drivers/firmware/efi/libstub/Makefile

   1 #
   2 # The stub may be linked into the kernel proper or into a separate boot binary,
   3 # but in either case, it executes before the kernel does (with MMU disabled) so
   4 # things like ftrace and stack-protector are likely to cause trouble if left
   5 # enabled, even if doing so doesn't break the build.
   6 #
   7 cflags-$(CONFIG_X86_32)         := -march=i386
   8 cflags-$(CONFIG_X86_64)         := -mcmodel=small
   9 cflags-$(CONFIG_X86)            += -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 \
  10                                    -fPIC -fno-strict-aliasing -mno-red-zone \
  11                                    -mno-mmx -mno-sse -DDISABLE_BRANCH_PROFILING
  12
  13 cflags-$(CONFIG_ARM64)          := $(subst -pg,,$(KBUILD_CFLAGS))
  14 cflags-$(CONFIG_ARM)            := $(subst -pg,,$(KBUILD_CFLAGS)) \
  15                                    -fno-builtin -fpic -mno-single-pic-base
  16
  17 cflags-$(CONFIG_EFI_ARMSTUB)    += -I$(srctree)/scripts/dtc/libfdt
  18
  19 KBUILD_CFLAGS                   := $(cflags-y) \
  20                                    $(call cc-option,-ffreestanding) \
  21                                    $(call cc-option,-fno-stack-protector)
  22
  23 GCOV_PROFILE                    := n
  24 KASAN_SANITIZE                  := n
  25
  26 lib-y                           := efi-stub-helper.o
  27
  28 # include the stub's generic dependencies from lib/ when building for ARM/arm64
  29 arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
  30
  31 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
  32         $(call if_changed_rule,cc_o_c)
  33
  34 lib-$(CONFIG_EFI_ARMSTUB)       += arm-stub.o fdt.o string.o \
  35                                    $(patsubst %.c,lib-%.o,$(arm-deps))
  36
  37 lib-$(CONFIG_ARM64)             += arm64-stub.o
  38 CFLAGS_arm64-stub.o             := -DTEXT_OFFSET=$(TEXT_OFFSET)
  39
  40 #
  41 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
  42 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
  43 # So let's apply the __init annotations at the section level, by prefixing
  44 # the section names directly. This will ensure that even all the inline string
  45 # literals are covered.
  46 # The fact that the stub and the kernel proper are essentially the same binary
  47 # also means that we need to be extra careful to make sure that the stub does
  48 # not rely on any absolute symbol references, considering that the virtual
  49 # kernel mapping that the linker uses is not active yet when the stub is
  50 # executing. So build all C dependencies of the EFI stub into libstub, and do
  51 # a verification pass to see if any absolute relocations exist in any of the
  52 # object files.
  53 #
  54 extra-$(CONFIG_EFI_ARMSTUB)     := $(lib-y)
  55 lib-$(CONFIG_EFI_ARMSTUB)       := $(patsubst %.o,%.stub.o,$(lib-y))
  56
  57 STUBCOPY_FLAGS-y                := -R .debug* -R *ksymtab* -R *kcrctab*
  58 STUBCOPY_FLAGS-$(CONFIG_ARM64)  += --prefix-alloc-sections=.init \
  59                                    --prefix-symbols=__efistub_
  60 STUBCOPY_RELOC-$(CONFIG_ARM64)  := R_AARCH64_ABS
  61
  62 $(obj)/%.stub.o: $(obj)/%.o FORCE
  63         $(call if_changed,stubcopy)
  64
  65 quiet_cmd_stubcopy = STUBCPY $@
  66       cmd_stubcopy = if $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; then      \
  67                      $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y)        \
  68                      && (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \
  69                          rm -f $@; /bin/false); else /bin/false; fi