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Commit af9b897e authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
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[PATCH] tty layer comment the locking assumptions and functions somewhat 

Doesn't fix them but does show up some interesting areas that need review
and fixing.
Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9c275a83
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Showing with 715 additions and 62 deletions
drivers/char/tty_io.c
View file @ af9b897e
......@@ -153,6 +153,15 @@ int tty_ioctl(struct inode * inode, struct file * file,
static int tty_fasync(int fd, struct file * filp, int on);
static void release_mem(struct tty_struct *tty, int idx);
/**
* alloc_tty_struct - allocate a tty object
*
* Return a new empty tty structure. The data fields have not
* been initialized in any way but has been zeroed
*
* Locking: none
* FIXME: use kzalloc
*/
static struct tty_struct *alloc_tty_struct(void)
{
......@@ -166,6 +175,15 @@ static struct tty_struct *alloc_tty_struct(void)
static void tty_buffer_free_all(struct tty_struct *);
/**
* free_tty_struct - free a disused tty
* @tty: tty struct to free
*
* Free the write buffers, tty queue and tty memory itself.
*
* Locking: none. Must be called after tty is definitely unused
*/
static inline void free_tty_struct(struct tty_struct *tty)
{
kfree(tty->write_buf);
......@@ -175,6 +193,17 @@ static inline void free_tty_struct(struct tty_struct *tty)
#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)
/**
* tty_name - return tty naming
* @tty: tty structure
* @buf: buffer for output
*
* Convert a tty structure into a name. The name reflects the kernel
* naming policy and if udev is in use may not reflect user space
*
* Locking: none
*/
char *tty_name(struct tty_struct *tty, char *buf)
{
if (!tty) /* Hmm. NULL pointer. That's fun. */
......@@ -235,6 +264,17 @@ static int check_tty_count(struct tty_struct *tty, const char *routine)
* Tty buffer allocation management
*/
/**
* tty_buffer_free_all - free buffers used by a tty
* @tty: tty to free from
*
* Remove all the buffers pending on a tty whether queued with data
* or in the free ring. Must be called when the tty is no longer in use
*
* Locking: none
*/
static void tty_buffer_free_all(struct tty_struct *tty)
{
struct tty_buffer *thead;
......@@ -347,6 +387,18 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
}
EXPORT_SYMBOL_GPL(tty_buffer_request_room);
/**
* tty_insert_flip_string - Add characters to the tty buffer
* @tty: tty structure
* @chars: characters
* @size: size
*
* Queue a series of bytes to the tty buffering. All the characters
* passed are marked as without error. Returns the number added.
*
* Locking: Called functions may take tty->buf.lock
*/
int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars,
size_t size)
{
......@@ -370,6 +422,20 @@ int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars,
}
EXPORT_SYMBOL(tty_insert_flip_string);
/**
* tty_insert_flip_string_flags - Add characters to the tty buffer
* @tty: tty structure
* @chars: characters
* @flags: flag bytes
* @size: size
*
* Queue a series of bytes to the tty buffering. For each character
* the flags array indicates the status of the character. Returns the
* number added.
*
* Locking: Called functions may take tty->buf.lock
*/
int tty_insert_flip_string_flags(struct tty_struct *tty,
const unsigned char *chars, const char *flags, size_t size)
{
......@@ -394,6 +460,17 @@ int tty_insert_flip_string_flags(struct tty_struct *tty,
}
EXPORT_SYMBOL(tty_insert_flip_string_flags);
/**
* tty_schedule_flip - push characters to ldisc
* @tty: tty to push from
*
* Takes any pending buffers and transfers their ownership to the
* ldisc side of the queue. It then schedules those characters for
* processing by the line discipline.
*
* Locking: Takes tty->buf.lock
*/
void tty_schedule_flip(struct tty_struct *tty)
{
unsigned long flags;
......@@ -405,12 +482,19 @@ void tty_schedule_flip(struct tty_struct *tty)
}
EXPORT_SYMBOL(tty_schedule_flip);
/*
/**
* tty_prepare_flip_string - make room for characters
* @tty: tty
* @chars: return pointer for character write area
* @size: desired size
*
* Prepare a block of space in the buffer for data. Returns the length
* available and buffer pointer to the space which is now allocated and
* accounted for as ready for normal characters. This is used for drivers
* that need their own block copy routines into the buffer. There is no
* guarantee the buffer is a DMA target!
