Unverified Commit ca09f772 authored by Mingzheng Xing's avatar Mingzheng Xing Committed by Palmer Dabbelt
Browse files

riscv: Handle zicsr/zifencei issue between gcc and binutils 

Binutils-2.38 and GCC-12.1.0 bumped[0][1] the default ISA spec to the newer
20191213 version which moves some instructions from the I extension to the
Zicsr and Zifencei extensions. So if one of the binutils and GCC exceeds
that version, we should explicitly specifying Zicsr and Zifencei via -march
to cope with the new changes. but this only occurs when binutils >= 2.36
and GCC >= 11.1.0. It's a different story when binutils < 2.36.

binutils-2.36 supports the Zifencei extension[2] and splits Zifencei and
Zicsr from I[3]. GCC-11.1.0 is particular[4] because it add support Zicsr
and Zifencei extension for -march. binutils-2.35 does not support the
Zifencei extension, and does not need to specify Zicsr and Zifencei when
working with GCC >= 12.1.0.

To make our lives easier, let's relax the check to binutils >= 2.36 in
CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI. For the other two cases,
where clang < 17 or GCC < 11.1.0, we will deal with them in
CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC.

For more information, please refer to:
commit 6df2a016 ("riscv: fix build with binutils 2.38")
commit e89c2e81 ("riscv: Handle zicsr/zifencei issues between clang and binutils")

Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc [0]
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98416dbb0a62579d4a7a4a76bab51b5b52fec2cd [1]
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=5a1b31e1e1cee6e9f1c92abff59cdcfff0dddf30 [2]
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=729a53530e86972d1143553a415db34e6e01d5d2 [3]
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b03be74bad08c382da47e048007a78fa3fb4ef49 [4]
Link: https://lore.kernel.org/all/20230308220842.1231003-1-conor@kernel.org
Link: https://lore.kernel.org/all/20230223220546.52879-1-conor@kernel.org


Reviewed-by: default avatarConor Dooley <conor.dooley@microchip.com>
Acked-by: default avatarGuo Ren <guoren@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarMingzheng Xing <xingmingzheng@iscas.ac.cn>
Link: https://lore.kernel.org/r/20230809165648.21071-1-xingmingzheng@iscas.ac.cn


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 4b05b993

arch/riscv/Kconfig

+19 −13
Original line number Diff line number Diff line
@@ -570,24 +570,30 @@ config TOOLCHAIN_HAS_ZIHINTPAUSE 
config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI

	def_bool y

	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc

	depends on AS_IS_GNU && AS_VERSION >= 23800

	help

	  Newer binutils versions default to ISA spec version 20191213 which

	  moves some instructions from the I extension to the Zicsr and Zifencei

	  extensions.

	# https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98416dbb0a62579d4a7a4a76bab51b5b52fec2cd

	depends on AS_IS_GNU && AS_VERSION >= 23600

	help

	  Binutils-2.38 and GCC-12.1.0 bumped the default ISA spec to the newer

	  20191213 version, which moves some instructions from the I extension to

	  the Zicsr and Zifencei extensions. This requires explicitly specifying

	  Zicsr and Zifencei when binutils >= 2.38 or GCC >= 12.1.0. Zicsr

	  and Zifencei are supported in binutils from version 2.36 onwards.

	  To make life easier, and avoid forcing toolchains that default to a

	  newer ISA spec to version 2.2, relax the check to binutils >= 2.36.

	  For clang < 17 or GCC < 11.1.0, for which this is not possible, this is

	  dealt with in CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC.



config TOOLCHAIN_NEEDS_OLD_ISA_SPEC

	def_bool y

	depends on TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI

	# https://github.com/llvm/llvm-project/commit/22e199e6afb1263c943c0c0d4498694e15bf8a16

	depends on CC_IS_CLANG && CLANG_VERSION < 170000

	help

	  Certain versions of clang do not support zicsr and zifencei via -march

	  but newer versions of binutils require it for the reasons noted in the

	  help text of CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI. This

	  option causes an older ISA spec compatible with these older versions

	  of clang to be passed to GAS, which has the same result as passing zicsr

	  and zifencei to -march.

	# https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b03be74bad08c382da47e048007a78fa3fb4ef49

	depends on (CC_IS_CLANG && CLANG_VERSION < 170000) || (CC_IS_GCC && GCC_VERSION < 110100)

	help

	  Certain versions of clang and GCC do not support zicsr and zifencei via

	  -march. This option causes an older ISA spec compatible with these older

	  versions of clang and GCC to be passed to GAS, which has the same result

	  as passing zicsr and zifencei to -march.



config FPU

	bool "FPU support"

arch/riscv/kernel/compat_vdso/Makefile

+7 −1
Original line number Diff line number Diff line
@@ -11,7 +11,13 @@ compat_vdso-syms += flush_icache 
COMPAT_CC := $(CC)

COMPAT_LD := $(LD)



# binutils 2.35 does not support the zifencei extension, but in the ISA

# spec 20191213, G stands for IMAFD_ZICSR_ZIFENCEI.

ifdef CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI

	COMPAT_CC_FLAGS := -march=rv32g -mabi=ilp32

else

	COMPAT_CC_FLAGS := -march=rv32imafd -mabi=ilp32

endif

COMPAT_LD_FLAGS := -melf32lriscv



# Disable attributes, as they're useless and break the build.