[PATCH v2 2/2] arm64/vdso: fix flip/flop vdso build bug

From: Naohiro Aota
Date: Fri Jul 12 2019 - 06:16:52 EST


Running "make" on an already compiled kernel tree will rebuild the kernel
even without any modifications:

$ make ARCH=arm64 CROSS_COMPILE=/usr/bin/aarch64-unknown-linux-gnu-
arch/arm64/Makefile:58: CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will not be built
CALL scripts/checksyscalls.sh
CALL scripts/atomic/check-atomics.sh
VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
VDSOSYM include/generated/vdso-offsets.h
CHK include/generated/compile.h
CC arch/arm64/kernel/signal.o
CC arch/arm64/kernel/vdso.o
CC arch/arm64/kernel/signal32.o
LD arch/arm64/kernel/vdso/vdso.so.dbg
OBJCOPY arch/arm64/kernel/vdso/vdso.so
AS arch/arm64/kernel/vdso/vdso.o
AR arch/arm64/kernel/vdso/built-in.a
AR arch/arm64/kernel/built-in.a
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
AR init/built-in.a
LD vmlinux.o

This is the same bug fixed in commit 92a4728608a8 ("x86/boot: Fix
if_changed build flip/flop bug"). We cannot use two "if_changed" in one
target. Fix this build bug by merging two commands into one function.

Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Fixes: 28b1a824a4f4 ("arm64: vdso: Substitute gettimeofday() with C implementation")
Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
---
arch/arm64/kernel/vdso/Makefile | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 4ab863045188..068c614b1231 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -57,8 +57,7 @@ $(obj)/vdso.o : $(obj)/vdso.so

# Link rule for the .so file, .lds has to be first
$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
- $(call if_changed,ld)
- $(call if_changed,vdso_check)
+ $(call if_changed,ld_and_vdso_check)

# Strip rule for the .so file
$(obj)/%.so: OBJCOPYFLAGS := -S
@@ -77,6 +76,9 @@ include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
quiet_cmd_vdsocc = VDSOCC $@
cmd_vdsocc = $(CC) $(a_flags) $(c_flags) -c -o $@ $<

+quiet_cmd_ld_and_vdso_check = LD $@
+ cmd_ld_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
+
# Install commands for the unstripped file
quiet_cmd_vdso_install = INSTALL $@
cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
--
2.22.0