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MIPS: VDSO: Move disabling the VDSO logic to Kconfig

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After commit 9553d16fa6 ("init/kconfig: Add LD_VERSION Kconfig"), we
have access to GNU ld's version at configuration time. As a result, we
can make it clearer under what configuration circumstances the MIPS VDSO
needs to be disabled.

This is a prerequisite for getting rid of the MIPS VDSO binutils
warning and linking the VDSO when LD is ld.lld. Wrapping the call to
ld-ifversion with CONFIG_LD_IS_LLD does not work because the config
values are wiped away during 'make clean'.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
This commit is contained in:
Nathan Chancellor 2020-04-28 15:14:16 -07:00 committed by Thomas Bogendoerfer
parent b744b43f79
commit e91946d6d9
4 changed files with 23 additions and 29 deletions
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2
arch/mips/Kconfig
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@ -3214,3 +3214,5 @@ endmenu
source "drivers/firmware/Kconfig"
source "arch/mips/kvm/Kconfig"
source "arch/mips/vdso/Kconfig"

18
arch/mips/vdso/Kconfig Normal file
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@ -0,0 +1,18 @@
# For the pre-R6 code in arch/mips/vdso/vdso.h for locating
# the base address of VDSO, the linker will emit a R_MIPS_PC32
# relocation in binutils > 2.25 but it will fail with older versions
# because that relocation is not supported for that symbol. As a result
# of which we are forced to disable the VDSO symbols when building
# with < 2.25 binutils on pre-R6 kernels. For more references on why we
# can't use other methods to get the base address of VDSO please refer to
# the comments on that file.
#
# GCC (at least up to version 9.2) appears to emit function calls that make use
# of the GOT when targeting microMIPS, which we can't use in the VDSO due to
# the lack of relocations. As such, we disable the VDSO for microMIPS builds.
config MIPS_LD_CAN_LINK_VDSO
def_bool LD_VERSION >= 225000000
config MIPS_DISABLE_VDSO
def_bool CPU_MICROMIPS || (!CPU_MIPSR6 && !MIPS_LD_CAN_LINK_VDSO)

30
arch/mips/vdso/Makefile
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@ -52,37 +52,11 @@ endif
CFLAGS_REMOVE_vgettimeofday.o = -pg
DISABLE_VDSO := n
#
# For the pre-R6 code in arch/mips/vdso/vdso.h for locating
# the base address of VDSO, the linker will emit a R_MIPS_PC32
# relocation in binutils > 2.25 but it will fail with older versions
# because that relocation is not supported for that symbol. As a result
# of which we are forced to disable the VDSO symbols when building
# with < 2.25 binutils on pre-R6 kernels. For more references on why we
# can't use other methods to get the base address of VDSO please refer to
# the comments on that file.
#
ifndef CONFIG_CPU_MIPSR6
ifeq ($(call ld-ifversion, -lt, 225000000, y),y)
ifdef CONFIG_MIPS_DISABLE_VDSO
ifndef CONFIG_MIPS_LD_CAN_LINK_VDSO
$(warning MIPS VDSO requires binutils >= 2.25)
DISABLE_VDSO := y
endif
endif
#
# GCC (at least up to version 9.2) appears to emit function calls that make use
# of the GOT when targeting microMIPS, which we can't use in the VDSO due to
# the lack of relocations. As such, we disable the VDSO for microMIPS builds.
#
ifdef CONFIG_CPU_MICROMIPS
DISABLE_VDSO := y
endif
ifeq ($(DISABLE_VDSO),y)
obj-vdso-y := $(filter-out vgettimeofday.o, $(obj-vdso-y))
ccflags-vdso += -DDISABLE_MIPS_VDSO
endif
# VDSO linker flags.

2
arch/mips/vdso/vdso.lds.S
View File

@ -91,7 +91,7 @@ PHDRS
VERSION
{
LINUX_2.6 {
#ifndef DISABLE_MIPS_VDSO
#ifndef CONFIG_MIPS_DISABLE_VDSO
global:
__vdso_clock_gettime;
__vdso_gettimeofday;