Re: [PATCH v3] /proc/sysrq-trigger: accept multiple keys at once

Jiri Slaby
2023-11-14T09:50:49Z

On 14. 11. 23, 10:49, Tomas Mudrunka wrote:
> Just for convenience.
> This way we can do:
> `echo _reisub > /proc/sysrq-trigger`
> Instead of:
> `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;`
>
> This can be very useful when trying to execute sysrq combo remotely
> or from userspace. When sending keys in multiple separate writes,
> userspace can be killed before whole combo is completed.
> Therefore putting all keys in single write is more robust approach.
>
> Signed-off-by: Tomas Mudrunka <tomas.mudrunka@gmail.com>
> ---

What has changed in v2, v3?

> Documentation/admin-guide/sysrq.rst | 4 ++++
> drivers/tty/sysrq.c | 19 +++++++++++++++----
> 2 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst
> index 51906e473..9d46a33e5 100644
> --- a/Documentation/admin-guide/sysrq.rst
> +++ b/Documentation/admin-guide/sysrq.rst
> @@ -79,6 +79,10 @@ On all
>
> echo t > /proc/sysrq-trigger
>
> + Alternatively write key combo prepended by underscore. e.g.::
> +
> + echo _reisub > /proc/sysrq-trigger
> +
> The :kbd:`<command key>` is case sensitive.
>
> What are the 'command' keys?
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 6b4a28bcf..367028b1e 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -1150,16 +1150,27 @@ EXPORT_SYMBOL(unregister_sysrq_key);
> #ifdef CONFIG_PROC_FS
> /*
> * writing 'C' to /proc/sysrq-trigger is like sysrq-C
> + * If first character in write is underscore, all characters are interpreted.
> */
> static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
> size_t count, loff_t *ppos)
> {
> - if (count) {
> - char c;
> + char bulk = false;
> + size_t i;
>
> - if (get_user(c, buf))
> + for (i = 0; i < count; i++) {
> + bool c;

bool c?

--
js
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