minix/drivers/tty/pty.c
David van Moolenbroek 20173cb5d7 TTY: fix for PTY open/close logic
Opening and closing the master side of a pseudo terminal without
opening the slave side would result in the pseudo terminal becoming
permanently unavailable.  In addition, reopening the slave side
would be possible but not allow for I/O.  Finally, attempting to
open an in-use master would wipe its I/O state.  These issues have
been resolved.

Change-Id: I9235e3d9aba321803f9280b86b6b5e3646ad5ef3
2014-02-18 11:25:03 +01:00

594 lines
16 KiB
C

/* pty.c - pseudo terminal driver Author: Kees J. Bot
* 30 Dec 1995
* PTYs can be seen as a bidirectional pipe with TTY
* input and output processing. For example a simple rlogin session:
*
* keyboard -> rlogin -> in.rld -> /dev/ptypX -> /dev/ttypX -> shell
* shell -> /dev/ttypX -> /dev/ptypX -> in.rld -> rlogin -> screen
*
* This file takes care of copying data between the tty/pty device pairs and
* the open/read/write/close calls on the pty devices. The TTY task takes
* care of the input and output processing (interrupt, backspace, raw I/O,
* etc.) using the pty_read() and pty_write() functions as the "keyboard" and
* "screen" functions of the ttypX devices.
* Be careful when reading this code, the terms "reading" and "writing" are
* used both for the tty and the pty end of the pseudo tty. Writes to one
* end are to be read at the other end and vice-versa.
*/
#include <minix/drivers.h>
#include <assert.h>
#include <termios.h>
#include <signal.h>
#include <minix/com.h>
#include <minix/callnr.h>
#include <sys/select.h>
#include "tty.h"
#if NR_PTYS > 0
/* PTY bookkeeping structure, one per pty/tty pair. */
typedef struct pty {
tty_t *tty; /* associated TTY structure */
char state; /* flags: busy, closed, ... */
/* Read call on /dev/ptypX. */
int rdcaller; /* process making the call (usually FS) */
int rdproc; /* process that wants to read from the pty */
cp_grant_id_t rdgrant; /* grant for readers address space */
vir_bytes rdoffset; /* offset in above grant */
int rdleft; /* # bytes yet to be read */
int rdcum; /* # bytes written so far */
/* Write call to /dev/ptypX. */
int wrcaller; /* process making the call (usually FS) */
int wrproc; /* process that wants to write to the pty */
cp_grant_id_t wrgrant; /* grant for writers address space */
vir_bytes wroffset; /* offset in above grant */
int wrleft; /* # bytes yet to be written */
int wrcum; /* # bytes written so far */
/* Output buffer. */
int ocount; /* # characters in the buffer */
char *ohead, *otail; /* head and tail of the circular buffer */
char obuf[2048]; /* buffer for bytes going to the pty reader */
/* select() data. */
int select_ops; /* Which operations do we want to know about? */
int select_proc; /* Who wants to know about it? */
dev_t select_minor; /* sanity check only, can be removed */
} pty_t;
#define TTY_ACTIVE 0x01 /* tty is open/active */
#define PTY_ACTIVE 0x02 /* pty is open/active */
#define TTY_CLOSED 0x04 /* tty side has closed down */
#define PTY_CLOSED 0x08 /* pty side has closed down */
static pty_t pty_table[NR_PTYS]; /* PTY bookkeeping */
static int pty_write(tty_t *tp, int try);
static void pty_echo(tty_t *tp, int c);
static void pty_start(pty_t *pp);
static void pty_finish(pty_t *pp);
static int pty_read(tty_t *tp, int try);
