[RFC PATCH 6/7] arch: x86: no MAX_ORDER exceeds SECTION_SIZE check for 32bit vdso.

Zi Yan
2021-05-06T15:26:22Z

From: Zi Yan <ziy@nvidia.com>

For x86_64, 32bit vdso is compiled for compatibility reason and 32bit
SECTION_SIZE_BITS value is used during compilation. It causes
compilation time error when MAX_ORDER is increased in the 64bit
environment even if it is OK for 64bit SECTION_SIZE_BITS. Remove the
check during 32bit vdso compilation. It will be checked when other
kernel components are compiled.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
arch/x86/entry/vdso/Makefile | 1 +
include/linux/mmzone.h | 2 ++
2 files changed, 3 insertions(+)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 05c4abc2fdfd..cad339136ed1 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -156,6 +156,7 @@ KBUILD_CFLAGS_32 += -fno-stack-protector
KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
+KBUILD_CFLAGS_32 += -DNO_MAX_ORDER_CHECK

ifdef CONFIG_RETPOLINE
ifneq ($(RETPOLINE_VDSO_CFLAGS),)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 965a0cd5eac1..fb5a0c2ab528 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1211,9 +1211,11 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
#define SECTION_BLOCKFLAGS_BITS \
((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)

+#ifndef NO_MAX_ORDER_CHECK
#if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
#error Allocator MAX_ORDER exceeds SECTION_SIZE
#endif
+#endif

static inline unsigned long pfn_to_section_nr(unsigned long pfn)
{
--
2.30.2