e8c07082a8
During a patch discussion, Linus brought up the option of changing the C standard version from gnu89 to gnu99, which allows using variable declaration inside of a for() loop. While the C99, C11 and later standards introduce many other features, most of these are already available in gnu89 as GNU extensions as well. An earlier attempt to do this when gcc-5 started defaulting to -std=gnu11 failed because at the time that caused warnings about designated initializers with older compilers. Now that gcc-5.1 is the minimum compiler version used for building kernels, that is no longer a concern. Similarly, the behavior of 'inline' functions changes between gnu89 using gnu_inline behavior and gnu11 using standard c99+ behavior, but this was taken care of by defining 'inline' to include __attribute__((gnu_inline)) in order to allow building with clang a while ago. Nathan Chancellor reported a new -Wdeclaration-after-statement warning that appears in a system header on arm, this still needs a workaround. The differences between gnu99, gnu11, gnu1x and gnu17 are fairly minimal and mainly impact warnings at the -Wpedantic level that the kernel never enables. Between these, gnu11 is the newest version that is supported by all supported compiler versions, though it is only the default on gcc-5, while all other supported versions of gcc or clang default to gnu1x/gnu17. Link: https://lore.kernel.org/lkml/CAHk-=wiyCH7xeHcmiFJ-YgXUy2Jaj7pnkdKpcovt8fYbVFW3TA@mail.gmail.com/ Link: https://github.com/ClangBuiltLinux/linux/issues/1603 Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Marco Elver <elver@google.com> Acked-by: Jani Nikula <jani.nikula@intel.com> Acked-by: David Sterba <dsterba@suse.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Reviewed-by: Alex Shi <alexs@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
192 lines
6.6 KiB
Makefile
192 lines
6.6 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# Makefile for vdso32
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#
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# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
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# the inclusion of generic Makefile.
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ARCH_REL_TYPE_ABS := R_ARM_JUMP_SLOT|R_ARM_GLOB_DAT|R_ARM_ABS32
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include $(srctree)/lib/vdso/Makefile
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# Same as cc-*option, but using CC_COMPAT instead of CC
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ifeq ($(CONFIG_CC_IS_CLANG), y)
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CC_COMPAT ?= $(CC)
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CC_COMPAT += --target=arm-linux-gnueabi
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else
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CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
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endif
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ifeq ($(CONFIG_LD_IS_LLD), y)
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LD_COMPAT ?= $(LD)
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else
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LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld
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endif
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cc32-option = $(call try-run,\
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$(CC_COMPAT) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
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cc32-disable-warning = $(call try-run,\
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$(CC_COMPAT) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
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# We cannot use the global flags to compile the vDSO files, the main reason
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# being that the 32-bit compiler may be older than the main (64-bit) compiler
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# and therefore may not understand flags set using $(cc-option ...). Besides,
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# arch-specific options should be taken from the arm Makefile instead of the
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# arm64 one.
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# As a result we set our own flags here.
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# KBUILD_CPPFLAGS and NOSTDINC_FLAGS from top-level Makefile
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VDSO_CPPFLAGS := -DBUILD_VDSO -D__KERNEL__ -nostdinc
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VDSO_CPPFLAGS += -isystem $(shell $(CC_COMPAT) -print-file-name=include 2>/dev/null)
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VDSO_CPPFLAGS += $(LINUXINCLUDE)
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# Common C and assembly flags
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# From top-level Makefile
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VDSO_CAFLAGS := $(VDSO_CPPFLAGS)
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VDSO_CAFLAGS += $(call cc32-option,-fno-PIE)
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ifdef CONFIG_DEBUG_INFO
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VDSO_CAFLAGS += -g
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endif
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# From arm Makefile
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VDSO_CAFLAGS += $(call cc32-option,-fno-dwarf2-cfi-asm)
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VDSO_CAFLAGS += -mabi=aapcs-linux -mfloat-abi=soft
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ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
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VDSO_CAFLAGS += -mbig-endian
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else
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VDSO_CAFLAGS += -mlittle-endian
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endif
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# From arm vDSO Makefile
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VDSO_CAFLAGS += -fPIC -fno-builtin -fno-stack-protector
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VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING
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VDSO_CAFLAGS += -march=armv8-a
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VDSO_CFLAGS := $(VDSO_CAFLAGS)
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VDSO_CFLAGS += -DENABLE_COMPAT_VDSO=1
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# KBUILD_CFLAGS from top-level Makefile
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VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
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-fno-strict-aliasing -fno-common \
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-Werror-implicit-function-declaration \
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-Wno-format-security \
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-Wdeclaration-after-statement \
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-std=gnu11
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VDSO_CFLAGS += -O2
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# Some useful compiler-dependent flags from top-level Makefile
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VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)
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VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
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VDSO_CFLAGS += -fno-strict-overflow
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VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
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VDSO_CFLAGS += -Werror=date-time
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VDSO_CFLAGS += $(call cc32-option,-Werror=incompatible-pointer-types)
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# The 32-bit compiler does not provide 128-bit integers, which are used in
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# some headers that are indirectly included from the vDSO code.
