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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 24 Apr 2020 19:26:07 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03OIQWVG61538480 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Apr 2020 18:26:32 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 256E65204E; Fri, 24 Apr 2020 18:26:32 +0000 (GMT) Received: from localhost (unknown [9.85.74.26]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id AA3065204F; Fri, 24 Apr 2020 18:26:31 +0000 (GMT) Date: Fri, 24 Apr 2020 23:56:25 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH 3/3] powerpc/kprobes: Check return value of patch_instruction() To: Christophe Leroy , Steven Rostedt References: <3a132ac385340244b8d74179ac7bbbda7bf1f503.1587654213.git.naveen.n.rao@linux.vnet.ibm.com> <20200424092202.71cfc549@gandalf.local.home> In-Reply-To: <20200424092202.71cfc549@gandalf.local.home> 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: quoted-printable X-TM-AS-GCONF: 00 x-cbid: 20042418-0012-0000-0000-000003AA6D38 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20042418-0013-0000-0000-000021E7C648 Message-Id: <1587751684.agx3nt8uvf.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-24_09:2020-04-24, 2020-04-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 adultscore=0 malwarescore=0 suspectscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004240134 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Steven Rostedt wrote: > On Thu, 23 Apr 2020 17:41:52 +0200 > Christophe Leroy wrote: > =20 >> > diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/opt= probes.c >> > index 024f7aad1952..046485bb0a52 100644 >> > --- a/arch/powerpc/kernel/optprobes.c >> > +++ b/arch/powerpc/kernel/optprobes.c >> > @@ -139,52 +139,67 @@ void arch_remove_optimized_kprobe(struct optimiz= ed_kprobe *op) >> > } >> > } >> > =20 >> > +#define PATCH_INSN(addr, instr) \ >> > +do { \ >> > + int rc =3D patch_instruction((unsigned int *)(addr), instr); \ >> > + if (rc) { \ >> > + pr_err("%s:%d Error patching instruction at 0x%pK (%pS): %d\n", \ >> > + __func__, __LINE__, \ >> > + (void *)(addr), (void *)(addr), rc); \ >> > + return rc; \ >> > + } \ >> > +} while (0) >> > + =20 >>=20 >> I hate this kind of macro which hides the "return". >>=20 >> What about keeping the return action in the caller ? >>=20 >> Otherwise, what about implementing something based on the use of goto,=20 >> on the same model as unsafe_put_user() for instance ? Thanks for the review. I noticed this as a warning from checkpatch.pl, but this looked compact=20 and correct for use in the two following functions. You'll notice that I=20 added it just before the two functions this is used in. I suppose 'goto err' is usable too, but the ftrace code (patch 2) will=20 end up with more changes. I'm also struggling to see how a 'goto' is=20 less offensive. I think Steve's suggestion below would be the better way=20 to go, to make things explicit. >=20 > #define PATCH_INSN(addr, instr) \ > ({ > int rc =3D patch_instruction((unsigned int *)(addr), instr); \ > if (rc) \ > pr_err("%s:%d Error patching instruction at 0x%pK (%pS): %d\n", \ > __func__, __LINE__, \ > (void *)(addr), (void *)(addr), rc); \ > rc; \ > }) >=20 >=20 > Then you can just do: >=20 > ret =3D PATCH_INSN(...); > if (ret) > return ret; >=20 > in the code. That's really nice. However, in this case, I guess I can simply use an=20 inline function? The primary reason I used the macro was for including a=20 'return' statement in it. Thanks for the review! - Naveen