Re: [RFC PATCH 1/5] powerpc/64s/hash: convert SLB miss handlers to C

[Michael Ellerman <mpe@ellerman.id.au>]

Nicholas Piggin <npiggin@gmail.com> writes:
> On Tue, 21 Aug 2018 16:46:02 +1000
> Michael Ellerman <mpe@ellerman.id.au> wrote:
>> Nicholas Piggin <npiggin@gmail.com> writes:
>> > This patch moves SLB miss handlers completely to C, using the standard
>> > exception handler macros to set up the stack and branch to C.
>> >
>> > This can be done because the segment containing the kernel stack is
>> > always bolted, so accessing it with relocation on will not cause an
>> > SLB exception.
>> >
>> > Arbitrary kernel memory may not be accessed when handling kernel space
>> > SLB misses, so care should be taken there.  
>> 
>> We'll need to mark everything that's used in slb.c as notrace, otherwise
>> 
>> Probably we just need to mark the whole file as not traceable.
>
> Yeah good point there. I'll do that. The whole file including things we
> allow today? How do we do that, like this?

For now yeah do the whole file, if there's anything in there we're sure
is safe then we can move it out later.

> CFLAGS_REMOVE_slb.o = -mno-sched-epilog $(CC_FLAGS_FTRACE)

Yeah AFAIK.

And yet another reminder for me to finally work out if we still need the
epilog crap.

cheers