On Wed, Feb 07, 2018 at 11:03:42AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 10:49 AM, Peter Zijlstra <pet...@infradead.org> wrote: > > > > Right, we picked UD0 because we _thought_ everybody agreed it being 2 > > bytes, just like UD2. This is now not true anymore? > > Both UD0 and UD1 are documented to have modrm in the latest Intel SDM > I can find (Order number 325462-065US, December 2017):
Thanks, and yes :/ They changed it in October17 (which I actually had a copy of so I'm not sure why I was looking at March17). Back when we did that patch the SDM didn't have that extra ModR/M on, and binutils disassembled it as the 2 byte (bad) thing, which was all good. Then someone went and wrecked it.