On Tue, Mar 18, 2025 at 11:14:55AM +0100, Miroslav Benes wrote:
> Hi,
>
> On Mon, 17 Mar 2025, Song Liu wrote:
>
> > On Mon, Mar 17, 2025 at 11:59 AM Joe Lawrence <joe.lawrence@xxxxxxxxxx> wrote:
> > >
> > > On 3/17/25 12:51, Song Liu wrote:
> > > > CONFIG_KPROBES_ON_FTRACE is required for test-kprobe. Skip test-kprobe
> > > > when CONFIG_KPROBES_ON_FTRACE is not set.
> > > >
> > > > Signed-off-by: Song Liu <song@xxxxxxxxxx>
> > > > ---
> > > > tools/testing/selftests/livepatch/test-kprobe.sh | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/tools/testing/selftests/livepatch/test-kprobe.sh b/tools/testing/selftests/livepatch/test-kprobe.sh
> > > > index 115065156016..fd823dd5dd7f 100755
> > > > --- a/tools/testing/selftests/livepatch/test-kprobe.sh
> > > > +++ b/tools/testing/selftests/livepatch/test-kprobe.sh
> > > > @@ -5,6 +5,8 @@
> > > >
> > > > . $(dirname $0)/functions.sh
> > > >
> > > > +zgrep KPROBES_ON_FTRACE /proc/config.gz || skip "test-kprobe requires CONFIG_KPROBES_ON_FTRACE"
> > > > +
> > >
> > > Hi Song,
> > >
> > > This in turn depends on CONFIG_IKCONFIG_PROC for /proc/config.gz (not
> > > set for RHEL distro kernels).
> >
> > I was actually worrying about this when testing it.
> >
> > > Is there a dynamic way to figure out CONFIG_KPROBES_ON_FTRACE support?
> >
> > How about we grep kprobe_ftrace_ops from /proc/kallsyms?
>
> which relies on having KALLSYMS_ALL enabled but since CONFIG_LIVEPATCH
> depends on it, we are good. So I would say yes, it is a better option.
> Please, add a comment around.
>
Kallsyms is a good workaround as kprobe_ftrace_ops should be stable (I
hope :)
Since Song probably noticed this when upgrading and the new kprobes test
unexpectedly failed, I'd add a Fixes tag to help out backporters:
Fixes: 62597edf6340 ("selftests: livepatch: test livepatching a kprobed function")
but IMHO not worth rushing as important through the merge window.
Also, while poking at this today with virtme-ng, my initial attempt had
build a fairly minimal kernel without CONFIG_DYNAMIC_DEBUG. We can also
check for that via the sysfs interface to avoid confusing path-not-found
msgs, like the following ...
-- Joe
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