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 6df2a016c0c8 ("riscv: fix build with binutils 2.38") commit e89c2e815e76 ("riscv: Handle zicsr/zifencei issues between clang and binutils") Link: https://sourceware.org/git/?p=binutils-gdb.git%3Ba=commit%3Bh=aed44286efa8ae... [0] Link: https://gcc.gnu.org/git/?p=gcc.git%3Ba=commit%3Bh=98416dbb0a62579d4a7a4a76ba... [1] Link: https://sourceware.org/git/?p=binutils-gdb.git%3Ba=commit%3Bh=5a1b31e1e1cee6... [2] Link: https://sourceware.org/git/?p=binutils-gdb.git%3Ba=commit%3Bh=729a53530e8697... [3] Link: https://gcc.gnu.org/git/?p=gcc.git%3Ba=commit%3Bh=b03be74bad08c382da47e04800... [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: Conor Dooley conor.dooley@microchip.com Acked-by: Guo Ren guoren@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Mingzheng Xing xingmingzheng@iscas.ac.cn ---

Changelog and test results:

v4 -> v5: - Add Reviewed-by and Acked-by to commit message, no other code changes.

v3 -> v4: - Update the Kconfig help text and commit message. Link: https://lore.kernel.org/all/20230731150511.38140-1-xingmingzheng@iscas.ac.cn

v2 -> v3: - Relax the check to binutils >= 2.36. - Update the Kconfig help text and commit message. Link: https://lore.kernel.org/all/20230731095936.23397-1-xingmingzheng@iscas.ac.cn

v1 -> v2: - Update the Kconfig help text and commit message. - Add considerations for low version gcc case. Link: https://lore.kernel.org/all/20230726174524.340952-1-xingmingzheng@iscas.ac.c...

v1: Link: https://lore.kernel.org/all/20230725170405.251011-1-xingmingzheng@iscas.ac.c...

Here are my test results: * Compiling the kernel for the master branch with a combination of multiple versions of gcc and binutils.

gcc binutils patched no patch 11.4.0 2.35 ok ok 11.4.0 2.36 ok ok 11.4.0 2.38 ok ok

12.2.0 2.35 ok error[1] 12.2.0 2.36 ok error[2] 12.2.0 2.38 ok ok

10.5.0 2.35 ok ok 10.5.0 2.36 ok ok 10.5.0 2.38 ok error[3]

11.1.0 2.35 ok ok 11.1.0 2.36 ok ok 11.1.0 2.38 ok ok

11.2.0 2.35 ok ok 11.2.0 2.36 ok ok 11.2.0 2.38 ok ok

[1] Assembler messages: Fatal error: -march=rv32imafd_zicsr_zifencei: Invalid or unknown z ISA extension: 'zifencei' make[2]: *** [arch/riscv/kernel/compat_vdso/Makefile:47: arch/riscv/kernel/compat_vdso/rt_sigreturn.o] Error 1

[2] ./arch/riscv/include/asm/vdso/gettimeofday.h: Assembler messages: ./arch/riscv/include/asm/vdso/gettimeofday.h:79: Error: unrecognized opcode `csrr a5,0xc01' ./arch/riscv/include/asm/vdso/gettimeofday.h:79: Error: unrecognized opcode `csrr a5,0xc01' ./arch/riscv/include/asm/vdso/gettimeofday.h:79: Error: unrecognized opcode `csrr a5,0xc01' ./arch/riscv/include/asm/vdso/gettimeofday.h:79: Error: unrecognized opcode `csrr a5,0xc01' make[2]: *** [scripts/Makefile.build:243: arch/riscv/kernel/vdso/vgettimeofday.o] Error 1

[3] cc1: error: '-march=rv64imac_zicsr_zifencei': unsupported ISA subset 'z' cc1: error: ABI requires '-march=rv64' make[2]: *** [scripts/Makefile.build:243: scripts/mod/empty.o] Error 1 make[2]: *** Waiting for unfinished jobs.... cc1: error: '-march=rv64imac_zicsr_zifencei': unsupported ISA subset 'z' cc1: error: ABI requires '-march=rv64'

arch/riscv/Kconfig | 32 +++++++++++++++----------- arch/riscv/kernel/compat_vdso/Makefile | 8 ++++++- 2 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index f52dd125ac5e..ce3a6667cfdb 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -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%3Ba=commit%3Bh=aed44286efa8ae... - 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%3Ba=commit%3Bh=98416dbb0a62579d4a7a4a76ba... + 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/22e199e6afb1263c943c0c0d4498694e... - 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%3Ba=commit%3Bh=b03be74bad08c382da47e04800... + 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" diff --git a/arch/riscv/kernel/compat_vdso/Makefile b/arch/riscv/kernel/compat_vdso/Makefile index 189345773e7e..b86e5e2c3aea 100644 --- a/arch/riscv/kernel/compat_vdso/Makefile +++ b/arch/riscv/kernel/compat_vdso/Makefile @@ -11,7 +11,13 @@ compat_vdso-syms += flush_icache COMPAT_CC := $(CC) COMPAT_LD := $(LD)

-COMPAT_CC_FLAGS := -march=rv32g -mabi=ilp32 +# 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.