static int pty_close(tty_t *tp, int try);
static int pty_icancel(tty_t *tp, int try);
static int pty_ocancel(tty_t *tp, int try);
static void pty_select(tty_t *tp, message *m);
/*===========================================================================*
* do_pty *
*===========================================================================*/
void do_pty(tty_t *tp, message *m_ptr)
{
/* Perform an open/close/read/write call on a /dev/ptypX device. */
pty_t *pp = tp->tty_priv;
int r;
switch (m_ptr->m_type) {
case DEV_READ_S:
/* Check, store information on the reader, do I/O. */
if (pp->state & TTY_CLOSED) {
r = 0;
break;
}
if (pp->rdleft != 0 || pp->rdcum != 0) {
r = EIO;
break;
}
if (m_ptr->COUNT <= 0) {
r = EINVAL;
break;
}
if (pp->rdgrant != GRANT_INVALID) {
r = ENOBUFS;
break;
}
pp->rdcaller = m_ptr->m_source;
pp->rdproc = m_ptr->USER_ENDPT;
pp->rdgrant = (cp_grant_id_t) m_ptr->IO_GRANT;
pp->rdoffset = 0;
pp->rdleft = m_ptr->COUNT;
pty_start(pp);
handle_events(tp);
if (pp->rdleft == 0) {
pp->rdgrant = GRANT_INVALID;
return; /* already done */
}
if (m_ptr->FLAGS & FLG_OP_NONBLOCK) {
r = pp->rdcum > 0 ? pp->rdcum : EAGAIN;
pp->rdleft = pp->rdcum = 0;
pp->rdgrant = GRANT_INVALID;
} else {
return; /* do suspend */
}
break;
case DEV_WRITE_S:
/* Check, store information on the writer, do I/O. */
if (pp->state & TTY_CLOSED) {
r = EIO;
break;
}
if (pp->wrleft != 0 || pp->wrcum != 0) {
r = EIO;
break;
}
if (m_ptr->COUNT <= 0) {
r = EINVAL;
break;
}
if (pp->wrgrant != GRANT_INVALID) {
r = ENOBUFS;
break;
}
pp->wrcaller = m_ptr->m_source;
pp->wrproc = m_ptr->USER_ENDPT;
pp->wrgrant = (cp_grant_id_t) m_ptr->IO_GRANT;
pp->wroffset = 0;
pp->wrleft = m_ptr->COUNT;
handle_events(tp);
if (pp->wrleft == 0) {
pp->wrgrant = GRANT_INVALID;
return; /* already done */
}
if (m_ptr->FLAGS & FLG_OP_NONBLOCK) {
r = pp->wrcum > 0 ? pp->wrcum : EAGAIN;
pp->wrleft = pp->wrcum = 0;
pp->wrgrant = GRANT_INVALID;
r = EAGAIN;
} else {
return; /* do suspend */
}
break;
case DEV_OPEN:
if (!(pp->state & PTY_ACTIVE)) {
pp->state |= PTY_ACTIVE;
pp->rdcum = 0;
pp->wrcum = 0;
r = OK;
} else {
r = EIO;
}
tty_reply(DEV_OPEN_REPL, m_ptr->m_source, m_ptr->USER_ENDPT,
(cp_grant_id_t) m_ptr->IO_GRANT, r);
return;
case DEV_CLOSE:
if ((pp->state & (TTY_ACTIVE | TTY_CLOSED)) != TTY_ACTIVE) {
pp->state = 0;
} else {
pp->state |= PTY_CLOSED;
sigchar(tp, SIGHUP, 1);
}
tty_reply(DEV_CLOSE_REPL, m_ptr->m_source, m_ptr->USER_ENDPT,
(cp_grant_id_t) m_ptr->IO_GRANT, OK);
return;
case DEV_SELECT:
pty_select(tp, m_ptr);
return;
case CANCEL:
r = EINTR;
if (m_ptr->USER_ENDPT == pp->rdproc) {
/* Cancel a read from a PTY. */
r = pp->rdcum > 0 ? pp->rdcum : EAGAIN;
pp->rdleft = pp->rdcum = 0;
pp->rdgrant = GRANT_INVALID;
}
if (m_ptr->USER_ENDPT == pp->wrproc) {
/* Cancel a write to a PTY. */
r = pp->wrcum > 0 ? pp->wrcum : EAGAIN;
pp->wrleft = pp->wrcum = 0;
pp->wrgrant = GRANT_INVALID;
}
break;
default:
r = EINVAL;
}
tty_reply(DEV_REVIVE, m_ptr->m_source, m_ptr->USER_ENDPT,
(cp_grant_id_t) m_ptr->IO_GRANT, r);
}
/*===========================================================================*
* pty_write *
*===========================================================================*/
static int pty_write(tty_t *tp, int try)
{
/* (*dev_write)() routine for PTYs. Transfer bytes from the writer on
* /dev/ttypX to the output buffer.
