Re: [PATCH v2 5/8] ftrace: Add swap_func to ftrace_process_locs()

Mike Rapoport
2024-08-27T15:43:29Z

On Mon, Aug 26, 2024 at 01:29:09PM -0400, Steven Rostedt wrote:
> On Mon, 26 Aug 2024 09:55:29 +0300
> Mike Rapoport <rppt@kernel.org> wrote:
>
> > From: Song Liu <song@kernel.org>
> >
> > ftrace_process_locs sorts module mcount, which is inside RO memory. Add a
> > ftrace_swap_func so that archs can use RO-memory-poke function to do the
> > sorting.
>
> Can you add the above as a comment above the ftrace_swap_func() function?

Sure.

> Thanks,
>
> -- Steve
>
> >
> > Signed-off-by: Song Liu <song@kernel.org>
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> > include/linux/ftrace.h | 2 ++
> > kernel/trace/ftrace.c | 13 ++++++++++++-
> > 2 files changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index fd5e84d0ec47..b794dcb7cae8 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -1188,4 +1188,6 @@ unsigned long arch_syscall_addr(int nr);
> >
> > #endif /* CONFIG_FTRACE_SYSCALLS */
> >
> > +void ftrace_swap_func(void *a, void *b, int n);
> > +
> > #endif /* _LINUX_FTRACE_H */
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 4c28dd177ca6..9829979f3a46 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -6989,6 +6989,17 @@ static void test_is_sorted(unsigned long *start,
> > unsigned long count) }
> > #endif
> >
> > +void __weak ftrace_swap_func(void *a, void *b, int n)
> > +{
> > + unsigned long t;
> > +
> > + WARN_ON_ONCE(n != sizeof(t));
> > +
> > + t = *((unsigned long *)a);
> > + *(unsigned long *)a = *(unsigned long *)b;
> > + *(unsigned long *)b = t;
> > +}
> > +
> > static int ftrace_process_locs(struct module *mod,
> > unsigned long *start,
> > unsigned long *end)
> > @@ -7016,7 +7027,7 @@ static int ftrace_process_locs(struct module *mod,
> > */
> > if (!IS_ENABLED(CONFIG_BUILDTIME_MCOUNT_SORT) || mod) {
> > sort(start, count, sizeof(*start),
> > - ftrace_cmp_ips, NULL);
> > + ftrace_cmp_ips, ftrace_swap_func);
> > } else {
> > test_is_sorted(start, count);
> > }
>

--
Sincerely yours,
Mike.