Re: [PATCH 17/22] arm64: vdso: disable LTO

Nick Desaulniers
2020-06-24T21:09:53Z

On Wed, Jun 24, 2020 at 1:58 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > Filter out CC_FLAGS_LTO for the vDSO.
>
> Just curious about this patch (and the following one for x86's vdso),
> do you happen to recall specifically what the issues with the vdso's
> are?

+ Andi (tangential, I actually have a bunch of tabs open with slides
from http://halobates.de/ right now)
58edae3aac9f2
67424d5a22124
$ git log -S DISABLE_LTO

>
> >
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > ---
> > arch/arm64/kernel/vdso/Makefile | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > index 556d424c6f52..cfad4c296ca1 100644
> > --- a/arch/arm64/kernel/vdso/Makefile
> > +++ b/arch/arm64/kernel/vdso/Makefile
> > @@ -29,8 +29,8 @@ ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \
> > ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
> > ccflags-y += -DDISABLE_BRANCH_PROFILING
> >
> > -CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS)
> > -KBUILD_CFLAGS += $(DISABLE_LTO)
> > +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \
> > + $(CC_FLAGS_LTO)
> > KASAN_SANITIZE := n
> > UBSAN_SANITIZE := n
> > OBJECT_FILES_NON_STANDARD := y
> > --

--
Thanks,
~Nick Desaulniers