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Sun, 23 Nov 2025 16:23:26 -0800 (PST) From: Asuna Yang X-Google-Original-From: Asuna Yang Date: Mon, 24 Nov 2025 01:23:24 +0100 Subject: [PATCH v4 4/4] RISC-V: fix gcc + rust builds Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251124-gcc-rust-v4-v4-4-4e06e07421ae@gmail.com> References: <20251124-gcc-rust-v4-v4-0-4e06e07421ae@gmail.com> In-Reply-To: <20251124-gcc-rust-v4-v4-0-4e06e07421ae@gmail.com> To: Nathan Chancellor , Nicolas Schier , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Nick Desaulniers , Bill Wendling , Justin Stitt , Nicolas Schier , Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Vivian Wang , Han Gao , Jason Montleon , Conor Dooley Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, Asuna Yang X-Mailer: b4 0.14.3 Commit 33549fcf37ec ("RISC-V: disallow gcc + rust builds") disabled GCC + Rust builds for RISC-V due to differences in extension handling compared to LLVM. Add `rust-bindgen-option` conditions for the availability of libclang to the RISC-V extension Kconfig symbols that depend on the `cc-option` function. For Zicsr/Zifencei special handling, since LLVM/Clang always enables these two extensions, either don't pass them to `-march`, or pass them explicitly and Rust bindgen libclang must recognize them. Clang does not support `-mno-riscv-attribute` flag, filter it out to resolve error: unknown argument: '-mno-riscv-attribute'. Define `BINDGEN_TARGET_riscv` to pass the target triplet to Rust bindgen libclang for RISC-V to resolve error: unsupported argument 'medany' to option '-mcmodel=' for target 'unknown'. Update the documentation, GCC + Rust builds for RISC-V are now supported. Signed-off-by: Asuna Yang --- Documentation/rust/arch-support.rst | 2 +- arch/riscv/Kconfig | 35 ++++++++++++++++++++++++++++++++++- rust/Makefile | 3 ++- scripts/Makefile.rust | 1 + 4 files changed, 38 insertions(+), 3 deletions(-) diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst index 6e6a515d0899..5282e0e174e8 100644 --- a/Documentation/rust/arch-support.rst +++ b/Documentation/rust/arch-support.rst @@ -18,7 +18,7 @@ Architecture Level of support Constraints ``arm`` Maintained ARMv7 Little Endian only. ``arm64`` Maintained Little Endian only. ``loongarch`` Maintained \- -``riscv`` Maintained ``riscv64`` and LLVM/Clang only. +``riscv`` Maintained ``riscv64`` only. ``um`` Maintained \- ``x86`` Maintained ``x86_64`` only. ============= ================ ============================================== diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index fadec20b87a8..e3ea132191d1 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -193,7 +193,7 @@ config RISCV select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RETHOOK if !XIP_KERNEL select HAVE_RSEQ - select HAVE_RUST if RUSTC_SUPPORTS_RISCV && CC_IS_CLANG + select HAVE_RUST if RUSTC_SUPPORTS_RISCV && TOOLCHAIN_MATCHES_ZICSR_ZIFENCEI select HAVE_SAMPLE_FTRACE_DIRECT select HAVE_SAMPLE_FTRACE_DIRECT_MULTI select HAVE_STACKPROTECTOR @@ -617,6 +617,8 @@ config TOOLCHAIN_HAS_V depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32imv) depends on LD_IS_LLD || LD_VERSION >= 23800 depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64imv) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32imv) config RISCV_ISA_V bool "Vector extension support" @@ -681,6 +683,8 @@ config TOOLCHAIN_HAS_ZABHA depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zabha) depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zabha) depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zabha) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zabha) config RISCV_ISA_ZABHA bool "Zabha extension support for atomic byte/halfword operations" @@ -699,6 +703,8 @@ config TOOLCHAIN_HAS_ZACAS depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zacas) depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zacas) depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zacas) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zacas) config