kernel_optimize_test/arch/mips/vdso/Kconfig
Nathan Chancellor e91946d6d9 MIPS: VDSO: Move disabling the VDSO logic to Kconfig
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>
2020-05-12 10:01:45 +02:00

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# 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)