linux-yocto/arch/x86/entry/vdso/Makefile

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

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

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

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

quiet_cmd_vdso_and_check = VDSO $@ cmd_vdso_and_check = $(cmd_vdso); $(cmd_vdso_check)