Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753413AbeAQPDW (ORCPT + 1 other); Wed, 17 Jan 2018 10:03:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60546 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752068AbeAQPDV (ORCPT ); Wed, 17 Jan 2018 10:03:21 -0500 Subject: Re: [PATCH v3] arm64: fix unwind_frame() for filtered out fn for function graph tracing To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, Pratyush Anand , Will Deacon , linux-kernel@vger.kernel.org References: <20180112104832.9417-1-jmarchan@redhat.com> <20180116175734.4rp4bewr7us4jypk@armageddon.cambridge.arm.com> From: Jerome Marchand Message-ID: Date: Wed, 17 Jan 2018 16:03:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180116175734.4rp4bewr7us4jypk@armageddon.cambridge.arm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cPhDu4ZlNaikbTvaq3DDxtIZTzra0ZzC2" X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 17 Jan 2018 15:03:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --cPhDu4ZlNaikbTvaq3DDxtIZTzra0ZzC2 Content-Type: multipart/mixed; boundary="oqFORemOoTAkDJ3uvsrpGg15K8S6MN6Zt"; protected-headers="v1" From: Jerome Marchand To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, Pratyush Anand , Will Deacon , linux-kernel@vger.kernel.org Message-ID: Subject: Re: [PATCH v3] arm64: fix unwind_frame() for filtered out fn for function graph tracing References: <20180112104832.9417-1-jmarchan@redhat.com> <20180116175734.4rp4bewr7us4jypk@armageddon.cambridge.arm.com> In-Reply-To: <20180116175734.4rp4bewr7us4jypk@armageddon.cambridge.arm.com> --oqFORemOoTAkDJ3uvsrpGg15K8S6MN6Zt Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 16/01/18 18:57, Catalin Marinas wrote: > On Fri, Jan 12, 2018 at 11:48:32AM +0100, Jerome Marchand wrote: >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stackt= race.c >> index 76809ccd309c..5a528c58ef68 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -59,6 +59,10 @@ int notrace unwind_frame(struct task_struct *tsk, s= truct stackframe *frame) >> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >> if (tsk->ret_stack && >> (frame->pc =3D=3D (unsigned long)return_to_handler)) { >> + WARN_ON(frame->graph =3D=3D -1); >> + if (frame->graph < -1) >> + frame->graph +=3D FTRACE_NOTRACE_DEPTH; >> + >> /* >> * This is a case where function graph tracer has >> * modified a return address (LR) in a stack frame >=20 > So do we still allow this to continue if graph =3D=3D -1? The following= line > doesn't seem safe: >=20 > frame->pc =3D tsk->ret_stack[frame->graph--].ret; >=20 You're right. We probably should return a error (-EINVAL I guess) if this happens. Note that this shouldn't happen here and if we're confident enough that profile_pc() was the only faulty caller, we could just drop the warning. Jerome --oqFORemOoTAkDJ3uvsrpGg15K8S6MN6Zt-- --cPhDu4ZlNaikbTvaq3DDxtIZTzra0ZzC2 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEKhfvHc6w3BYc12CSdPMckK2y6gIFAlpfZbEACgkQdPMckK2y 6gKlxwf5ASzkTTT5LiakB5mZ2Rrd7dOW+dBT3fDMFTQIO2yqYcbrcVjbU7+s0c0g 2vU+nEltjxpw6xbF620pQOS4s2zUiUT8zWm8QMc/iKP1ND0pLe+MprE0xbZ8CDht HG3XEDmperwX5MWeqvz4r+nVvytsXuGV455fPALl5qx+XD76KQrEYPRsdd7zL0+M F4znj5jT3kXaElPWX7Wgq1/FVdB+UXpEbWmloWvltPa9d4AELzF7SBQPFaqqKzDf Zifhjoji53EMGRdgtmNJA3nv+XDFMzG6YEHVf+wyAv2NvouOJU0Ii9klh+wKPW7o CaILDgxHOq3SiDMWpeeoDsscULfz1Q== =I7P5 -----END PGP SIGNATURE----- --cPhDu4ZlNaikbTvaq3DDxtIZTzra0ZzC2--