*
* Locking: May call functions taking tty->buf.lock
*/
int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, size_t size)
......@@ -427,12 +511,20 @@ int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, size_
EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
/*
/**
* tty_prepare_flip_string_flags - make room for characters
* @tty: tty
* @chars: return pointer for character write area
* @flags: return pointer for status flag write area
* @size: desired size
*
* Prepare a block of space in the buffer for data. Returns the length
* available and buffer pointer to the space which is now allocated and
* accounted for as ready for characters. This is used for drivers
* that need their own block copy routines into the buffer. There is no
* guarantee the buffer is a DMA target!
*
* Locking: May call functions taking tty->buf.lock
*/
int tty_prepare_flip_string_flags(struct tty_struct *tty, unsigned char **chars, char **flags, size_t size)
......@@ -451,10 +543,16 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
/*
/**
* tty_set_termios_ldisc - set ldisc field
* @tty: tty structure
* @num: line discipline number
*
* This is probably overkill for real world processors but
* they are not on hot paths so a little discipline won't do
* any harm.
*
* Locking: takes termios_sem
*/
static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
......@@ -474,6 +572,19 @@ static DEFINE_SPINLOCK(tty_ldisc_lock);
static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
static struct tty_ldisc tty_ldiscs[NR_LDISCS]; /* line disc dispatch table */
/**
* tty_register_ldisc - install a line discipline
* @disc: ldisc number
* @new_ldisc: pointer to the ldisc object
*
* Installs a new line discipline into the kernel. The discipline
* is set up as unreferenced and then made available to the kernel
* from this point onwards.
*
* Locking:
* takes tty_ldisc_lock to guard against ldisc races
*/
int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
unsigned long flags;
......@@ -493,6 +604,18 @@ int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
}
EXPORT_SYMBOL(tty_register_ldisc);
/**
* tty_unregister_ldisc - unload a line discipline
* @disc: ldisc number
* @new_ldisc: pointer to the ldisc object
*
* Remove a line discipline from the kernel providing it is not
* currently in use.
*
* Locking:
* takes tty_ldisc_lock to guard against ldisc races
*/
int tty_unregister_ldisc(int disc)
{
unsigned long flags;
......@@ -512,6 +635,19 @@ int tty_unregister_ldisc(int disc)
}
EXPORT_SYMBOL(tty_unregister_ldisc);
/**
* tty_ldisc_get - take a reference to an ldisc
* @disc: ldisc number
*
* Takes a reference to a line discipline. Deals with refcounts and
* module locking counts. Returns NULL if the discipline is not available.
* Returns a pointer to the discipline and bumps the ref count if it is
* available
*
* Locking:
* takes tty_ldisc_lock to guard against ldisc races
*/
struct tty_ldisc *tty_ldisc_get(int disc)
{
unsigned long flags;
......@@ -540,6 +676,17 @@ struct tty_ldisc *tty_ldisc_get(int disc)
EXPORT_SYMBOL_GPL(tty_ldisc_get);
/**
* tty_ldisc_put - drop ldisc reference
* @disc: ldisc number
*
* Drop a reference to a line discipline. Manage refcounts and
* module usage counts
*
* Locking:
* takes tty_ldisc_lock to guard against ldisc races
*/
void tty_ldisc_put(int disc)
{
struct tty_ldisc *ld;
......@@ -557,6 +704,19 @@ void tty_ldisc_put(int disc)
EXPORT_SYMBOL_GPL(tty_ldisc_put);
/**
* tty_ldisc_assign - set ldisc on a tty
* @tty: tty to assign
* @ld: line discipline
*
* Install an instance of a line discipline into a tty structure. The
* ldisc must have a reference count above zero to ensure it remains/
* The tty instance refcount starts at zero.
*
* Locking:
* Caller must hold references
*/
static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
{
tty->ldisc = *ld;
......@@ -571,6 +731,8 @@ static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
* the tty ldisc. Return 0 on failure or 1 on success. This is
* used to implement both the waiting and non waiting versions
* of tty_ldisc_ref
*
* Locking: takes tty_ldisc_lock
*/
static int tty_ldisc_try(struct tty_struct *tty)
......@@ -602,6 +764,8 @@ static int tty_ldisc_try(struct tty_struct *tty)
* must also be careful not to hold other locks that will deadlock
* against a discipline change, such as an existing ldisc reference
* (which we check for)
*
* Locking: call functions take tty_ldisc_lock
*/
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
......@@ -622,6 +786,8 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
* Dereference the line discipline for the terminal and take a
* reference to it. If the line discipline is in flux then
* return NULL. Can be called from IRQ and timer functions.
*
* Locking: called functions take tty_ldisc_lock
*/
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
......@@ -639,6 +805,8 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref);
*
* Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
* be called in IRQ context.
