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Peter Anvin" , Peter Zijlstra Subject: Re: [PATCH v3 0/6] Enable strict percpu address space checks Message-Id: <20241212193541.fa3dcac867421a971c38135c@linux-foundation.org> In-Reply-To: <20241208204708.3742696-1-ubizjak@gmail.com> References: <20241208204708.3742696-1-ubizjak@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B2DE0160006 X-Stat-Signature: ken46ssc9kpbzrtp1s4g3t9ytahi1h4e X-Rspam-User: X-HE-Tag: 1734060927-762486 X-HE-Meta: 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 z36DJBTi t+PmLbvxCvTrv063j0+eSWplZa/Heaa76YLAVyAcC6K68pkvt2OhRquB9+JEjvhkbkm7tjgSyB6Z0ir5D20SpKLnanCIQRWvRcb64k6MwhJX7EiliMVRcUSHBgld5FbjlpbpGIamQSamVBI8IaM0wOxAa+bcQxhc+658jFZPDNYT3H3akXYjbRzsxbHfMaUpSJq/gXh8Wkkz04RMDkul3iLwfwFY9MRKlkYyUXnSwjlvD1HDVbK/brg8FCxnF+RKUO64ZPcJsIKjvLSbIo67VoUAnlH7jtBtCg3t5SwSv+rYh7TKDHxTLqpBEGxlaeRJrVJjOq1Yd7vxHJUzumNc/8gmxNg== 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 Sun, 8 Dec 2024 21:45:15 +0100 Uros Bizjak wrote: > Enable strict percpu address space checks via x86 named address space > qualifiers. Percpu variables are declared in __seg_gs/__seg_fs named > AS and kept named AS qualified until they are dereferenced via percpu > accessor. This approach enables various compiler checks for > cross-namespace variable assignments. > > Please note that current version of sparse doesn't know anything about > __typeof_unqual__() operator. Avoid the usage of __typeof_unqual__() > when sparse checking is active to prevent sparse errors with unknowing > keyword. The proposed patch by Dan Carpenter to implement > __typeof_unqual__() handling in sparse is located at: google("what the hell is typeof_unequal") failed me. I think it would be nice to include within the changelog (and code comments!) an explanation-for-others of what this thing is and why anyone would want to use it. Rather than assuming that all kernel developers are typeof() experts!