From: Christophe Leroy <christophe.leroy@c-s.fr>
To: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] powerpc/kprobes: Remove redundant code
Date: Wed, 19 Feb 2020 08:48:09 +0100 [thread overview]
Message-ID: <0fc8e46e-968b-c779-0721-03bb0ba0c33c@c-s.fr> (raw)
In-Reply-To: <1582036611.9hm2t8ijhz.naveen@linux.ibm.com>
Le 18/02/2020 à 15:39, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> At the time being we have something like
>>
>> if (something) {
>> p = get();
>> if (p) {
>> if (something_wrong)
>> goto out;
>> ...
>> return;
>> } else if (a != b) {
>> if (some_error)
>> goto out;
>> ...
>> }
>> goto out;
>> }
>> p = get();
>> if (!p) {
>> if (a != b) {
>> if (some_error)
>> goto out;
>> ...
>> }
>> goto out;
>> }
>>
>> This is similar to
>>
>> p = get();
>> if (something) {
>> if (p) {
>> if (something_wrong)
>> goto out;
>> ...
>> return;
>> }
>> }
>> if (!p) {
>> if (a != b) {
>> if (some_error)
>> goto out;
>> ...
>> }
>> goto out;
>> }
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>> arch/powerpc/kernel/kprobes.c | 15 +--------------
>> 1 file changed, 1 insertion(+), 14 deletions(-)
>
> Good cleanup, thanks.
>
>>
>> diff --git a/arch/powerpc/kernel/kprobes.c
>> b/arch/powerpc/kernel/kprobes.c
>> index f8b848aa65bd..7a925eb76ec0 100644
>> --- a/arch/powerpc/kernel/kprobes.c
>> +++ b/arch/powerpc/kernel/kprobes.c
>> @@ -276,8 +276,8 @@ int kprobe_handler(struct pt_regs *regs)
>> kcb = get_kprobe_ctlblk();
>>
>> /* Check we're not actually recursing */
>> + p = get_kprobe(addr);
>> if (kprobe_running()) {
>> - p = get_kprobe(addr);
>> if (p) {
>> kprobe_opcode_t insn = *p->ainsn.insn;
>> if (kcb->kprobe_status == KPROBE_HIT_SS &&
>> @@ -308,22 +308,9 @@ int kprobe_handler(struct pt_regs *regs)
>> }
>> prepare_singlestep(p, regs);
>> return 1;
>> - } else if (*addr != BREAKPOINT_INSTRUCTION) {
>> - /* If trap variant, then it belongs not to us */
>> - kprobe_opcode_t cur_insn = *addr;
>> -
>> - if (is_trap(cur_insn))
>> - goto no_kprobe;
>> - /* The breakpoint instruction was removed by
>> - * another cpu right after we hit, no further
>> - * handling of this interrupt is appropriate
>> - */
>> - ret = 1;
>> }
>> - goto no_kprobe;
>
> A minot nit -- removing the above goto makes a slight change to the
> logic. But, see my comments for the next patch.
All legs of the (p) case are have either a return or a goto, so that
goto no_kprobe is limited to the !p case, we have to fall_through now.
Christophe
prev parent reply other threads:[~2020-02-19 7:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 13:44 [PATCH 1/2] powerpc/kprobes: Remove redundant code Christophe Leroy
2020-02-14 13:44 ` [PATCH 2/2] powerpc/kprobes: Reduce depth of a test Christophe Leroy
2020-02-18 14:40 ` Naveen N. Rao
2020-02-18 14:39 ` [PATCH 1/2] powerpc/kprobes: Remove redundant code Naveen N. Rao
2020-02-19 7:48 ` Christophe Leroy [this message]
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