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>
mariux64 · Jan 20, 2021 · a5b8ca9 · a5b8ca9
1 parent 19c329f
commit a5b8ca9
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Showing 6 changed files with 9 additions and 8 deletions.
diff --git 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
@@ -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 → arch/arm64/kernel/vdso-wrap.S b/arch/arm64/kernel/vdso/vdso.S → arch/arm64/kernel/vdso-wrap.S
diff --git 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 → arch/arm64/kernel/vdso32-wrap.S b/arch/arm64/kernel/vdso32/vdso.S → arch/arm64/kernel/vdso32-wrap.S
diff --git 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)