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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 18 Feb 2020 14:39:52 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 01IEcuUR40042880 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 18 Feb 2020 14:38:56 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CDD54A4051; Tue, 18 Feb 2020 14:39:51 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 60FFEA4040; Tue, 18 Feb 2020 14:39:51 +0000 (GMT) Received: from localhost (unknown [9.199.60.10]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 18 Feb 2020 14:39:51 +0000 (GMT) Date: Tue, 18 Feb 2020 20:09:49 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH 1/2] powerpc/kprobes: Remove redundant code To: Benjamin Herrenschmidt , Christophe Leroy , Michael Ellerman , Paul Mackerras Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <642c8b4ca59e658be38d8dde00f994e183790a6a.1581687838.git.christophe.leroy@c-s.fr> In-Reply-To: <642c8b4ca59e658be38d8dde00f994e183790a6a.1581687838.git.christophe.leroy@c-s.fr> MIME-Version: 1.0 User-Agent: astroid/v0.15-13-gb675b421 (https://github.com/astroidmail/astroid) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT X-TM-AS-GCONF: 00 x-cbid: 20021814-0020-0000-0000-000003AB4FEB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20021814-0021-0000-0000-000022034BEA Message-Id: <1582036611.9hm2t8ijhz.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-18_02:2020-02-17,2020-02-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1011 bulkscore=0 suspectscore=0 adultscore=0 impostorscore=0 mlxscore=0 mlxlogscore=788 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002180114 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 > >