On 19/11/24 15:39, Josh Poimboeuf wrote: > On Tue, Nov 19, 2024 at 04:34:53PM +0100, Valentin Schneider wrote: >> Later commits will cause objtool to warn about non __ro_after_init static >> keys being used in .noinstr sections in order to safely defer instruction >> patching IPIs targeted at NOHZ_FULL CPUs. > > Don't we need similar checking for static calls? > /sifts through my notes throwing paper all around Huh, I thought I had something, but no... Per the results they don't seem to be flipped around as much as static keys, but they also end up in text_poke_bp(), so yeah, we do. Welp, I'll add that to the list. >> Two such keys currently exist: mds_idle_clear and __sched_clock_stable, >> which can both be modified at runtime. > > Not sure if feasible, but it sure would be a lot simpler to just make > "no noinstr patching" a hard rule and then convert the above keys (or at > least their noinstr-specific usage) to regular branches. > > Then "no noinstr patching" could be unilaterally enforced in > text_poke_bp(). > >> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h >> index f5a2727ca4a9a..93e729545b941 100644 >> --- a/include/linux/jump_label.h >> +++ b/include/linux/jump_label.h >> @@ -200,7 +200,8 @@ struct module; >> #define JUMP_TYPE_FALSE 0UL >> #define JUMP_TYPE_TRUE 1UL >> #define JUMP_TYPE_LINKED 2UL >> -#define JUMP_TYPE_MASK 3UL >> +#define JUMP_TYPE_FORCEFUL 4UL > > JUMP_TYPE_NOINSTR_ALLOWED ? > That's better, I'll take it. Thanks! > -- > Josh
