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

Masami Hiramatsu
2020-08-29T09:31:46Z

On Fri, 28 Aug 2020 20:34:22 +0800
Guo Ren <guoren@kernel.org> wrote:

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

Thanks Guo! I'll add it to the next version.

>
> 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/

--
Masami Hiramatsu <mhiramat@kernel.org>