Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index
From: Nathan Chancellor <hidden>
Date: 2021-01-07 22:43:48
Also in:
lkml, platform-driver-x86
On Thu, Jan 07, 2021 at 11:34:15PM +0100, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@arndb.de>
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 <arnd@arndb.de>Reviewed-by: Nathan Chancellor <redacted> Tested-by: Nathan Chancellor <redacted>
quoted hunk ↗ jump to hunk
--- 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