linux-stable.git/drivers/tty/sysrq.c, branch linux-3.16.y

sysrq: attach sysrq handler correctly for 32-bit kernel

2017-03-16T02:26:56+00:00

commit 802c03881f29844af0252b6e22be5d2f65f93fd0 upstream.

The sysrq input handler should be attached to the input device which has
a left alt key.

On 32-bit kernels, some input devices which has a left alt key cannot
attach sysrq handler.  Because the keybit bitmap in struct input_device_id
for sysrq is not correctly initialized.  KEY_LEFTALT is 56 which is
greater than BITS_PER_LONG on 32-bit kernels.

I found this problem when using a matrix keypad device which defines
a KEY_LEFTALT (56) but doesn't have a KEY_O (24 == 56%32).

Cc: Jiri Slaby 
Signed-off-by: Akinobu Mita 
Acked-by: Dmitry Torokhov 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

sysrq: Fix warning in sysrq generated crash.

2016-02-02T19:39:38+00:00

commit 984cf355aeaa8f2eda3861b50d0e8d3e3f77e83b upstream.

Commit 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq") replaced
spin_lock_irqsave() calls with rcu_read_lock() calls in sysrq. Since
rcu_read_lock() does not disable preemption, faulthandler_disabled() in
__do_page_fault() in x86/fault.c returns false. When the code later calls
might_sleep() in the pagefault handler, we get the following warning:

BUG: sleeping function called from invalid context at ../arch/x86/mm/fault.c:1187
in_atomic(): 0, irqs_disabled(): 0, pid: 4706, name: bash
Preemption disabled at:[] printk+0x48/0x4a

To fix this, we release the RCU read lock before we crash.

Tested this patch on linux 3.18 by booting off one of our boards.

Fixes: 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq")

Signed-off-by: Ani Sinha 
Reviewed-by: Rik van Riel 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Luis Henriques

tty: remove platform_sysrq_reset_seq

2015-07-15T09:01:19+00:00

commit abab381feea7e61a0b5125504aa955cf339676ca upstream.

The platform_sysrq_reset_seq code was intended as a way for an embedded
platform to provide its own sysrq sequence at compile time. After over
two years, nobody has started using it in an upstream kernel, and
the platforms that were interested in it have moved on to devicetree,
which can be used to configure the sequence without requiring kernel
changes. The method is also incompatible with the way that most
architectures build support for multiple platforms into a single
kernel.

Now the code is producing warnings when built with gcc-5.1:

drivers/tty/sysrq.c: In function 'sysrq_init':
drivers/tty/sysrq.c:959:33: warning: array subscript is above array bounds [-Warray-bounds]
   key = platform_sysrq_reset_seq[i];

We could fix this, but it seems unlikely that it will ever be used,
so let's just remove the code instead. We still have the option to
pass the sequence either in DT, using the kernel command line,
or using the /sys/module/sysrq/parameters/reset_seq file.

Signed-off-by: Arnd Bergmann 
Fixes: 154b7a489a ("Input: sysrq - allow specifying alternate reset sequence")
----
v2: moved sysrq_reset_downtime_ms variable to avoid introducing a compile
    warning when CONFIG_INPUT is disabled
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Luis Henriques

sysrq,rcu: suppress RCU stall warnings while sysrq runs

2014-06-06T23:08:17+00:00

Some sysrq handlers can run for a long time, because they dump a lot of
data onto a serial console.  Having RCU stall warnings pop up in the
middle of them only makes the problem worse.

This patch temporarily disables RCU stall warnings while a sysrq request
is handled.

Signed-off-by: Rik van Riel 
Suggested-by: Paul McKenney 
Signed-off-by: Paul E. McKenney 
Cc: Madper Xie 
Cc: Randy Dunlap 
Cc: Richard Weinberger 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sysrq: rcu-ify __handle_sysrq

2014-06-06T23:08:17+00:00

Echoing values into /proc/sysrq-trigger seems to be a popular way to get
information out of the kernel.  However, dumping information about
thousands of processes, or hundreds of CPUs to serial console can result
in IRQs being blocked for minutes, resulting in various kinds of cascade
failures.

The most common failure is due to interrupts being blocked for a very
long time.  This can lead to things like failed IO requests, and other
things the system cannot easily recover from.

This problem is easily fixable by making __handle_sysrq use RCU instead
of spin_lock_irqsave.

This leaves the warning that RCU grace periods have not elapsed for a
long time, but the system will come back from that automatically.

It also leaves sysrq-from-irq-context when the sysrq keys are pressed,
but that is probably desired since people want that to work in
situations where the system is already hosed.

The callers of register_sysrq_key and unregister_sysrq_key appear to be
capable of sleeping.