*
* Locking: takes tty_ldisc_lock
*/
void tty_ldisc_deref(struct tty_ldisc *ld)
......@@ -683,6 +851,9 @@ static void tty_ldisc_enable(struct tty_struct *tty)
*
* Set the discipline of a tty line. Must be called from a process
* context.
*
* Locking: takes tty_ldisc_lock.
* called functions take termios_sem
*/
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
......@@ -846,9 +1017,17 @@ static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
return retval;
}
/*
* This routine returns a tty driver structure, given a device number
/**
* get_tty_driver - find device of a tty
* @dev_t: device identifier
* @index: returns the index of the tty
*
* This routine returns a tty driver structure, given a device number
* and also passes back the index number.
*
* Locking: caller must hold tty_mutex
*/
static struct tty_driver *get_tty_driver(dev_t device, int *index)
{
struct tty_driver *p;
......@@ -863,11 +1042,17 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
return NULL;
}
/*
* If we try to write to, or set the state of, a terminal and we're
* not in the foreground, send a SIGTTOU. If the signal is blocked or
* ignored, go ahead and perform the operation. (POSIX 7.2)
/**
* tty_check_change - check for POSIX terminal changes
* @tty: tty to check
*
* If we try to write to, or set the state of, a terminal and we're
* not in the foreground, send a SIGTTOU. If the signal is blocked or
* ignored, go ahead and perform the operation. (POSIX 7.2)
*
* Locking: none
*/
int tty_check_change(struct tty_struct * tty)
{
if (current->signal->tty != tty)
......@@ -1005,10 +1190,27 @@ void tty_ldisc_flush(struct tty_struct *tty)
EXPORT_SYMBOL_GPL(tty_ldisc_flush);
/*
* This can be called by the "eventd" kernel thread. That is process synchronous,
* but doesn't hold any locks, so we need to make sure we have the appropriate
* locks for what we're doing..
/**
* do_tty_hangup - actual handler for hangup events
* @data: tty device
*
* This can be called by the "eventd" kernel thread. That is process
* synchronous but doesn't hold any locks, so we need to make sure we
* have the appropriate locks for what we're doing.
*
* The hangup event clears any pending redirections onto the hung up
* device. It ensures future writes will error and it does the needed
* line discipline hangup and signal delivery. The tty object itself
* remains intact.
*
* Locking:
* BKL
* redirect lock for undoing redirection
* file list lock for manipulating list of ttys
* tty_ldisc_lock from called functions
* termios_sem resetting termios data
* tasklist_lock to walk task list for hangup event
*
*/
static void do_tty_hangup(void *data)
{
......@@ -1133,6 +1335,14 @@ static void do_tty_hangup(void *data)
fput(f);
}
/**
* tty_hangup - trigger a hangup event
* @tty: tty to hangup
*
* A carrier loss (virtual or otherwise) has occurred on this like
* schedule a hangup sequence to run after this event.
*/
void tty_hangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
......@@ -1145,6 +1355,15 @@ void tty_hangup(struct tty_struct * tty)
EXPORT_SYMBOL(tty_hangup);
/**
* tty_vhangup - process vhangup
* @tty: tty to hangup
*
* The user has asked via system call for the terminal to be hung up.
* We do this synchronously so that when the syscall returns the process
* is complete. That guarantee is neccessary for security reasons.
*/
void tty_vhangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
......@@ -1156,6 +1375,14 @@ void tty_vhangup(struct tty_struct * tty)
}
EXPORT_SYMBOL(tty_vhangup);
/**
* tty_hung_up_p - was tty hung up
* @filp: file pointer of tty
*
* Return true if the tty has been subject to a vhangup or a carrier
* loss
*/
int tty_hung_up_p(struct file * filp)
{
return (filp->f_op == &hung_up_tty_fops);
......@@ -1163,19 +1390,28 @@ int tty_hung_up_p(struct file * filp)
EXPORT_SYMBOL(tty_hung_up_p);
/*
* This function is typically called only by the session leader, when
* it wants to disassociate itself from its controlling tty.
/**
* disassociate_ctty - disconnect controlling tty
* @on_exit: true if exiting so need to "hang up" the session
*
* It performs the following functions:
* This function is typically called only by the session leader, when
* it wants to disassociate itself from its controlling tty.
*
* It performs the following functions:
* (1) Sends a SIGHUP and SIGCONT to the foreground process group
* (2) Clears the tty from being controlling the session
* (3) Clears the controlling tty for all processes in the
* session group.
*
* The argument on_exit is set to 1 if called when a process is
* exiting; it is 0 if called by the ioctl TIOCNOTTY.
* The argument on_exit is set to 1 if called when a process is
* exiting; it is 0 if called by the ioctl TIOCNOTTY.
