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linux/arch/arm64/kernel/vdso32/Makefile
Nathan Chancellor 0fa97e9403 arm64: vdso32: Allow ld.lld to properly link the VDSO 
As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd
using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO
Makefile, as the comment notes, done in commit d2b30cd4b722 ("ARM:
8384/1: VDSO: force use of BFD linker").

Commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to
link VDSO") changed that Makefile to use $(LD) directly instead of
through $(CC), which matches how the rest of the kernel operates. Since
then, LD=ld.lld means that the arm vDSO will be linked with ld.lld,
which has shown no problems so far.

Allow ld.lld to link this vDSO as we do the regular arm vDSO. To do
this, we need to do a few things:

* Add a LD_COMPAT variable, which defaults to $(CROSS_COMPILE_COMPAT)ld
  with gcc and $(LD) if LLVM is 1, which will be ld.lld, or
  $(CROSS_COMPILE_COMPAT)ld if not, which matches the logic of the main
  Makefile. It is overrideable for further customization and avoiding
  breakage.

* Eliminate cc32-ldoption, which matches commit 055efab3120b ("kbuild:
  drop support for cc-ldoption").

With those, we can use $(LD_COMPAT) in cmd_ldvdso and change the flags
from compiler linker flags to linker flags directly. We eliminate
-mfloat-abi=soft because it is not handled by the linker.

Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1033
Link: https://lore.kernel.org/r/20201020011406.1818918-1-natechancellor@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
2020-10-26 13:17:41 +00:00

