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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Uladzislau Rezki , Kees Cook Cc: David Stevens , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 10/13] fork: Store task pointer in unpopulated stack ptes In-Reply-To: <20260424191456.2679717-11-stevensd@google.com> References: <20260424191456.2679717-1-stevensd@google.com> <20260424191456.2679717-11-stevensd@google.com> Date: Sat, 27 Jun 2026 00:46:35 +0200 Message-ID: <87wlvkhqd0.ffs@fw13> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Stat-Signature: n8h9ukwru7ox31kz3bsx94yt7uxn5opn X-Rspamd-Queue-Id: 9B623A0002 X-Rspamd-Server: rspam06 X-HE-Tag: 1782513999-684191 X-HE-Meta: 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 Oi3tXJFn 0OIh60Q1o+BioHHAcBjGbihTVZGQA+tNe3wS1iBy8OysUeFy4lSxXzOeD1miSehgfLblPxh/JZnK9FmGv2UHsTXh/SC5KvW6vtBk4mc8fn572Lg9mleBs9Axc3reEbVBbMYtEPyq/LmWkqVnyQXh5DRhj7uAskxpUBhgqw7ah8gVoA0yBodOEOyVYqgfvywQ7lHwwLkm02C4UzpGts7aVcHoggEhc8PDUuZzMnx4Wk3kkB/aoNGlpZ/wxrg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 24 2026 at 12:14, David Stevens wrote: > Store the task pointer in the ptes of the unpopulated pages of dynamic > stacks, to allow the vm_struct pointer to be retrieved without relying > on any locks or current. You fail to explain why you can't use current. Changelogs have to describe the WHY and not the WHAT. > > -bool is_vmalloc_addr(const void *x) > +noinstr bool is_vmalloc_addr(const void *x) > { > unsigned long addr = (unsigned long)kasan_reset_tag(x); noinstr is not enough here unless this depends on !KASAN because kasan_reset_tag() is a 'static inline' which CLANG happily puts out of line into the instrumentable section...