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Wed, 14 Jan 2026 13:25:13 -0800 (PST) Date: Wed, 14 Jan 2026 22:25:11 +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: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: X-Rspam-User: X-Stat-Signature: 8nt9gewzghsqk9h3gx46c48ad7ts7s8n X-Rspamd-Queue-Id: 0C27640003 X-Rspamd-Server: rspam04 X-HE-Tag: 1768425915-400565 X-HE-Meta: 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 LSLHM1Q/ z2A7DNF3/WEqJN7OtGaUCkhZzrgXP22Mk7HPGWve+TxAL2D08mLfkPxb50sYLvsU2+URv8Bx9/hA+xJZkPKpzVkwJ9PfmHuxEkaaGaCTwvUlhu0eUgoOTUi4OMsWrZ2i4qHEPn6vPgKCVWmW7fbiZPkFZF2EMFcRyYQ5QPb4iPTetm1CeAyZI3bN0ubWk6zCdG/w4ESfDxjp9OlGWObrZJOL4fhf55dG9+1yl50YLpPRIse/aYII2xQ52Wgh/Jn81P6j2263YgFKebNNTc4J/vvrw3pyB77CFfZPuvm+oLg5uhpt1mR6e03TwjOoi8EhkReNIMJst6sML66Ojjrmt+QBLdEVkCfYDGMhuBCFK6ABGv+k= 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 Mon, Jan 12, 2026 at 02:18:18PM -0800, Andrei Vagin = wrote: > It is true for all existing arch-es. I can't imagine why we would want to > define ELF_HWCAP{n+1} without having ELF_HWCAP{n}. If you think we need > to handle this case, I can address it in the next version. >=20 > It is just a small optimization to stop iterating after handling all > entries. The code will work correctly even when HWCAP n+1 exists but n > doesn't. Indeed (I accidentally ignored the AT_VECTOR_SIZE condition), it turns out no big deal then. I like that it's not needlessly searched (and copied altogether). > The inherit_hwcap function is only called if MMF_USER_HWCAP is set (auxv = was > modified via prctl). However, even if mm->saved_auxv hasn't been > modified, it still contains valid values. Hm, bprm_mm_init/mm_alloc/mm_init would tranfser the flag from current, I'm still unclear whether it is necessary here. (It should make no harm though.) saved_auxv validity seems OK then. One more thing came up to my mind -- synchronization between prctl'ing and exec'ing threads (I see de_thread() is relatively late after bprm__mm_init()). Thanks, Michal