Re: [RFC PATCH 3/5] kprobe: Simplify prepare_kprobe() by dropping redundant version

Masami Hiramatsu
2021-06-09T14:42:44Z

On Wed, 9 Jun 2021 19:50:17 +0900
Punit Agrawal <punitagrawal@gmail.com> wrote:

> The function prepare_kprobe() is called during kprobe registration and
> is responsible for ensuring any architecture related preparation for
> the kprobe is done before returning.
>
> One of two versions of prepare_kprobe() is chosen depending on the
> availability of KPROBE_ON_FTRACE in the kernel configuration.
>
> Simplify the code by dropping the version when KPROBE_ON_FTRACE is not
> selected - instead relying on kprobe_ftrace() to return false when
> KPROBE_ON_FTRACE is not set.
>

OK, since kprobe_ftrace() just checks a flag is set or not,
it is always usable in kprobes.c.
Looks good to me :)

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you!

> No functional change.
>
> Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
> ---
> include/linux/kprobes.h | 5 +++++
> kernel/kprobes.c | 23 +++++++++--------------
> 2 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 1883a4a9f16a..771013bab18a 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -362,6 +362,11 @@ static inline void wait_for_kprobe_optimizer(void) { }
> extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *ops, struct ftrace_regs *fregs);
> extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
> +#else
> +static inline int arch_prepare_kprobe_ftrace(struct kprobe *p)
> +{
> + return -EINVAL;
> +}
> #endif
>
> int arch_check_ftrace_location(struct kprobe *p);
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 1a11d3c411bf..54d37d4ab897 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1022,15 +1022,6 @@ static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = {
> static int kprobe_ipmodify_enabled;
> static int kprobe_ftrace_enabled;
>
> -/* Must ensure p->addr is really on ftrace */
> -static int prepare_kprobe(struct kprobe *p)
> -{
> - if (!kprobe_ftrace(p))
> - return arch_prepare_kprobe(p);
> -
> - return arch_prepare_kprobe_ftrace(p);
> -}
> -
> /* Caller must lock kprobe_mutex */
> static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
> int *cnt)
> @@ -1102,11 +1093,6 @@ static int disarm_kprobe_ftrace(struct kprobe *p)
> ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
> }
> #else /* !CONFIG_KPROBES_ON_FTRACE */
> -static inline int prepare_kprobe(struct kprobe *p)
> -{
> - return arch_prepare_kprobe(p);
> -}
> -
> static inline int arm_kprobe_ftrace(struct kprobe *p)
> {
> return -ENODEV;
> @@ -1118,6 +1104,15 @@ static inline int disarm_kprobe_ftrace(struct kprobe *p)
> }
> #endif
>
> +static int prepare_kprobe(struct kprobe *p)
> +{
> + /* Must ensure p->addr is really on ftrace */
> + if (kprobe_ftrace(p))
> + return arch_prepare_kprobe_ftrace(p);
> +
> + return arch_prepare_kprobe(p);
> +}
> +
> /* Arm a kprobe with text_mutex */
> static int arm_kprobe(struct kprobe *kp)
> {
> --
> 2.30.2
>

--
Masami Hiramatsu <mhiramat@kernel.org>