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Fri, 26 Feb 2021 09:47:32 -0800 (PST) Received: from google.com ([2620:15c:f:10:e190:bf4c:e355:6c55]) by smtp.gmail.com with ESMTPSA id 7sm9924571pfh.142.2021.02.26.09.47.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Feb 2021 09:47:32 -0800 (PST) Date: Fri, 26 Feb 2021 09:47:25 -0800 From: Sean Christopherson To: Nadav Amit Cc: Linux-MM , LKML , Hugh Dickins , Andy Lutomirski , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Borislav Petkov , Andrew Morton , x86@kernel.org Subject: Re: [RFC 1/6] vdso/extable: fix calculation of base Message-ID: References: <20210225072910.2811795-1-namit@vmware.com> <20210225072910.2811795-2-namit@vmware.com> <2CDFE432-90D3-43EE-BA9F-2CFEB8BB343C@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2CDFE432-90D3-43EE-BA9F-2CFEB8BB343C@gmail.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 13ED24080F50 X-Stat-Signature: x4uutdpnetuxwihnt5m8w5sxj6ft3rz5 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=mail-pj1-f52.google.com; client-ip=209.85.216.52 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614361647-101020 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Feb 26, 2021, Nadav Amit wrote: >=20 > > On Feb 25, 2021, at 1:16 PM, Sean Christopherson = wrote: > > It's been literally years since I wrote this code, but I distinctly r= emember the > > addresses being relative to the base. I also remember testing multip= le entries, > > but again, that was a long time ago. > >=20 > > Assuming things have changed, or I was flat out wrong, the comment ab= ove the > > macro magic should also be updated. > >=20 > > /* > > * Inject exception fixup for vDSO code. Unlike normal exception fixu= p, > > * vDSO uses a dedicated handler the addresses are relative to the ove= rall > > * exception table, not each individual entry. > > */ >=20 > I will update the comment. I am not very familiar with pushsection stuf= f, > but the offsets were wrong. >=20 > Since you say you checked it, I wonder whether it can somehow be caused > by having exception table entries defined from multiple object files. Oooh, I think that would do it. Have you checked what happens if there a= re multiple object files and multiple fixups within an object file? > Anyhow, this change follows the kernel=E2=80=99s (not vDSO) exception t= able > scheme.