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Users of GNU ld (BFD) from binutils 2.39+ will observe multiple instances of a new warning when linking kernels in the form: ld: warning: arch/x86/boot/pmjump.o: missing .note.GNU-stack section implies executable stack ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker ld: warning: arch/x86/boot/compressed/vmlinux has a LOAD segment with RWX permissions Generally, we would like to avoid the stack being executable. Because there could be a need for the stack to be executable, assembler sources have to opt-in to this security feature via explicit creation of the .note.GNU-stack feature (which compilers create by default) or command line flag --noexecstack. Or we can simply tell the linker the production of such sections is irrelevant and to link the stack as --noexecstack. LLVM's LLD linker defaults to -z noexecstack, so this flag isn't strictly necessary when linking with LLD, only BFD, but it doesn't hurt to be explicit here for all linkers IMO. --no-warn-rwx-segments is currently BFD specific and only available in the current latest release, so it's wrapped in an ld-option check. While the kernel makes extensive usage of ELF sections, it doesn't use permissions from ELF segments. Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/ Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 Link: https://github.com/llvm/llvm-project/issues/57009 Reported-and-tested-by: Jens Axboe <axboe@kernel.dk> Suggested-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
159 lines
5.2 KiB
Makefile
159 lines
5.2 KiB
Makefile
#
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# arch/x86/boot/Makefile
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#
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# This file is subject to the terms and conditions of the GNU General Public
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# License. See the file "COPYING" in the main directory of this archive
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# for more details.
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#
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# Copyright (C) 1994 by Linus Torvalds
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# Changed by many, many contributors over the years.
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#
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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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OBJECT_FILES_NON_STANDARD := y
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# Kernel does not boot with kcov instrumentation here.
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# One of the problems observed was insertion of __sanitizer_cov_trace_pc()
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# callback into middle of per-cpu data enabling code. Thus the callback observed
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# inconsistent state and crashed. We are interested mostly in syscall coverage,
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# so boot code is not interesting anyway.
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KCOV_INSTRUMENT := n
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# If you want to preset the SVGA mode, uncomment the next line and
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# set SVGA_MODE to whatever number you want.
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# Set it to -DSVGA_MODE=NORMAL_VGA if you just want the EGA/VGA mode.
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# The number is the same as you would ordinarily press at bootup.
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SVGA_MODE := -DSVGA_MODE=NORMAL_VGA
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targets := vmlinux.bin setup.bin setup.elf bzImage
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targets += fdimage fdimage144 fdimage288 image.iso hdimage
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subdir- := compressed
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setup-y += a20.o bioscall.o cmdline.o copy.o cpu.o cpuflags.o cpucheck.o
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setup-y += early_serial_console.o edd.o header.o main.o memory.o
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setup-y += pm.o pmjump.o printf.o regs.o string.o tty.o video.o
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setup-y += video-mode.o version.o
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setup-$(CONFIG_X86_APM_BOOT) += apm.o
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# The link order of the video-*.o modules can matter. In particular,
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# video-vga.o *must* be listed first, followed by video-vesa.o.
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# Hardware-specific drivers should follow in the order they should be
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# probed, and video-bios.o should typically be last.
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setup-y += video-vga.o
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setup-y += video-vesa.o
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setup-y += video-bios.o
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targets += $(setup-y)
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hostprogs := tools/build
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hostprogs += mkcpustr
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HOST_EXTRACFLAGS += -I$(srctree)/tools/include \
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-include include/generated/autoconf.h \
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-D__EXPORTED_HEADERS__
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ifdef CONFIG_X86_FEATURE_NAMES
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$(obj)/cpu.o: $(obj)/cpustr.h
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quiet_cmd_cpustr = CPUSTR $@
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cmd_cpustr = $(obj)/mkcpustr > $@
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$(obj)/cpustr.h: $(obj)/mkcpustr FORCE
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$(call if_changed,cpustr)
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endif
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targets += cpustr.h
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# ---------------------------------------------------------------------------
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KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP
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KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
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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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GCOV_PROFILE := n
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UBSAN_SANITIZE := n
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$(obj)/bzImage: asflags-y := $(SVGA_MODE)
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quiet_cmd_image = BUILD $@
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silent_redirect_image = >/dev/null
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cmd_image = $(obj)/tools/build $(obj)/setup.bin $(obj)/vmlinux.bin \
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$(obj)/zoffset.h $@ $($(quiet)redirect_image)
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$(obj)/bzImage: $(obj)/setup.bin $(obj)/vmlinux.bin $(obj)/tools/build FORCE
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$(call if_changed,image)
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@$(kecho) 'Kernel: $@ is ready' ' (#'`cat .version`')'
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OBJCOPYFLAGS_vmlinux.bin := -O binary -R .note -R .comment -S
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$(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
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$(call if_changed,objcopy)
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SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
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sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|efi32_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|z_.*\)$$/\#define ZO_\2 0x\1/p'
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quiet_cmd_zoffset = ZOFFSET $@
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cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@
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targets += zoffset.h
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$(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
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$(call if_changed,zoffset)
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AFLAGS_header.o += -I$(objtree)/$(obj)
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$(obj)/header.o: $(obj)/zoffset.h
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LDFLAGS_setup.elf := -m elf_i386 -z noexecstack -T
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$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
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$(call if_changed,ld)
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OBJCOPYFLAGS_setup.bin := -O binary
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$(obj)/setup.bin: $(obj)/setup.elf FORCE
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$(call if_changed,objcopy)
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$(obj)/compressed/vmlinux: FORCE
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$(Q)$(MAKE) $(build)=$(obj)/compressed $@
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# Set this if you want to pass append arguments to the
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# bzdisk/fdimage/hdimage/isoimage kernel
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FDARGS =
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# Set this if you want one or more initrds included in the image
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FDINITRD =
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imgdeps = $(obj)/bzImage $(obj)/mtools.conf $(src)/genimage.sh
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$(obj)/mtools.conf: $(src)/mtools.conf.in
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sed -e 's|@OBJ@|$(obj)|g' < $< > $@
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targets += mtools.conf
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# genimage.sh requires bash, but it also has a bunch of other
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# external dependencies.
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quiet_cmd_genimage = GENIMAGE $3
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cmd_genimage = $(BASH) $(srctree)/$(src)/genimage.sh $2 $3 $(obj)/bzImage \
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$(obj)/mtools.conf '$(FDARGS)' $(FDINITRD)
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PHONY += bzdisk fdimage fdimage144 fdimage288 hdimage isoimage
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# This requires write access to /dev/fd0
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# All images require syslinux to be installed; hdimage also requires
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# EDK2/OVMF if the kernel is compiled with the EFI stub.
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bzdisk: $(imgdeps)
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$(call cmd,genimage,bzdisk,/dev/fd0)
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fdimage fdimage144: $(imgdeps)
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$(call cmd,genimage,fdimage144,$(obj)/fdimage)
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@$(kecho) 'Kernel: $(obj)/fdimage is ready'
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fdimage288: $(imgdeps)
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$(call cmd,genimage,fdimage288,$(obj)/fdimage)
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@$(kecho) 'Kernel: $(obj)/fdimage is ready'
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hdimage: $(imgdeps)
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$(call cmd,genimage,hdimage,$(obj)/hdimage)
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@$(kecho) 'Kernel: $(obj)/hdimage is ready'
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isoimage: $(imgdeps)
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$(call cmd,genimage,isoimage,$(obj)/image.iso)
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@$(kecho) 'Kernel: $(obj)/image.iso is ready'
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