Signed-off-by: Rik van Riel 
Reported-by: Madper Xie 
Cc: Randy Dunlap 
Cc: Richard Weinberger 
Cc: Paul E. McKenney 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/printk: use symbolic defines for console loglevels

2014-06-04T23:54:17+00:00

... instead of naked numbers.

Stuff in sysrq.c used to set it to 8 which is supposed to mean above
default level so set it to DEBUG instead as we're terminating/killing all
tasks and we want to be verbose there.

Also, correct the check in x86_64_start_kernel which should be >= as
we're clearly issuing the string there for all debug levels, not only
the magical 10.

Signed-off-by: Borislav Petkov 
Acked-by: Kees Cook 
Acked-by: Randy Dunlap 
Cc: Joe Perches 
Cc: Valdis Kletnieks 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sysrq: Allow magic SysRq key functions to be disabled through Kconfig

2013-10-16T20:01:44+00:00

Turn the initial value of sysctl kernel.sysrq (SYSRQ_DEFAULT_ENABLE)
into a Kconfig variable.

Original version by Bastian Blank .

Signed-off-by: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input

2013-09-07T17:38:46+00:00

Pull input updates from Dmitry Torokhov:
 "A new driver for slidebar on Ideapad laptops and a bunch of assorted
  driver fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input: (32 commits)
  Input: add SYN_MAX and SYN_CNT constants
  Input: max11801_ts - convert to devm
  Input: egalax-ts - fix typo and improve text
  Input: MAINTAINERS - change maintainer for cyttsp driver
  Input: cyttsp4 - kill 'defined but not used' compiler warnings
  Input: add driver for slidebar on Lenovo IdeaPad laptops
  Input: omap-keypad - set up irq type from DT
  Input: omap-keypad - enable wakeup capability for keypad.
  Input: omap-keypad - clear interrupts on open
  Input: omap-keypad - convert to threaded IRQ
  Input: omap-keypad - use bitfiled instead of hardcoded values
  Input: cyttsp4 - remove useless NULL test from cyttsp4_watchdog_timer()
  Input: wacom - fix error return code in wacom_probe()
  Input: as5011 - fix error return code in as5011_probe()
  Input: keyboard, serio - simplify use of devm_ioremap_resource
  Input: tegra-kbc - simplify use of devm_ioremap_resource
  Input: htcpen - fix incorrect placement of __initdata
  Input: qt1070 - add power management ops
  Input: wistron_btns - add MODULE_DEVICE_TABLE
  Input: wistron_btns - mark the Medion MD96500 keymap as tested
  ...

Input: sysrq - DT binding for key sequence

2013-08-13T05:31:55+00:00

Adding a simple device tree binding for the specification of key
sequences. Definition of the keys found in the sequence are located in
'include/uapi/linux/input.h'.

For the sysrq driver, holding the sequence of keys down for a specific
amount of time will reset the system.

Signed-off-by: Mathieu Poirier 
Acked-by: Grant Likely 
Signed-off-by: Dmitry Torokhov

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input

2013-07-04T22:35:08+00:00

Pull input updates from Dmitry Torokhov:
 "First round of updates for the input subsystem.

  You will get a new touchsreen driver for Cypress 4th generation
  devices, a driver for a special controller implementing PS/2 protocol
  in OLPC devices, and a driver for power key for SiRFprimaII PWRC.

  HID and bcm5497 now support for the 2013 MacBook Air.

  EVIOCGKEY and the rest of evdev ioctls now flush events of matching
  type from the client's event queue so that clients can be sure any
  events received after issuing EVIOCG* ioctl are new events.

  And a host of cleanups and improvements in other drivers"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input: (87 commits)
  Input: cyttsp4 - kfree xfer_buf on error path in probe()
  Input: tps6507x-ts - select INPUT_POLLDEV
  Input: bcm5974 - add support for the 2013 MacBook Air
  HID: apple: Add support for the 2013 Macbook Air
  Input: cyttsp4 - leak on error path in probe()
  Input: cyttsp4 - silence NULL dereference warning
  Input: cyttsp4 - silence shift wrap warning
  Input: tps6507x-ts - convert to polled input device infrastructure
  ARM: davinci: da850-evm: remove vref from touchscreen platform data
  Input: cyttsp4 - SPI driver for Cypress TMA4XX touchscreen devices
  Input: cyttsp4 - I2C driver for Cypress TMA4XX touchscreen devices
  Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices
  Input: cyttsp - I2C driver split into two modules
  Input: add OLPC AP-SP driver
  Input: nspire-keypad - remove redundant dev_err call in nspire_keypad_probe()
  Input: tps6507x-ts - remove vref from platform data
  Input: tps6507x-ts - use bool for booleans
  Input: tps6507x-ts - remove bogus unreachable code
  Input: samsung-keypad - let device core setup the default pin configuration
  Input: wacom_i2c - implement hovering capability
  ...