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| author | Kevin Brodsky <kevin.brodsky@arm.com> | 2016-05-12 17:39:15 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-07-11 17:10:11 +0100 |
| commit | a66649dab35033bd67988670fa60c268b0444cda (patch) | |
| tree | 7fc2a35a8054e5e78c1be1a5bdb7f9d1f8ef68ba /arch/arm64/Makefile | |
| parent | 7d9a7086319daf826ebf06c1abe31728823e1240 (diff) | |
| download | linux-a66649dab35033bd67988670fa60c268b0444cda.tar.bz2 | |
arm64: fix vdso-offsets.h dependency
arm64/kernel/{vdso,signal}.c include vdso-offsets.h, as well as any
file that includes asm/vdso.h. Therefore, vdso-offsets.h must be
generated before these files are compiled.
The current rules in arm64/kernel/Makefile do not actually enforce
this, because even though $(obj)/vdso is listed as a prerequisite for
vdso-offsets.h, this does not result in the intended effect of
building the vdso subdirectory (before all the other objects). As a
consequence, depending on the order in which the rules are followed,
vdso-offsets.h is updated or not before arm64/kernel/{vdso,signal}.o
are built. The current rules also impose an unnecessary dependency on
vdso-offsets.h for all arm64/kernel/*.o, resulting in unnecessary
rebuilds. This is made obvious when using make -j:
touch arch/arm64/kernel/vdso/gettimeofday.S && make -j$NCPUS arch/arm64/kernel
will sometimes result in none of arm64/kernel/*.o being
rebuilt, sometimes all of them, or even just some of them.
It is quite difficult to ensure that a header is generated before it
is used with recursive Makefiles by using normal rules. Instead,
arch-specific generated headers are normally built in the archprepare
recipe in the arch Makefile (see for instance arch/ia64/Makefile).
Unfortunately, asm-offsets.h is included in gettimeofday.S, and must
therefore be generated before vdso-offsets.h, which is not the case if
archprepare is used. For this reason, a rule run after archprepare has
to be used.
This commit adds rules in arm64/Makefile to build vdso-offsets.h
during the prepare step, ensuring that vdso-offsets.h is generated
before building anything. It also removes the now-unnecessary
dependencies on vdso-offsets.h in arm64/kernel/Makefile. Finally, it
removes the duplication of asm-offsets.h between arm64/kernel/vdso/
and include/generated/ and makes include/generated/vdso-offsets.h a
target in arm64/kernel/vdso/Makefile.
Cc: Will Deacon <will.deacon@arm.com>
Cc: Michal Marek <mmarek@suse.com>
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/Makefile')
| -rw-r--r-- | arch/arm64/Makefile | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 7085e322dc42..4b6f84bf2ab9 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -121,6 +121,16 @@ archclean: $(Q)$(MAKE) $(clean)=$(boot) $(Q)$(MAKE) $(clean)=$(boot)/dts +# We need to generate vdso-offsets.h before compiling certain files in kernel/. +# In order to do that, we should use the archprepare target, but we can't since +# asm-offsets.h is included in some files used to generate vdso-offsets.h, and +# asm-offsets.h is built in prepare0, for which archprepare is a dependency. +# Therefore we need to generate the header after prepare0 has been made, hence +# this hack. +prepare: vdso_prepare +vdso_prepare: prepare0 + $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h + define archhelp echo '* Image.gz - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)' echo ' Image - Uncompressed kernel image (arch/$(ARCH)/boot/Image)' |