Messages in this thread | | | Date | Fri, 8 Mar 2019 20:50:12 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 05/20] x86/uaccess/xen: Suppress SMAP warnings |
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On Fri, Mar 08, 2019 at 01:00:38PM -0600, Josh Poimboeuf wrote: > On Thu, Mar 07, 2019 at 12:45:16PM +0100, Peter Zijlstra wrote: > > drivers/xen/privcmd.o: warning: objtool: privcmd_ioctl()+0x1414: call to hypercall_page() with UACCESS enabled > > > > Xen needs to do HV calls with AC=1 for hysterical raisins. Make the > > warning go away. > > > > XXX: arguably we should rename ANNOTATE_NOSPEC_ALTERNATIVE to > > ANNOTATE_IGNORE_ALTERNATIVE. > > > > Cc: andrew.cooper3@citrix.com > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > arch/x86/include/asm/xen/hypercall.h | 26 ++++++++++++++++++++++---- > > 1 file changed, 22 insertions(+), 4 deletions(-) > > > > --- a/arch/x86/include/asm/xen/hypercall.h > > +++ b/arch/x86/include/asm/xen/hypercall.h > > @@ -214,6 +214,24 @@ xen_single_call(unsigned int call, > > return (long)__res; > > } > > > > +static __always_inline void __xen_stac(void) > > +{ > > + /* > > + * This is just about as horrible as this interface; we abuse the > > + * nospec alternative annotation to supress objtool seeing the > > + * STAC/CLAC and getting confused about it calling random code with > > + * AC=1. > > + */ > > + asm volatile(ANNOTATE_NOSPEC_ALTERNATIVE > > + ASM_STAC ::: "memory", "flags"); > > +} > > + > > +static __always_inline void __xen_clac(void) > > +{ > > + asm volatile(ANNOTATE_NOSPEC_ALTERNATIVE > > + ASM_CLAC ::: "memory", "flags"); > > +} > > + > > Shouldn't these be using SMAP-based alternatives like stac()/clac() do?
They are, __ASM_{ST,CL}AC are the raw instructions ASM_{ST,CL}AC are the alternatives.
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