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arm64: do not descend to vdso directories twice

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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>
This commit is contained in:
Masahiro Yamada 2020-12-18 11:45:40 +09:00 committed by Will Deacon
parent 19c329f680
commit a5b8ca97fb
6 changed files with 9 additions and 8 deletions
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10
arch/arm64/Makefile
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@ -188,10 +188,12 @@ ifeq ($(KBUILD_EXTMOD),)
# this hack. # this hack.
prepare: vdso_prepare prepare: vdso_prepare
vdso_prepare: prepare0 vdso_prepare: prepare0
$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso \
$(if $(CONFIG_COMPAT_VDSO),$(Q)$(MAKE) \ include/generated/vdso-offsets.h arch/arm64/kernel/vdso/vdso.so
$(build)=arch/arm64/kernel/vdso32 \ ifdef CONFIG_COMPAT_VDSO
include/generated/vdso32-offsets.h) $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso32 \
include/generated/vdso32-offsets.h arch/arm64/kernel/vdso32/vdso.so
endif
endif endif
define archhelp define archhelp

5
arch/arm64/kernel/Makefile
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@ -59,9 +59,10 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
obj-$(CONFIG_ARM64_MTE) += mte.o obj-$(CONFIG_ARM64_MTE) += mte.o
obj-y += vdso-wrap.o
obj-$(CONFIG_COMPAT_VDSO) += vdso32-wrap.o
obj-y += vdso/ probes/ obj-y += probes/
obj-$(CONFIG_COMPAT_VDSO) += vdso32/
head-y := head.o head-y := head.o
extra-y += $(head-y) vmlinux.lds extra-y += $(head-y) vmlinux.lds

0
arch/arm64/kernel/vdso/vdso.S → arch/arm64/kernel/vdso-wrap.S
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1
arch/arm64/kernel/vdso/Makefile
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@ -44,7 +44,6 @@ endif
# Disable gcov profiling for VDSO code # Disable gcov profiling for VDSO code
GCOV_PROFILE := n GCOV_PROFILE := n
obj-y += vdso.o
targets += vdso.lds targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH) CPPFLAGS_vdso.lds += -P -C -U$(ARCH)

0
arch/arm64/kernel/vdso32/vdso.S → arch/arm64/kernel/vdso32-wrap.S
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1
arch/arm64/kernel/vdso32/Makefile
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@ -155,7 +155,6 @@ c-obj-vdso-gettimeofday := $(addprefix $(obj)/, $(c-obj-vdso-gettimeofday))
asm-obj-vdso := $(addprefix $(obj)/, $(asm-obj-vdso)) asm-obj-vdso := $(addprefix $(obj)/, $(asm-obj-vdso))
obj-vdso := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso) obj-vdso := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso)
obj-y += vdso.o
targets += vdso.lds targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH) CPPFLAGS_vdso.lds += -P -C -U$(ARCH)