*
* Locking: tty_mutex is taken to protect current->signal->tty
* BKL is taken for hysterical raisins
* Tasklist lock is taken (under tty_mutex) to walk process
* lists for the session.
*/
void disassociate_ctty(int on_exit)
{
struct tty_struct *tty;
......@@ -1222,6 +1458,25 @@ void disassociate_ctty(int on_exit)
unlock_kernel();
}
/**
* stop_tty - propogate flow control
* @tty: tty to stop
*
* Perform flow control to the driver. For PTY/TTY pairs we
* must also propogate the TIOCKPKT status. May be called
* on an already stopped device and will not re-call the driver
* method.
*
* This functionality is used by both the line disciplines for
* halting incoming flow and by the driver. It may therefore be
* called from any context, may be under the tty atomic_write_lock
* but not always.
*
* Locking:
* Broken. Relies on BKL which is unsafe here.
*/
void stop_tty(struct tty_struct *tty)
{
if (tty->stopped)
......@@ -1238,6 +1493,19 @@ void stop_tty(struct tty_struct *tty)
EXPORT_SYMBOL(stop_tty);
/**
* start_tty - propogate flow control
* @tty: tty to start
*
* Start a tty that has been stopped if at all possible. Perform
* any neccessary wakeups and propogate the TIOCPKT status. If this
* is the tty was previous stopped and is being started then the
* driver start method is invoked and the line discipline woken.
*
* Locking:
* Broken. Relies on BKL which is unsafe here.
*/
void start_tty(struct tty_struct *tty)
{
if (!tty->stopped || tty->flow_stopped)
......@@ -1258,6 +1526,23 @@ void start_tty(struct tty_struct *tty)
EXPORT_SYMBOL(start_tty);
/**
* tty_read - read method for tty device files
* @file: pointer to tty file
* @buf: user buffer
* @count: size of user buffer
* @ppos: unused
*
* Perform the read system call function on this terminal device. Checks
* for hung up devices before calling the line discipline method.
*
* Locking:
* Locks the line discipline internally while needed
* For historical reasons the line discipline read method is
* invoked under the BKL. This will go away in time so do not rely on it
* in new code. Multiple read calls may be outstanding in parallel.
*/
static ssize_t tty_read(struct file * file, char __user * buf, size_t count,
loff_t *ppos)
{
......@@ -1302,6 +1587,7 @@ static inline ssize_t do_tty_write(
ssize_t ret = 0, written = 0;
unsigned int chunk;
/* FIXME: O_NDELAY ... */
if (mutex_lock_interruptible(&tty->atomic_write_lock)) {
return -ERESTARTSYS;
}
......@@ -1318,6 +1604,9 @@ static inline ssize_t do_tty_write(
* layer has problems with bigger chunks. It will
* claim to be able to handle more characters than
* it actually does.
*
* FIXME: This can probably go away now except that 64K chunks
* are too likely to fail unless switched to vmalloc...
*/
chunk = 2048;
if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
......@@ -1375,6 +1664,24 @@ static inline ssize_t do_tty_write(
}
/**
* tty_write - write method for tty device file
* @file: tty file pointer
* @buf: user data to write
* @count: bytes to write
* @ppos: unused
*
* Write data to a tty device via the line discipline.
*
* Locking:
* Locks the line discipline as required
* Writes to the tty driver are serialized by the atomic_write_lock
* and are then processed in chunks to the device. The line discipline
* write method will not be involked in parallel for each device
* The line discipline write method is called under the big
* kernel lock for historical reasons. New code should not rely on this.
*/
static ssize_t tty_write(struct file * file, const char __user * buf, size_t count,
loff_t *ppos)
{
......@@ -1422,7 +1729,18 @@ ssize_t redirected_tty_write(struct file * file, const char __user * buf, size_t
static char ptychar[] = "pqrstuvwxyzabcde";
static inline void pty_line_name(struct tty_driver *driver, int index, char *p)
/**
* pty_line_name - generate name for a pty
* @driver: the tty driver in use
* @index: the minor number
* @p: output buffer of at least 6 bytes
*
* Generate a name from a driver reference and write it to the output
* buffer.
*
* Locking: None
*/
static void pty_line_name(struct tty_driver *driver, int index, char *p)
{
int i = index + driver->name_base;
/* ->name is initialized to "ttyp", but "tty" is expected */
......@@ -1431,24 +1749,53 @@ static inline void pty_line_name(struct tty_driver *driver, int index, char *p)
ptychar[i >> 4 & 0xf], i & 0xf);
}
static inline void tty_line_name(struct tty_driver *driver, int index, char *p)
/**
* pty_line_name - generate name for a tty
* @driver: the tty driver in use
* @index: the minor number
* @p: output buffer of at least 7 bytes
*
* Generate a name from a driver reference and write it to the output
* buffer.
