54a702f705
GNU Make automatically deletes intermediate files that are updated
in a chain of pattern rules.
Example 1) %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
Example 2) %.o <- %.c <- %.c_shipped
A couple of makefiles mark such targets as .PRECIOUS to prevent Make
from deleting them, but the correct way is to use .SECONDARY.
.SECONDARY
Prerequisites of this special target are treated as intermediate
files but are never automatically deleted.
.PRECIOUS
When make is interrupted during execution, it may delete the target
file it is updating if the file was modified since make started.
If you mark the file as precious, make will never delete the file
if interrupted.
Both can avoid deletion of intermediate files, but the difference is
the behavior when Make is interrupted; .SECONDARY deletes the target,
but .PRECIOUS does not.
The use of .PRECIOUS is relatively rare since we do not want to keep
partially constructed (possibly corrupted) targets.
Another difference is that .PRECIOUS works with pattern rules whereas
.SECONDARY does not.
.PRECIOUS: $(obj)/%.lex.c
works, but
.SECONDARY: $(obj)/%.lex.c
has no effect. However, for the reason above, I do not want to use
.PRECIOUS which could cause obscure build breakage.
The targets specified as .SECONDARY must be explicit. $(targets)
contains all targets that need to include .*.cmd files. So, the
intermediates you want to keep are mostly in there. Therefore, mark
$(targets) as .SECONDARY. It means primary targets are also marked
as .SECONDARY, but I do not see any drawback for this.
I replaced some .SECONDARY / .PRECIOUS markers with 'targets'. This
will make Kbuild search for non-existing .*.cmd files, but this is
not a noticeable performance issue.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Frank Rowand <frowand.list@gmail.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
200 lines
6.2 KiB
Makefile
200 lines
6.2 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# Building vDSO images for x86.
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#
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KBUILD_CFLAGS += $(DISABLE_LTO)
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KASAN_SANITIZE := n
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UBSAN_SANITIZE := n
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OBJECT_FILES_NON_STANDARD := y
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# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
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KCOV_INSTRUMENT := n
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VDSO64-$(CONFIG_X86_64) := y
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VDSOX32-$(CONFIG_X86_X32_ABI) := y
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VDSO32-$(CONFIG_X86_32) := y
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VDSO32-$(CONFIG_IA32_EMULATION) := y
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# files to link into the vdso
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vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
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# files to link into kernel
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obj-y += vma.o
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OBJECT_FILES_NON_STANDARD_vma.o := n
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# vDSO images to build
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vdso_img-$(VDSO64-y) += 64
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vdso_img-$(VDSOX32-y) += x32
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vdso_img-$(VDSO32-y) += 32
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obj-$(VDSO32-y) += vdso32-setup.o
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vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
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$(obj)/vdso.o: $(obj)/vdso.so
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targets += vdso.lds $(vobjs-y)
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# Build the vDSO image C files and link them in.
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vdso_img_objs := $(vdso_img-y:%=vdso-image-%.o)
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vdso_img_cfiles := $(vdso_img-y:%=vdso-image-%.c)
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vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg)
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obj-y += $(vdso_img_objs)
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targets += $(vdso_img_cfiles)
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targets += $(vdso_img_sodbg) $(vdso_img-y:%=vdso%.so)
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export CPPFLAGS_vdso.lds += -P -C
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VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
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-Wl,--no-undefined \
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-Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 \
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$(DISABLE_LTO)
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$(obj)/vdso64.so.dbg: $(src)/vdso.lds $(vobjs) FORCE
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$(call if_changed,vdso)
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HOST_EXTRACFLAGS += -I$(srctree)/tools/include -I$(srctree)/include/uapi -I$(srctree)/arch/$(SUBARCH)/include/uapi
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hostprogs-y += vdso2c
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quiet_cmd_vdso2c = VDSO2C $@
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define cmd_vdso2c
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$(obj)/vdso2c $< $(<:%.dbg=%) $@
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endef
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$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
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$(call if_changed,vdso2c)
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#
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# Don't omit frame pointers for ease of userspace debugging, but do
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# optimize sibling calls.
