It is possible to hang pty devices in this case, the reader was
blocking at epoll on master side, the writer was sleeping at
wait_woken inside n_tty_write on slave side, and the write buffer
on tty_port was full, we found that the reader and writer would
never be woken again and blocked forever.
The problem was caused by a race between reader and kworker:
n_tty_read(reader): n_tty_receive_buf_common(kworker):
copy_from_read_buf()|
|room = N_TTY_BUF_SIZE - (ldata->read_head - tail)
|room <= 0
n_tty_kick_worker() |
|ldata->no_room = true
After writing to slave device, writer wakes up kworker to flush
data on tty_port to reader, and the kworker finds that reader
has no room to store data so room <= 0 is met. At this moment,
reader consumes all the data on reader buffer and calls
n_tty_kick_worker to check ldata->no_room which is false and
reader quits reading. Then kworker sets ldata->no_room=true
and quits too.
If write buffer is not full, writer will wake kworker to flush data
again after following writes, but if write buffer is full and writer
goes to sleep, kworker will never be woken again and tty device is
blocked.
This problem can be solved with a check for read buffer size inside
n_tty_receive_buf_common, if read buffer is empty and ldata->no_room
is true, a call to n_tty_kick_worker is necessary to keep flushing
data to reader.
Cc: <stable@vger.kernel.org>
Fixes: 42458f41d0 ("n_tty: Ensure reader restarts worker for next reader")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Hui Li <caelli@tencent.com>
Message-ID: <1680749090-14106-1-git-send-email-caelli@tencent.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When PARMRK is set, a character can result in up to 3 chars in the read
buffer. Receive code calculates for how many characters there (at
least) is room. Convert an opencoded rounding in the calculation to use
DIV_ROUND_UP().
Note: the room variable is decremented afterwards by one which ensures
the characters will fit into the buffer for real so the code is okay
despite rounding upwards.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-6-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The no_space_left variable is only assigned with 0 and 1.
Change its type to boolean and move negation from its name into the
check.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309082035.14880-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The local tail variable in n_tty_read() is used for one purpose, it
keeps the old tail. Thus, rename it appropriately to improve code
readability.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/22b37499-ff9a-7fc1-f6e0-58411328d122@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There should be no reason to adjust old ktermios which is going to get
discarded anyway.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-6-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use n_tty_receive_char_flow_ctrl also on the closing path. This makes
the code cleaner and consistent.
However, there a small change of regression!
The earlier closing path has a small difference compared with the
normal receive path. If START_CHAR and STOP_CHAR are equal, their
precedence is different depending on which path a character is
processed. I don't know whether this difference was intentional or
not, and if equal START_CHAR and STOP_CHAR is actually used anywhere.
But it feels not so useful corner case.
While this change would logically belong to those earlier changes,
having a separate patch for this is useful. If this regresses, bisect
can pinpoint this change rather than the large patch. Also, this
change is not necessary to minimal fix for the issue addressed in
the previous patch.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When tty is not read from, XON/XOFF may get stuck into an
intermediate buffer. As those characters are there to do software
flow-control, it is not very useful. In the case where neither end
reads from ttys, the receiving ends might not be able receive the
XOFF characters and just keep sending more data to the opposite
direction. This problem is almost guaranteed to occur with DMA
which sends data in large chunks.
If TTY is slow to process characters, that is, eats less than given
amount in receive_buf, invoke lookahead for the rest of the chars
to process potential XON/XOFF characters.
We need to keep track of how many characters have been processed by the
lookahead to avoid processing the flow control char again on the normal
path. Bookkeeping occurs parallel on two layers (tty_buffer and n_tty)
to avoid passing the lookahead_count through the whole call chain.
When a flow-control char is processed, two things must occur:
a) it must not be treated as normal char
b) if not yet processed, flow-control actions need to be taken
The return value of n_tty_receive_char_flow_ctrl() tells caller a), and
b) is kept internal to n_tty_receive_char_flow_ctrl().
If characters were previous looked ahead, __receive_buf() makes two
calls to the appropriate n_tty_receive_buf_* function. First call is
made with lookahead_done=true for the characters that were subject to
lookahead earlier and then with lookahead=false for the new characters.
Either of the calls might be skipped when it has no characters to
handle.
