9c55461040
Currently, the EFI stub invokes the EFI memory attributes protocol to strip any NX restrictions from the entire loaded kernel, resulting in all code and data being mapped read-write-execute. The point of the EFI memory attributes protocol is to remove the need for all memory allocations to be mapped with both write and execute permissions by default, and make it the OS loader's responsibility to transition data mappings to code mappings where appropriate. Even though the UEFI specification does not appear to leave room for denying memory attribute changes based on security policy, let's be cautious and avoid relying on the ability to create read-write-execute mappings. This is trivially achievable, given that the amount of kernel code executing via the firmware's 1:1 mapping is rather small and limited to the .head.text region. So let's drop the NX restrictions only on that subregion, but not before remapping it as read-only first. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
166 lines
5.9 KiB
Makefile
166 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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# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
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KASAN_SANITIZE := n
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KCSAN_SANITIZE := n
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KMSAN_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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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 $(CLANG_FLAGS)
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KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
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KBUILD_CFLAGS += -Wundef
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KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
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cflags-$(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 += $(call cc-disable-warning, gnu)
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KBUILD_CFLAGS += -Wno-pointer-sign
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KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
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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.c indirectly includes inat-table.h which is generated during
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# compilation and stored in $(objtree). Add the directory to the includes so
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# that the compiler finds it even with out-of-tree builds (make O=/some/path).
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CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
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KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
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GCOV_PROFILE := n
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UBSAN_SANITIZE :=n
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KBUILD_LDFLAGS := -m elf_$(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/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__start_rodata\|__bss_start\|_end\)$$/\#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) += $(obj)/sev.o
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endif
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vmlinux-objs-$(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) += $(obj)/efi.o
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vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
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vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
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$(obj)/vmlinux: $(vmlinux-objs-y) FORCE
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$(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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# vmlinux.relocs is created by the vmlinux postlink step.
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$(obj)/vmlinux.relocs: vmlinux
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@true
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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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