On Tue, Oct 17, 2017 at 04:59:41PM -0400, Boris Ostrovsky wrote: > On 10/17/2017 04:50 PM, Josh Poimboeuf wrote: > > On Tue, Oct 17, 2017 at 04:36:00PM -0400, Boris Ostrovsky wrote: > >> On 10/17/2017 04:17 PM, Josh Poimboeuf wrote: > >>> On Tue, Oct 17, 2017 at 11:36:57AM -0400, Boris Ostrovsky wrote: > >>>> On 10/17/2017 10:36 AM, Josh Poimboeuf wrote: > >>>>> Maybe we can add a new field to the alternatives entry struct which > >>>>> specifies the offset to the CALL instruction, so apply_alternatives() > >>>>> can find it. > >>>> We'd also have to assume that the restore part of an alternative entry > >>>> is the same size as the save part. Which is true now. > >>> Why? > >>> > >> Don't you need to know the size of the instruction without save and > >> restore part? > >> > >> + if (a->replacementlen == 6 && *insnbuf == 0xff && *(insnbuf+1) == 0x15) > >> > >> Otherwise you'd need another field for the actual instruction length. > > If we know where the CALL instruction starts, and can verify that it > > starts with "ff 15", then we know the instruction length: 6 bytes. > > Right? > > > > Oh, OK. Then you shouldn't need a->replacementlen test(s?) in > apply_alternatives()? Right. Though in the above code it was needed for a different reason, to make sure it wasn't reading past the end of the buffer. -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