220 lines
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Makefile
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# SPDX-License-Identifier: GPL-2.0
#
# Makefile for vdso32
#
# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
# the inclusion of generic Makefile.
ARCH_REL_TYPE_ABS := R_ARM_JUMP_SLOT|R_ARM_GLOB_DAT|R_ARM_ABS32
include $(srctree)/lib/vdso/Makefile
# Same as cc-*option, but using CC_COMPAT instead of CC
ifeq ($(CONFIG_CC_IS_CLANG), y)
COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
ifneq ($(COMPAT_GCC_TOOLCHAIN),)
CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
endif
CC_COMPAT ?= $(CC)
CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS)
ifneq ($(LLVM),)
LD_COMPAT ?= $(LD)
else
LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld
endif
else
CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld
endif
cc32-option = $(call try-run,\
$(CC_COMPAT) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
cc32-disable-warning = $(call try-run,\
$(CC_COMPAT) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
cc32-as-instr = $(call try-run,\
printf "%b\n" "$(1)" | $(CC_COMPAT) $(VDSO_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
# We cannot use the global flags to compile the vDSO files, the main reason
# being that the 32-bit compiler may be older than the main (64-bit) compiler
# and therefore may not understand flags set using $(cc-option ...). Besides,
# arch-specific options should be taken from the arm Makefile instead of the
# arm64 one.
# As a result we set our own flags here.
# KBUILD_CPPFLAGS and NOSTDINC_FLAGS from top-level Makefile
VDSO_CPPFLAGS := -D__KERNEL__ -nostdinc -isystem $(shell $(CC_COMPAT) -print-file-name=include)
VDSO_CPPFLAGS += $(LINUXINCLUDE)
# Common C and assembly flags
# From top-level Makefile
VDSO_CAFLAGS := $(VDSO_CPPFLAGS)
ifneq ($(shell $(CC_COMPAT) --version 2>&1 | head -n 1 | grep clang),)
VDSO_CAFLAGS += --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
endif
VDSO_CAFLAGS += $(call cc32-option,-fno-PIE)
ifdef CONFIG_DEBUG_INFO
VDSO_CAFLAGS += -g
endif
# From arm Makefile
VDSO_CAFLAGS += $(call cc32-option,-fno-dwarf2-cfi-asm)
VDSO_CAFLAGS += -mabi=aapcs-linux -mfloat-abi=soft
ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
VDSO_CAFLAGS += -mbig-endian
else
VDSO_CAFLAGS += -mlittle-endian
endif
# From arm vDSO Makefile
VDSO_CAFLAGS += -fPIC -fno-builtin -fno-stack-protector
VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING
# Try to compile for ARMv8. If the compiler is too old and doesn't support it,
# fall back to v7. There is no easy way to check for what architecture the code
# is being compiled, so define a macro specifying that (see arch/arm/Makefile).
VDSO_CAFLAGS += $(call cc32-option,-march=armv8-a -D__LINUX_ARM_ARCH__=8,\
-march=armv7-a -D__LINUX_ARM_ARCH__=7)
VDSO_CFLAGS := $(VDSO_CAFLAGS)
VDSO_CFLAGS += -DENABLE_COMPAT_VDSO=1
# KBUILD_CFLAGS from top-level Makefile
VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
-std=gnu89
VDSO_CFLAGS += -O2
# Some useful compiler-dependent flags from top-level Makefile
VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)
VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
VDSO_CFLAGS += -fno-strict-overflow
VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
VDSO_CFLAGS += -Werror=date-time
VDSO_CFLAGS += $(call cc32-option,-Werror=incompatible-pointer-types)
# The 32-bit compiler does not provide 128-bit integers, which are used in
# some headers that are indirectly included from the vDSO code.
# This hack makes the compiler happy and should trigger a warning/error if
# variables of such type are referenced.
VDSO_CFLAGS += -D__uint128_t='void*'
# Silence some warnings coming from headers that operate on long's
# (on GCC 4.8 or older, there is unfortunately no way to silence this warning)
VDSO_CFLAGS += $(call cc32-disable-warning,shift-count-overflow)
VDSO_CFLAGS += -Wno-int-to-pointer-cast
# Compile as THUMB2 or ARM. Unwinding via frame-pointers in THUMB2 is
# unreliable.
ifeq ($(CONFIG_THUMB2_COMPAT_VDSO), y)
VDSO_CFLAGS += -mthumb -fomit-frame-pointer
else
VDSO_CFLAGS += -marm
endif
VDSO_AFLAGS := $(VDSO_CAFLAGS)
VDSO_AFLAGS += -D__ASSEMBLY__
# Check for binutils support for dmb ishld
dmbinstr := $(call cc32-as-instr,dmb ishld,-DCONFIG_AS_DMB_ISHLD=1)
VDSO_CFLAGS += $(dmbinstr)
VDSO_AFLAGS += $(dmbinstr)
# From arm vDSO Makefile
VDSO_LDFLAGS += -Bsymbolic --no-undefined -soname=linux-vdso.so.1
VDSO_LDFLAGS += -z max-page-size=4096 -z common-page-size=4096
VDSO_LDFLAGS += -nostdlib -shared --hash-style=sysv --build-id=sha1
# Borrow vdsomunge.c from the arm vDSO
# We have to use a relative path because scripts/Makefile.host prefixes
# $(hostprogs) with $(obj)
munge := ../../../arm/vdso/vdsomunge
hostprogs := $(munge)
c-obj-vdso := note.o
c-obj-vdso-gettimeofday := vgettimeofday.o
ifneq ($(c-gettimeofday-y),)
VDSO_CFLAGS_gettimeofday_o += -include $(c-gettimeofday-y)
endif
VDSO_CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
# Build rules
targets := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso) vdso.so vdso.so.dbg vdso.so.raw
c-obj-vdso := $(addprefix $(obj)/, $(c-obj-vdso))
c-obj-vdso-gettimeofday := $(addprefix $(obj)/, $(c-obj-vdso-gettimeofday))
asm-obj-vdso := $(addprefix $(obj)/, $(asm-obj-vdso))
obj-vdso := $(c-obj-vdso) $(c-obj-vdso-gettimeofday) $(asm-obj-vdso)
obj-y += vdso.o
targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
# Force dependency (vdso.s includes vdso.so through incbin)
$(obj)/vdso.o: $(obj)/vdso.so
include/generated/vdso32-offsets.h: $(obj)/vdso.so.dbg FORCE
$(call if_changed,vdsosym)
# Strip rule for vdso.so
$(obj)/vdso.so: OBJCOPYFLAGS := -S
$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
$(call if_changed,objcopy)
$(obj)/vdso.so.dbg: $(obj)/vdso.so.raw $(obj)/$(munge) FORCE
$(call if_changed,vdsomunge)
# Link rule for the .so file, .lds has to be first
$(obj)/vdso.so.raw: $(src)/vdso.lds $(obj-vdso) FORCE
$(call if_changed,vdsold_and_vdso_check)
# Compilation rules for the vDSO sources
$(c-obj-vdso): %.o: %.c FORCE
$(call if_changed_dep,vdsocc)
$(c-obj-vdso-gettimeofday): %.o: %.c FORCE
$(call if_changed_dep,vdsocc_gettimeofday)
$(asm-obj-vdso): %.o: %.S FORCE
$(call if_changed_dep,vdsoas)
# Actual build commands
quiet_cmd_vdsold_and_vdso_check = LD32 $@
cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check)
quiet_cmd_vdsold = LD32 $@
cmd_vdsold = $(LD_COMPAT) $(VDSO_LDFLAGS) \
-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
quiet_cmd_vdsocc = CC32 $@
cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $<
quiet_cmd_vdsocc_gettimeofday = CC32 $@
cmd_vdsocc_gettimeofday = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) $(VDSO_CFLAGS_gettimeofday_o) -c -o $@ $<
quiet_cmd_vdsoas = AS32 $@
cmd_vdsoas = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_AFLAGS) -c -o $@ $<
quiet_cmd_vdsomunge = MUNGE $@
cmd_vdsomunge = $(obj)/$(munge) $< $@
# Generate vDSO offsets using helper script (borrowed from the 64-bit vDSO)
gen-vdsosym := $(srctree)/$(src)/../vdso/gen_vdso_offsets.sh
quiet_cmd_vdsosym = VDSOSYM $@
# The AArch64 nm should be able to read an AArch32 binary
cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
# Install commands for the unstripped file
quiet_cmd_vdso_install = INSTALL32 $@
cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/vdso32.so
vdso.so: $(obj)/vdso.so.dbg
@mkdir -p $(MODLIB)/vdso
$(call cmd,vdso_install)
vdso_install: vdso.so
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