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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd0dacd1sm37877453f8f.4.2026.01.12.04.46.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jan 2026 04:46:45 -0800 (PST) Date: Mon, 12 Jan 2026 13:46:44 +0100 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Andrei Vagin Cc: Kees Cook , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, criu@lists.linux.dev, Andrew Morton , Chen Ridong , Christian Brauner , David Hildenbrand , Eric Biederman , Lorenzo Stoakes Subject: Re: [PATCH 2/3] exec: inherit HWCAPs from the parent process Message-ID: References: <20260108050748.520792-1-avagin@google.com> <20260108050748.520792-3-avagin@google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="o7rqwh4s3kscjtie" Content-Disposition: inline In-Reply-To: <20260108050748.520792-3-avagin@google.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CDA64A0012 X-Rspam-User: X-Stat-Signature: tjqc4skkjc5g6igraecf4wmgwmno795x X-HE-Tag: 1768222007-56843 X-HE-Meta: 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 RVcCsXiY cCtYsCn1wxZLIWtMb15olOkIWCSDrWnPycHzgzbfU+ZlG6jThmVmHt7ablSyMG5FNMQmKuCIzFNcTQ4w= 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: --o7rqwh4s3kscjtie Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 2/3] exec: inherit HWCAPs from the parent process MIME-Version: 1.0 On Thu, Jan 08, 2026 at 05:07:47AM +0000, Andrei Vagin = wrote: > @@ -1780,6 +1791,50 @@ static int bprm_execve(struct linux_binprm *bprm) > return retval; > } > =20 > +static void inherit_hwcap(struct linux_binprm *bprm) > +{ > + int i, n; > + > +#ifdef ELF_HWCAP4 > + n =3D 4; > +#elif defined(ELF_HWCAP3) > + n =3D 3; > +#elif defined(ELF_HWCAP2) > + n =3D 2; > +#else > + n =3D 1; > +#endif Is it guaranteed that HWCAP n+1 exists only when n does? (To make this work.) > + > + for (i =3D 0; n && i < AT_VECTOR_SIZE; i +=3D 2) { > + long val =3D current->mm->saved_auxv[i + 1]; > + > + switch (current->mm->saved_auxv[i]) { > + case AT_HWCAP: > + bprm->hwcap =3D val & ELF_HWCAP; > + break; > +#ifdef ELF_HWCAP2 > + case AT_HWCAP2: > + bprm->hwcap2 =3D val & ELF_HWCAP2; > + break; > +#endif > +#ifdef ELF_HWCAP3 > + case AT_HWCAP3: > + bprm->hwcap3 =3D val & ELF_HWCAP3; > + break; > +#endif > +#ifdef ELF_HWCAP4 > + case AT_HWCAP4: > + bprm->hwcap4 =3D val & ELF_HWCAP4; > + break; > +#endif > + default: > + continue; > + } > + n--; > + } > + mm_flags_set(MMF_USER_HWCAP, bprm->mm); Will this work when mm->saved_auxv isn't set by the prctl (it is zeroes?)? Thanks, Michal --o7rqwh4s3kscjtie Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCaWTtMRsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMSwyLDIACgkQfj0C55Tb+AisSAEA3jOw1q2q7fyDcfOoeTcd ydeYIa3MJ59Bw5P1NbVJP0YA/0e1/9IiJ/h7y8JbPASpknLbuJY7oLSlA/zl9MUy MJQF =Iqi6 -----END PGP SIGNATURE----- --o7rqwh4s3kscjtie--