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McKenney" , Dave Hansen , Sean Christopherson , Juergen Gross , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Pawan Gupta , Paolo Bonzini , Arnd Bergmann , Jason Baron , Steven Rostedt , Ard Biesheuvel , Luis Chamberlain , Petr Pavlu , Sami Tolvanen , Daniel Gomez , Naveen N Rao , Anil S Keshavamurthy , "David S. Miller" , Masami Hiramatsu , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Kees Cook , Shuah Khan , Masahiro Yamada , Alice Ryhl , Miguel Ojeda , "Mike Rapoport (Microsoft)" , Rong Xu , Rafael Aquini , Song Liu , Andrii Nakryiko , Dan Carpenter , Brian Gerst , "Kirill A. Shutemov" , Benjamin Berg , Vishal Annapurve , Randy Dunlap , John Stultz , Tiezhu Yang Subject: [PATCH v5 20/25] stackleack: Mark stack_erasing_bypass key as allowed in .noinstr Date: Tue, 29 Apr 2025 13:32:37 +0200 Message-ID: <20250429113242.998312-21-vschneid@redhat.com> In-Reply-To: <20250429113242.998312-1-vschneid@redhat.com> References: <20250429113242.998312-1-vschneid@redhat.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 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/stackleak.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/stackleak.c b/kernel/stackleak.c index bb65321761b43..51b24d1e04ba2 100644 --- a/kernel/stackleak.c +++ b/kernel/stackleak.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,