*/
pty_t *pp = tp->tty_priv;
int count, ocount, s;
/* PTY closed down? */
if (pp->state & PTY_CLOSED) {
if (try) return 1;
if (tp->tty_outleft > 0) {
tty_reply(DEV_REVIVE, tp->tty_outcaller, tp->tty_outproc,
tp->tty_outgrant, EIO);
tp->tty_outleft = tp->tty_outcum = 0;
tp->tty_outgrant = GRANT_INVALID;
}
return 0;
}
/* While there is something to do. */
for (;;) {
ocount = buflen(pp->obuf) - pp->ocount;
if (try) return (ocount > 0);
count = bufend(pp->obuf) - pp->ohead;
if (count > ocount) count = ocount;
if (count > tp->tty_outleft) count = tp->tty_outleft;
if (count == 0 || tp->tty_inhibited)
break;
/* Copy from user space to the PTY output buffer. */
if (tp->tty_outcaller == KERNEL) {
/* We're trying to print on kernel's behalf */
memcpy(pp->ohead, (void *) tp->tty_outgrant + tp->tty_outoffset,
count);
} else {
if ((s = sys_safecopyfrom(tp->tty_outcaller, tp->tty_outgrant,
tp->tty_outoffset, (vir_bytes) pp->ohead,
count)) != OK) {
break;
}
}
/* Perform output processing on the output buffer. */
out_process(tp, pp->obuf, pp->ohead, bufend(pp->obuf), &count, &ocount);
if (count == 0) break;
/* Assume echoing messed up by output. */
tp->tty_reprint = TRUE;
/* Bookkeeping. */
pp->ocount += ocount;
if ((pp->ohead += ocount) >= bufend(pp->obuf))
pp->ohead -= buflen(pp->obuf);
pty_start(pp);
tp->tty_outoffset += count;
tp->tty_outcum += count;
if ((tp->tty_outleft -= count) == 0) {
/* Output is finished, reply to the writer. */
tty_reply(DEV_REVIVE, tp->tty_outcaller, tp->tty_outproc,
tp->tty_outgrant, tp->tty_outcum);
tp->tty_outcum = 0;
tp->tty_outgrant = GRANT_INVALID;
}
}
pty_finish(pp);
return 1;
}
/*===========================================================================*
* pty_echo *
*===========================================================================*/
static void pty_echo(tty_t *tp, int c)
{
/* Echo one character. (Like pty_write, but only one character, optionally.) */
pty_t *pp = tp->tty_priv;
int count, ocount;
ocount = buflen(pp->obuf) - pp->ocount;
if (ocount == 0) return; /* output buffer full */
count = 1;
*pp->ohead = c; /* add one character */
out_process(tp, pp->obuf, pp->ohead, bufend(pp->obuf), &count, &ocount);
if (count == 0) return;
pp->ocount += ocount;
if ((pp->ohead += ocount) >= bufend(pp->obuf)) pp->ohead -= buflen(pp->obuf);
pty_start(pp);
}
/*===========================================================================*
* pty_start *
*===========================================================================*/
static void pty_start(pty_t *pp)
{
/* Transfer bytes written to the output buffer to the PTY reader. */
int count;
/* While there are things to do. */
for (;;) {
int s;
count = bufend(pp->obuf) - pp->otail;
if (count > pp->ocount) count = pp->ocount;
if (count > pp->rdleft) count = pp->rdleft;
if (count == 0) break;
/* Copy from the output buffer to the readers address space. */
if((s = sys_safecopyto(pp->rdcaller, pp->rdgrant,
pp->rdoffset, (vir_bytes) pp->otail, count)) != OK) {
break;
}
pp->rdoffset += count;
/* Bookkeeping. */
pp->ocount -= count;
if ((pp->otail += count) == bufend(pp->obuf)) pp->otail = pp->obuf;
pp->rdcum += count;
pp->rdleft -= count;
}
}
/*===========================================================================*
* pty_finish *
*===========================================================================*/
static void pty_finish(pty_t *pp)
{
/* Finish the read request of a PTY reader if there is at least one byte
* transferred.
