linux-kernel - Re: [PATCH v3 20/21] dyndbg: add user-flag, negating-flags, and filtering on flags

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Date:   Wed, 17 Jun 2020 16:57:45 -0600
From:   jim.cromie@...il.com
To:     Joe Perches <joe@...ches.com>
Cc:     Jason Baron <jbaron@...mai.com>,
        LKML <linux-kernel@...r.kernel.org>, akpm@...uxfoundation.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Orson Zhai <orson.zhai@...soc.com>,
        Petr Mladek <pmladek@...e.com>,
        Linux Documentation List <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3 20/21] dyndbg: add user-flag, negating-flags, and
 filtering on flags

On Wed, Jun 17, 2020 at 4:13 PM Joe Perches <joe@...ches.com> wrote:
>
> On Wed, 2020-06-17 at 10:25 -0600, Jim Cromie wrote:
> > 1. Add a user-flag [u] which works like the [pfmlt] flags, but has no
> > effect on callsite behavior; it allows incremental marking of
> > arbitrary sets of callsites.
> >
> > 2. Add [PFMLTU] flags, which negate their counterparts; P===!p etc.
> > And in ddebug_read_flags():
> >    current code does: [pfmltu_] -> flags
> >    copy it to:                [PFMLTU_] -> mask
> >
> > also disallow both of a pair: ie no 'pP', no true & false.
> >
> > 3. Add filtering ops into ddebug_change(), right after all the
> > callsite-property selections are complete.  These filter on the
> > callsite's current flagstate before applying modflags.
> >
> > Why ?
> >
> > The u-flag & filter flags
> >
> > The 'u' flag lets the user assemble an arbitary set of callsites.
> > Then using filter flags, user can activate the 'u' callsite set.
> >
> >   #> echo 'file foo.c +u; file bar.c +u' > control   # and repeat
> >   #> echo 'u+p' > control
> >
> > Of course, you can continue to just activate your set without ever
> > marking it 1st, but you could trivially add the markup as you go, then
> > be able to use it as a constraint later, to undo or modify your set.
>
> Does this set selection also allow for selection by
> increasing decimal level?
>
> Can sites be enabled for a value less than x?
>
>

no, theres no levels added here.
that would be a variation on the WIP pr-class patch in v2, dropped from v3

legacy dyndbg - select on RO callsite info only - file, module, func, line.
    flag state is write only.
filterflags -   additionally select on callsite's flagstate, ie
reading the current flagstate

please look at the export patch 15/21
for how I now think levels, and drm.debug=0x03 can be done.