Reported-by: Gilles Buloz <gilles.buloz@kontron.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add a helper to check if the character is a flow control one. This
rework prepares for adding lookahead done check cleanly to
n_tty_receive_char_flow_ctrl() between n_tty_is_char_flow_ctrl() and
the actions taken on the flow control characters.
No functional changes intended.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220426144935.54893-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
TTYs in ICANON mode have a special case that allows "pushing" a line
without a regular EOL character (like newline), by using EOF (the EOT
character - ASCII 0x4) as a pseudo-EOL. It is silently discarded, so
the reader of the PTS will receive the line *without* EOF or any other
terminating character.
This special case has an edge case: What happens if the readers buffer
is the same size as the line (without EOF)? Will they be able to tell
if the whole line is received, i.e. if the next read() will return more
of the same line or the next line?
There are two possibilities, that both have (dis)advantages:
1. The next read() returns 0. FreeBSD (13.0) and OSX (10.11) do this.
Advantage: The reader can interpret this as "the line is over".
Disadvantage: read() returning 0 means EOF, the reader could also
interpret it as "there's no more data" and stop reading or even
close the PT.
2. The next read() returns the next line, the EOF is silently discarded.
Solaris (or at least OpenIndiana 2021.10) does this, Linux has done
do this since commit 40d5e0905a ("n_tty: Fix EOF push handling");
this behavior was recently broken by commit 3593030761 ("tty:
n_tty: do not look ahead for EOL character past the end of the buffer").
Advantage: read() won't return 0 (EOF), reader less likely to be
confused (and things like `while(read(..)>0)` don't break)
Disadvantage: The reader can't really know if the read() continues
the last line (that filled the whole read buffer) or starts a
new line.
As both options are defensible (and are used by other Unix-likes), it's
best to stick to the "old" behavior since "n_tty: Fix EOF push handling"
of 2013, i.e. silently discard that EOF.
This patch - that I actually got from Linus for testing and only
modified slightly - restores that behavior by skipping an EOF
character if it's the next character after reading is done.
Based on a patch from Linus Torvalds.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215611
Fixes: 3593030761 ("tty: n_tty: do not look ahead for EOL character past the end of the buffer")
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Reviewed-and-tested-by: Daniel Gibson <daniel@gibson.sh>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Daniel Gibson <daniel@gibson.sh>
Link: https://lore.kernel.org/r/20220329235810.452513-2-daniel@gibson.sh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Daniel Gibson reports that the n_tty code gets line termination wrong in
very specific cases:
"If you feed a line with exactly 64 chars + terminating newline, and
directly afterwards (without reading) another line into a pseudo
terminal, the the first read() on the other side will return the 64
char line *without* terminating newline, and the next read() will
return the missing terminating newline AND the complete next line (if
it fits in the buffer)"
and bisected the behavior to commit 3b830a9c34 ("tty: convert
tty_ldisc_ops 'read()' function to take a kernel pointer").
Now, digging deeper, it turns out that the behavior isn't exactly new:
what changed in commit 3b830a9c34 was that the tty line discipline
.read() function is now passed an intermediate kernel buffer rather than
the final user space buffer.
And that intermediate kernel buffer is 64 bytes in size - thus that
special case with exactly 64 bytes plus terminating newline.
The same problem did exist before, but historically the boundary was not
the 64-byte chunk, but the user-supplied buffer size, which is obviously
generally bigger (and potentially bigger than N_TTY_BUF_SIZE, which
would hide the issue entirely).
The reason is that the n_tty canon_copy_from_read_buf() code would look
ahead for the EOL character one byte further than it would actually
copy. It would then decide that it had found the terminator, and unmark
it as an EOL character - which in turn explains why the next read
wouldn't then be terminated by it.
Now, the reason it did all this in the first place is related to some
historical and pretty obscure EOF behavior, see commit ac8f3bf883
("n_tty: Fix poll() after buffer-limited eof push read") and commit
40d5e0905a ("n_tty: Fix EOF push handling").
And the reason for the EOL confusion is that we treat EOF as a special
EOL condition, with the EOL character being NUL (aka "__DISABLED_CHAR"
in the kernel sources).
So that EOF look-ahead also affects the normal EOL handling.
This patch just removes the look-ahead that causes problems, because EOL
is much more critical than the historical "EOF in the middle of a line
that coincides with the end of the buffer" handling ever was.