*/
if (pp->rdcum > 0) {
tty_reply(DEV_REVIVE, pp->rdcaller, pp->rdproc, pp->rdgrant,
pp->rdcum);
pp->rdleft = pp->rdcum = 0;
pp->rdgrant = GRANT_INVALID;
}
}
/*===========================================================================*
* pty_read *
*===========================================================================*/
static int pty_read(tty_t *tp, int try)
{
/* Offer bytes from the PTY writer for input on the TTY. (Do it one byte at
* a time, 99% of the writes will be for one byte, so no sense in being smart.)
*/
pty_t *pp = tp->tty_priv;
char c;
if (pp->state & PTY_CLOSED) {
if (try) return 1;
if (tp->tty_inleft > 0) {
tty_reply(DEV_REVIVE, tp->tty_incaller, tp->tty_inproc,
tp->tty_ingrant, tp->tty_incum);
tp->tty_inleft = tp->tty_incum = 0;
tp->tty_ingrant = GRANT_INVALID;
}
return 1;
}
if (try) {
if (pp->wrleft > 0)
return 1;
return 0;
}
while (pp->wrleft > 0) {
int s;
/* Transfer one character to 'c'. */
if ((s = sys_safecopyfrom(pp->wrcaller, pp->wrgrant, pp->wroffset,
(vir_bytes) &c, 1)) != OK) {
printf("pty: safecopy failed (error %d)\n", s);
break;
}
pp->wroffset++;
/* Input processing. */
if (in_process(tp, &c, 1, -1) == 0) break;
/* PTY writer bookkeeping. */
pp->wrcum++;
if (--pp->wrleft == 0) {
tty_reply(DEV_REVIVE, pp->wrcaller, pp->wrproc, pp->wrgrant,
pp->wrcum);
pp->wrcum = 0;
pp->wrgrant = GRANT_INVALID;
}
}
return 0;
}
/*===========================================================================*
* pty_open *
*===========================================================================*/
static int pty_open(tty_t *tp, int UNUSED(try))
{
/* The tty side has been opened. */
pty_t *pp = tp->tty_priv;
/* TTY_ACTIVE may already be set, which would indicate that the slave is
* reopened after being fully closed while the master is still open. In that
* case TTY_CLOSED will also be set, so clear that one.
