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[2a02:3100:a189:2701:8c58:155a:279:7389]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a1b481b7f8sm5237345e9.3.2026.10.13.13.32.09 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 13 Oct 2026 13:32:12 -0700 (PDT) From: Karl Mehltretter To: Russell King , Miguel Ojeda Cc: Karl Mehltretter , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?UTF-8?q?Onur=20=C3=96zkan?= , Arnd Bergmann , Linus Walleij , Christian Schrefl , Bradley Morgan , "Paul E . McKenney" , Peter Zijlstra , FUJITA Tomonori , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-arm-kernel@lists.infradead.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 5/6] ARM: rust: Enable Rust support for ARMv4T Date: Tue, 13 Oct 2026 22:31:39 +0200 Message-Id: <20261013203140.31741-6-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20261013203140.31741-1-kmehltretter@gmail.com> References: <20261013203140.31741-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The armv5te target emits clz and blx, which ARMv4T lacks. Use rustc's armv4t-unknown-linux-gnueabi target for CPU_32v4T. A combined ARMv4T and ARMv5 kernel then uses ARMv4T code for both C and Rust. Plain ARMv4 remains excluded because rustc has no matching Linux target. This also depends on the preceding 16-bit xchg() support for pre-ARMv6 CPUs. Tested the Rust samples, KUnit suites and doctests in QEMU sx1 (ARM925T) with omap1_defconfig and on a Microchip SAM9X75 Curiosity board with at91_dt_defconfig. Assisted-by: LLM Signed-off-by: Karl Mehltretter --- Documentation/rust/arch-support.rst | 8 ++++---- arch/arm/Kconfig | 2 +- arch/arm/Makefile | 1 + 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst index d6d1bef44c8f..3f39cf55b6f4 100644 --- a/Documentation/rust/arch-support.rst +++ b/Documentation/rust/arch-support.rst @@ -12,15 +12,15 @@ which uses ``libclang``. Below is a general summary of architectures that currently work. Level of support corresponds to ``S`` values in the ``MAINTAINERS`` file. -============= ================ ============================================== +============= ================ ====================================================== Architecture Level of support Constraints -============= ================ ============================================== -``arm`` Maintained ARMv5TE, ARMv6K and ARMv7, Little Endian only. +============= ================ ====================================================== +``arm`` Maintained ARMv4T, ARMv5TE, ARMv6K and ARMv7, Little Endian only. ``arm64`` Maintained Little Endian only. ``loongarch`` Maintained \- ``riscv`` Maintained ``riscv64`` and LLVM/Clang only. ``s390`` Maintained ``CONFIG_EXPOLINE`` must be disabled. ``um`` Maintained \- ``x86`` Maintained ``x86_64`` only. -============= ================ ============================================== +============= ================ ====================================================== diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 9275a85f95e9..cf782fc04872 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -176,7 +176,7 @@ config ARM config ARM_RUST_TARGET def_bool y depends on (CPU_32v6K && !CPU_V6) || \ - (CPU_32v5 && !CPU_32v4T && !CPU_32v4) + ((CPU_32v5 || CPU_32v4T) && !CPU_32v4) config ARM_HAS_GROUP_RELOCS def_bool !COMPILE_TEST diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 168779e9e93d..a72843890241 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -77,6 +77,7 @@ arch-$(CONFIG_CPU_32v3) :=-march=armv3m # the +v6 of the generic target, so older CPUs need their own target. rust-target-y :=arm-unknown-linux-gnueabi rust-target-$(CONFIG_CPU_32v5) :=armv5te-unknown-linux-gnueabi +rust-target-$(CONFIG_CPU_32v4T) :=armv4t-unknown-linux-gnueabi # Note that GCC does not numerically define an architecture version # macro, but instead defines a whole series of macros which makes -- 2.39.5 (Apple Git-154)