*
* Locking: None
*/
static void tty_line_name(struct tty_driver *driver, int index, char *p)
{
sprintf(p, "%s%d", driver->name, index + driver->name_base);
}
/*
/**
* init_dev - initialise a tty device
* @driver: tty driver we are opening a device on
* @idx: device index
* @tty: returned tty structure
*
* Prepare a tty device. This may not be a "new" clean device but
* could also be an active device. The pty drivers require special
* handling because of this.
*
* Locking:
* The function is called under the tty_mutex, which
* protects us from the tty struct or driver itself going away.
*
* On exit the tty device has the line discipline attached and
* a reference count of 1. If a pair was created for pty/tty use
* and the other was a pty master then it too has a reference count of 1.
*
* WSH 06/09/97: Rewritten to remove races and properly clean up after a
* failed open. The new code protects the open with a mutex, so it's
* really quite straightforward. The mutex locking can probably be
* relaxed for the (most common) case of reopening a tty.
*/
static int init_dev(struct tty_driver *driver, int idx,
struct tty_struct **ret_tty)
{
struct tty_struct *tty, *o_tty;
struct termios *tp, **tp_loc, *o_tp, **o_tp_loc;
struct termios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
int retval=0;
int retval = 0;
/* check whether we're reopening an existing tty */
if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
......@@ -1662,10 +2009,20 @@ static int init_dev(struct tty_driver *driver, int idx,
goto end_init;
}
/*
* Releases memory associated with a tty structure, and clears out the
* driver table slots.
/**
* release_mem - release tty structure memory
*
* Releases memory associated with a tty structure, and clears out the
* driver table slots. This function is called when a device is no longer
* in use. It also gets called when setup of a device fails.
*
* Locking:
* tty_mutex - sometimes only
* takes the file list lock internally when working on the list
* of ttys that the driver keeps.
* FIXME: should we require tty_mutex is held here ??
*/
static void release_mem(struct tty_struct *tty, int idx)
{
struct tty_struct *o_tty;
......@@ -2006,18 +2363,27 @@ static void release_dev(struct file * filp)
}
/*
* tty_open and tty_release keep up the tty count that contains the
* number of opens done on a tty. We cannot use the inode-count, as
* different inodes might point to the same tty.
/**
* tty_open - open a tty device
* @inode: inode of device file
* @filp: file pointer to tty
*
* Open-counting is needed for pty masters, as well as for keeping
* track of serial lines: DTR is dropped when the last close happens.
* (This is not done solely through tty->count, now. - Ted 1/27/92)
* tty_open and tty_release keep up the tty count that contains the
* number of opens done on a tty. We cannot use the inode-count, as
* different inodes might point to the same tty.
*
* The termios state of a pty is reset on first open so that
* settings don't persist across reuse.
* Open-counting is needed for pty masters, as well as for keeping
* track of serial lines: DTR is dropped when the last close happens.
* (This is not done solely through tty->count, now. - Ted 1/27/92)
*
* The termios state of a pty is reset on first open so that
* settings don't persist across reuse.
*
* Locking: tty_mutex protects current->signal->tty, get_tty_driver and
* init_dev work. tty->count should protect the rest.
* task_lock is held to update task details for sessions
*/
static int tty_open(struct inode * inode, struct file * filp)
{
struct tty_struct *tty;
......@@ -2132,6 +2498,18 @@ static int tty_open(struct inode * inode, struct file * filp)
}
#ifdef CONFIG_UNIX98_PTYS
/**
* ptmx_open - open a unix 98 pty master
* @inode: inode of device file
* @filp: file pointer to tty
*
* Allocate a unix98 pty master device from the ptmx driver.
*
* Locking: tty_mutex protects theinit_dev work. tty->count should
protect the rest.
* allocated_ptys_lock handles the list of free pty numbers
*/
static int ptmx_open(struct inode * inode, struct file * filp)
{
struct tty_struct *tty;
......@@ -2191,6 +2569,18 @@ static int ptmx_open(struct inode * inode, struct file * filp)
}
#endif
/**
* tty_release - vfs callback for close
* @inode: inode of tty
* @filp: file pointer for handle to tty
*
* Called the last time each file handle is closed that references
* this tty. There may however be several such references.
*
* Locking:
* Takes bkl. See release_dev
*/
static int tty_release(struct inode * inode, struct file * filp)
{
lock_kernel();
......@@ -2199,7 +2589,18 @@ static int tty_release(struct inode * inode, struct file * filp)
return 0;
}
/* No kernel lock held - fine */
/**
* tty_poll - check tty status
* @filp: file being polled
* @wait: poll wait structures to update
*
* Call the line discipline polling method to obtain the poll
* status of the device.
