On Tue, Jul 07, 2020 at 07:49:25PM -0700, Kees Cook wrote: > On Tue, Jul 07, 2020 at 05:59:25PM -0400, Arvind Sankar wrote: > > On Mon, Jul 06, 2020 at 08:45:58PM -0700, Nick Terrell wrote: > > > From: Nick Terrell <terrelln@xxxxxx> > > > > > > Don't export symbols if XXH_PREBOOT is defined. > > > > > > This change is necessary to get xxhash to work in a preboot environment, > > > which is needed to support zstd-compressed kernels. > > > > The usual way to do it is by adding -D__DISABLE_EXPORTS to the CFLAGS, which will > > cause EXPORT_SYMBOL to be stubbed out. Doesn't that work here? > > This is quite rare, actually: > > $ git grep DISABLE_EXPORTS > arch/s390/purgatory/Makefile:CFLAGS_sha256.o := -D__DISABLE_EXPORTS > arch/x86/boot/compressed/kaslr.c:#define __DISABLE_EXPORTS > arch/x86/purgatory/Makefile:CFLAGS_sha256.o := -D__DISABLE_EXPORTS > drivers/firmware/efi/libstub/Makefile: -D__DISABLE_EXPORTS > include/linux/export.h:#if !defined(CONFIG_MODULES) || defined(__DISABLE_EXPORTS) > > But yes, it seems that would be the better approach. > > -- > Kees Cook Looks like Ard added it a couple of years back [0] but it got used only for the EFI stub and not the decompressors. [0] http://lkml.kernel.org/r/20180704083651.24360-3-ard.biesheuvel@xxxxxxxxxx
