Re: [PATCH 3/3] jump_label: make initial NOP patching the special case

Ard Biesheuvel
2022-06-15T10:22:02Z

On Wed, 15 Jun 2022 at 12:06, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Jun 15, 2022 at 10:52:41AM +0100, Mark Rutland wrote:
> > On Wed, Jun 08, 2022 at 12:45:12PM +0200, Ard Biesheuvel wrote:
> > > Instead of defaulting to patching NOP opcodes at init time, and leaving
> > > it to the architectures to override this if this is not needed, switch
> > > to a model where doing nothing is the default. This is the common case
> > > by far, as only MIPS requires NOP patching at init time. On all other
> > > architectures, the correct encodings are emitted by the compiler and so
> > > no initial patching is needed.
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > > Documentation/staging/static-keys.rst | 3 ---
> > > arch/arc/kernel/jump_label.c | 13 -------------
> > > arch/arm/kernel/jump_label.c | 6 ------
> > > arch/arm64/kernel/jump_label.c | 11 -----------
> > > arch/mips/include/asm/jump_label.h | 2 ++
> > > arch/parisc/kernel/jump_label.c | 11 -----------
> > > arch/riscv/kernel/jump_label.c | 12 ------------
> > > arch/s390/kernel/jump_label.c | 5 -----
> > > arch/x86/kernel/jump_label.c | 13 -------------
> > > kernel/jump_label.c | 14 +++-----------
> > > 10 files changed, 5 insertions(+), 85 deletions(-)
> >
> > I have one minor comment below, but either way this is a nice cleanup (and I'm
> > always happy to see __weak functions disappear), so FWIW:
>
> (I've got a new found hatred for __weak after having had to fix so many
> objtool issues with it, so yeah, that).
>
> >
> > Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> With the thing Mark pointed out fixed:
>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> (although, I'll probably be the one to eventually apply these I suppose,
> unless they're needed in a different tree?)

Not really - this just came up when Jason was looking into how to
enable jump labels extremely early on every single architecture, but
fortunately, that issue got fixed in a different way.

I'll respin and resend and leave it to you to apply them whenever convenient.