On Thu, 7 Jan 2021 at 23:34, Arnd Bergmann <[email protected]> wrote: > > From: Arnd Bergmann <[email protected]> > > When 5-level page tables are enabled, clang triggers a BUILD_BUG_ON(): > > x86_64-linux-ld: arch/x86/platform/efi/efi_64.o: in function > `efi_sync_low_kernel_mappings': > efi_64.c:(.text+0x22c): undefined reference to `__compiletime_assert_354' > > Use the same method as in commit c65e774fb3f6 ("x86/mm: Make PGDIR_SHIFT > and PTRS_PER_P4D variable") and change it to MAYBE_BUILD_BUG_ON(), > so it only triggers for constant input. > > Link: https://github.com/ClangBuiltLinux/linux/issues/256 > Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]> This can go via the x86 tree directly, IMO > --- > arch/x86/platform/efi/efi_64.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > index e1e8d4e3a213..62bb1616b4a5 100644 > --- a/arch/x86/platform/efi/efi_64.c > +++ b/arch/x86/platform/efi/efi_64.c > @@ -137,8 +137,8 @@ void efi_sync_low_kernel_mappings(void) > * As with PGDs, we share all P4D entries apart from the one entry > * that covers the EFI runtime mapping space. > */ > - BUILD_BUG_ON(p4d_index(EFI_VA_END) != p4d_index(MODULES_END)); > - BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != (EFI_VA_END & P4D_MASK)); > + MAYBE_BUILD_BUG_ON(p4d_index(EFI_VA_END) != p4d_index(MODULES_END)); > + MAYBE_BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != (EFI_VA_END & > P4D_MASK)); > > pgd_efi = efi_pgd + pgd_index(EFI_VA_END); > pgd_k = pgd_offset_k(EFI_VA_END); > -- > 2.29.2 >
