On Mon, 26 Aug 2024 09:55:29 +0300
Mike Rapoport <r...@kernel.org> wrote:

> From: Song Liu <s...@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 <s...@kernel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <r...@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);
>       }


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