Re: [PATCH] tty: only print sysrq help for handlers that are enabled

[Peter Hurley]

On 12/24/2013 12:04 AM, shawn@xxxxxxxxxxxxxxx wrote:
> > On Tue, Dec 03, 2013 at 07:55:25AM -0800, Shawn Landden wrote:
> > > Also print out a notice when sysrq is in selective mode.
> > >
> > > Signed-off-by: Shawn Landden <shawn@xxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/tty/sysrq.c | 7 ++++++-
> > >   1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > > index ce396ec..4eee0e4 100644
> > > --- a/drivers/tty/sysrq.c
> > > +++ b/drivers/tty/sysrq.c
> > > @@ -548,9 +548,14 @@ void __handle_sysrq(int key, bool check_mask)
> > >   					;
> > >   				if (j != i)
> > >   					continue;
> > > -				printk("%s ", sysrq_key_table[i]->help_msg);
> > > +				/* only print if handler is enabled */
> > > +				if (sysrq_enabled & 1 ||
> > > +				    sysrq_enabled & sysrq_key_table[i]->enable_mask)
> > > +					printk("%s ", sysrq_key_table[i]->help_msg);
> > >   			}
> > >   		}
> > > +		if (!(sysrq_enabled & 1))
> > > +			printk("(some options are disabled)");
> > >   		printk("\n");
> > >   		console_loglevel = orig_log_level;
> > >   	}
> >
> > What exactly is this fixing?  What is broken here that this change
> > resolves?  Where is it applicable?  I need a lot more context here
> > please.
>
> Without this patch you get something like
> re[b]oot [r]aw [s]ync [h]elp ....
> even if none of these sysrq triggers are available because of the setting
> mask of
> kernel.sysrq
> With this patch then if (e.g.)
> kernel.sysrq = 16
> then you will only see
> [s]ync
> i.e. those commands you have privilege to issue via sysrq keypresses.
> Contact me if you need more,
> Shawn

But all operations are enabled when triggered via /proc/sysrq-trigger.
How about indicating key-disabled operations with a symbol instead?

Regards,
Peter Hurley

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