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linux-next/arch/x86/boot/Makefile
George Rimar 927185c124 x86/build: Specify elf_i386 linker emulation explicitly for i386 objects 
The kernel uses the OUTPUT_FORMAT linker script command in it's linker
scripts. Most of the time, the -m option is passed to the linker with
correct architecture, but sometimes (at least for x86_64) the -m option
contradicts the OUTPUT_FORMAT directive.

Specifically, arch/x86/boot and arch/x86/realmode/rm produce i386 object
files, but are linked with the -m elf_x86_64 linker flag when building
for x86_64.

The GNU linker manpage doesn't explicitly state any tie-breakers between
-m and OUTPUT_FORMAT. But with BFD and Gold linkers, OUTPUT_FORMAT
overrides the emulation value specified with the -m option.

LLVM lld has a different behavior, however. When supplied with
contradicting -m and OUTPUT_FORMAT values it fails with the following
error message:

  ld.lld: error: arch/x86/realmode/rm/header.o is incompatible with elf_x86_64

Therefore, just add the correct -m after the incorrect one (it overrides
it), so the linker invocation looks like this:

  ld -m elf_x86_64 -z max-page-size=0x200000 -m elf_i386 --emit-relocs -T \
    realmode.lds header.o trampoline_64.o stack.o reboot.o -o realmode.elf

This is not a functional change for GNU ld, because (although not
explicitly documented) OUTPUT_FORMAT overrides -m EMULATION.

Tested by building x86_64 kernel with GNU gcc/ld toolchain and booting
it in QEMU.

 [ bp: massage and clarify text. ]

Suggested-by: Dmitry Golovin <dima@golovin.in>
Signed-off-by: George Rimar <grimar@accesssoftek.com>
Signed-off-by: Tri Vo <trong@android.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Tri Vo <trong@android.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Matz <matz@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morbo@google.com
Cc: ndesaulniers@google.com
Cc: ruiu@google.com
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190111201012.71210-1-trong@android.com
2019-01-12 00:11:39 +01:00

