| From | Nick Desaulniers <> | Date | Fri, 18 Oct 2019 10:32:20 -0700 | Subject | Re: [PATCH 05/18] arm64: kbuild: reserve reg x18 from general allocation by the compiler |
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On Fri, Oct 18, 2019 at 9:11 AM Sami Tolvanen <samitolvanen@google.com> wrote: > > From: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > Before we can start using register x18 for a special purpose (as permitted > by the AAPCS64 ABI), we need to tell the compiler that it is off limits > for general allocation. So tag it as 'fixed',
yep, but...
> and remove the mention from > the LL/SC compiler flag override.
was that cut/dropped from this patch?
> > Link: https://patchwork.kernel.org/patch/9836881/
^ Looks like it. Maybe it doesn't matter, but if sending a V2, maybe the commit message to be updated?
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
If sending a V2 with the above cleaned up, you may also include: Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
I like how this does not conditionally reserve it based on the CONFIG for SCS. Hopefully later patches don't wrap it, but I haven't looked through all of them yet.
> --- > arch/arm64/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 2c0238ce0551..1c7b276bc7c5 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -55,7 +55,7 @@ endif > > KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) \ > $(compat_vdso) $(cc_has_k_constraint) > -KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -ffixed-x18 > KBUILD_CFLAGS += $(call cc-disable-warning, psabi) > KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) $(compat_vdso) > > -- > 2.23.0.866.gb869b98d4c-goog >
-- Thanks, ~Nick Desaulniers
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