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

Steven Rostedt
2024-08-26T17:28:37Z

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?

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);
> }