*
* Locking: locks called line discipline but ldisc poll method
* may be re-entered freely by other callers.
*/
static unsigned int tty_poll(struct file * filp, poll_table * wait)
{
struct tty_struct * tty;
......@@ -2243,6 +2644,21 @@ static int tty_fasync(int fd, struct file * filp, int on)
return 0;
}
/**
* tiocsti - fake input character
* @tty: tty to fake input into
* @p: pointer to character
*
* Fake input to a tty device. Does the neccessary locking and
* input management.
*
* FIXME: does not honour flow control ??
*
* Locking:
* Called functions take tty_ldisc_lock
* current->signal->tty check is safe without locks
*/
static int tiocsti(struct tty_struct *tty, char __user *p)
{
char ch, mbz = 0;
......@@ -2258,6 +2674,18 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
return 0;
}
/**
* tiocgwinsz - implement window query ioctl
* @tty; tty
* @arg: user buffer for result
*
* Copies the kernel idea of the window size into the user buffer. No
* locking is done.
*
* FIXME: Returning random values racing a window size set is wrong
* should lock here against that
*/
static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
{
if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
......@@ -2265,6 +2693,24 @@ static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
return 0;
}
/**
* tiocswinsz - implement window size set ioctl
* @tty; tty
* @arg: user buffer for result
*
* Copies the user idea of the window size to the kernel. Traditionally
* this is just advisory information but for the Linux console it
* actually has driver level meaning and triggers a VC resize.
*
* Locking:
* The console_sem is used to ensure we do not try and resize
* the console twice at once.
* FIXME: Two racing size sets may leave the console and kernel
* parameters disagreeing. Is this exploitable ?
* FIXME: Random values racing a window size get is wrong
* should lock here against that
*/
static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
struct winsize __user * arg)
{
......@@ -2294,6 +2740,15 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
return 0;
}
/**
* tioccons - allow admin to move logical console
* @file: the file to become console
*
* Allow the adminstrator to move the redirected console device
*
* Locking: uses redirect_lock to guard the redirect information
*/
static int tioccons(struct file *file)
{
if (!capable(CAP_SYS_ADMIN))
......@@ -2319,6 +2774,17 @@ static int tioccons(struct file *file)
return 0;
}
/**
* fionbio - non blocking ioctl
* @file: file to set blocking value
* @p: user parameter
*
* Historical tty interfaces had a blocking control ioctl before
* the generic functionality existed. This piece of history is preserved
* in the expected tty API of posix OS's.
*
* Locking: none, the open fle handle ensures it won't go away.
*/
static int fionbio(struct file *file, int __user *p)
{
......@@ -2334,6 +2800,23 @@ static int fionbio(struct file *file, int __user *p)
return 0;
}
/**
* tiocsctty - set controlling tty
* @tty: tty structure
* @arg: user argument
*
* This ioctl is used to manage job control. It permits a session
* leader to set this tty as the controlling tty for the session.
*
* Locking:
* Takes tasklist lock internally to walk sessions
* Takes task_lock() when updating signal->tty
*
* FIXME: tty_mutex is needed to protect signal->tty references.
* FIXME: why task_lock on the signal->tty reference ??
*
*/
static int tiocsctty(struct tty_struct *tty, int arg)
{
struct task_struct *p;
......@@ -2374,6 +2857,18 @@ static int tiocsctty(struct tty_struct *tty, int arg)
return 0;
}
/**
* tiocgpgrp - get process group
* @tty: tty passed by user
* @real_tty: tty side of the tty pased by the user if a pty else the tty
* @p: returned pid
*
* Obtain the process group of the tty. If there is no process group
* return an error.
*
* Locking: none. Reference to ->signal->tty is safe.
*/
static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
/*
......@@ -2385,6 +2880,20 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
return put_user(real_tty->pgrp, p);
}
/**
* tiocspgrp - attempt to set process group
* @tty: tty passed by user
* @real_tty: tty side device matching tty passed by user
* @p: pid pointer
*
* Set the process group of the tty to the session passed. Only
* permitted where the tty session is our session.
*
* Locking: None
*
* FIXME: current->signal->tty referencing is unsafe.
*/
static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
pid_t pgrp;
......@@ -2408,6 +2917,18 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
return 0;
}
/**
* tiocgsid - get session id
* @tty: tty passed by user
* @real_tty: tty side of the tty pased by the user if a pty else the tty
* @p: pointer to returned session id
*
* Obtain the session id of the tty. If there is no session
* return an error.
*
* Locking: none. Reference to ->signal->tty is safe.
