From a5b8ca97fbf8300a5e21c393df25ce6f521e7939 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Fri, 18 Dec 2020 11:45:40 +0900
Subject: [PATCH] arm64: do not descend to vdso directories twice
arm64 descends into each vdso directory twice; first in vdso_prepare,
second during the ordinary build process.
PPC mimicked it and uncovered a problem [1]. In the first descend,
Kbuild directly visits the vdso directories, therefore it does not
inherit subdir-ccflags-y from upper directories.
This means the command line parameters may differ between the two.
If it happens, the offset values in the generated headers might be
different from real offsets of vdso.so in the kernel.
This potential danger should be avoided. The vdso directories are
built in the vdso_prepare stage, so the second descend is unneeded.
[1]: https://lore.kernel.org/linux-kbuild/CAK7LNARAkJ3_-4gX0VA2UkapbOftuzfSTVMBbgbw=HD8n7N+7w@mail.gmail.com/T/#ma10dcb961fda13f36d42d58fa6cb2da988b7e73a
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20201218024540.1102650-1-masahiroy@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/Makefile | 10 ++++++----
arch/arm64/kernel/Makefile | 5 +++--
arch/arm64/kernel/{vdso/vdso.S => vdso-wrap.S} | 0
arch/arm64/kernel/vdso/Makefile | 1 -
arch/arm64/kernel/{vdso32/vdso.S => vdso32-wrap.S} | 0
arch/arm64/kernel/vdso32/Makefile | 1 -
6 files changed, 9 insertions(+), 8 deletions(-)
rename arch/arm64/kernel/{vdso/vdso.S => vdso-wrap.S} (100%)
rename arch/arm64/kernel/{vdso32/vdso.S => vdso32-wrap.S} (100%)
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 90309208bb28..5b84aec31ed3 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -188,10 +188,12 @@ ifeq ($(KBUILD_EXTMOD),)
# this hack.
prepare: vdso_prepare
vdso_prepare: prepare0
- $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h
- $(if $(CONFIG_COMPAT_VDSO),$(Q)$(MAKE) \
- $(build)=arch/arm64/kernel/vdso32 \
- include/generated/vdso32-offsets.h)
+ $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso \
+ include/generated/vdso-offsets.h arch/arm64/kernel/vdso/vdso.so
+ifdef CONFIG_COMPAT_VDSO
+ $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso32 \
+ include/generated/vdso32-offsets.h arch/arm64/kernel/vdso32/vdso.so
+endif
endif
define archhelp
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 86364ab6f13f..42f6ad2c7eac 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -59,9 +59,10 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
obj-$(CONFIG_ARM64_MTE) += mte.o
+obj-y += vdso-wrap.o
+obj-$(CONFIG_COMPAT_VDSO) += vdso32-wrap.o
-obj-y += vdso/ probes/
-obj-$(CONFIG_COMPAT_VDSO) += vdso32/
+obj-y += probes/
head-y := head.o
extra-y += $(head-y) vmlinux.lds
diff --git a/arch/arm64/kernel/vdso/vdso.S b/arch/arm64/kernel/vdso-wrap.S
similarity index 100%
rename from arch/arm64/kernel/vdso/vdso.S
rename to arch/arm64/kernel/vdso-wrap.S
diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index cd9c3fa25902..76c0255ecc91 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -44,7 +44,6 @@ endif
# Disable gcov profiling for VDSO code
GCOV_PROFILE := n
-obj-y += vdso.o
targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
diff --git a/arch/arm64/kernel/vdso32/vdso.S b/arch/arm64/kernel/vdso32-wrap.S
similarity index 100%
rename from arch/arm64/kernel/vdso32/vdso.S
rename to arch/arm64/kernel/vdso32-wrap.S
diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index a1e0f91e6cea..789ad420f16b 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -155,7 +155,6 @@ c-obj-vdso-gettimeofday := $(addprefix $(obj)/, $(c-obj-vdso-gettimeofday))
asm-obj-vdso := $(addprefix $(obj)/, $(asm-obj-vdso))
obj-vdso := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso)
-obj-y += vdso.o
targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
--
2.42.0