Now, it is possible that we should indeed re-introduce the "look at next
character to see if it's a EOF" behavior, but if so, that should be done
not at the kernel buffer chunk boundary in canon_copy_from_read_buf(),
but at a higher level, when we run out of the user buffer.
In particular, the place to do that would be at the top of
'n_tty_read()', where we check if it's a continuation of a previously
started read, and there is no more buffer space left, we could decide to
just eat the __DISABLED_CHAR at that point.
But that would be a separate patch, because I suspect nobody actually
cares, and I'd like to get a report about it before bothering.
Fixes: 3b830a9c34 ("tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer")
Fixes: ac8f3bf883 ("n_tty: Fix poll() after buffer-limited eof push read")
Fixes: 40d5e0905a ("n_tty: Fix EOF push handling")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215611
Reported-and-tested-by: Daniel Gibson <metalcaedes@gmail.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The poll man page says POLLRDNORM is equivalent to POLLIN when used as
an event.
$ man poll
<snip>
POLLRDNORM
Equivalent to POLLIN.
However, in n_tty driver, POLLRDNORM does not return until timeout even
if there is terminal input, whereas POLLIN returns.
The following test program works until kernel-3.17, but the test stops
in poll() after commit 57087d5154 ("tty: Fix spurious poll() wakeups").
[Steps to run test program]
$ cc -o test-pollrdnorm test-pollrdnorm.c
$ ./test-pollrdnorm
foo <-- Type in something from the terminal followed by [RET].
The string should be echoed back.
------------------------< test-pollrdnorm.c >------------------------
#include <stdio.h>
#include <errno.h>
#include <poll.h>
#include <unistd.h>
void main(void)
{
int n;
unsigned char buf[8];
struct pollfd fds[1] = {{ 0, POLLRDNORM, 0 }};
n = poll(fds, 1, -1);
if (n < 0)
perror("poll");
n = read(0, buf, 8);
if (n < 0)
perror("read");
if (n > 0)
write(1, buf, n);
}
------------------------------------------------------------------------
The attached patch fixes this problem. Many calls to
wake_up_interruptible_poll() in the kernel source code already specify
"POLLIN | POLLRDNORM".
Fixes: 57087d5154 ("tty: Fix spurious poll() wakeups")
Cc: stable@vger.kernel.org
Signed-off-by: Kosuke Tatsukawa <tatsu-ab1@nec.com>
Link: https://lore.kernel.org/r/TYCPR01MB81901C0F932203D30E452B3EA5209@TYCPR01MB8190.jpnprd01.prod.outlook.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'bitmap-5.17-rc1' of git://github.com/norov/linux
Pull bitmap updates from Yury Norov:
- introduce for_each_set_bitrange()
- use find_first_*_bit() instead of find_next_*_bit() where possible
- unify for_each_bit() macros
* tag 'bitmap-5.17-rc1' of git://github.com/norov/linux:
vsprintf: rework bitmap_list_string
lib: bitmap: add performance test for bitmap_print_to_pagebuf
bitmap: unify find_bit operations
mm/percpu: micro-optimize pcpu_is_populated()
Replace for_each_*_bit_from() with for_each_*_bit() where appropriate
find: micro-optimize for_each_{set,clear}_bit()
include/linux: move for_each_bit() macros from bitops.h to find.h
cpumask: replace cpumask_next_* with cpumask_first_* where appropriate
tools: sync tools/bitmap with mother linux
all: replace find_next{,_zero}_bit with find_first{,_zero}_bit where appropriate
cpumask: use find_first_and_bit()
lib: add find_first_and_bit()
arch: remove GENERIC_FIND_FIRST_BIT entirely
include: move find.h from asm_generic to linux
bitops: move find_bit_*_le functions from le.h to find.h
bitops: protect find_first_{,zero}_bit properly
find_first{,_zero}_bit is a more effective analogue of 'next' version if
start == 0. This patch replaces 'next' with 'first' where things look
trivial.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Kernel-doc is a bit strict about some formatting. So fix these:
1) When there is a tab in comments, it thinks the line is a continuation
one. So the description of the functions end up as descriptions of
the last parameter described. Remove the tabs.
2) Remove newlines before parameters description and after the comments.
This was not wrong per se, only inconsistent with the rest of the
file.
3) Add periods to the end of sentences where appropriate.
