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b=EO1AKxM9atAW5ijESg1UGQbijOEntefJ4W7hvVziFA0UrM4OUrijGVaBzcLEs6wYr OjSIBHChIOgwKca7pXNbM5Cobz19+3leTFG2K/9EVjkOotzvVw0v6ez05ByOvLbcwV +CEf8bXXKN6XhhDI0KQZwE7hmlaMqLtNtNfWohmrOO5PLVL5FNBfFfrfun8qdbWle6 BBkj3Iud3EUQQytsOc+psDxTBNOG28HZowRKkkW/VLD4pWv0zXFVJLZNdlQZAg0FeB on/Je8QMYpg2sD3Y5jNv2RyOVaFeGMIIzBve14j+nne6Gk0zkfJUvj0vvAw6pPQKrV 0fcsjUUDb1b7Q== Date: Wed, 21 Feb 2024 00:44:43 +0000 From: Mark Brown To: "Edgecombe, Rick P" Cc: "dalias@libc.org" , "linux-arch@vger.kernel.org" , "suzuki.poulose@arm.com" , "Szabolcs.Nagy@arm.com" , "musl@lists.openwall.com" , "linux-fsdevel@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "kvmarm@lists.linux.dev" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "catalin.marinas@arm.com" , "oliver.upton@linux.dev" , "palmer@dabbelt.com" , "debug@rivosinc.com" , "aou@eecs.berkeley.edu" , "shuah@kernel.org" , "arnd@arndb.de" , "maz@kernel.org" , "oleg@redhat.com" , "fweimer@redhat.com" , "keescook@chromium.org" , "james.morse@arm.com" , "ebiederm@xmission.com" , "will@kernel.org" , "brauner@kernel.org" , "hjl.tools@gmail.com" , "linux-kselftest@vger.kernel.org" , "paul.walmsley@sifive.com" , "ardb@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mm@kvack.org" , "thiago.bauermann@linaro.org" , "akpm@linux-foundation.org" , "sorear@fastmail.com" , "linux-doc@vger.kernel.org" Subject: Re: [musl] Re: [PATCH v8 00/38] arm64/gcs: Provide support for GCS in userspace Message-ID: References: <20240203-arm64-gcs-v8-0-c9fec77673ef@kernel.org> <22a53b78-10d7-4a5a-a01e-b2f3a8c22e94@app.fastmail.com> <4c7bdf8fde9cc45174f10b9221fa58ffb450b755.camel@intel.com> <20240220185714.GO4163@brightrain.aerifal.cx> <9fc9c45ff6e14df80ad023e66ff7a978bd4ec91c.camel@intel.com> <20240220235415.GP4163@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="zmCyS0Odp0mOsqor" Content-Disposition: inline In-Reply-To: X-Cookie: E = MC ** 2 +- 3db X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DF30940011 X-Stat-Signature: qsighgdycou7w1gdppnm7wbyqzshkfpa X-HE-Tag: 1708476298-586461 X-HE-Meta: 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 /ukdolig FIzyzbCxIkkwpglsGrYLtzZhn272/87+rGTjHJbQ6Ee8pMAwjZiCFYtFeKQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --zmCyS0Odp0mOsqor Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Feb 21, 2024 at 12:35:48AM +0000, Edgecombe, Rick P wrote: > doing. But those threads might be using shadow stack instructions > (INCSSP, RSTORSSP, etc). These are a collection of instructions that > allow limited control of the SSP. When shadow stack gets disabled, > these suddenly turn into #UD generating instructions. So any other > threads executing those instructions when shadow stack got disabled > would be in for a nasty surprise. > Glibc's permissive mode (that disables shadow stack when dlopen()ing a > DSO that doesn't support shadow stack) is quite limited because of > this. There was a POC for working around it, but I'll stop there for > now, to not spam you with the details. I'm not sure of arm and risc-v > details on this specific corner, but for x86. We have the same issue with disabling GCS causing GCS instructions to become undefined. --zmCyS0Odp0mOsqor Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmXVR3oACgkQJNaLcl1U h9BO9Qf/bgPI/9ROkHiV6cP5ag9FVPBuoU4y8o043FWrLxXipYjgLbjIps3r7NYd VLNWiX+sScsGrwtujlkAC3JYU0QAro+3+MY0cp+MjZopgqrEpOHlREM+dZO4FSB+ BH4GTQgpADdgkbaukCb71Yd8D8HkPkpjvvsEGO6Kv2Bq4kMF6w2sd5O/llI+5BPN 0v1hps6/0VWFICJibmb4hRIRPMjb91mxGQRdpF8OTCgHa0w4UXaTHLttIE3iqCd4 nyeOZPkoIxUv3fYTVZjAqm6emWXXodOaOQrOtjTM1shBFck2DtY+hJJopNkuwE2j qeuz0TLv83oNLhiCiSUgT5gKjQrvdA== =VhGm -----END PGP SIGNATURE----- --zmCyS0Odp0mOsqor--