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Edgecombe" , Deepak Gupta , Ard Biesheuvel , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 03/36] arm64/gcs: Document the ABI for Guarded Control Stacks Message-ID: <4e215e53-c7d1-4338-8df9-3f9bf783ced9@sirena.org.uk> References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-3-68cfa37f9069@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="HX3zqelcmaABHbLq" Content-Disposition: inline In-Reply-To: X-Cookie: Reunite Gondwondaland! X-Rspamd-Queue-Id: A181C1C001D X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: dzded5ruaexibqakog7ke8atxh61pgp3 X-HE-Tag: 1691667679-308376 X-HE-Meta: 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 BZMel6va ZweiBKjG4n2fpVwyioA8Elw0Ii7oo19JQOQuDr7rNwgBZ1K/phATFQDjVHFTB5RA+z0ZPuex/aP1DssyqWjRj8yeR+zfe+wEZpbj5+HfyMPQScHF0eXiYXTZTH73ar0QfXxtTiPojhAhTTU5QUsqUhqHGN9AbgGT5ZAMV3Xj3GJyLOFs+trkQYMVLhCgcKz4ZTuLZHDZmiOut7z2Ey6KMB1EoQnMhNQL4sxToDfxU2nlsIRyYkoB/HXlyQD57Px0FwO6Sp8jmlYLTVdNWPfuF1TAHEC1SwWGqjUiZHAXhRBs4AW78/O9a/VvJYswGihMK9kxtJEa1zcUSVK/u9b7TiJlVUnB4rMvpgJChicJQYm8+4AZUAbWe37YoXVAM06EDa0wB/4Yut4UwG+GwT3cnkw477HEq6UCLrbv4w53L/lj0u5K5CH4WR3wEbpt26jbs0iOe 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: --HX3zqelcmaABHbLq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Aug 10, 2023 at 09:55:50AM +0100, Szabolcs Nagy wrote: > The 08/09/2023 16:34, Mark Brown wrote: > > It's actually based on bitrot that I'd initially chosen a smaller value > > since it's likely that functions will push at least something as you > > suggest, the patches now just use RLIMIT_STACK. I'll fix. > the pcs requires 16byte aligned stack frames, with 8byte per gcs entry > there is no need for same gcs size as stack size in userspace. I agree that it's going to be excessive for pretty much all applications, I adjusted it to match x86 as part of the general effort to avoid divergence and because I was a bit concerned about non-PCS cases (eg, JITed code) potentially running into trouble, especially with smaller stack limits. It's not an issue I have super strong opinions on though, as you can see I had implemented it both ways at various times. --HX3zqelcmaABHbLq Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmTUzNQACgkQJNaLcl1U h9CX2Af/ZivuFjFTpJA8oad5auH8pxkhXVEAIPD0ff/7T6abVR9+lSwBwNj9fu7u QzV10fINsZecsGZed5ZdpIR3HeeSZW2rAVaF2fIu1u7L6gXy0UwG1jPkOB21G4Ca LApqqi+p4OfTtZtySK1optntQ4+DJRFrhFESNYwt/UyKffuB9bbr5xaIB/23ghe+ ZLmOWBXMpL4NaZMPdi9Tm43gAvVlDnXsANCWTZfq0uRGZBJBggQIM7Mwrz9JwmVy 3633R9GviRxPWQm83UqZI7n51wspiOfjdhYYtsqqo7jYwawpnfb4Jj89/3j6QmJO WdrDN78D2wpFLApdojZDDftk6sXHkg== =m3b4 -----END PGP SIGNATURE----- --HX3zqelcmaABHbLq--