4) Add "()" to function names and "%" to constants, so that they are
properly highlighted.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-17-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* process_echoes doc was a misnomer
* isig and n_tty_receive_char docs were misplaced
* n_tty_read parameters were incorrect (from pre-cookie times)
So fix all the warnings at once:
624: warning: expecting prototype for process_echoes(). Prototype was for __process_echoes() instead
1110: warning: expecting prototype for isig(). Prototype was for __isig() instead
1264: warning: expecting prototype for n_tty_receive_char(). Prototype was for n_tty_receive_char_special() instead
2067: warning: Excess function parameter 'buf' description in 'n_tty_read'
624: warning: expecting prototype for process_echoes(). Prototype was for __process_echoes() instead
1110: warning: expecting prototype for isig(). Prototype was for __isig() instead
1264: warning: expecting prototype for n_tty_receive_char(). Prototype was for n_tty_receive_char_special() instead
2067: warning: Function parameter or member 'kbuf' not described in 'n_tty_read'
2067: warning: Function parameter or member 'cookie' not described in 'n_tty_read'
2067: warning: Function parameter or member 'offset' not described in 'n_tty_read'
2067: warning: Excess function parameter 'buf' description in 'n_tty_read'
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-16-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the previous patches, noone needs 'file' parameter in neither
ioctl hook from tty_ldisc_ops. So remove 'file' from both of them.
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> [NFC]
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211122094529.24171-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the previous patch, there are no users of 'file' in
n_tty_ioctl_helper. So remove it also from there.
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914091134.17426-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The last user was apparently removed by commit a352def21a (tty: Ldisc
revamp) in 2008. So remove the field completely, the only setter
(n_tty_inherit_ops) and also its only possible value
(LDISC_FLAG_DEFINED).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914091134.17426-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The refcount is checked only in tty_unregister_ldisc and EBUSY returned
if it is nonzero. But none of the tty_unregister_ldisc callers act
anyhow if this (or any other) error is returned. So remove
tty_ldisc_ops::refcount completely and make tty_unregister_ldisc return
'void' in the next patches. That means we assume tty_unregister_ldisc is
not called while the ldisc might be in use. That relies on
try_module_get in get_ldops and module_put in put_ldops.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-18-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There is no reason to pass the ldisc number to tty_register_ldisc
separately. Just set it in the already defined tty_ldisc_ops in all the
ldiscs.
This simplifies tty_register_ldisc a bit too (no need to set the num
member there).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Link: https://lore.kernel.org/r/20210505091928.22010-15-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Group the ctrl members under a single struct called ctrl. The new struct
contains 'pgrp', 'session', 'pktstatus', and 'packet'. 'pktstatus' and
'packet' used to be bits in a bitfield. The struct also contains the
lock protecting them to share the same cache line.
Note that commit c545b66c69 (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::ctrl_unused) is aligned to a 8B boundary too and occupies
some bytes from the next word.
So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
pads the end.
Add a kerneldoc comment for this grouped members.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20210505091928.22010-14-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Group the flow flags under a single struct called flow. The new struct
contains 'stopped' and 'tco_stopped' bools which used to be bits in a
bitfield. The struct also contains the lock protecting them to
potentially share the same cache line.
Note that commit c545b66c69 (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::unused) is aligned to a 8B boundary too and occupies some
bytes from the next word.
So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
pads the end.
This is also the perfect time to start the documentation of tty_struct
where all this lives. So we start by documenting what these bools
actually serve for. And why we do all the alignment dances. Only the few
up-to-date information from the Theodore's comment made it into this new
Kerneldoc comment.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Char pointer (cp) passed to tty_ldisc_ops::receive_buf{,2} is const.
There is no reason for flag pointer (fp) not to be too. So switch it in
the definition and all uses.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@reisers.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://lore.kernel.org/r/20210505091928.22010-12-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A return at the end of a void-returning function is superfluous. Get rid
of it.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-11-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Handle !TTY_NORMAL as a short path and 'continue' the loop. Do the rest as
a normal code flow. This decreases the indentation level by one and
makes the code flow more understandable.
IOW, we avoid
if (cond) {
LONG CODE;
} else
single_line();
by
if (!cond) {
single_line();
continue;
}
LONG CODE;
While at it, invert also the 'if (!test_bit) A else B' into 'if
(test_bit) B else A'.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-10-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It might be confusing for readers: there are three distinct dereferences
and increments of 'cp' in n_tty_receive_buf_standard. Do it on a single
place, along with/before the 'fp' dereference.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the previous patch, noone cares about the return value of
n_tty_receive_char_special. ldata->lnext is checked instead.
