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Howlett" , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Guo Ren , Huacai Chen , WANG Xuerui , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Chris Zankel , Max Filippov , Andrew Morton , Vlastimil Babka , Lorenzo Stoakes , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org, loongarch@lists.linux.dev, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, Rick Edgecombe Subject: Re: [PATCH 3/3] mm: Care about shadow stack guard gap when getting an unmapped area Message-ID: References: <20240902-mm-generic-shadow-stack-guard-v1-0-9acda38b3dd3@kernel.org> <20240902-mm-generic-shadow-stack-guard-v1-3-9acda38b3dd3@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: 9bzkk6xoayp11cor3xycka47h46gh5oe X-Rspamd-Queue-Id: 37AFE1A000B X-Rspamd-Server: rspam11 X-HE-Tag: 1725476838-954622 X-HE-Meta: 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 kzNdUMYF cwLus/+P77Lj1x+afmKtjfiWCr892vgvWgciJbfVeCtntnEN2TIQfbxfAWiioxw2O++NnOloPLGOoU2Cza05jWS3Fh2PyNoWY1ehUo6SrvZcc9uj+lvnU3O4u8RbDsReJUQ+/iFi02ycPKKYOFn1NNww3TK/adbo/4umMmWkdenplxgn/RzEm07hxyZh+tgHrE40amoPjJ3TLbG1+BqPwAiWcDDKKEakGqKZxHB+BHhh73tkUwoD+6cyHmDbcQHvT2hk73SS4YqPzNMQup/5HgwYdcu4aTBRGO9KyyGWZMW7V8SoMM/OQHTdKa81X8Ge330deOu49tNMMJrmXiDd0tc1aBN8NOLDClv54kXEZAN19BTzC9m/uOIdiaavRPcXlqdNzsyH9M5PpOec= 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: List-Subscribe: List-Unsubscribe: On Tue, Sep 03, 2024 at 08:57:20PM +0100, Mark Brown wrote: >On Tue, Sep 03, 2024 at 03:41:49PM -0400, Liam R. Howlett wrote: >> * Mark Brown [240902 15:09]: > >> > +static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) >> > +{ >> > + if (vm_flags & VM_SHADOW_STACK) >> > + return PAGE_SIZE; > >> Is PAGE_SIZE is enough? > >It's what x86 currently uses so it'll be no worse off if it gets moved >to the generic code (there's a comment in the arch code explaing what's >needed there) and it's enough for arm64, we only do single record >pushes/pops or (optionally) writes to unconstrained addresses. It's enough for RISC-V too.