On Thu, Aug 20, 2020 at 3:24 AM <peterz@xxxxxxxxxxxxx> wrote: > > On Sat, Jul 04, 2020 at 05:49:10PM -0000, tip-bot2 for Andy Lutomirski wrote: > > > diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c > > index f392a8b..e83b3f1 100644 > > --- a/arch/x86/entry/common.c > > +++ b/arch/x86/entry/common.c > > @@ -49,6 +49,23 @@ > > static void check_user_regs(struct pt_regs *regs) > > { > > if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) { > > + /* > > + * Make sure that the entry code gave us a sensible EFLAGS > > + * register. Native because we want to check the actual CPU > > + * state, not the interrupt state as imagined by Xen. > > + */ > > + unsigned long flags = native_save_fl(); > > + WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF | > > + X86_EFLAGS_NT)); > > This triggers with AC|TF on my !SMAP enabled machine. > > something like so then? > > diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h > index a8f9315b9eae..76410964585f 100644 > --- a/arch/x86/include/asm/entry-common.h > +++ b/arch/x86/include/asm/entry-common.h > @@ -18,8 +18,15 @@ static __always_inline void arch_check_user_regs(struct pt_regs *regs) > * state, not the interrupt state as imagined by Xen. > */ > unsigned long flags = native_save_fl(); > - WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF | > - X86_EFLAGS_NT)); > + unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT; > + > + /* > + * For !SMAP hardware we patch out CLAC on entry. > + */ > + if (boot_cpu_has(X86_FEATURE_SMAP)) > + mask |= X86_EFLAGS_AC; > + > + WARN_ON_ONCE(flags & mask); > > /* We think we came from user mode. Make sure pt_regs agrees. */ > WARN_ON_ONCE(!user_mode(regs)); LGTM. Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
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