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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , Shrikanth Hegde Subject: [PATCH v7 21/31] stackleack: Mark stack_erasing_bypass key as allowed in .noinstr Date: Fri, 14 Nov 2025 16:14:18 +0100 Message-ID: <20251114151428.1064524-1-vschneid@redhat.com> In-Reply-To: <20251114150133.1056710-1-vschneid@redhat.com> References: <20251114150133.1056710-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: AB1F320026 X-Stat-Signature: 8omz81ydqsca7bpgk7bir5txphiym3wr X-Rspam-User: X-HE-Tag: 1763133303-605049 X-HE-Meta: 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 Lo8mlZ6e 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 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: Later commits will cause objtool to warn about static keys being used in .noinstr sections in order to safely defer instruction patching IPIs targeted at NOHZ_FULL CPUs. stack_erasing_bypass is used in .noinstr code, and can be modified at runtime (proc/sys/kernel/stack_erasing write). However it is not expected that it will be flipped during latency-sensitive operations, and thus shouldn't be a source of interference wrt the text patching IPI. Mark it to let objtool know not to warn about it. Reported-by: Josh Poimboeuf Signed-off-by: Valentin Schneider --- kernel/kstack_erase.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/kstack_erase.c b/kernel/kstack_erase.c index e49bb88b4f0a3..99ba44cf939bf 100644 --- a/kernel/kstack_erase.c +++ b/kernel/kstack_erase.c @@ -19,7 +19,11 @@ #include #include -static DEFINE_STATIC_KEY_FALSE(stack_erasing_bypass); +/* + * NOINSTR: This static key can only be modified via its sysctl interface. It is + * expected it will remain stable during latency-senstive operations. + */ +static DEFINE_STATIC_KEY_FALSE_NOINSTR(stack_erasing_bypass); #ifdef CONFIG_SYSCTL static int stack_erasing_sysctl(const struct ctl_table *table, int write, -- 2.51.0