Re: [PATCH v4 7/7] powerpc/64s: Blacklist rtas entry/exit from kprobes

[Nicholas Piggin <npiggin@gmail.com>]

On Thu, 29 Jun 2017 16:11:10 +0530
"Naveen N. Rao" <naveen.n.rao@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@linux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/entry_64.S | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 0c27084800b6..16f4c4a1a294 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -1082,6 +1082,7 @@ _GLOBAL(enter_rtas)
>  	sync				/* disable interrupts so SRR0/1 */
>  	mtmsrd	r0			/* don't get trashed */
>  
> +__enter_rtas:

Hmm, am I missing something, or is there a reason to put these labels
after the mtmsr? Even if kprobes does the right thing, I think it's
easier to read the code if you cover the mtmsr as well.

Thanks,
Nick