[PATCH v3 6/6] powerpc/64s: Blacklist rtas entry/exit from kprobes

[Nicholas Piggin]

On Thu, 22 Jun 2017 00:08:42 +0530
"Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote:

> We can't take traps with relocation off, so blacklist enter_rtas() and
> rtas_return_loc(). However, instead of blacklisting all of enter_rtas(),
> introduce a new symbol __enter_rtas from where on we can't take a trap
> and blacklist that.
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/entry_64.S | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index d376f07153d7..49c35450f399 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -1076,6 +1076,8 @@ _GLOBAL(enter_rtas)
>          rldicr  r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
>  	ori	r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
>  	andc	r6,r0,r9
> +
> +__enter_rtas:
>  	sync				/* disable interrupts so SRR0/1 */
>  	mtmsrd	r0			/* don't get trashed */

Along the lines of the system call patch... For consistency, could we
put the __enter_rtas right after mtmsrd? And I wonder if we shoul
come up with a common prefix or postfix naming convention for these
such labels used to control probing?

How do opal calls avoid tracing?

Thanks,
Nick