Messages in this thread | | | Date | Mon, 2 May 2022 15:01:09 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/3] jump_label,noinstr: Avoid instrumentation for JUMP_LABEL=n builds |
| |
On Mon, May 02, 2022 at 01:23:49PM +0200, Marco Elver wrote: > On Mon, 2 May 2022 at 13:12, Peter Zijlstra <peterz@infradead.org> wrote: > > > > When building x86_64 with JUMP_LABEL=n it's possible for > > instrumentation to sneak into noinstr: > > > > vmlinux.o: warning: objtool: exit_to_user_mode+0x14: call to static_key_count.constprop.0() leaves .noinstr.text section > > vmlinux.o: warning: objtool: syscall_exit_to_user_mode+0x2d: call to static_key_count.constprop.0() leaves .noinstr.text section > > vmlinux.o: warning: objtool: irqentry_exit_to_user_mode+0x1b: call to static_key_count.constprop.0() leaves .noinstr.text section > > > > Reported-by: kernel test robot <lkp@intel.com> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > include/linux/jump_label.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- a/include/linux/jump_label.h > > +++ b/include/linux/jump_label.h > > @@ -256,9 +256,9 @@ extern void static_key_disable_cpuslocke > > #include <linux/atomic.h> > > #include <linux/bug.h> > > > > -static inline int static_key_count(struct static_key *key) > > +static __always_inline int static_key_count(struct static_key *key) > > { > > - return atomic_read(&key->enabled); > > + return READ_ONCE_NOCHECK(&key->enabled.count); > > } > > Did arch_atomic_read() not work? Or should this also be unchecked in > instrumented functions?
Urgh, also I think the above is broken for me forgetting to remove the &.
I think arch_atomic_read() should work, lemme try.
| |