Re: [PATCH v10 00/18] Enable FSGSBASE instructions

[Andi Kleen]

> [ 6402.786418] ------------[ cut here ]------------
> [ 6402.787769] WARNING: CPU: 0 PID: 13802 at arch/x86/kernel/traps.c:811
> do_debug+0x16c/0x210
...

> [ 6402.848299]  ? trace_hardirqs_off_thunk+0x1a/0x33
> [ 6402.849593]  trace_hardirqs_off_caller+0xa6/0xd0
> [ 6402.850862]  ? debug+0x4e/0x70
> [ 6402.851727]  trace_hardirqs_off_thunk+0x1a/0x33
> [ 6402.852983]  debug+0x53/0x70
> [ 6402.853785] RIP: 0033:0x400060dd

So this is a check that checks if you're running in user mode if
you have a debug trap with single step, but somehow it triggered
for a user segment.

Probably the regs got corrupted. 

Sasha, I suspect you're missing a mov %rsp,%rdi somewhere in the
debug entry path that sets up the regs argument for the C code.

-Andi