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#
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CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
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$(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
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-fno-omit-frame-pointer -foptimize-sibling-calls \
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-DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
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$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
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#
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# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
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#
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CFLAGS_REMOVE_vdso-note.o = -pg
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CFLAGS_REMOVE_vclock_gettime.o = -pg
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CFLAGS_REMOVE_vgetcpu.o = -pg
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CFLAGS_REMOVE_vvar.o = -pg
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#
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# X32 processes use x32 vDSO to access 64bit kernel data.
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#
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# Build x32 vDSO image:
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# 1. Compile x32 vDSO as 64bit.
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# 2. Convert object files to x32.
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# 3. Build x32 VDSO image with x32 objects, which contains 64bit codes
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# so that it can reach 64bit address space with 64bit pointers.
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#
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CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \
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-Wl,-soname=linux-vdso.so.1 \
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-Wl,-z,max-page-size=4096 \
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-Wl,-z,common-page-size=4096
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# 64-bit objects to re-brand as x32
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vobjs64-for-x32 := $(filter-out $(vobjs-nox32),$(vobjs-y))
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# x32-rebranded versions
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vobjx32s-y := $(vobjs64-for-x32:.o=-x32.o)
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# same thing, but in the output directory
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vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)
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# Convert 64bit object file to x32 for x32 vDSO.
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quiet_cmd_x32 = X32 $@
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cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
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$(obj)/%-x32.o: $(obj)/%.o FORCE
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$(call if_changed,x32)
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targets += vdsox32.lds $(vobjx32s-y)
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$(obj)/%.so: OBJCOPYFLAGS := -S
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$(obj)/%.so: $(obj)/%.so.dbg
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$(call if_changed,objcopy)
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$(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE
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$(call if_changed,vdso)
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CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-m,elf_i386 -Wl,-soname=linux-gate.so.1
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targets += vdso32/vdso32.lds
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targets += vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o
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targets += vdso32/vclock_gettime.o
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KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS)) -DBUILD_VDSO
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$(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
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$(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
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KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
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KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
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KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
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KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
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KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
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KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
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$(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
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$(obj)/vdso32.so.dbg: FORCE \
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$(obj)/vdso32/vdso32.lds \
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$(obj)/vdso32/vclock_gettime.o \
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$(obj)/vdso32/note.o \
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$(obj)/vdso32/system_call.o \
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$(obj)/vdso32/sigreturn.o
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$(call if_changed,vdso)
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#
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# The DSO images are built using a special linker script.
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#
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quiet_cmd_vdso = VDSO $@
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cmd_vdso = $(CC) -nostdlib -o $@ \
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$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
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-Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
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sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
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VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=both) \
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$(call cc-ldoption, -Wl$(comma)--build-id) -Wl,-Bsymbolic $(LTO_CFLAGS)
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GCOV_PROFILE := n
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#
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# Install the unstripped copies of vdso*.so. If our toolchain supports
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# build-id, install .build-id links as well.
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#
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quiet_cmd_vdso_install = INSTALL $(@:install_%=%)
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define cmd_vdso_install
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cp $< "$(MODLIB)/vdso/$(@:install_%=%)"; \
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if readelf -n $< |grep -q 'Build ID'; then \
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buildid=`readelf -n $< |grep 'Build ID' |sed -e 's/^.*Build ID: \(.*\)$$/\1/'`; \
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first=`echo $$buildid | cut -b-2`; \
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last=`echo $$buildid | cut -b3-`; \
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mkdir -p "$(MODLIB)/vdso/.build-id/$$first"; \
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ln -sf "../../$(@:install_%=%)" "$(MODLIB)/vdso/.build-id/$$first/$$last.debug"; \
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fi
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endef
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vdso_img_insttargets := $(vdso_img_sodbg:%.dbg=install_%)
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$(MODLIB)/vdso: FORCE
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@mkdir -p $(MODLIB)/vdso
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$(vdso_img_insttargets): install_%: $(obj)/%.dbg $(MODLIB)/vdso
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$(call cmd,vdso_install)
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PHONY += vdso_install $(vdso_img_insttargets)
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vdso_install: $(vdso_img_insttargets)
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clean-files := vdso32.so vdso32.so.dbg vdso64* vdso-image-*.c vdsox32.so*
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