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 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;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98416dbb0a62579d4a7a4a76bab51b5b52fec2cd
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=5a1b31e1e1cee6e9f1c92abff59cdcfff0dddf30
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=729a53530e86972d1143553a415db34e6e01d5d2
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b03be74bad08c382da47e048007a78fa3fb4ef49
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>
Link: https://lore.kernel.org/r/20230809165648.21071-1-xingmingzheng@iscas.ac.cn
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4c07b91..10e7a7a 100644 (file)
--- 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;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"

diff --git a/arch/riscv/kernel/compat_vdso/Makefile b/arch/riscv/kernel/compat_vdso/Makefile
index 1893457..b86e5e2 100644 (file)
--- 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.