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arm64: Fix vdso-offsets.h dependency 

arch/arm64/kernel/{vdso,signal}.c include generated/vdso-offsets.h, and
therefore the symbol offsets must be generated before these files are
compiled.

The current rules in arm64/kernel/Makefile do not actually enforce
this, because even though $(obj)/vdso is listed as a prerequisite for
vdso-offsets.h, this does not result in the intended effect of
building the vdso subdirectory (before all the other objects). As a
consequence, depending on the order in which the rules are followed,
vdso-offsets.h is updated or not before arm64/kernel/{vdso,signal}.o
are built. The current rules also impose an unnecessary dependency on
vdso-offsets.h for all arm64/kernel/*.o, resulting in unnecessary
rebuilds.

This patch removes the arch/arm64/kernel/vdso/vdso-offsets.h file
generation, leaving only the include/generated/vdso-offsets.h one. It
adds a forced dependency check of the vdso-offsets.h file in
arch/arm64/kernel/Makefile which, if not up to date according to the
arch/arm64/kernel/vdso/Makefile rules (depending on vdso.so.dbg), will
trigger the vdso/ subdirectory build and vdso-offsets.h re-generation.
Automatic kbuild dependency rules between kernel/{vdso,signal}.c rules
and vdso-offsets.h will guarantee that the vDSO object is built first,
followed by the generated symbol offsets header file.

Reported-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Catalin Marinas 2016-07-08 12:13:20 +01:00
parent 40f87d3114
commit 90f777beb7
2 changed files with 7 additions and 7 deletions
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7
arch/arm64/kernel/Makefile
View File

@ -54,6 +54,7 @@ obj-m += $(arm64-obj-m)
head-y := head.o
extra-y += $(head-y) vmlinux.lds
# vDSO - this must be built first to generate the symbol offsets
$(call objectify,$(arm64-obj-y)): $(obj)/vdso/vdso-offsets.h
$(obj)/vdso/vdso-offsets.h: $(obj)/vdso
# Check that the vDSO symbol offsets header file is up to date and re-generate
# it if necessary.
$(objtree)/include/generated/vdso-offsets.h: FORCE
$(Q)$(MAKE) $(build)=$(obj)/vdso $@

7
arch/arm64/kernel/vdso/Makefile
View File

@ -23,7 +23,7 @@ GCOV_PROFILE := n
ccflags-y += -Wl,-shared
obj-y += vdso.o
extra-y += vdso.lds vdso-offsets.h
extra-y += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
# Force dependency (incbin is bad)
@ -42,11 +42,10 @@ $(obj)/%.so: $(obj)/%.so.dbg FORCE
gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
quiet_cmd_vdsosym = VDSOSYM $@
define cmd_vdsosym
$(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@ && \
cp $@ include/generated/
$(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
endef
$(obj)/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
$(objtree)/include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
$(call if_changed,vdsosym)
# Assembly rules for the .S files