*/
static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
/*
......@@ -2421,6 +2942,16 @@ static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t _
return put_user(real_tty->session, p);
}
/**
* tiocsetd - set line discipline
* @tty: tty device
* @p: pointer to user data
*
* Set the line discipline according to user request.
*
* Locking: see tty_set_ldisc, this function is just a helper
*/
static int tiocsetd(struct tty_struct *tty, int __user *p)
{
int ldisc;
......@@ -2430,6 +2961,21 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
return tty_set_ldisc(tty, ldisc);
}
/**
* send_break - performed time break
* @tty: device to break on
* @duration: timeout in mS
*
* Perform a timed break on hardware that lacks its own driver level
* timed break functionality.
*
* Locking:
* None
*
* FIXME:
* What if two overlap
*/
static int send_break(struct tty_struct *tty, unsigned int duration)
{
tty->driver->break_ctl(tty, -1);
......@@ -2442,8 +2988,19 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
return 0;
}
static int
tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p)
/**
* tiocmget - get modem status
* @tty: tty device
* @file: user file pointer
* @p: pointer to result
*
* Obtain the modem status bits from the tty driver if the feature
* is supported. Return -EINVAL if it is not available.
*
* Locking: none (up to the driver)
*/
static int tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p)
{
int retval = -EINVAL;
......@@ -2456,8 +3013,20 @@ tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p)
return retval;
}
static int
tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int cmd,
/**
* tiocmset - set modem status
* @tty: tty device
* @file: user file pointer
* @cmd: command - clear bits, set bits or set all
* @p: pointer to desired bits
*
* Set the modem status bits from the tty driver if the feature
* is supported. Return -EINVAL if it is not available.
*
* Locking: none (up to the driver)
*/
static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int cmd,
unsigned __user *p)
{
int retval = -EINVAL;
......@@ -2573,6 +3142,7 @@ int tty_ioctl(struct inode * inode, struct file * file,
clear_bit(TTY_EXCLUSIVE, &tty->flags);
return 0;
case TIOCNOTTY:
/* FIXME: taks lock or tty_mutex ? */
if (current->signal->tty != tty)
return -ENOTTY;
if (current->signal->leader)
......@@ -2753,9 +3323,16 @@ void do_SAK(struct tty_struct *tty)
EXPORT_SYMBOL(do_SAK);
/*
* This routine is called out of the software interrupt to flush data
* from the buffer chain to the line discipline.
/**
* flush_to_ldisc
* @private_: tty structure passed from work queue.
*
* This routine is called out of the software interrupt to flush data
* from the buffer chain to the line discipline.
*
* Locking: holds tty->buf.lock to guard buffer list. Drops the lock
* while invoking the line discipline receive_buf method. The
* receive_buf method is single threaded for each tty instance.
*/
static void flush_to_ldisc(void *private_)
......@@ -2831,6 +3408,8 @@ static int n_baud_table = ARRAY_SIZE(baud_table);
* Convert termios baud rate data into a speed. This should be called
* with the termios lock held if this termios is a terminal termios
* structure. May change the termios data.
*
* Locking: none
*/
int tty_termios_baud_rate(struct termios *termios)
......@@ -2859,6 +3438,8 @@ EXPORT_SYMBOL(tty_termios_baud_rate);
* Returns the baud rate as an integer for this terminal. The
* termios lock must be held by the caller and the terminal bit
* flags may be updated.
*
* Locking: none
*/
int tty_get_baud_rate(struct tty_struct *tty)
......@@ -2888,6 +3469,8 @@ EXPORT_SYMBOL(tty_get_baud_rate);
*
* In the event of the queue being busy for flipping the work will be
* held off and retried later.
*
* Locking: tty buffer lock. Driver locks in low latency mode.
*/
void tty_flip_buffer_push(struct tty_struct *tty)
......@@ -2907,9 +3490,16 @@ void tty_flip_buffer_push(struct tty_struct *tty)
EXPORT_SYMBOL(tty_flip_buffer_push);
/*
* This subroutine initializes a tty structure.
/**
* initialize_tty_struct
* @tty: tty to initialize
*
* This subroutine initializes a tty structure that has been newly
* allocated.
*
* Locking: none - tty in question must not be exposed at this point
*/
static void initialize_tty_struct(struct tty_struct *tty)
{
memset(tty, 0, sizeof(struct tty_struct));
......@@ -2935,6 +3525,7 @@ static void initialize_tty_struct(struct tty_struct *tty)
/*
* The default put_char routine if the driver did not define one.
