Re: [Xen-devel] x86_64: Fix off-by-one error setting up the Interrupt Stack Tables

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-05-09 at 11:55 +0100, Jan Beulich wrote:
> >>> On 09.05.12 at 12:31, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > On Wed, 2012-05-09 at 11:22 +0100, Andrew Cooper wrote:
> >> diff -r 8f1e0cc4a507 xen/include/asm-x86/processor.h
> >> --- a/xen/include/asm-x86/processor.h
> >> +++ b/xen/include/asm-x86/processor.h
> >> @@ -424,7 +424,9 @@ struct tss_struct {
> >>      union { u64 rsp1, esp1; };
> >>      union { u64 rsp2, esp2; };
> >>      u64 reserved1;
> >> -    u64 ist[7];
> >> +    u64 ist[7]; /* Interrupt Stack Table is 1-based so tss->ist[0]
> >> +                 * corresponds to an IST value of 1 in an Interrupt
> >> +                 * Descriptor */
> > 
> > Would it be too sneaky to drop "reserved1" and make ist be 8 elements?
> > then ist[1] would actually be the slot corresponding to a value of 1 in
> > an IDT entry.
> 
> While appealing at a first glance, I wouldn't recommend doing so:
> Documentation specifies it the way it's defined currently, and Linux
> also uses the same definition, so we'd only call for future bugs if
> we did it differently in our code.

I thought someone would say something like that ;-) OK then.

> 
> Jan
> 
> >>      u64 reserved2;
> >>      u16 reserved3; 
> 
> 
> 



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