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Nathan ChancellorandIngo Molnar
4a9ec5ec95
After a recent upstream LLVM change to start generating jump and lookup
tables in switch statements in more instances [1], linking the
compressed x86 boot image when CONFIG_KERNEL_ZSTD is enabled fails with:
ld.lld: error: Unexpected run-time relocations (.rela) detected!
Dumping the relocations in misc.o, which is the only file influenced by
CONFIG_KERNEL_ZSTD in the decompressor, shows dynamic relocations to
some string constants, which correspond to the string literals in the
switch statement in handle_zstd_error():
Relocation section '.rela.data.rel.ro' at offset 0x277b0 contains 31 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 73a
0000000000000008 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
0000000000000010 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
0000000000000018 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e
...
This optimization is problematic for the decompressor environment, as it
is built as -fPIE without any explicit absolute references (as described
at the top of misc.c) while not applying any dynamic relocations, hence
the linker assertion. To opt out of this optimization, which is of
little value in this special early boot code, and to mirror the other
x86 startup code in arch/x86/boot/startup, disable jump tables in the
decompressor.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/commit/fa02a6ed66b1700c996b49c96c6bc0eb014c9518 [1]
Link: https://patch.msgid.link/20260722-x86-boot-compressed-disable-jt-clang-v2-1-7373d38482fb@kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/2165
164 lines
5.9 KiB
Makefile
164 lines
5.9 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# linux/arch/x86/boot/compressed/Makefile
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#
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# create a compressed vmlinux image from the original vmlinux
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#
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# vmlinuz is:
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# decompression code (*.o)
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# asm globals (piggy.S), including:
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# vmlinux.bin.(gz|bz2|lzma|...)
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#
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# vmlinux.bin is:
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# vmlinux stripped of debugging and comments
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# vmlinux.bin.all is:
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# vmlinux.bin + vmlinux.relocs
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# vmlinux.bin.(gz|bz2|lzma|...) is:
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# (see scripts/Makefile.lib size_append)
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# compressed vmlinux.bin.all + u32 size of vmlinux.bin.all
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targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
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vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst
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# CLANG_FLAGS must come before any cc-disable-warning or cc-option calls in
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# case of cross compiling, as it has the '--target=' flag, which is needed to
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# avoid errors with '-march=i386', and future flags may depend on the target to
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# be valid.
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KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
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KBUILD_CFLAGS += $(CC_FLAGS_DIALECT)
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KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
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KBUILD_CFLAGS += -fno-jump-tables
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KBUILD_CFLAGS += -Wundef
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KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
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cflags-$(CONFIG_X86_32) := -march=i386
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cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone
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KBUILD_CFLAGS += $(cflags-y)
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KBUILD_CFLAGS += -mno-mmx -mno-sse
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KBUILD_CFLAGS += -ffreestanding -fshort-wchar
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KBUILD_CFLAGS += -fno-stack-protector
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KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
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KBUILD_CFLAGS += -Wno-pointer-sign
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KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
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KBUILD_CFLAGS += -D__DISABLE_EXPORTS
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# Disable relocation relaxation in case the link is not PIE.
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KBUILD_CFLAGS += $(call cc-option,-Wa$(comma)-mrelax-relocations=no)
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KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
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# sev-decode-insn.c indirectly includes inat-table.c which is generated during
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# compilation and stored in $(objtree). Add the directory to the includes so
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# that the compiler finds it even with out-of-tree builds (make O=/some/path).
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CFLAGS_sev-handle-vc.o += -I$(objtree)/arch/x86/lib/
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KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
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KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
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KBUILD_LDFLAGS += $(call ld-option,--no-ld-generated-unwind-info)
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# Compressed kernel should be built as PIE since it may be loaded at any
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# address by the bootloader.