*/
static void tty_default_put_char(struct tty_struct *tty, unsigned char ch)
{
tty->driver->write(tty, &ch, 1);
......@@ -2943,19 +3534,23 @@ static void tty_default_put_char(struct tty_struct *tty, unsigned char ch)
static struct class *tty_class;
/**
* tty_register_device - register a tty device
* @driver: the tty driver that describes the tty device
* @index: the index in the tty driver for this tty device
* @device: a struct device that is associated with this tty device.
* This field is optional, if there is no known struct device for this
* tty device it can be set to NULL safely.
* tty_register_device - register a tty device
* @driver: the tty driver that describes the tty device
* @index: the index in the tty driver for this tty device
* @device: a struct device that is associated with this tty device.
* This field is optional, if there is no known struct device
* for this tty device it can be set to NULL safely.
*
* Returns a pointer to the class device (or ERR_PTR(-EFOO) on error).
* Returns a pointer to the class device (or ERR_PTR(-EFOO) on error).
*
* This call is required to be made to register an individual tty device if
* the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set. If that
* bit is not set, this function should not be called by a tty driver.
* This call is required to be made to register an individual tty device
* if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set. If
* that bit is not set, this function should not be called by a tty
* driver.
*
* Locking: ??
*/
struct class_device *tty_register_device(struct tty_driver *driver,
unsigned index, struct device *device)
{
......@@ -2977,13 +3572,16 @@ struct class_device *tty_register_device(struct tty_driver *driver,
}
/**
* tty_unregister_device - unregister a tty device
* @driver: the tty driver that describes the tty device
* @index: the index in the tty driver for this tty device
* tty_unregister_device - unregister a tty device
* @driver: the tty driver that describes the tty device
* @index: the index in the tty driver for this tty device
*
* If a tty device is registered with a call to tty_register_device() then
* this function must be made when the tty device is gone.
* If a tty device is registered with a call to tty_register_device() then
* this function must be called when the tty device is gone.
*
* Locking: ??
*/
void tty_unregister_device(struct tty_driver *driver, unsigned index)
{
class_device_destroy(tty_class, MKDEV(driver->major, driver->minor_start) + index);
......
drivers/char/tty_ioctl.c
View file @ af9b897e
......@@ -36,6 +36,18 @@
#define TERMIOS_WAIT 2
#define TERMIOS_TERMIO 4
/**
* tty_wait_until_sent - wait for I/O to finish
* @tty: tty we are waiting for
* @timeout: how long we will wait
*
* Wait for characters pending in a tty driver to hit the wire, or
* for a timeout to occur (eg due to flow control)
*
* Locking: none
*/
void tty_wait_until_sent(struct tty_struct * tty, long timeout)
{
DECLARE_WAITQUEUE(wait, current);
......@@ -94,6 +106,18 @@ static void unset_locked_termios(struct termios *termios,
old->c_cc[i] : termios->c_cc[i];
}
/**
* change_termios - update termios values
* @tty: tty to update
* @new_termios: desired new value
*
* Perform updates to the termios values set on this terminal. There
* is a bit of layering violation here with n_tty in terms of the
* internal knowledge of this function.
*
* Locking: termios_sem
*/
static void change_termios(struct tty_struct * tty, struct termios * new_termios)
{
int canon_change;
......@@ -155,6 +179,19 @@ static void change_termios(struct tty_struct * tty, struct termios * new_termios
up(&tty->termios_sem);
}
/**
* set_termios - set termios values for a tty
* @tty: terminal device
* @arg: user data
* @opt: option information
*
* Helper function to prepare termios data and run neccessary other
* functions before using change_termios to do the actual changes.
*
* Locking:
* Called functions take ldisc and termios_sem locks
*/
static int set_termios(struct tty_struct * tty, void __user *arg, int opt)
{
struct termios tmp_termios;
......@@ -284,6 +321,17 @@ static void set_sgflags(struct termios * termios, int flags)
}
}
/**
* set_sgttyb - set legacy terminal values
* @tty: tty structure
* @sgttyb: pointer to old style terminal structure
*
* Updates a terminal from the legacy BSD style terminal information
* structure.
*
* Locking: termios_sem
*/
static int set_sgttyb(struct tty_struct * tty, struct sgttyb __user * sgttyb)
{
int retval;
......@@ -369,9 +417,16 @@ static int set_ltchars(struct tty_struct * tty, struct ltchars __user * ltchars)
}
#endif
/*
* Send a high priority character to the tty.
/**
* send_prio_char - send priority character
*
* Send a high priority character to the tty even if stopped
*
* Locking: none
*
* FIXME: overlapping calls with start/stop tty lose state of tty
*/
static void send_prio_char(struct tty_struct *tty, char ch)
{
int was_stopped = tty->stopped;
......
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