linux-kernel - Re: [PATCH v3 06/16] csky: kprobes: Use generic kretprobe trampoline handler

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Date:   Fri, 28 Aug 2020 20:34:22 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Eddy Wu <Eddy_Wu@...ndmicro.com>, x86@...nel.org,
        "David S . Miller" <davem@...emloft.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v3 06/16] csky: kprobes: Use generic kretprobe trampoline handler

Looks more clear.

Acked-by: Guo Ren <guoren@...nel.org>

On Fri, Aug 28, 2020 at 12:39 AM Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  arch/csky/kernel/probes/kprobes.c |   78 +------------------------------------
>  1 file changed, 3 insertions(+), 75 deletions(-)
>
> diff --git a/arch/csky/kernel/probes/kprobes.c b/arch/csky/kernel/probes/kprobes.c
> index f0f733b7ac5a..a891fb422e76 100644
> --- a/arch/csky/kernel/probes/kprobes.c
> +++ b/arch/csky/kernel/probes/kprobes.c
> @@ -404,87 +404,15 @@ int __init arch_populate_kprobe_blacklist(void)
>
>  void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
>  {
> -       struct kretprobe_instance *ri = NULL;
> -       struct hlist_head *head, empty_rp;
> -       struct hlist_node *tmp;
> -       unsigned long flags, orig_ret_address = 0;
> -       unsigned long trampoline_address =
> -               (unsigned long)&kretprobe_trampoline;
> -       kprobe_opcode_t *correct_ret_addr = NULL;
> -
> -       INIT_HLIST_HEAD(&empty_rp);
> -       kretprobe_hash_lock(current, &head, &flags);
> -
> -       /*
> -        * It is possible to have multiple instances associated with a given
> -        * task either because multiple functions in the call path have
> -        * return probes installed on them, and/or more than one
> -        * return probe was registered for a target function.
> -        *
> -        * We can handle this because:
> -        *     - instances are always pushed into the head of the list
> -        *     - when multiple return probes are registered for the same
> -        *       function, the (chronologically) first instance's ret_addr
> -        *       will be the real return address, and all the rest will
> -        *       point to kretprobe_trampoline.
> -        */
> -       hlist_for_each_entry_safe(ri, tmp, head, hlist) {
> -               if (ri->task != current)
> -                       /* another task is sharing our hash bucket */
> -                       continue;
> -
> -               orig_ret_address = (unsigned long)ri->ret_addr;
> -
> -               if (orig_ret_address != trampoline_address)
> -                       /*
> -                        * This is the real return address. Any other
> -                        * instances associated with this task are for
> -                        * other calls deeper on the call stack
> -                        */
> -                       break;
> -       }
> -
> -       kretprobe_assert(ri, orig_ret_address, trampoline_address);
> -
> -       correct_ret_addr = ri->ret_addr;
> -       hlist_for_each_entry_safe(ri, tmp, head, hlist) {
> -               if (ri->task != current)
> -                       /* another task is sharing our hash bucket */
> -                       continue;
> -
> -               orig_ret_address = (unsigned long)ri->ret_addr;
> -               if (ri->rp && ri->rp->handler) {
> -                       __this_cpu_write(current_kprobe, &ri->rp->kp);
> -                       get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
> -                       ri->ret_addr = correct_ret_addr;
> -                       ri->rp->handler(ri, regs);
> -                       __this_cpu_write(current_kprobe, NULL);
> -               }
> -
> -               recycle_rp_inst(ri, &empty_rp);
> -
> -               if (orig_ret_address != trampoline_address)
> -                       /*
> -                        * This is the real return address. Any other
> -                        * instances associated with this task are for
> -                        * other calls deeper on the call stack
> -                        */
> -                       break;
> -       }
> -
> -       kretprobe_hash_unlock(current, &flags);
> -
> -       hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
> -               hlist_del(&ri->hlist);
> -               kfree(ri);
> -       }
> -       return (void *)orig_ret_address;
> +       return (void *)kretprobe_trampoline_handler(regs,
> +                       (unsigned long)&kretprobe_trampoline, NULL);
>  }
>
>  void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
>                                       struct pt_regs *regs)
>  {
>         ri->ret_addr = (kprobe_opcode_t *)regs->lr;
> +       ri->fp = NULL;
>         regs->lr = (unsigned long) &kretprobe_trampoline;
>  }
>
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/