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b1992c3772
linux/arch/x86/entry/vdso/Makefile
Masahiro Yamada b1992c3772 kbuild: use $(src) instead of $(srctree)/$(src) for source directory 
Kbuild conventionally uses $(obj)/ for generated files, and $(src)/ for
checked-in source files. It is merely a convention without any functional
difference. In fact, $(obj) and $(src) are exactly the same, as defined
in scripts/Makefile.build:

    src := $(obj)

When the kernel is built in a separate output directory, $(src) does
not accurately reflect the source directory location. While Kbuild
resolves this discrepancy by specifying VPATH=$(srctree) to search for
source files, it does not cover all cases. For example, when adding a
header search path for local headers, -I$(srctree)/$(src) is typically
passed to the compiler.

This introduces inconsistency between upstream and downstream Makefiles
because $(src) is used instead of $(srctree)/$(src) for the latter.

To address this inconsistency, this commit changes the semantics of
$(src) so that it always points to the directory in the source tree.

Going forward, the variables used in Makefiles will have the following
meanings:

  $(obj)     - directory in the object tree
  $(src)     - directory in the source tree  (changed by this commit)
  $(objtree) - the top of the kernel object tree
  $(srctree) - the top of the kernel source tree

Consequently, $(srctree)/$(src) in upstream Makefiles need to be replaced
with $(src).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-05-10 04:34:52 +09:00

