On Wed, Oct 30, 2013 at 03:53:11PM -0700, H. Peter Anvin wrote: > On 10/30/2013 03:22 PM, Kees Cook wrote: > >> > >> - /* > >> - * sizeof(unsigned long) coming from an extra "long" at the end > >> - * of the iobitmap. See tss_struct definition in processor.h > >> - * > >> - * -1? seg base+limit should be pointing to the address of the > >> - * last valid byte > > > > I think it might be better to keep at least a minimal comment near the > > TSS_LIMIT declaration, just to explain the "-1" part, which is not > > entirely obvious from just reading the code. > > > > Agreed, although it doesn't need to be an unsigned long at all... the > CPU will only ever access one extra byte past the end. True, but the thing immediately following the iobitmap is a stack, which needs aligning, so the array does need to contain a full additional unsigned long even if the CPU only accesses a byte of it. In any case, that isn't the reason for the -1, just the reason for the sizeof(unsigned long) mentioned in the comment above, which goes away now that TSS_LIMIT uses the offset of the *following* field rather than recalculating the size of the iobitmap. - Josh Triplett _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
