Commits · 9335e23ddc33b5298b4cefdecc962736449fe596 · Kirill Smelkov / linux

13 Jan, 2021 1 commit

tty: serial: owl: Add support for kernel debugger · 9335e23d

Cristian Ciocaltea authored Jan 12, 2021

Implement 'poll_put_char' and 'poll_get_char' callbacks in struct
'owl_uart_ops' that enables OWL UART to be used for kernel debugging
over serial line.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Link: https://lore.kernel.org/r/026543195b9aeefb339d90abc5660a6ac7463c63.1610484108.git.cristian.ciocaltea@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

9335e23d

07 Jan, 2021 23 commits

tty: Protect disc_data in n_tty_close and n_tty_flush_buffer · c9cd57bf

Yan.Gao authored Dec 10, 2020

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.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

c9cd57bf

drivers:tty:pty: Fix a race causing data loss on close · 33d4ae98

Corey Minyard authored Nov 23, 2020

Remove the tty_vhangup() from the pty code and just release the
redirect.  The tty_vhangup() results in data loss and data out of order
issues.

If you write to a pty master an immediately close the pty master, the
receiver might get a chunk of data dropped, but then receive some later
data.  That's obviously something rather unexpected for a user.  It
certainly confused my test program.

It turns out that tty_vhangup() on the slave pty gets called from
pty_close(), and that causes the data on the slave side to be flushed,
but due to races more data can be copied into the slave side's buffer
after that.  Consider the following sequence:

thread1          thread2         thread3
-------          -------         -------
 |                |-write data into buffer,
 |                | n_tty buffer is filled
 |                | along with other buffers
 |                |-pty_close(master)
 |                |--tty_vhangup(slave)
 |                |---tty_ldisc_hangup()
 |                |----n_tty_flush_buffer()
 |                |-----reset_buffer_flags()
 |-n_tty_read()   |
 |--up_read(&tty->termios_rwsem);
 |                |------down_read(&tty->termios_rwsem)
 |                |------clear n_tty buffer contents
 |                |------up_read(&tty->termios_rwsem)
 |--tty_buffer_flush_work()       |
 |--schedules work calling        |
 |  flush_to_ldisc()              |
 |                                |-flush_to_ldisc()
 |                                |--receive_buf()
 |                                |---tty_port_default_receive_buf()
 |                                |----tty_ldisc_receive_buf()
 |                                |-----n_tty_receive_buf2()
 |                                |------n_tty_receive_buf_common()
 |                                |-------down_read(&tty->termios_rwsem)
 |                                |-------__receive_buf()
 |                                |       copies data into n_tty buffer
 |                                |-------up_read(&tty->termios_rwsem)
 |--down_read(&tty->termios_rwsem)
 |--copy buffer data to user

>From this sequence, you can see that thread2 writes to the buffer then
only clears the part of the buffer in n_tty.  The n_tty receive buffer
code then copies more data into the n_tty buffer.

But part of the vhangup, releasing the redirect, is still required to
avoid issues with consoles running on pty slaves.  So do that.
As far as I can tell, that is all that should be required.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Link: https://lore.kernel.org/r/20201124004902.1398477-3-minyard@acm.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

33d4ae98

tty: Export redirect release · f446776e

Corey Minyard authored Nov 23, 2020

This will be required by the pty code when it removes tty_vhangup() on
master close.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Link: https://lore.kernel.org/r/20201124004902.1398477-2-minyard@acm.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

f446776e

serial: stm32: update transmission complete error message in shutdown · c31c3ea0

Erwan Le Ray authored Jan 06, 2021

The transmission complete error message provides the status of the
ISR_USART_TC bit. This bit, when set, indicates that the transmission
has not been completed.
The bit status indication is not a very understandable information.
The error message sent on console should indicate that the transmission is
not complete, instead of providing USART_TC bit status.
Update the error message and add a comment for better understanding.
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-9-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

c31c3ea0

serial: stm32: clean probe and remove port deinit · 97f3a085

Erwan Le Ray authored Jan 06, 2021

Clean probe and remove port deinit by moving clk_disable_unprepare in a
new dedicated deinit_port function.
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-8-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

97f3a085

serial: stm32: update conflicting RTS/CTS config comment · 9359369a

Erwan Le Ray authored Jan 06, 2021

The comment for conflicting RTS/CTS config refers to "st, hw-flow-ctrl",
but this property is deprecated since the generic RTS/CTS property has
been introduced by the patch 'serial: stm32: Use generic DT binding for
announcing RTS/CTS lines'.
Update the comment to refer to both generic and deprecated RTS/CTS
properties.
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-7-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

9359369a

dt-bindings: serial: stm32: update rts-gpios and cts-gpios · 9ba8377c

Erwan Le Ray authored Jan 06, 2021

Update rts-gpios and cts-gpios:
- remove max-items as already defined in serial.yaml
- add a note describing rts-gpios and cts-gpios usage with stm32

Document the use of cts-gpios and rts-gpios for flow control in STM32 UART
controller. These properties can be used instead of 'uart-has-rtscts' or
'st,hw-flow-ctrl' (deprecated) for making use of any gpio pins for flow
control instead of dedicated pins.
It should be noted that both cts-gpios/rts-gpios and 'uart-has-rtscts' or
'st,hw-flow-ctrl' (deprecated) properties cannot co-exist in a design.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-6-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

9ba8377c

serial: stm32: add author · 8ebd9665

Erwan Le Ray authored Jan 06, 2021

Update email address add new author in authors list.
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-5-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

8ebd9665

serial: stm32: add "_usart" prefix in functions name · 56f9a76c

Erwan Le Ray authored Jan 06, 2021

Adds the prefix "_usart" in the name of stm32 usart functions in order to
ease the usage of kernel trace and tools, such as f-trace.
Allows to trace "stm32_usart_*" functions with f-trace. Without this patch,
all the driver functions needs to be added manually in f-trace filter.
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-4-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

56f9a76c

serial: stm32: fix code cleaning warnings and checks · 92fc0023

Erwan Le Ray authored Jan 06, 2021

Fixes checkpatch --strict warnings and checks:
- checkpatch --strict "Unnecessary parentheses"
- checkpatch --strict "Blank lines aren't necessary before a close brace
- checkpatch --strict "Alignment should match open parenthesis"
- checkpatch --strict "Please don't use multiple blank lines"
- checkpatch --strict "Comparison to NULL could be written ..."
- visual check code ordering warning
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-3-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

92fc0023

serial: stm32: fix DMA initialization error handling · e7997f7f

Erwan Le Ray authored Jan 06, 2021

DMA initialization error handling is not properly implemented in the
driver.
Fix DMA initialization error handling by:
- moving TX DMA descriptor request error handling in a new dedicated
fallback_err label
- adding error handling to TX DMA descriptor submission
- adding error handling to RX DMA descriptor submission

This patch depends on '24832ca3 ("tty: serial: stm32-usart: Remove set
but unused 'cookie' variables")' which unfortunately doesn't include a
"Fixes" tag.

Fixes: 34891872 ("serial: stm32: adding dma support")
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210106162203.28854-2-erwan.leray@foss.st.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

e7997f7f