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

Guo Ren
2020-08-28T12:34:53Z

Looks more clear.

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

On Fri, Aug 28, 2020 at 12:39 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.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/