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| author | Dmitry Safonov <dima@arista.com> | 2020-03-02 17:51:34 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-03-07 09:52:02 +0100 |
| commit | eaee41727e6d8a7d2b94421c25e82b00cb2fded5 (patch) | |
| tree | 1b9f0cdd393854d1d8cc5bfc58c895a1d06f0f5a /drivers/tty/sysrq.c | |
| parent | 7f9803072ff636fc22ad941ff059e020e9d77ed4 (diff) | |
| download | lwn-eaee41727e6d8a7d2b94421c25e82b00cb2fded5.tar.gz lwn-eaee41727e6d8a7d2b94421c25e82b00cb2fded5.zip | |
sysctl/sysrq: Remove __sysrq_enabled copy
Many embedded boards have a disconnected TTL level serial which can
generate some garbage that can lead to spurious false sysrq detects.
Currently, sysrq can be either completely disabled for serial console
or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since
commit 732dbf3a6104 ("serial: do not accept sysrq characters via serial port")
At Arista, we have such boards that can generate BREAK and random
garbage. While disabling sysrq for serial console would solve
the problem with spurious false sysrq triggers, it's also desirable
to have a way to enable sysrq back.
Having the way to enable sysrq was beneficial to debug lockups with
a manual investigation in field and on the other side preventing false
sysrq detections.
As a preparation to add sysrq_toggle_support() call into uart,
remove a private copy of sysrq_enabled from sysctl - it should reflect
the actual status of sysrq.
Furthermore, the private copy isn't correct already in case
sysrq_always_enabled is true. So, remove __sysrq_enabled and use a
getter-helper sysrq_mask() to check sysrq_key_op enabled status.
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200302175135.269397-2-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/sysrq.c')
| -rw-r--r-- | drivers/tty/sysrq.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index f724962a5906..5e0d0813da55 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -63,6 +63,18 @@ static bool sysrq_on(void) return sysrq_enabled || sysrq_always_enabled; } +/** + * sysrq_mask - Getter for sysrq_enabled mask. + * + * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. + */ +int sysrq_mask(void) +{ + if (sysrq_always_enabled) + return 1; + return sysrq_enabled; +} + /* * A value of 1 means 'all', other nonzero values are an op mask: */ |