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linux/arch/arm64/kernel/vdso32/Makefile
Fangrui Song aff69273af vdso: Improve cmd_vdso_check to check all dynamic relocations 
The actual intention is that no dynamic relocation exists in the VDSO. For
this the VDSO build validates that the resulting .so file does not have any
relocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture,
which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Aside
of that ARCH_REL_TYPE_ABS is a misnomer as it checks for relative
relocations too.

However, some GNU ld ports produce unneeded R_*_NONE relocation entries. If
a port fails to determine the exact .rel[a].dyn size, the trailing zeros
become R_*_NONE relocations. E.g. ld's powerpc port recently fixed
https://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE are
generally a no-op in the dynamic loaders. So just ignore them.

Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting
.so file does not contain any R_* relocation entries except R_*_NONE.

Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for aarch64
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for vDSO, aarch64
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lore.kernel.org/r/20230310190750.3323802-1-maskray@google.com
2023-03-21 21:15:34 +01:00

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Makefile
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# SPDX-License-Identifier: GPL-2.0
#
# Makefile for vdso32
#
include $(srctree)/lib/vdso/Makefile
# Same as cc-*option, but using CC_COMPAT instead of CC
ifeq ($(CONFIG_CC_IS_CLANG), y)
CC_COMPAT ?= $(CC)
CC_COMPAT += --target=arm-linux-gnueabi
else
CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
endif
ifeq ($(CONFIG_LD_IS_LLD), y)
LD_COMPAT ?= $(LD)
else
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)))
# 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 := -DBUILD_VDSO -D__KERNEL__ -nostdinc
VDSO_CPPFLAGS += -isystem $(shell $(CC_COMPAT) -print-file-name=include 2>/dev/null)
VDSO_CPPFLAGS += $(LINUXINCLUDE)
# Common C and assembly flags
# From top-level Makefile
VDSO_CAFLAGS := $(VDSO_CPPFLAGS)
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
VDSO_CAFLAGS += -march=armv8-a
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 \
-Wdeclaration-after-statement \
-std=gnu11
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 := $(VDSO_CAFLAGS)
VDSO_AFLAGS += -D__ASSEMBLY__
# From arm vDSO Makefile
VDSO_LDFLAGS += -Bsymbolic --no-undefined -soname=linux-vdso.so.1
VDSO_LDFLAGS += -z max-page-size=4096 -z common-page-size=4096
VDSO_LDFLAGS += -shared --hash-style=sysv --build-id=sha1
VDSO_LDFLAGS += --orphan-handling=$(CONFIG_LD_ORPHAN_WARN_LEVEL)
# 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) $(asm-obj-vdso)
targets += vdso.lds
CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
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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