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

H. Peter Anvin
2011-08-22T04:06:26Z

Borislav,

We're tracking down an issue with the way system call arguments are
handled on 32 bits. We have a solution for SYSENTER but not SYSCALL;
fixing SYSCALL "properly" appears to be very difficult at best.

So the question is: how much overhead would it be to simply fall back to
int $0x80 or some other legacy-style domain crossing instruction for
32-bit system calls on AMD64 processors? We don't ever use SYSCALL in
legacy mode, so native i386 kernels are unaffected.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.