drivers/firmware/efi/libstub/Makefile

   1 # SPDX-License-Identifier: GPL-2.0
   2 #
   3 # The stub may be linked into the kernel proper or into a separate boot binary,
   4 # but in either case, it executes before the kernel does (with MMU disabled) so
   5 # things like ftrace and stack-protector are likely to cause trouble if left
   6 # enabled, even if doing so doesn't break the build.
   7 #
   8 cflags-$(CONFIG_X86_32)         := -march=i386
   9 cflags-$(CONFIG_X86_64)         := -mcmodel=small
  10 cflags-$(CONFIG_X86)            += -m$(BITS) -D__KERNEL__ \
  11                                    -fPIC -fno-strict-aliasing -mno-red-zone \
  12                                    -mno-mmx -mno-sse -fshort-wchar \
  13                                    -Wno-pointer-sign \
  14                                    $(call cc-disable-warning, address-of-packed-member) \
  15                                    $(call cc-disable-warning, gnu) \
  16                                    -fno-asynchronous-unwind-tables
  17
  18 # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
  19 # disable the stackleak plugin
  20 cflags-$(CONFIG_ARM64)          := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
  21                                    -fpie $(DISABLE_STACKLEAK_PLUGIN)
  22 cflags-$(CONFIG_ARM)            := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
  23                                    -fno-builtin -fpic \
  24                                    $(call cc-option,-mno-single-pic-base)
  25
  26 cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
  27
  28 KBUILD_CFLAGS                   := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \
  29                                    -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \
  30                                    -D__NO_FORTIFY \
  31                                    -ffreestanding \
  32                                    -fno-stack-protector \
  33                                    $(call cc-option,-fno-addrsig) \
  34                                    -D__DISABLE_EXPORTS
  35
  36 # remove SCS flags from all objects in this directory
  37 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
  38
  39 GCOV_PROFILE                    := n
  40 # Sanitizer runtimes are unavailable and cannot be linked here.
  41 KASAN_SANITIZE                  := n
  42 KCSAN_SANITIZE                  := n
  43 UBSAN_SANITIZE                  := n
  44 OBJECT_FILES_NON_STANDARD       := y
  45
  46 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
  47 KCOV_INSTRUMENT                 := n
  48
  49 lib-y                           := efi-stub-helper.o gop.o secureboot.o tpm.o \
  50                                    file.o mem.o random.o randomalloc.o pci.o \
  51                                    skip_spaces.o lib-cmdline.o lib-ctype.o \
  52                                    alignedmem.o relocate.o vsprintf.o
  53
  54 # include the stub's generic dependencies from lib/ when building for ARM/arm64
  55 efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
  56
  57 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
  58         $(call if_changed_rule,cc_o_c)
  59
  60 lib-$(CONFIG_EFI_GENERIC_STUB)  += efi-stub.o fdt.o string.o \
  61                                    $(patsubst %.c,lib-%.o,$(efi-deps-y))
  62
  63 lib-$(CONFIG_ARM)               += arm32-stub.o
  64 lib-$(CONFIG_ARM64)             += arm64-stub.o
  65 lib-$(CONFIG_X86)               += x86-stub.o
  66 CFLAGS_arm32-stub.o             := -DTEXT_OFFSET=$(TEXT_OFFSET)
  67 CFLAGS_arm64-stub.o             := -DTEXT_OFFSET=$(TEXT_OFFSET)
  68
  69 #
  70 # For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
  71 # .bss section, so the .bss section of the EFI stub needs to be included in the
  72 # .data section of the compressed kernel to ensure initialization. Rename the
  73 # .bss section here so it's easy to pick out in the linker script.
  74 #
  75 STUBCOPY_FLAGS-$(CONFIG_X86)    += --rename-section .bss=.bss.efistub,load,alloc
  76 STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
  77 STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
  78
  79 #
  80 # ARM discards the .data section because it disallows r/w data in the
  81 # decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
  82 # which are preserved explicitly by the decompressor linker script.
  83 #
  84 STUBCOPY_FLAGS-$(CONFIG_ARM)    += --rename-section .data=.data.efistub \
  85                                    --rename-section .bss=.bss.efistub,load,alloc
  86 STUBCOPY_RELOC-$(CONFIG_ARM)    := R_ARM_ABS
  87
  88 #
  89 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
  90 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
  91 # So let's apply the __init annotations at the section level, by prefixing
  92 # the section names directly. This will ensure that even all the inline string
  93 # literals are covered.
  94 # The fact that the stub and the kernel proper are essentially the same binary
  95 # also means that we need to be extra careful to make sure that the stub does
  96 # not rely on any absolute symbol references, considering that the virtual
  97 # kernel mapping that the linker uses is not active yet when the stub is
  98 # executing. So build all C dependencies of the EFI stub into libstub, and do
  99 # a verification pass to see if any absolute relocations exist in any of the
 100 # object files.
 101 #
 102 extra-y                         := $(lib-y)
 103 lib-y                           := $(patsubst %.o,%.stub.o,$(lib-y))
 104
 105 STUBCOPY_FLAGS-$(CONFIG_ARM64)  += --prefix-alloc-sections=.init \
 106                                    --prefix-symbols=__efistub_
 107 STUBCOPY_RELOC-$(CONFIG_ARM64)  := R_AARCH64_ABS
 108
 109 $(obj)/%.stub.o: $(obj)/%.o FORCE
 110         $(call if_changed,stubcopy)
 111
 112 #
 113 # Strip debug sections and some other sections that may legally contain
 114 # absolute relocations, so that we can inspect the remaining sections for
 115 # such relocations. If none are found, regenerate the output object, but
 116 # this time, use objcopy and leave all sections in place.
 117 #
 118 quiet_cmd_stubcopy = STUBCPY $@
 119       cmd_stubcopy =                                                    \
 120         $(STRIP) --strip-debug -o $@ $<;                                \
 121         if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then            \
 122                 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
 123                 /bin/false;                                             \
 124         fi;                                                             \
 125         $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@