Re: [RESEND PATCH] arch: arm64: set __nocfi on swsusp_arch_resume

[Will Deacon <will@kernel.org>]

On Thu, Jan 22, 2026 at 07:39:34PM +0800, Zhaoyang Huang wrote:
> On Thu, Jan 22, 2026 at 6:32 PM Will Deacon <will@kernel.org> wrote:
> > On Tue, Jan 20, 2026 at 02:06:19PM +0800, zhaoyang.huang wrote:
> > > diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> > > index 18749e9a6c2d..9717568518ba 100644
> > > --- a/arch/arm64/kernel/hibernate.c
> > > +++ b/arch/arm64/kernel/hibernate.c
> > > @@ -402,7 +402,7 @@ int swsusp_arch_suspend(void)
> > >   * Memory allocated by get_safe_page() will be dealt with by the hibernate code,
> > >   * we don't need to free it here.
> > >   */
> > > -int swsusp_arch_resume(void)
> > > +int __nocfi swsusp_arch_resume(void)
> > >  {
> > >       int rc;
> > >       void *zero_page;
> >
> > Why does is the '__nocfi' annotation here rather than on the
> > 'hibernate_exit' pointer?
> Our first try is to have the callee function(swsusp_arch_suspend_exit)
> waived by set __nocfi but failed. It seems like the CFI watched the
> caller of function pointer and plant stub code.

Thinking about this some more, you're right that the '__nocfi'
annotation has to happen at the call-site, because that's where the
check takes place.

I did start looking at what it would take to emit the CFI type prefix
for swsusp_arch_suspend_exit() using SYM_TYPED_FUNC_START() but it's a
bit grotty having to offset into .hibernate_exit.text when jumping to
the copy and, given that trans_pgd_idmap_page doesn't seem to bother
with BTI at all, your patch looks like the simplest point fix.

I'll ack the resend...

Will