Re: [RFC] tty/sysrq: Add alternative SysRq key

From: Greg Kroah-Hartman
Date: Thu Nov 04 2021 - 05:52:40 EST


On Thu, Nov 04, 2021 at 10:34:29AM +0100, Andrzej Pietrasiewicz wrote:
> There exist machines which don't have SysRq key at all, e.g. chromebooks.
>
> This patch allows configuring an alternative key to act as SysRq. Devices
> which declare KEY_SYSRQ in their 'keybit' bitmap continue using KEY_SYSRQ,
> but other devices use the alternative SysRq key instead, by default F10.
> Which key is actually used can be modified with sysrq's module parameter.
>
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
> ---
>
>
> A corrected version with completed conflict resolution.
>
>
>
> drivers/tty/sysrq.c | 28 +++++++++++++++++++++++++---
> 1 file changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index c911196ac893..fb59745b23c9 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -634,6 +634,7 @@ EXPORT_SYMBOL(handle_sysrq);
>
> #ifdef CONFIG_INPUT
> static int sysrq_reset_downtime_ms;
> +static unsigned short alternative_sysrq_key = KEY_F10;
>
> /* Simple translation table for the SysRq keys */
> static const unsigned char sysrq_xlate[KEY_CNT] =
> @@ -653,6 +654,7 @@ struct sysrq_state {
> unsigned int alt_use;
> unsigned int shift;
> unsigned int shift_use;
> + unsigned short sysrq_key;
> bool active;
> bool need_reinject;
> bool reinjecting;
> @@ -802,10 +804,10 @@ static void sysrq_reinject_alt_sysrq(struct work_struct *work)
>
> /* Simulate press and release of Alt + SysRq */
> input_inject_event(handle, EV_KEY, alt_code, 1);
> - input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
> + input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 1);
> input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>
> - input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
> + input_inject_event(handle, EV_KEY, sysrq->sysrq_key, 0);
> input_inject_event(handle, EV_KEY, alt_code, 0);
> input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
>
> @@ -845,6 +847,7 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
> sysrq->shift = code;
> break;
>
> +key_sysrq:
> case KEY_SYSRQ:
> if (value == 1 && sysrq->alt != KEY_RESERVED) {
> sysrq->active = true;
> @@ -867,11 +870,15 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
> * triggering print screen function.
> */
> if (sysrq->active)
> - clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
> + clear_bit(sysrq->sysrq_key, sysrq->handle.dev->key);
>
> break;
>
> default:
> + /* handle non-default sysrq key */
> + if (code == sysrq->sysrq_key)
> + goto key_sysrq;
> +
> if (sysrq->active && value && value != 2) {
> unsigned char c = sysrq_xlate[code];
>
> @@ -970,6 +977,14 @@ static int sysrq_connect(struct input_handler *handler,
> sysrq->handle.private = sysrq;
> timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
>
> + if (test_bit(KEY_SYSRQ, dev->keybit)) {
> + sysrq->sysrq_key = KEY_SYSRQ;
> + pr_info("%s: using default sysrq key [%x]\n", dev->name, KEY_SYSRQ);
> + } else {
> + sysrq->sysrq_key = alternative_sysrq_key;
> + pr_info("%s: Using alternative sysrq key: [%x]\n", dev->name, sysrq->sysrq_key);
> + }
> +
> error = input_register_handle(&sysrq->handle);
> if (error) {
> pr_err("Failed to register input sysrq handler, error %d\n",
> @@ -1078,6 +1093,13 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
>
> module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
>
> +module_param(alternative_sysrq_key, ushort, 0644);
> +MODULE_PARM_DESC(alternative_sysrq_key,
> + "Alternative SysRq key for input devices that don't have SysRq key. F10 by default.\n"
> + "Example\n"
> + "Using F9 as SysRq:\n"
> + "sysrq.alternative_sysrq_key=0x43\n");
> +
> #else
>
> static inline void sysrq_register_handler(void)
> --
> 2.17.1
>

Hi,

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