On Thu, Aug 20, 2020 at 03:51:22PM -0700, David Miller wrote:
> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Date: Thu, 20 Aug 2020 20:36:12 +0100
>
> > We have
> > asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
> > {
> > enum direction dir;
> >
> > if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
> > (((insn >> 30) & 3) != 3))
> > goto kill_user;
> >
> > there, followed by some work on emulating the insn. So while the default
> > behaviour is to hit the process with SIGBUS, it can overridden by setting
> > SPARC_FLAG_UNALIGNED in current->thread.flags. Fair enough, but... Just
> > what could possibly set that flag?
> >
> > That stuff had been introduced back in 2.1.9 and even there (or through
> > the 2.2, etc.) I don't see anything that would ever set it.
> >
> > Am I missing something, or had it really been dead code all along?
>
> Relic from the SunOS and/or Solaris syscall emulation probably.
Thought so, but... no such thing in either. And it's not done from assembler -
arch/sparc64 used to access ->tss.flags that way (and that was only for
SPARC_FLAG_NEWCHILD), but arch/sparc never did...
I don't have sunos toolchain to try and build such a binary and test it on
a 2.2 kernel, but I would be rather surprised if that had been it.
Anyway, it really looks like that's dead code these days...