So switch return type of n_tty_receive_char_special to void.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-8-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move lnext handling from __receive_buf to n_tty_receive_buf_standard. It
simplifies the handling as it needs not fetching 'flag' and decrement
'count' in __receive_buf. Instead, all this is left up to the loop in
n_tty_receive_buf_standard which already does that.
This way, no need to repeat the action when n_tty_receive_char_special
returns true -- ldata->lnext is set there in that case, so the 'if
(ldata->lnext)' check is sufficient. The next patch will switch
n_tty_receive_char_special to return 'void'.
The result is much simplified code flow.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the previous cleanup patches, parmrk_dbl parameter is always true
-- I_PARMRK is checked only in n_tty_receive_char now. So remove
parmrk_dbl completely.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After the previous patches, n_tty_receive_buf_standard and
n_tty_receive_buf_fast differ only in handling of tty line and input
controls. Unlike n_tty_receive_buf_fast, n_tty_receive_buf_standard
handles them all (I_ISTRIP, I_IUCLC, L_IEXTEN, L_EXTPROC, and I_PARMRK).
So remove n_tty_receive_buf_fast and let n_tty_receive_buf_standard do
the handling. Actually most of the tests are only moved from
__receive_buf to n_tty_receive_buf_standard.
Again, the code duplication is not worth the theoretical speedup.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-5-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
n_tty_receive_char_fast is a copy of n_tty_receive_char with one
exception: PARMRK is not doubled in the former. Unify these two and
double PARMRK depending on a newly added parameter (bool parmrk_dbl).
I don't think the theoretical speedup is worth the code duplication.
Which is directly connected with maintenance burden.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The wrapper was meant as an optimization in commits eb3e4668bd (n_tty:
Un-inline slow-path n_tty_receive_char()) and e60d27c4d8 (n_tty:
Factor LNEXT processing from per-char i/o path). But the current
compiler (gcc 10) inlines it anyway (as expected). Actually, I'm not
sure it ever didn't. It would need to be marked with the noinline
attribute.
So remove this useless wrapper.
And if we ever introduce something similar, we need confirming numbers
first.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There are a number of functions and #defines in include/linux/tty.h that
do not belong there as they are private to the tty core code.
Create an initial drivers/tty/tty.h file and copy the odd "tty logging"
macros into it to seed the file with some initial things that we know
nothing outside of the tty core should be calling.
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20210408125134.3016837-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Set tty_ldisc_ops::owner to THIS_MODULE. This has no effect currently as
n_tty cannot be built as a module. If someone ever tries to modularize
tty, we wouldn't manage module's reference count as in other ldiscs. So
fix this just in case.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
First, it is never checked. Second, use of it as a debugging aid is
at least questionable. With the current tools, I don't think anyone used
this kind of thing for debugging purposes for years.
On the top of that, e.g. serdev does not set this field of tty_ldisc_ops
at all.
So get rid of this legacy.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-8-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Here is the big set of tty/serial driver changes for 5.12-rc1.
Nothing huge, just lots of good cleanups and additions:
- Your n_tty line discipline cleanups
- vt core cleanups and reworks to make the code more "modern"
- stm32 driver additions
- tty led support added to the tty core and led layer
- minor serial driver fixups and additions
All of these have been in linux-next for a while with no reported
issues.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty/serial driver updates from Greg KH:
"Here is the big set of tty/serial driver changes for 5.12-rc1.
Nothing huge, just lots of good cleanups and additions:
- n_tty line discipline cleanups
- vt core cleanups and reworks to make the code more "modern"
- stm32 driver additions
- tty led support added to the tty core and led layer
- minor serial driver fixups and additions
All of these have been in linux-next for a while with no reported
issues"
* tag 'tty-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (54 commits)
serial: core: Remove BUG_ON(in_interrupt()) check
vt_ioctl: Remove in_interrupt() check
dt-bindings: serial: imx: Switch to my personal address
vt: keyboard, use new API for keyboard_tasklet
serial: stm32: improve platform_get_irq condition handling in init_port
serial: ifx6x60: Remove driver for deprecated platform
tty: fix up iterate_tty_read() EOVERFLOW handling
tty: fix up hung_up_tty_read() conversion
tty: fix up hung_up_tty_write() conversion
tty: teach the n_tty ICANON case about the new "cookie continuations" too
tty: teach n_tty line discipline about the new "cookie continuations"
tty: clean up legacy leftovers from n_tty line discipline
tty: implement read_iter
tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer
serial: remove sirf prima/atlas driver
serial: mxs-auart: Remove <asm/cacheflush.h>
serial: mxs-auart: Remove serial_mxs_probe_dt()
serial: fsl_lpuart: Use of_device_get_match_data()
dt-bindings: serial: renesas,hscif: Add r8a779a0 support
tty: serial: Drop unused efm32 serial driver
...