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# This hack makes the compiler happy and should trigger a warning/error if
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# variables of such type are referenced.
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VDSO_CFLAGS += -D__uint128_t='void*'
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# Silence some warnings coming from headers that operate on long's
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# (on GCC 4.8 or older, there is unfortunately no way to silence this warning)
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VDSO_CFLAGS += $(call cc32-disable-warning,shift-count-overflow)
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VDSO_CFLAGS += -Wno-int-to-pointer-cast
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# Compile as THUMB2 or ARM. Unwinding via frame-pointers in THUMB2 is
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# unreliable.
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ifeq ($(CONFIG_THUMB2_COMPAT_VDSO), y)
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VDSO_CFLAGS += -mthumb -fomit-frame-pointer
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else
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VDSO_CFLAGS += -marm
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endif
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VDSO_AFLAGS := $(VDSO_CAFLAGS)
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VDSO_AFLAGS += -D__ASSEMBLY__
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# From arm vDSO Makefile
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VDSO_LDFLAGS += -Bsymbolic --no-undefined -soname=linux-vdso.so.1
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VDSO_LDFLAGS += -z max-page-size=4096 -z common-page-size=4096
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VDSO_LDFLAGS += -shared --hash-style=sysv --build-id=sha1
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# Borrow vdsomunge.c from the arm vDSO
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# We have to use a relative path because scripts/Makefile.host prefixes
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# $(hostprogs) with $(obj)
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munge := ../../../arm/vdso/vdsomunge
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hostprogs := $(munge)
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c-obj-vdso := note.o
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c-obj-vdso-gettimeofday := vgettimeofday.o
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ifneq ($(c-gettimeofday-y),)
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VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y)
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endif
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VDSO_CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
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# Build rules
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targets := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso) vdso.so vdso.so.dbg vdso.so.raw
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c-obj-vdso := $(addprefix $(obj)/, $(c-obj-vdso))
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c-obj-vdso-gettimeofday := $(addprefix $(obj)/, $(c-obj-vdso-gettimeofday))
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asm-obj-vdso := $(addprefix $(obj)/, $(asm-obj-vdso))
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obj-vdso := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso)
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targets += vdso.lds
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CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
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# Force dependency (vdso.s includes vdso.so through incbin)
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$(obj)/vdso.o: $(obj)/vdso.so
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include/generated/vdso32-offsets.h: $(obj)/vdso.so.dbg FORCE
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$(call if_changed,vdsosym)
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# Strip rule for vdso.so
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$(obj)/vdso.so: OBJCOPYFLAGS := -S
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$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
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$(call if_changed,objcopy)
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$(obj)/vdso.so.dbg: $(obj)/vdso.so.raw $(obj)/$(munge) FORCE
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$(call if_changed,vdsomunge)
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# Link rule for the .so file, .lds has to be first
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$(obj)/vdso.so.raw: $(src)/vdso.lds $(obj-vdso) FORCE
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$(call if_changed,vdsold_and_vdso_check)
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# Compilation rules for the vDSO sources
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$(c-obj-vdso): %.o: %.c FORCE
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$(call if_changed_dep,vdsocc)
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$(c-obj-vdso-gettimeofday): %.o: %.c FORCE
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$(call if_changed_dep,vdsocc_gettimeofday)
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$(asm-obj-vdso): %.o: %.S FORCE
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$(call if_changed_dep,vdsoas)
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# Actual build commands
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quiet_cmd_vdsold_and_vdso_check = LD32 $@
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cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check)
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quiet_cmd_vdsold = LD32 $@
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cmd_vdsold = $(LD_COMPAT) $(VDSO_LDFLAGS) \
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-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
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quiet_cmd_vdsocc = CC32 $@
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cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $<
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quiet_cmd_vdsocc_gettimeofday = CC32 $@
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cmd_vdsocc_gettimeofday = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) $(VDSO_CFLAGS_gettimeofday_o) -c -o $@ $<
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quiet_cmd_vdsoas = AS32 $@
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cmd_vdsoas = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_AFLAGS) -c -o $@ $<
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quiet_cmd_vdsomunge = MUNGE $@
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cmd_vdsomunge = $(obj)/$(munge) $< $@
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# Generate vDSO offsets using helper script (borrowed from the 64-bit vDSO)
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gen-vdsosym := $(srctree)/$(src)/../vdso/gen_vdso_offsets.sh
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quiet_cmd_vdsosym = VDSOSYM $@
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# The AArch64 nm should be able to read an AArch32 binary
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cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
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# Install commands for the unstripped file
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quiet_cmd_vdso_install = INSTALL32 $@
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cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/vdso32.so
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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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