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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 22/35] arm64/mm: Implement map_shadow_stack() Message-ID: <8ea03eda-e630-40c5-acc1-a63f5c5b3102@sirena.org.uk> References: <20230716-arm64-gcs-v1-0-bf567f93bba6@kernel.org> <20230716-arm64-gcs-v1-22-bf567f93bba6@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Y5hKtc1qLwv4bVDN" Content-Disposition: inline In-Reply-To: X-Cookie: Nothing happens. X-Rspamd-Queue-Id: A71362000F X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: ihfjfw7e1ria6qkwrwgm55eq1kbmwbsm X-HE-Tag: 1689688518-866930 X-HE-Meta: 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 ScNEHQMb jwRsNNLnCTAgN+zN/ifZfhs6NYQMkSz8+NPQAD4SNBrYTGa8S2RlsT98TBCSPTkRWOo5wxkHV12okmLncOhXWZ8w5RUH8Y4SRqVetPTTpvSUH5J4aXJQvDI5TtAU2g+Ot+ouilX7WQ1/rPueMIejgS2szRZ+HBqOIYTNqKtJaAe3/FzeK7KDed/jcWE08uMJg8Fb5+J5eW41mQqgMy9wOF+W4T4t+baD3O/VuCFRrIi8po6N2KhEqV06oYX2avNLldu6Trj7SFyVuWjW3crhYIsPvTqsGLDoZZwKn6on7wlYZXTPlitCuSu9sGoFSej8WyTaVEXCzRJdGqPCsfoRSEA5P7ekX8FlohAXfjWSkfSaIJvI8xtnl1jvzwOjTomiMDwEamezyUA5vyJTL3aWQSsTL5AA3krsaNEvK+zxR5hBqEPCOsX9orXbbYJA2/PuaRRa07uuCHiWjR+vwK+pYk1EOPQ== 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: --Y5hKtc1qLwv4bVDN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Jul 18, 2023 at 10:10:04AM +0100, Szabolcs Nagy wrote: > uint64_t *p = map_shadow_stack(0, N*8, 0); > i'd expect p[N-1] to be the end token and p[N-2] to be the cap token, > not p[PAGE_ALIGN(N*8)/8-2]. Yes, that probably would be more helpful. > if we allow misalligned size here (and in munmap) then i think it's > better to not page align. size%8!=0 || size<16 can be an error. Honestly I'd be a lot happier to just not allow misalignment but that raises the issue with binaries randomly not working when moved to a kernel with a different page size. I'll have a think but possibly the safest thing would be requiring a multiple of 4K then rounding up to our actual page size. --Y5hKtc1qLwv4bVDN Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmS2mbsACgkQJNaLcl1U h9AzZAf6AmpARgwgG4zNQzt85k9TDh62vFVaeaSCfpyqUZ4UEHeRf0DJ2hib8MGt aDz/k1E7ReyhGJhez+M19TlHMBHDoj2Fkh4bdOwzcTERDFTgMTGw8FFyyDjAP3fz TkDlo1EwKyXZnGnkqYbSFozVhOEZm6WVu6kpN62D5Q2jSEkL96f7C3WjXU0UbR3K X4Ey8EzUPGBf7SmYnOnGaG9+1bnKutkKj7unAMb6rJVFaAP/FTMpof5WI2kW4ngD nu5z6uyG6x2pFBgA3wTKmlDUEkhLsvfbDMtSwZTyHfDf6ayYVdMkeVkpxqvc+Nag BDtHeJXm98VwgwHiGPA6ln6uOvDbOQ== =EMfO -----END PGP SIGNATURE----- --Y5hKtc1qLwv4bVDN--