On Wed, Jan 10, 2018 at 08:55:40PM +0100, Thomas Gleixner wrote: > On Wed, 10 Jan 2018, Linus Torvalds wrote: > > > On Wed, Jan 10, 2018 at 3:28 AM, Borislav Petkov <[email protected]> wrote: > > > > > > Make sure we scan all bytes before we decide to optimize the NOPs in > > > there. > > > > Can we also add compile-time checking (presumably in objtool, but who > > knows) that there are no relocations in the alternative section? > > Cc'ing the overlor^Haded objtool wizard > > > Because that was the other "oops, this really doesn't work with > > altinstructions" issue, wasn't it?
I think .altinstruction relocations *do* work if they're for the first instruction, and it's a jump or a call. There's some alternatives code which adjusts the jump/call offset in that case, and there are some users of alternatives who rely on that. I think Boris had a patch floating around to add an instruction decoder to alternatives, so you can do a call/jmp anywhere. -- Josh
