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a66649dab3
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>
70 lines
1.8 KiB
Makefile
70 lines
1.8 KiB
Makefile
#
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# Building a vDSO image for AArch64.
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#
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# Author: Will Deacon <will.deacon@arm.com>
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# Heavily based on the vDSO Makefiles for other archs.
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#
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obj-vdso := gettimeofday.o note.o sigreturn.o
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# Build rules
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targets := $(obj-vdso) vdso.so vdso.so.dbg
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obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
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ccflags-y := -shared -fno-common -fno-builtin
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ccflags-y += -nostdlib -Wl,-soname=linux-vdso.so.1 \
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$(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
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# Disable gcov profiling for VDSO code
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GCOV_PROFILE := n
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# Workaround for bare-metal (ELF) toolchains that neglect to pass -shared
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# down to collect2, resulting in silent corruption of the vDSO image.
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ccflags-y += -Wl,-shared
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obj-y += vdso.o
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extra-y += vdso.lds
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CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
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# Force dependency (incbin is bad)
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$(obj)/vdso.o : $(obj)/vdso.so
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# Link rule for the .so file, .lds has to be first
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$(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso)
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$(call if_changed,vdsold)
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# Strip rule for the .so file
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$(obj)/%.so: OBJCOPYFLAGS := -S
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$(obj)/%.so: $(obj)/%.so.dbg FORCE
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$(call if_changed,objcopy)
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# Generate VDSO offsets using helper script
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gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
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quiet_cmd_vdsosym = VDSOSYM $@
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define cmd_vdsosym
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$(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
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endef
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include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
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$(call if_changed,vdsosym)
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# Assembly rules for the .S files
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$(obj-vdso): %.o: %.S FORCE
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$(call if_changed_dep,vdsoas)
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# Actual build commands
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quiet_cmd_vdsold = VDSOL $@
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cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $^ -o $@
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quiet_cmd_vdsoas = VDSOA $@
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cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $<
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# Install commands for the unstripped file
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quiet_cmd_vdso_install = INSTALL $@
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cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
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vdso.so: $(obj)/vdso.so.dbg
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@mkdir -p $(MODLIB)/vdso
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$(call cmd,vdso_install)
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vdso_install: vdso.so
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