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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 Subject: [PATCH v6 20/29] stackleack: Mark stack_erasing_bypass key as allowed in .noinstr Date: Fri, 10 Oct 2025 17:38:30 +0200 Message-ID: <20251010153839.151763-21-vschneid@redhat.com> In-Reply-To: <20251010153839.151763-1-vschneid@redhat.com> References: <20251010153839.151763-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Stat-Signature: pxypgbpqf4bgq4ix7rof856tzj5ngyfm X-Rspamd-Queue-Id: E9E73C0002 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760111173-36007 X-HE-Meta: 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 t92YS710 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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..1abc94a38ce14 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); +/* + * 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