*/
pp->state |= TTY_ACTIVE;
pp->state &= ~TTY_CLOSED;
return 0;
}
/*===========================================================================*
* pty_close *
*===========================================================================*/
static int pty_close(tty_t *tp, int UNUSED(try))
{
/* The tty side has closed, so shut down the pty side. */
pty_t *pp = tp->tty_priv;
if (!(pp->state & PTY_ACTIVE)) return 0;
if (pp->rdleft > 0) {
tty_reply(DEV_REVIVE, pp->rdcaller, pp->rdproc, pp->rdgrant,
pp->rdcum);
pp->rdleft = pp->rdcum = 0;
pp->rdgrant = GRANT_INVALID;
}
if (pp->wrleft > 0) {
tty_reply(DEV_REVIVE, pp->wrcaller, pp->wrproc, pp->wrgrant,
pp->wrcum);
pp->wrcum = 0;
pp->wrgrant = GRANT_INVALID;
}
if (pp->state & PTY_CLOSED) pp->state = 0;
else pp->state |= TTY_CLOSED;
return 0;
}
/*===========================================================================*
* pty_icancel *
*===========================================================================*/
static int pty_icancel(tty_t *tp, int UNUSED(try))
{
/* Discard waiting input. */
pty_t *pp = tp->tty_priv;
if (pp->wrleft > 0) {
tty_reply(DEV_REVIVE, pp->wrcaller, pp->wrproc, pp->wrgrant,
pp->wrcum + pp->wrleft);
pp->wrcum = pp->wrleft = 0;
pp->wrgrant = GRANT_INVALID;
}
return 0;
}
/*===========================================================================*
* pty_ocancel *
*===========================================================================*/
static int pty_ocancel(tty_t *tp, int UNUSED(try))
{
/* Drain the output buffer. */
pty_t *pp = tp->tty_priv;
pp->ocount = 0;
pp->otail = pp->ohead;
return 0;
}
/*===========================================================================*
* pty_init *
*===========================================================================*/
void pty_init(tty_t *tp)
{
pty_t *pp;
int line;
/* Associate PTY and TTY structures. */
line = tp - &tty_table[NR_CONS + NR_RS_LINES];
pp = tp->tty_priv = &pty_table[line];
pp->tty = tp;
pp->select_ops = 0;
pp->rdgrant = GRANT_INVALID;
pp->wrgrant = GRANT_INVALID;
/* Set up output queue. */
pp->ohead = pp->otail = pp->obuf;
/* Fill in TTY function hooks. */
tp->tty_devread = pty_read;
tp->tty_devwrite = pty_write;
tp->tty_echo = pty_echo;
tp->tty_icancel = pty_icancel;
tp->tty_ocancel = pty_ocancel;
tp->tty_open = pty_open;
tp->tty_close = pty_close;
tp->tty_select_ops = 0;
}
/*===========================================================================*
* select_try_pty *
*===========================================================================*/
static int select_try_pty(tty_t *tp, int ops)
{
pty_t *pp = tp->tty_priv;
int r = 0;
if (ops & SEL_WR) {
/* Write won't block on error. */
if (pp->state & TTY_CLOSED) r |= SEL_WR;
else if (pp->wrleft != 0 || pp->wrcum != 0) r |= SEL_WR;
else r |= SEL_WR;
}
if (ops & SEL_RD) {
/* Read won't block on error. */
if (pp->state & TTY_CLOSED) r |= SEL_RD;
else if (pp->rdleft != 0 || pp->rdcum != 0) r |= SEL_RD;
else if (pp->ocount > 0) r |= SEL_RD; /* Actual data. */
}
return r;
}
/*===========================================================================*
* select_retry_pty *
*===========================================================================*/
void select_retry_pty(tty_t *tp)
{
pty_t *pp = tp->tty_priv;
dev_t minor;
int r;
/* See if the pty side of a pty is ready to return a select. */
if (pp->select_ops && (r=select_try_pty(tp, pp->select_ops))) {
minor = PTYPX_MINOR + (int) (pp - pty_table);
assert(minor == pp->select_minor);
select_reply(DEV_SEL_REPL2, pp->select_proc, minor, r);
pp->select_ops &= ~r;
}
}
/*===========================================================================*
* pty_select *
*===========================================================================*/
static void pty_select(tty_t *tp, message *m)
{
pty_t *pp = tp->tty_priv;
int ops, ready_ops = 0, watch;
ops = m->DEV_SEL_OPS & (SEL_RD|SEL_WR|SEL_ERR);
watch = (m->DEV_SEL_OPS & SEL_NOTIFY) ? 1 : 0;
ready_ops = select_try_pty(tp, ops);
if (!ready_ops && ops && watch) {
pp->select_ops |= ops;
pp->select_proc = m->m_source;
pp->select_minor = m->DEV_MINOR;
}
select_reply(DEV_SEL_REPL1, m->m_source, m->DEV_MINOR, ready_ops);
}
#endif /* NR_PTYS > 0 */