From: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Christophe Leroy <christophe.leroy@c-s.fr>,
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: Tue, 18 Feb 2020 20:09:49 +0530 [thread overview]
Message-ID: <1582036611.9hm2t8ijhz.naveen@linux.ibm.com> (raw)
In-Reply-To: <642c8b4ca59e658be38d8dde00f994e183790a6a.1581687838.git.christophe.leroy@c-s.fr>
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.
- Naveen
> }
>
> - p = get_kprobe(addr);
> if (!p) {
> if (*addr != BREAKPOINT_INSTRUCTION) {
> /*
> --
> 2.25.0
>
>
next prev parent reply other threads:[~2020-02-18 14:42 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 ` Naveen N. Rao [this message]
2020-02-19 7:48 ` [PATCH 1/2] powerpc/kprobes: Remove redundant code Christophe Leroy
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