Re: [Xen-devel] [PATCH 3/3] xen/arm: Don't crash the domain on invalid HVC immediate

[Julien Grall <julien.grall@xxxxxxx>]

On 30/01/18 18:24, Stefano Stabellini wrote:
> On Tue, 30 Jan 2018, Julien Grall wrote:
> > domain_crash_synchronous() should only be used when something went wrong
> > in Xen. It is better to inject to the guest as it will be in better
>                                                                ^ a better
>
>
> > position to provide helpful information (stack trace...).
> >
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> >
> > ---
> >
> >      We potentially want to return -1 instead. This would make Xen more
> >      future-proof if we decide to implement the other HVC immediate.
> > ---
> >   xen/arch/arm/traps.c | 13 ++++++++-----
> >   1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> > index 843adf4959..18da45dff3 100644
> > --- a/xen/arch/arm/traps.c
> > +++ b/xen/arch/arm/traps.c
> > @@ -1473,14 +1473,17 @@ static void do_debug_trap(struct cpu_user_regs *regs, 
> > unsigned int code)
> >   #endif
> >   
> >   static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr,
> > -                              unsigned long iss)
> > +                              const union hsr hsr)
> >   {
> >       arm_hypercall_fn_t call = NULL;
> >   
> >       BUILD_BUG_ON(NR_hypercalls < ARRAY_SIZE(arm_hypercall_table) );
> >   
> > -    if ( iss != XEN_HYPERCALL_TAG )
> > -        domain_crash_synchronous();
> > +    if ( hsr.iss != XEN_HYPERCALL_TAG )
> > +    {
> > +        gprintk(XENLOG_WARNING, "Invalid HVC imm 0x%x\n", hsr.iss);
> > +        return inject_undef_exception(regs, hsr);
> It looks a bit weird, given that inject_undef_exception doesn't return
> anything. This is just code style so anyway:
I followed coding style in other part of the emulation (see do_sysreg 
for instance). I am happy to change that though.
Cheers,

> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
>
> > +    }
> >   
> >       if ( *nr >= ARRAY_SIZE(arm_hypercall_table) )
> >       {
> > @@ -2150,7 +2153,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
> >           if ( hsr.iss == 0 )
> >               return do_trap_hvc_smccc(regs);
> >           nr = regs->r12;
> > -        do_trap_hypercall(regs, &nr, hsr.iss);
> > +        do_trap_hypercall(regs, &nr, hsr);
> >           regs->r12 = (uint32_t)nr;
> >           break;
> >       }
> > @@ -2164,7 +2167,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
> >   #endif
> >           if ( hsr.iss == 0 )
> >               return do_trap_hvc_smccc(regs);
> > -        do_trap_hypercall(regs, &regs->x16, hsr.iss);
> > +        do_trap_hypercall(regs, &regs->x16, hsr);
> >           break;
> >       case HSR_EC_SMC64:
> >           /*
> > --
> > 2.11.0
--
Julien Grall

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