[PATCH 2/4] x86/vdso: Use 32-bit CHECKFLAGS for compat vDSO

[Thomas Weißschuh]

When building the compat vDSO the CHECKFLAGS from the 64-bit kernel
are used. These are combined with the 32-bit CFLAGS. This confuses
sparse, producing false-positive warnings or potentially missing
real issues.

Manually override the CHECKFLAGS for the compat vDSO with the correct
32-bit configuration.

Reported-by: Sun Jian <sun.jian.kdev@xxxxxxxxx>
Closes: https://lore.kernel.org/lkml/20260114084529.1676356-1-sun.jian.kdev@xxxxxxxxx/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
---
 arch/x86/entry/vdso/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index f247f5f5cb44..ab571ad9b9ac 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -142,7 +142,10 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),)
 endif
 endif
 
+CHECKFLAGS_32 := $(CHECKFLAGS) -U__x86_64__ -D__i386__ -m32
+
 $(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
+$(obj)/vdso32.so.dbg: CHECKFLAGS = $(CHECKFLAGS_32)
 
 $(obj)/vdso32.so.dbg: $(obj)/vdso32/vdso32.lds $(vobjs32) FORCE
 	$(call if_changed,vdso_and_check)

-- 
2.52.0