linux-yocto/arch/x86/boot/compressed/Makefile

SPDX-License-Identifier: GPL-2.0

linux/arch/x86/boot/compressed/Makefile

create a compressed vmlinux image from the original vmlinux

vmlinuz is:

decompression code (*.o)

asm globals (piggy.S), including:

vmlinux.bin.(gz|bz2|lzma|...)

vmlinux.bin is:

vmlinux stripped of debugging and comments

vmlinux.bin.all is:

vmlinux.bin + vmlinux.relocs

vmlinux.bin.(gz|bz2|lzma|...) is:

(see scripts/Makefile.lib size_append)

compressed vmlinux.bin.all + u32 size of vmlinux.bin.all

KASAN_SANITIZE := n OBJECT_FILES_NON_STANDARD := y

Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.

KCOV_INSTRUMENT := n

targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma
vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4

KBUILD_CFLAGS := -m$(BITS) -O2 KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC) KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING cflags-$(CONFIG_X86_32) := -march=i386 cflags-$(CONFIG_X86_64) := -mcmodel=small KBUILD_CFLAGS += $(cflags-y) KBUILD_CFLAGS += -mno-mmx -mno-sse KBUILD_CFLAGS += $(call cc-option,-ffreestanding) KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += -Wno-pointer-sign KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)

KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ GCOV_PROFILE := n UBSAN_SANITIZE :=n

KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)

Compressed kernel should be built as PIE since it may be loaded at any

address by the bootloader.

ifeq ($(CONFIG_X86_32),y) KBUILD_LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker) else

To build 64-bit compressed kernel as PIE, we disable relocation

overflow check to avoid relocation overflow error with a new linker

command-line option, -z noreloc-overflow.

KBUILD_LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "-z noreloc-overflow"
&& echo "-z noreloc-overflow -pie --no-dynamic-linker") endif LDFLAGS_vmlinux := -T

hostprogs-y := mkpiggy HOST_EXTRACFLAGS += -I$(srctree)/tools/include

sed-voffset := -e 's/^[0-9a-fA-F]* [ABCDGRSTVW] (_text|__bss_start|end)$$/#define VO\2 _AC(0x\1,UL)/p'

quiet_cmd_voffset = VOFFSET $@ cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@

targets += ../voffset.h

$(obj)/../voffset.h: vmlinux FORCE $(call if_changed,voffset)

$(obj)/misc.o: $(obj)/../voffset.h

vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o
$(obj)/string.o $(obj)/cmdline.o $(obj)/error.o
$(obj)/piggy.o $(obj)/cpuflags.o

vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o ifdef CONFIG_X86_64 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr_64.o vmlinux-objs-y += $(obj)/mem_encrypt.o vmlinux-objs-y += $(obj)/pgtable_64.o endif

$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone

vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o $(obj)/efi_stub_$(BITS).o
$(objtree)/drivers/firmware/efi/libstub/lib.a vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o

The compressed kernel is built with -fPIC/-fPIE so that a boot loader

can place it anywhere in memory and it will still run. However, since

it is executed as-is without any ELF relocation processing performed

(and has already had all relocation sections stripped from the binary),

none of the code can use data relocations (e.g. static assignments of

pointer values), since they will be meaningless at runtime. This check

will refuse to link the vmlinux if any of these relocations are found.

quiet_cmd_check_data_rel = DATAREL $@ define cmd_check_data_rel for obj in $(filter %.o,$^); do
${CROSS_COMPILE}readelf -S $$obj | grep -qF .rel.local && {
echo "error: $$obj has data relocations!" >&2;
exit 1;
} || true;
done endef

We need to run two commands under "if_changed", so merge them into a

single invocation.

quiet_cmd_check-and-link-vmlinux = LD $@ cmd_check-and-link-vmlinux = $(cmd_check_data_rel); $(cmd_ld)

$(obj)/vmlinux: $(vmlinux-objs-y) FORCE $(call if_changed,check-and-link-vmlinux)

OBJCOPYFLAGS_vmlinux.bin := -R .comment -S $(obj)/vmlinux.bin: vmlinux FORCE $(call if_changed,objcopy)

targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relocs

CMD_RELOCS = arch/x86/tools/relocs quiet_cmd_relocs = RELOCS $@ cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $< $(obj)/vmlinux.relocs: vmlinux FORCE $(call if_changed,relocs)

vmlinux.bin.all-y := $(obj)/vmlinux.bin vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs

$(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE $(call if_changed,gzip) $(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE $(call if_changed,bzip2) $(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y) FORCE $(call if_changed,lzma) $(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE $(call if_changed,xzkern) $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE $(call if_changed,lzo) $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE $(call if_changed,lz4)

suffix-$(CONFIG_KERNEL_GZIP) := gz suffix-$(CONFIG_KERNEL_BZIP2) := bz2 suffix-$(CONFIG_KERNEL_LZMA) := lzma suffix-$(CONFIG_KERNEL_XZ) := xz suffix-$(CONFIG_KERNEL_LZO) := lzo suffix-$(CONFIG_KERNEL_LZ4) := lz4

quiet_cmd_mkpiggy = MKPIGGY $@ cmd_mkpiggy = $(obj)/mkpiggy $< > $@

targets += piggy.S $(obj)/piggy.S: $(obj)/vmlinux.bin.$(suffix-y) $(obj)/mkpiggy FORCE $(call if_changed,mkpiggy)