head - 1 + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; + if (d->read_buf[prev] != ' ' && d->read_buf[prev] != '\t') + break; + erase_char(tty, d->read_buf[prev]); + d->read_head = prev; + } + /* Erase word */ + while (d->read_head != d->canon_head) { + int prev = (d->read_head - 1 + N_TTY_BUF_SIZE) % N_TTY_BUF_SIZE; + if (d->read_buf[prev] == ' ' || d->read_buf[prev] == '\t') + break; + erase_char(tty, d->read_buf[prev]); + d->read_head = prev; + } + continue; + } + + /* REPRINT (Ctrl+R) */ + if ((t.c_lflag & IEXTEN) && c == t.c_cc[VREPRINT]) { + tty_output_char(tty, '\n'); + int pos = d->canon_head; + while (pos != d->read_head) { + echo_char(tty, d->read_buf[pos]); + pos = (pos + 1) % N_TTY_BUF_SIZE; + } + continue; + } + + /* Regular character — buffer it */ + if (!buf_full(d)) { + buf_put(d, c); + echo_char(tty, c); + } + + /* Line complete on newline or EOL */ + if (c == '\n' || c == t.c_cc[VEOL] || + (t.c_cc[VEOL2] && c == t.c_cc[VEOL2])) { + d->canon_head = d->read_head; + tty->read_wait.wake_all(); + } + } else { + /* Raw / non-canonical mode */ + if (!buf_full(d)) { + buf_put(d, c); + echo_char(tty, c); + tty->read_wait.wake_all(); + } + } + } +} + +/* ================================================================== */ +/* N_TTY read — blocking read from the input buffer */ +/* ================================================================== */ + +static int n_tty_read(tty_struct* tty, file* fp, char* buf, uint64 count) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (!d) return -EIO; + + const termios& t = tty->termios_data; + TaskControlBlock* curr = current_task(); + int copied = 0; + + if (t.c_lflag & ICANON) { + /* Canonical mode: block until a complete line is available */ + while (canon_count(d) == 0 && !d->eof_pending) { + if (tty->flags & TTY_IO_ERROR) + return -EIO; + + /* Check for pending signals — return -EINTR so the + * trap return path can deliver them via do_signal() */ + if (signal_pending(curr)) + return -EINTR; + + tty->read_wait.prepare_to_wait(curr, TaskState::Sleeping); + if (canon_count(d) == 0 && !d->eof_pending) + schedule(); + tty->read_wait.finish_wait(curr); + } + + if (d->eof_pending && canon_count(d) == 0) { + d->eof_pending = false; + return 0; /* EOF */ + } + + /* Copy up to one line */ + LockGuard guard(d->lock); + while (copied < static_cast<int>(count) && d->read_tail != d->canon_head) { + buf[copied++] = buf_get(d); + } + } else { + /* Non-canonical mode */ + int vmin = t.c_cc[VMIN]; + /* VTIME not implemented (would need timers) */ + + if (vmin == 0) vmin = 1; + + while (buf_count(d) < vmin) { + if (tty->flags & TTY_IO_ERROR) + return -EIO; + + if (signal_pending(curr)) + return -EINTR; + + tty->read_wait.prepare_to_wait(curr, TaskState::Sleeping); + if (buf_count(d) < vmin) + schedule(); + tty->read_wait.finish_wait(curr); + } + + LockGuard guard(d->lock); + while (copied < static_cast<int>(count) && buf_count(d) > 0) { + buf[copied++] = buf_get(d); + } + } + + return copied; +} + +/* ================================================================== */ +/* N_TTY write — output through the driver with post-processing */ +/* ================================================================== */ + +static int n_tty_write(tty_struct* tty, file* fp, const char* buf, uint64 count) +{ + if (!tty->driver || !tty->driver->ops || !tty->driver->ops->write) + return -EIO; + + /* Apply output processing (OPOST) */ + if (tty->termios_data.c_oflag & OPOST) { + for (uint64 i = 0; i < count; i++) { + tty_output_char(tty, buf[i]); + } + return static_cast<int>(count); + } + + /* Raw output: pass directly to driver */ + return tty->driver->ops->write(tty, buf, static_cast<int>(count)); +} + +/* ================================================================== */ +/* N_TTY ioctl */ +/* ================================================================== */ + +static int n_tty_ioctl(tty_struct* tty, unsigned int cmd, uint64 arg) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + + switch (cmd) { + case FIONREAD: { + int count = buf_count(d); + auto* p = reinterpret_cast<int*>(arg); + *p = count; + return 0; + } + default: + return -ENOIOCTLCMD; + } +} + +/* ================================================================== */ +/* N_TTY open / close */ +/* ================================================================== */ + +static int n_tty_open(tty_struct* tty) +{ + auto* d = new n_tty_data{}; + if (!d) return -ENOMEM; + + d->read_head = 0; + d->read_tail = 0; + d->canon_head = 0; + d->eof_pending = false; + d->lock.init("n_tty"); + + tty->ldisc.data = d; + return 0; +} + +static void n_tty_close(tty_struct* tty) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (d) { + delete d; + tty->ldisc.data = nullptr; + } +} + +static void n_tty_flush_buffer(tty_struct* tty) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (!d) return; + LockGuard guard(d->lock); + d->read_head = 0; + d->read_tail = 0; + d->canon_head = 0; + d->eof_pending = false; +} + +static int n_tty_chars_in_buffer(tty_struct* tty) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (!d) return 0; + return buf_count(d); +} + +/* + * Probe input readiness for poll(). In canonical mode the read syscall + * blocks until a whole line is queued, so we mirror that: POLLIN only + * when canon_count() shows a finalized line (or pending EOF). In raw + * mode any character satisfies VMIN==1 immediately. Without this + * mirror, ppoll() would falsely signal POLLIN on partial canonical + * input, then read() would block — exactly the busy-loop the shell's + * ppoll-then-read pattern is trying to avoid. + */ +bool n_tty_input_ready(tty_struct* tty) +{ + auto* d = static_cast<n_tty_data*>(tty->ldisc.data); + if (!d) return false; + const termios& t = tty->termios_data; + if (t.c_lflag & ICANON) + return canon_count(d) != 0 || d->eof_pending; + int vmin = t.c_cc[VMIN]; + if (vmin == 0) vmin = 1; + return buf_count(d) >= vmin; +} + +static void n_tty_set_termios(tty_struct* /*tty*/, const termios* /*old*/) +{ + /* Nothing special needed for now */ +} + +static void n_tty_hangup(tty_struct* tty) +{ + n_tty_flush_buffer(tty); + tty->read_wait.wake_all(); +} + +/* ================================================================== */ +/* N_TTY ops table */ +/* ================================================================== */ + +const tty_ldisc_ops n_tty_ops = { + .name = "n_tty", + .num = 0, /* N_TTY */ + .open = n_tty_open, + .close = n_tty_close, + .read = n_tty_read, + .write = n_tty_write, + .receive_buf = n_tty_receive_buf, + .ioctl = n_tty_ioctl, + .flush_buffer = n_tty_flush_buffer, + .chars_in_buffer = n_tty_chars_in_buffer, + .set_termios = n_tty_set_termios, + .hangup = n_tty_hangup, +}; |