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5.2 KiB
Makefile
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#
# arch/x86/boot/Makefile
#
# This file is subject to the terms and conditions of the GNU General Public
# License. See the file "COPYING" in the main directory of this archive
# for more details.
#
# Copyright (C) 1994 by Linus Torvalds
# Changed by many, many contributors over the years.
#
KASAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y
# Kernel does not boot with kcov instrumentation here.
# One of the problems observed was insertion of __sanitizer_cov_trace_pc()
# callback into middle of per-cpu data enabling code. Thus the callback observed
# inconsistent state and crashed. We are interested mostly in syscall coverage,
# so boot code is not interesting anyway.
KCOV_INSTRUMENT := n
# If you want to preset the SVGA mode, uncomment the next line and
# set SVGA_MODE to whatever number you want.
# Set it to -DSVGA_MODE=NORMAL_VGA if you just want the EGA/VGA mode.
# The number is the same as you would ordinarily press at bootup.
SVGA_MODE := -DSVGA_MODE=NORMAL_VGA
targets := vmlinux.bin setup.bin setup.elf bzImage
targets += fdimage fdimage144 fdimage288 image.iso mtools.conf
subdir- := compressed
setup-y += a20.o bioscall.o cmdline.o copy.o cpu.o cpuflags.o cpucheck.o
setup-y += early_serial_console.o edd.o header.o main.o memory.o
setup-y += pm.o pmjump.o printf.o regs.o string.o tty.o video.o
setup-y += video-mode.o version.o
setup-$(CONFIG_X86_APM_BOOT) += apm.o
# The link order of the video-*.o modules can matter. In particular,
# video-vga.o *must* be listed first, followed by video-vesa.o.
# Hardware-specific drivers should follow in the order they should be
# probed, and video-bios.o should typically be last.
setup-y += video-vga.o
setup-y += video-vesa.o
setup-y += video-bios.o
targets += $(setup-y)
hostprogs-y := tools/build
hostprogs-$(CONFIG_X86_FEATURE_NAMES) += mkcpustr
HOST_EXTRACFLAGS += -I$(srctree)/tools/include \
-include include/generated/autoconf.h \
-D__EXPORTED_HEADERS__
ifdef CONFIG_X86_FEATURE_NAMES
$(obj)/cpu.o: $(obj)/cpustr.h
quiet_cmd_cpustr = CPUSTR $@
cmd_cpustr = $(obj)/mkcpustr > $@
targets += cpustr.h
$(obj)/cpustr.h: $(obj)/mkcpustr FORCE
$(call if_changed,cpustr)
endif
clean-files += cpustr.h
# ---------------------------------------------------------------------------
KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
GCOV_PROFILE := n
UBSAN_SANITIZE := n
$(obj)/bzImage: asflags-y := $(SVGA_MODE)
quiet_cmd_image = BUILD $@
silent_redirect_image = >/dev/null
cmd_image = $(obj)/tools/build $(obj)/setup.bin $(obj)/vmlinux.bin \
$(obj)/zoffset.h $@ $($(quiet)redirect_image)
$(obj)/bzImage: $(obj)/setup.bin $(obj)/vmlinux.bin $(obj)/tools/build FORCE
$(call if_changed,image)
@$(kecho) 'Kernel: $@ is ready' ' (#'`cat .version`')'
OBJCOPYFLAGS_vmlinux.bin := -O binary -R .note -R .comment -S
$(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
$(call if_changed,objcopy)
SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|_ehead\|_text\|z_.*\)$$/\#define ZO_\2 0x\1/p'
quiet_cmd_zoffset = ZOFFSET $@
cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@
targets += zoffset.h
$(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
$(call if_changed,zoffset)
AFLAGS_header.o += -I$(objtree)/$(obj)
$(obj)/header.o: $(obj)/zoffset.h
LDFLAGS_setup.elf := -m elf_i386 -T
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
$(call if_changed,ld)
OBJCOPYFLAGS_setup.bin := -O binary
$(obj)/setup.bin: $(obj)/setup.elf FORCE
$(call if_changed,objcopy)
$(obj)/compressed/vmlinux: FORCE
$(Q)$(MAKE) $(build)=$(obj)/compressed $@
# Set this if you want to pass append arguments to the
# bzdisk/fdimage/isoimage kernel
FDARGS =
# Set this if you want an initrd included with the
# bzdisk/fdimage/isoimage kernel
FDINITRD =
image_cmdline = default linux $(FDARGS) $(if $(FDINITRD),initrd=initrd.img,)
$(obj)/mtools.conf: $(src)/mtools.conf.in
sed -e 's|@OBJ@|$(obj)|g' < $< > $@
quiet_cmd_genimage = GENIMAGE $3
cmd_genimage = sh $(srctree)/$(src)/genimage.sh $2 $3 $(obj)/bzImage \
$(obj)/mtools.conf '$(image_cmdline)' $(FDINITRD)
# This requires write access to /dev/fd0
bzdisk: $(obj)/bzImage $(obj)/mtools.conf
$(call cmd,genimage,bzdisk,/dev/fd0)
# These require being root or having syslinux 2.02 or higher installed
fdimage fdimage144: $(obj)/bzImage $(obj)/mtools.conf
$(call cmd,genimage,fdimage144,$(obj)/fdimage)
@$(kecho) 'Kernel: $(obj)/fdimage is ready'
fdimage288: $(obj)/bzImage $(obj)/mtools.conf
$(call cmd,genimage,fdimage288,$(obj)/fdimage)
@$(kecho) 'Kernel: $(obj)/fdimage is ready'
isoimage: $(obj)/bzImage
$(call cmd,genimage,isoimage,$(obj)/image.iso)
@$(kecho) 'Kernel: $(obj)/image.iso is ready'
bzlilo: $(obj)/bzImage
if [ -f $(INSTALL_PATH)/vmlinuz ]; then mv $(INSTALL_PATH)/vmlinuz $(INSTALL_PATH)/vmlinuz.old; fi
if [ -f $(INSTALL_PATH)/System.map ]; then mv $(INSTALL_PATH)/System.map $(INSTALL_PATH)/System.old; fi
cat $(obj)/bzImage > $(INSTALL_PATH)/vmlinuz
cp System.map $(INSTALL_PATH)/
if [ -x /sbin/lilo ]; then /sbin/lilo; else /etc/lilo/install; fi
install:
sh $(srctree)/$(src)/install.sh $(KERNELRELEASE) $(obj)/bzImage \
System.map "$(INSTALL_PATH)"
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