On Jun 15, 2016 7:25 AM, "Borislav Petkov" <b...@alien8.de> wrote:
>
> On Wed, Jun 15, 2016 at 08:25:57PM +0800, kernel test robot wrote:
> > [ 0.556833] Mountpoint-cache hash table entries: 1024 (order: 0, 4096
> > bytes)
> > [ 0.559888] ------------[ cut here ]------------
> > [ 0.559888] ------------[ cut here ]------------
> > [ 0.561405] WARNING: CPU: 0 PID: 0 at arch/x86/mm/extable.c:50
> > ex_handler_rdmsr_unsafe+0x44/0x70
> > [ 0.561405] WARNING: CPU: 0 PID: 0 at arch/x86/mm/extable.c:50
> > ex_handler_rdmsr_unsafe+0x44/0x70
> > [ 0.567649] unchecked MSR access error: RDMSR from 0x1b0
> > [ 0.567649] unchecked MSR access error: RDMSR from 0x1b0
>
> Btw, Andy, this error message is completely useless - I
> wanna know *where* the RDMSR in the code is, not point me at
> ex_handler_rdmsr_unsafe().
Did the "Call Trace" not show up?
>
> IOW, I wanna convert the current thing into this:
>
> [ 0.028003] unchecked MSR access error: RDMSR from 0x1b0 at rIP:
> 0xffffffff81026d9f
> [ 0.030343] ENERGY_PERF_BIAS: Set to 'normal', was 'performance'
> [ 0.032003] ENERGY_PERF_BIAS: View and update with
> x86_energy_perf_policy(8)
> [ 0.036003] unchecked MSR access error: WRMSR to 0x1b0 (tried to write
> 0x0000000000000006) at rIP: 0xffffffff81026de1
>
> i.e.,
>
> ---
> diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
> index 4bb53b89f3c5..2028a5ad3433 100644
> --- a/arch/x86/mm/extable.c
> +++ b/arch/x86/mm/extable.c
> @@ -46,8 +46,8 @@ EXPORT_SYMBOL(ex_handler_ext);
> bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
> struct pt_regs *regs, int trapnr)
> {
> - WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n",
> - (unsigned int)regs->cx);
> + pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP:
> 0x%lx\n",
> + (unsigned int)regs->cx, regs->ip);
I have no fundamental issue adding ip to this, but let's keep it
WARN_ONCE (so we notice loudly and so we get the call trace) and use
%pF or whatever it's called instead of %lx.
Also, I want to add a variant of WARN that takes pt_regs as parameters
at some point. You'd get much better output. Even without that, Josh
Poimboeuf and I (mainly Josh) have some work slowly afoot that will
greatly improve call trace quality when crossing an exception
boundary.
--Andy
