Re: SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)

Al Viro
2011-08-22T04:26:28Z

On Sun, Aug 21, 2011 at 09:11:54PM -0700, H. Peter Anvin wrote:
> > lack of point - the *only* CPU where it would matter would be K6-2, IIRC,
> > and (again, IIRC) it had some differences in SYSCALL semantics compared to
> > K7 (which supports SYSENTER as well). Bugger if I remember what those
> > differences might've been... Some flag not cleared?
>
> The most likely reason for a binary to execute a stray SYSCALL is
> because they read it out of the vdso. Totally daft, but we certainly
> see a lot of stupid things as evidenced by the JIT thread earlier this
> month.

Um... What, blindly, no matter what surrounds it in there? What will
happen to the same eager JIT when it steps on SYSENTER?