layer to use write_iter. Fix the redirected_tty_write declaration
also in n_tty and change the comparisons to use write_iter instead of
write.
[ Also moved the declaration of redirected_tty_write() to the proper
location in a header file. The reason for the bug was the bogus extern
declaration in n_tty.c silently not matching the changed definition in
tty_io.c, and because it wasn't in a shared header file, there was no
cross-checking of the declaration.
Sami noticed because Clang's Control Flow Integrity checking ended up
incidentally noticing the inconsistent declaration. - Linus ]
Fixes: 9bb48c82ac ("tty: implement write_iter")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes both the "splice/sendfile to a tty" and "splice/sendfile from a
tty" regression from 5.10.
* 'tty-splice' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux:
tty: teach the n_tty ICANON case about the new "cookie continuations" too
tty: teach n_tty line discipline about the new "cookie continuations"
tty: clean up legacy leftovers from n_tty line discipline
tty: implement read_iter
tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer
tty: implement write_iter
The ICANON case is a bit messy, since it has to look for the line
ending, and has special code to then suppress line ending characters if
they match the __DISABLED_CHAR. So it actually looks up the line ending
even past the point where it knows it won't copy it to the result
buffer.
That said, apart from all those odd legacy N_TTY ICANON cases, the
actual "should we continue copying" logic isn't really all that
complicated or different from the non-canon case. In fact, the lack of
"wait for at least N characters" arguably makes the repeat case slightly
simpler. It really just boils down to "there's more of the line to be
copied".
So add the necessarily trivial logic, and now the N_TTY case will give
long result lines even when in canon mode.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With the conversion to do the tty ldisc read operations in small chunks,
the n_tty line discipline became noticeably slower for throughput
oriented loads, because rather than read things in up to 2kB chunks, it
would return at most 64 bytes per read() system call.
The cost is mainly all in the "do system calls over and over", not
really in the new "copy to an extra kernel buffer".
This can be fixed by teaching the n_tty line discipline about the
"cookie continuation" model, which the chunking code supports because
things like hdlc need to be able to handle packets up to 64kB in size.
Doing that doesn't just get us back to the old performace, but to much
better performance: my stupid "copy 10MB of data over a pty" test
program is now almost twice as fast as it used to be (going down from
0.1s to 0.054s).
This is entirely because it now creates maximal chunks (which happens to
be "one byte less than one page" due to how we do the circular tty
buffers).
NOTE! This case only handles the simpler non-icanon case, which is the
one where people may care about throughput. I'm going to do the icanon
case later too, because while performance isn't a major issue for that,
there may be programs that think they'll always get a full line and
don't like the 64-byte chunking for that reason.
Such programs are arguably buggy (signals etc can cause random partial
results from tty reads anyway), and good programs will handle such
partial reads, but expecting everybody to write "good programs" has
never been a winning policy for the kernel..
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Back when the line disciplines did their own direct user accesses, they
had to deal with the data copy possibly failing in the middle.
Now that the user copy is done by the tty_io.c code, that failure case
no longer exists.
Remove the left-over error handling code that cannot trigger.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The tty line discipline .read() function was passed the final user
pointer destination as an argument, which doesn't match the 'write()'
function, and makes it very inconvenient to do a splice method for
ttys.
This is a conversion to use a kernel buffer instead.
NOTE! It does this by passing the tty line discipline ->read() function
an additional "cookie" to fill in, and an offset into the cookie data.
The line discipline can fill in the cookie data with its own private
information, and then the reader will repeat the read until either the
cookie is cleared or it runs out of data.