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LDFLAGS_vmlinux := -pie $(call ld-option, --no-dynamic-linker)
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ifdef CONFIG_LD_ORPHAN_WARN
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LDFLAGS_vmlinux += --orphan-handling=$(CONFIG_LD_ORPHAN_WARN_LEVEL)
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endif
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LDFLAGS_vmlinux += -z noexecstack
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ifeq ($(CONFIG_LD_IS_BFD),y)
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LDFLAGS_vmlinux += $(call ld-option,--no-warn-rwx-segments)
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endif
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ifeq ($(CONFIG_EFI_STUB),y)
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# ensure that the static EFI stub library will be pulled in, even if it is
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# never referenced explicitly from the startup code
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LDFLAGS_vmlinux += -u efi_pe_entry
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endif
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LDFLAGS_vmlinux += -T
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hostprogs := mkpiggy
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HOST_EXTRACFLAGS += -I$(srctree)/tools/include
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sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABbCDGRSTtVW] \(_text\|__start_rodata\|_sinittext\|__inittext_end\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
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quiet_cmd_voffset = VOFFSET $@
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cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
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targets += ../voffset.h
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$(obj)/../voffset.h: vmlinux FORCE
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$(call if_changed,voffset)
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$(obj)/misc.o: $(obj)/../voffset.h
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vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/kernel_info.o $(obj)/head_$(BITS).o \
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$(obj)/misc.o $(obj)/string.o $(obj)/cmdline.o $(obj)/error.o \
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$(obj)/piggy.o $(obj)/cpuflags.o
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vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
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vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
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ifdef CONFIG_X86_64
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vmlinux-objs-y += $(obj)/ident_map_64.o
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vmlinux-objs-y += $(obj)/idt_64.o $(obj)/idt_handlers_64.o
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vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/mem_encrypt.o
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vmlinux-objs-y += $(obj)/pgtable_64.o
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vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/sev.o $(obj)/sev-handle-vc.o
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endif
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vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
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vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o $(obj)/tdx-shared.o
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vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/mem.o
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vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
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vmlinux-libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
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vmlinux-libs-$(CONFIG_X86_64) += $(objtree)/arch/x86/boot/startup/lib.a
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vmlinux-objs-$(CONFIG_EFI_SBAT) += $(obj)/sbat.o
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ifdef CONFIG_EFI_SBAT
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$(obj)/sbat.o: $(CONFIG_EFI_SBAT_FILE)
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AFLAGS_sbat.o += -I $(srctree)
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endif
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$(obj)/vmlinux: $(vmlinux-objs-y) $(vmlinux-libs-y) FORCE
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$(call if_changed,ld)
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OBJCOPYFLAGS_vmlinux.bin := -R .comment -S
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$(obj)/vmlinux.bin: vmlinux FORCE
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$(call if_changed,objcopy)
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targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relocs
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CMD_RELOCS = arch/x86/tools/relocs
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quiet_cmd_relocs = RELOCS $@
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cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $<
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$(obj)/vmlinux.relocs: vmlinux.unstripped FORCE
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$(call if_changed,relocs)
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vmlinux.bin.all-y := $(obj)/vmlinux.bin
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vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
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$(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,gzip)
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$(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,bzip2_with_size)
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$(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,lzma_with_size)
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$(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,xzkern_with_size)
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$(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,lzo_with_size)
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$(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,lz4_with_size)
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$(obj)/vmlinux.bin.zst: $(vmlinux.bin.all-y) FORCE
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$(call if_changed,zstd22_with_size)
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suffix-$(CONFIG_KERNEL_GZIP) := gz
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suffix-$(CONFIG_KERNEL_BZIP2) := bz2
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suffix-$(CONFIG_KERNEL_LZMA) := lzma
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suffix-$(CONFIG_KERNEL_XZ) := xz
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suffix-$(CONFIG_KERNEL_LZO) := lzo
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suffix-$(CONFIG_KERNEL_LZ4) := lz4
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suffix-$(CONFIG_KERNEL_ZSTD) := zst
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quiet_cmd_mkpiggy = MKPIGGY $@
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cmd_mkpiggy = $(obj)/mkpiggy $< > $@
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targets += piggy.S
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$(obj)/piggy.S: $(obj)/vmlinux.bin.$(suffix-y) $(obj)/mkpiggy FORCE
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$(call if_changed,mkpiggy)
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