Re: [PATCH 5/5] gcc-plugins/stackleak: Don't instrument vgettimeofday.c in arm64 VDSO

Jann Horn
2020-06-04T14:14:44Z

On Thu, Jun 4, 2020 at 3:58 PM Will Deacon <will@kernel.org> wrote:
> On Thu, Jun 04, 2020 at 04:49:57PM +0300, Alexander Popov wrote:
> > Don't try instrumenting functions in arch/arm64/kernel/vdso/vgettimeofday.c.
> > Otherwise that can cause issues if the cleanup pass of stackleak gcc plugin
> > is disabled.
> >
> > Signed-off-by: Alexander Popov <alex.popov@linux.com>
> > ---
> > arch/arm64/kernel/vdso/Makefile | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
> > index 3862cad2410c..9b84cafbd2da 100644
> > --- a/arch/arm64/kernel/vdso/Makefile
> > +++ b/arch/arm64/kernel/vdso/Makefile
> > @@ -32,7 +32,8 @@ UBSAN_SANITIZE := n
> > OBJECT_FILES_NON_STANDARD := y
> > KCOV_INSTRUMENT := n
> >
> > -CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables
> > +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables \
> > + $(DISABLE_STACKLEAK_PLUGIN)
>
> I can pick this one up via arm64, thanks. Are there any other plugins we
> should be wary of? It looks like x86 filters out $(GCC_PLUGINS_CFLAGS)
> when building the vDSO.

Maybe at some point we should replace exclusions based on
GCC_PLUGINS_CFLAGS and KASAN_SANITIZE and UBSAN_SANITIZE and
OBJECT_FILES_NON_STANDARD and so on with something more generic...
something that says "this file will not be built into the normal
kernel, it contains code that runs in realmode / userspace / some
similarly weird context, and none of our instrumentation
infrastructure is available there"...