RISCV_ISA_ZACAS bool "Zacas extension support for atomic CAS" @@ -717,6 +723,8 @@ config TOOLCHAIN_HAS_ZBB depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbb) depends on LD_IS_LLD || LD_VERSION >= 23900 depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zbb) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zbb) # This symbol indicates that the toolchain supports all v1.0 vector crypto # extensions, including Zvk*, Zvbb, and Zvbc. LLVM added all of these at once. @@ -732,6 +740,8 @@ config TOOLCHAIN_HAS_ZBA depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zba) depends on LD_IS_LLD || LD_VERSION >= 23900 depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zba) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zba) config RISCV_ISA_ZBA bool "Zba extension support for bit manipulation instructions" @@ -767,6 +777,8 @@ config TOOLCHAIN_HAS_ZBC depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbc) depends on LD_IS_LLD || LD_VERSION >= 23900 depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zbc) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zbc) config RISCV_ISA_ZBC bool "Zbc extension support for carry-less multiplication instructions" @@ -790,6 +802,8 @@ config TOOLCHAIN_HAS_ZBKB depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbkb) depends on LD_IS_LLD || LD_VERSION >= 23900 depends on AS_HAS_OPTION_ARCH + depends on !RUST || !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zbkb) + depends on !RUST || !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zbkb) config RISCV_ISA_ZBKB bool "Zbkb extension support for bit manipulation instructions" @@ -877,6 +891,25 @@ config TOOLCHAIN_NEEDS_OLD_ISA_SPEC versions of clang and GCC to be passed to GAS, which has the same result as passing zicsr and zifencei to -march. +config RUST_BINDGEN_HAS_ZICSR_ZIFENCEI + def_bool y + depends on !64BIT || $(rust-bindgen-option,-- -mabi=lp64 -march=rv64ima_zicsr_zifencei) + depends on !32BIT || $(rust-bindgen-option,-- -mabi=ilp32 -march=rv32ima_zicsr_zifencei) + +config TOOLCHAIN_MATCHES_ZICSR_ZIFENCEI + def_bool y + # https://github.com/llvm/llvm-project/commit/22e199e6afb1263c943c0c0d4498694e15bf8a16 + depends on TOOLCHAIN_NEEDS_OLD_ISA_SPEC || !TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI || RUST_BINDGEN_HAS_ZICSR_ZIFENCEI + help + LLVM/Clang >= 17.0.0 starts recognizing Zicsr/Zifencei in -march, passing + them to -march doesn't generate an error anymore, and passing them or not + doesn't have any real difference, it still follows ISA before version + 20190608 - Zicsr/Zifencei are included in base ISA. + + The current latest version of LLVM/Clang still does not require explicit + Zicsr/Zifencei to enable these two extensions, Clang just accepts them in + -march and then silently ignores them. + config FPU bool "FPU support" default y diff --git a/rust/Makefile b/rust/Makefile index ae7cbbd89da3..1f209e6025e4 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -298,7 +298,8 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \ -fno-inline-functions-called-once -fsanitize=bounds-strict \ -fstrict-flex-arrays=% -fmin-function-alignment=% \ -fzero-init-padding-bits=% -mno-fdpic \ - --param=% --param asan-% -fno-isolate-erroneous-paths-dereference + --param=% --param asan-% -fno-isolate-erroneous-paths-dereference \ + -mno-riscv-attribute # All warnings are inhibited since GCC builds are very experimental, # many GCC warnings are not supported by Clang, they may only appear in diff --git a/scripts/Makefile.rust b/scripts/Makefile.rust index b219244cd051..cee28a604830 100644 --- a/scripts/Makefile.rust +++ b/scripts/Makefile.rust @@ -3,6 +3,7 @@ BINDGEN_TARGET_x86 := x86_64-linux-gnu BINDGEN_TARGET_arm64 := aarch64-linux-gnu BINDGEN_TARGET_arm := arm-linux-gnueabi BINDGEN_TARGET_loongarch := loongarch64-linux-gnusf +BINDGEN_TARGET_riscv := riscv64-linux-gnu BINDGEN_TARGET_um := $(BINDGEN_TARGET_$(SUBARCH)) BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH)) -- 2.51.1