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Makefile
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# SPDX-License-Identifier: GPL-2.0
#
# Building vDSO images for x86.
#
# Include the generic Makefile to check the built vDSO:
include $(srctree)/lib/vdso/Makefile
# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
KMSAN_SANITIZE_vclock_gettime.o := n
KMSAN_SANITIZE_vdso32/vclock_gettime.o := n
KMSAN_SANITIZE_vgetcpu.o := n
KMSAN_SANITIZE_vdso32/vgetcpu.o := n
UBSAN_SANITIZE := n
KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
KCOV_INSTRUMENT := n
# Files to link into the vDSO:
vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
vobjs32-y := vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o
vobjs32-y += vdso32/vclock_gettime.o vdso32/vgetcpu.o
vobjs-$(CONFIG_X86_SGX) += vsgx.o
# Files to link into the kernel:
obj-y += vma.o extable.o
KASAN_SANITIZE_vma.o := y
UBSAN_SANITIZE_vma.o := y
KCSAN_SANITIZE_vma.o := y
OBJECT_FILES_NON_STANDARD_vma.o := n
OBJECT_FILES_NON_STANDARD_extable.o := n
# vDSO images to build:
obj-$(CONFIG_X86_64) += vdso-image-64.o
obj-$(CONFIG_X86_X32_ABI) += vdso-image-x32.o
obj-$(CONFIG_COMPAT_32) += vdso-image-32.o vdso32-setup.o
OBJECT_FILES_NON_STANDARD_vdso-image-32.o := n
OBJECT_FILES_NON_STANDARD_vdso-image-x32.o := n
OBJECT_FILES_NON_STANDARD_vdso-image-64.o := n
OBJECT_FILES_NON_STANDARD_vdso32-setup.o := n
vobjs := $(addprefix $(obj)/, $(vobjs-y))
vobjs32 := $(addprefix $(obj)/, $(vobjs32-y))
$(obj)/vdso.o: $(obj)/vdso.so
targets += vdso.lds $(vobjs-y)
targets += vdso32/vdso32.lds $(vobjs32-y)
targets += $(foreach x, 64 x32 32, vdso-image-$(x).c vdso$(x).so vdso$(x).so.dbg)
CPPFLAGS_vdso.lds += -P -C
VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -soname linux-vdso.so.1 --no-undefined \
-z max-page-size=4096
$(obj)/vdso64.so.dbg: $(obj)/vdso.lds $(vobjs) FORCE
$(call if_changed,vdso_and_check)
HOST_EXTRACFLAGS += -I$(srctree)/tools/include -I$(srctree)/include/uapi -I$(srctree)/arch/$(SUBARCH)/include/uapi
hostprogs += vdso2c
quiet_cmd_vdso2c = VDSO2C $@
cmd_vdso2c = $(obj)/vdso2c $< $(<:%.dbg=%) $@
$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
$(call if_changed,vdso2c)
#
# Don't omit frame pointers for ease of userspace debugging, but do
# optimize sibling calls.
#
CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
$(filter -g%,$(KBUILD_CFLAGS)) -fno-stack-protector \
-fno-omit-frame-pointer -foptimize-sibling-calls \
-DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
ifdef CONFIG_MITIGATION_RETPOLINE
ifneq ($(RETPOLINE_VDSO_CFLAGS),)
CFL += $(RETPOLINE_VDSO_CFLAGS)
endif
endif
$(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
$(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO
#
# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
#
CFLAGS_REMOVE_vclock_gettime.o = -pg
CFLAGS_REMOVE_vdso32/vclock_gettime.o = -pg
CFLAGS_REMOVE_vgetcpu.o = -pg
CFLAGS_REMOVE_vdso32/vgetcpu.o = -pg
CFLAGS_REMOVE_vsgx.o = -pg
#
# X32 processes use x32 vDSO to access 64bit kernel data.
#
# Build x32 vDSO image:
# 1. Compile x32 vDSO as 64bit.
# 2. Convert object files to x32.
# 3. Build x32 VDSO image with x32 objects, which contains 64bit codes
# so that it can reach 64bit address space with 64bit pointers.
#
CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds)
VDSO_LDFLAGS_vdsox32.lds = -m elf32_x86_64 -soname linux-vdso.so.1 \
-z max-page-size=4096
# x32-rebranded versions
vobjx32s-y := $(vobjs-y:.o=-x32.o)
# same thing, but in the output directory
vobjx32s := $(addprefix $(obj)/, $(vobjx32s-y))
# Convert 64bit object file to x32 for x32 vDSO.
quiet_cmd_x32 = X32 $@
cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
$(obj)/%-x32.o: $(obj)/%.o FORCE
$(call if_changed,x32)
targets += vdsox32.lds $(vobjx32s-y)
$(obj)/%.so: OBJCOPYFLAGS := -S --remove-section __ex_table
$(obj)/%.so: $(obj)/%.so.dbg FORCE
$(call if_changed,objcopy)
$(obj)/vdsox32.so.dbg: $(obj)/vdsox32.lds $(vobjx32s) FORCE
$(call if_changed,vdso_and_check)
CPPFLAGS_vdso32/vdso32.lds = $(CPPFLAGS_vdso.lds)
VDSO_LDFLAGS_vdso32.lds = -m elf_i386 -soname linux-gate.so.1
KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS)) -DBUILD_VDSO
$(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
$(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_CFI),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(PADDING_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
KBUILD_CFLAGS_32 += -fno-stack-protector
KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
ifdef CONFIG_MITIGATION_RETPOLINE
ifneq ($(RETPOLINE_VDSO_CFLAGS),)
KBUILD_CFLAGS_32 += $(RETPOLINE_VDSO_CFLAGS)
endif
endif
$(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
$(obj)/vdso32.so.dbg: $(obj)/vdso32/vdso32.lds $(vobjs32) FORCE
$(call if_changed,vdso_and_check)
#
# The DSO images are built using a special linker script.
#
quiet_cmd_vdso = VDSO $@
cmd_vdso = $(LD) -o $@ \
$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
-T $(filter %.lds,$^) $(filter %.o,$^) && \
sh $(src)/checkundef.sh '$(NM)' '$@'
VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 \
$(call ld-option, --eh-frame-hdr) -Bsymbolic -z noexecstack
GCOV_PROFILE := n
quiet_cmd_vdso_and_check = VDSO $@
cmd_vdso_and_check = $(cmd_vdso); $(cmd_vdso_check)
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