Re: [Xen-devel] [PATCH] x86/traps: Remove redundant trapnr parameter from fatal_trap()

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 09/01/14 12:27, Andrew Cooper wrote:
> On 01/09/14 17:10, Don Slutz wrote:
> > On 09/01/14 06:06, Andrew Cooper wrote:
> > > It is always available via regs->entry_vector.
> > >
> > > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > > CC: Jan Beulich <JBeulich@xxxxxxxx>
> > > ---
> > > -void fatal_trap(int trapnr, const struct cpu_user_regs *regs)
> > > +void fatal_trap(const struct cpu_user_regs *regs)
> > >    {
> > >        static DEFINE_PER_CPU(char, depth);
> > > +    unsigned int trapnr = regs->entry_vector;
> > Should this be:
> >
> > unsigned int trapnr = regs->entry_vector &
> > ~(TRAP_regs_partial|TRAP_syscall);
> >
> >
> > To get rid of the extra bits?
> >
> >    -Don Slutz
> No; I don't think so.  There should be no paths into fatal_trap() which
> would set these bits, as these bits are only set as a result of guest
> sys/hypercall interaction, while fatal_trap() is a terminal error condition.
>
> Furthermore, if a path is discovered then a) it will be more obvious
> from the error message and b) we probably have a security problem to fix.
>
> ~Andrew
Ok.

Reviewed-by: Don Slutz <dslutz@xxxxxxxxxxx>


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