The only real user of this is N_HDLC, which can use this to handle big
packets, even if the kernel buffer is smaller than the whole packet.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
n_tty_flush_buffer can happen in parallel with n_tty_close that the
tty->disc_data will be set to NULL. n_tty_flush_buffer accesses
tty->disc_data, so we must prevent n_tty_close clear tty->disc_data
while n_tty_flush_buffer has a non-NULL view of tty->disc_data.
So we need to make sure that accesses to disc_data are atomic using
tty->termios_rwsem.
There is an example I meet:
When n_tty_flush_buffer accesses tty struct, the disc_data is right.
However, then reset_buffer_flags accesses tty->disc_data, disc_data
become NULL, So kernel crash when accesses tty->disc_data->real_tail.
I guess there could be another thread change tty->disc_data to NULL,
and during N_TTY line discipline, n_tty_close will set tty->disc_data
to be NULL. So use tty->termios_rwsem to protect disc_data between close
and flush_buffer.
IP: reset_buffer_flags+0x9/0xf0
PGD 0 P4D 0
Oops: 0002 [#1] SMP
CPU: 23 PID: 2087626 Comm: (agetty) Kdump: loaded Tainted: G
Hardware name: UNISINSIGHT X3036P-G3/ST01M2C7S, BIOS 2.00.13 01/11/2019
task: ffff9c4e9da71e80 task.stack: ffffb30cfe898000
RIP: 0010:reset_buffer_flags+0x9/0xf0
RSP: 0018:ffffb30cfe89bca8 EFLAGS: 00010246
RAX: ffff9c4e9da71e80 RBX: ffff9c368d1bac00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9c4ea17b50f0 RDI: 0000000000000000
RBP: ffffb30cfe89bcc8 R08: 0000000000000100 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffff9c368d1bacc0
R13: ffff9c20cfd18428 R14: ffff9c4ea17b50f0 R15: ffff9c368d1bac00
FS: 00007f9fbbe97940(0000) GS:ffff9c375c740000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000002260 CR3: 0000002f72233003 CR4: 00000000007606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
? n_tty_flush_buffer+0x2a/0x60
tty_buffer_flush+0x76/0x90
tty_ldisc_flush+0x22/0x40
vt_ioctl+0x5a7/0x10b0
? n_tty_ioctl_helper+0x27/0x110
tty_ioctl+0xef/0x8c0
do_vfs_ioctl+0xa7/0x5e0
? __audit_syscall_entry+0xaf/0x100
? syscall_trace_enter+0x1d0/0x2b0
SyS_ioctl+0x79/0x90
do_syscall_64+0x6c/0x1b0
entry_SYSCALL64_slow_path+0x25/0x25
n_tty_flush_buffer --->tty->disc_data is OK
->reset_buffer_flags -->tty->disc_data is NULL
Signed-off-by: Yan.Gao <gao.yanB@h3c.com>
Reviewed-by: Xianting Tian <tian.xianting@h3c.com>
Link: https://lore.kernel.org/r/20201210022507.30729-1-gao.yanB@h3c.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes the following W=1 kernel build warning(s):
drivers/tty/n_tty.c:405: warning: Function parameter or member 'tty' not described in 'is_continuation'
drivers/tty/n_tty.c:1701: warning: Function parameter or member 'flow' not described in 'n_tty_receive_buf_common'
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: "Andrew J. Kroll" <ag784@freenet.buffalo.edu>
Cc: processes-Sapan Bhatia <sapan@corewars.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-11-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Variables declared in a switch statement before any case statements
cannot be automatically initialized with compiler instrumentation (as
they are not part of any execution flow). With GCC's proposed automatic
stack variable initialization feature, this triggers a warning (and they
don't get initialized). Clang's automatic stack variable initialization
(via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also
doesn't initialize such variables[1]. Note that these warnings (or silent
skipping) happen before the dead-store elimination optimization phase,
so even when the automatic initializations are later elided in favor of
direct initializations, the warnings remain.
To avoid these problems, move such variables into the "case" where
they're used or lift them up into the main function body.
drivers/tty/n_tty.c: In function ‘__process_echoes’:
drivers/tty/n_tty.c:657:18: warning: statement will never be executed [-Wswitch-unreachable]
657 | unsigned int num_chars, num_bs;
| ^~~~~~~~~
[1] https://bugs.llvm.org/show_bug.cgi?id=44916
Reviewed-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200220062313.69209-1-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
