Re: [kernel-hardening] Re: [PATCH RFC v2 1/1] gcc-plugins: Add stackleak feature erasing the kernel stack at the end of syscalls

[Mark Rutland <mark.rutland@arm.com>]

On Tue, Jun 13, 2017 at 02:51:59PM -0700, Laura Abbott wrote:
> On 06/09/2017 10:28 AM, Kees Cook wrote:
> > It seems like it shouldn't be too hard to add on-user-return erasure
> > code to other architectures too.
> 
> I played around getting this to compile for arm64 with a dummy
> stack clearing function. arm64 is doing something special with the
> efistub so it fails to link with
> 
> drivers/firmware/efi/libstub/arm-stub.c:45:(.init.text+0x54): relocation
> 	truncated to fit: R_AARCH64_CALL26 against undefined symbol `__efistub_track_stack'
> 
> The relocation to the .init.text section and appending __efistub happens after
> compilation so the checks in the plugin itself don't work. I haven't come up
> with a solution to not have the plugin run on the stub yet.

Can we do something like what we do for KCOV, and (only) place the
plugin-invoking flags to into CFLAGS_STACKLEAK, which we can filter out
in scripts/Makefile.lib?

Thanks,
Mark.