Re: [Xen-devel] [PATCH v3 1/2] x86/hvm: Always do SMAP check when updating runstate_guest(v)

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, July 29, 2014 5:05 PM
> To: Wu, Feng
> Cc: linux@xxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx;
> tim@xxxxxxx
> Subject: RE: [PATCH v3 1/2] x86/hvm: Always do SMAP check when updating
> runstate_guest(v)
> 
> >>> On 29.07.14 at 10:42, <feng.wu@xxxxxxxxx> wrote:
> 
> >
> >> -----Original Message-----
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: Tuesday, July 29, 2014 4:23 PM
> >> To: Wu, Feng
> >> Cc: linux@xxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx;
> >> tim@xxxxxxx
> >> Subject: RE: [PATCH v3 1/2] x86/hvm: Always do SMAP check when updating
> >> runstate_guest(v)
> >>
> >> >>> On 29.07.14 at 09:54, <feng.wu@xxxxxxxxx> wrote:
> >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> >> >>> On 08.01.01 at 23:52, <feng.wu@xxxxxxxxx> wrote:
> >> >> > +        switch ( v->arch.smap_check_policy )
> >> >> > +        {
> >> >> > +        case SMAP_CHECK_HONOR_CPL_AC:
> >> >> > +            hvm_get_segment_register(v, x86_seg_ss, &seg);
> >> >> > +
> >> >> > +            /*
> >> >> > +             * SMAP: kernel-mode data accesses from user-mode
> >> >> mappings
> >> >> > +             * should fault.
> >> >> > +             * A fault is considered as a SMAP violation if the
> following
> >> >> > +             * conditions come true:
> >> >> > +             *   - X86_CR4_SMAP is set in CR4
> >> >> > +             *   - A user page is accessed
> >> >> > +             *   - CPL = 3 or X86_EFLAGS_AC is clear
> >> >> > +             *   - Page fault in kernel mode
> >> >> > +             */
> >> >> > +            smap = hvm_smap_enabled(v) &&
> >> >> > +                   ((seg.attr.fields.dpl == 3) ||
> >> >> > +                   !(regs->eflags & X86_EFLAGS_AC));
> >> >>
> >> >> Indentation.
> >> >
> >> > Sorry, I don't find any indentation issue here. Do you mean
> >> > "((seg.attr.fields.dpl == 3) ||" and "!(regs->eflags & X86_EFLAGS_AC));"
> >> > are not indented with "hvm_smap_enabled(v) &&"? In fact they are in
> good
> >> > indentation. Maybe it is the display that make it look
> >> > like in wrong indentation?
> >>
> >> No, I specifically checked in a mono-spaced font. The parentheses
> >> around the || expression require its right side to be indented by one
> >> more space than the very opening parenthesis.
> >
> > In this case, do you mean I need to add another space before "!(regs->eflags
> &
> > X86_EFLAGS_AC))"?
> 
> Exactly.

Good to know this rule! BTW, is there some documents or something like that to 
tell
what is the correct coding style for Xen?

Thanks,
Feng

> 
> Jan


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