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 jpoimboe@kernel.org Signed-off-by: Valentin Schneider vschneid@redhat.com --- 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 <linux/sysctl.h> #include <linux/init.h>
-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,