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([2001:871:22a:99c5::1ad1]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-acaa1cb41besm789238466b.118.2025.04.13.14.10.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 13 Apr 2025 14:10:42 -0700 (PDT) Message-ID: Date: Sun, 13 Apr 2025 23:10:41 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] arm: rust: Enable Rust support for ARMv7 To: Linus Walleij Cc: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Jonathan Corbet , Russell King , Rudraksha Gupta , Ard Biesheuvel , Geert Stappers , Andrew Lunn , Jamie Cunliffe , Sven Van Asbroeck , rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20250123-rfl-arm32-v3-1-8f13623d42c5@gmail.com> Content-Language: en-US, de-DE From: Christian Schrefl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 21.03.25 8:24 AM, Linus Walleij wrote: > Hi Christian, > > thanks for your patch! > > Sorry for being late to the show. I missed this very nice patch > that was actually on my personal TODO but I have to much > to do and also I'm not smart with Rust, but I'm a big supporter. > > On Thu, Jan 23, 2025 at 11:40 PM Christian Schrefl > wrote: > >> + select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 > > Nothing in the patch series really explains this restriction, so it > should be in the commit message. Arnd mentions some atomics > etc, but we really need to know exactly why this is in the patch. > > I'm a bit surprised by this since the rustc LLVM backend nowadays > support all old ARM ISAs. I would have expected: > > select HAVE_RUST if AEABI > > Ideally this should work on any ARM core, but it's fair to require > EABI. > > The big reason: I think we want to be able to use Rust in kernel > core components sooner than ARMv5 goes away from the kernel. > > If testing is the only issue, I can provide testing on ARMv4, v5, > ARMv5 BE etc, just tell me how to test. (But I guess it's more than > that...) I've done a quick test on armv5 with the `armv5te-none-eabi` rust target and it needs some atomics (`AtomicU64` type and for `AtomicBool` the `compare_exchange` and `compare_exchange` functions) to build: ``` RUSTC L rust/kernel.o error[E0432]: unresolved import `core::sync::atomic::AtomicU64` --> rust/kernel/block/mq/operations.rs:15:33 | 15 | use core::{marker::PhantomData, sync::atomic::AtomicU64, sync::atomic::Ordering}; | ^^^^^^^^^^^^^^--------- | | | | | help: a similar name exists in the module: `AtomicU8` | no `AtomicU64` in `sync::atomic` error[E0432]: unresolved import `core::sync::atomic::AtomicU64` --> rust/kernel/block/mq/request.rs:16:20 | 16 | sync::atomic::{AtomicU64, Ordering}, | ^^^^^^^^^ | | | no `AtomicU64` in `sync::atomic` | help: a similar name exists in the module: `AtomicU8` error[E0599]: no method named `compare_exchange` found for struct `AtomicBool` in the current scope --> rust/kernel/list/arc.rs:518:14 | 517 | / self.inner 518 | | .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed) | | -^^^^^^^^^^^^^^^^ method not found in `AtomicBool` | |_____________| | error[E0599]: no method named `swap` found for struct `AtomicBool` in the current scope --> rust/kernel/revocable.rs:130:30 | 130 | if self.is_available.swap(false, Ordering::Relaxed) { | ^^^^ method not found in `AtomicBool` error: aborting due to 4 previous errors Some errors have detailed explanations: E0432, E0599. For more information about an error, try `rustc --explain E0432`. ``` When gating all the modules that need these linking fails because of missing __eabi__* intrinsics: ``` ld.lld: error: undefined symbol: __aeabi_memcpy >>> referenced by kernel.2bb770ae1dba3d33-cgu.0 >>> rust/kernel.o:(::write_char) in archive vmlinux.a >>> referenced by kernel.2bb770ae1dba3d33-cgu.0 >>> rust/kernel.o:(::write_char) in archive vmlinux.a >>> referenced by kernel.2bb770ae1dba3d33-cgu.0 >>> rust/kernel.o:(::read_raw) in archive vmlinux.a >>> referenced 29 more times ld.lld: error: undefined symbol: __aeabi_memclr8 >>> referenced by bindings.4cab29b7397d35cb-cgu.0 >>> rust/bindings.o:(::default) in archive vmlinux.a >>> referenced by uapi.fe46408b8870a0f6-cgu.0 >>> rust/uapi.o:(::default) in archive vmlinux.a >>> referenced by uapi.fe46408b8870a0f6-cgu.0 >>> rust/uapi.o:(::default) in archive vmlinux.a >>> referenced 86 more times ld.lld: error: undefined symbol: __aeabi_memclr4 >>> referenced by bindings.4cab29b7397d35cb-cgu.0 >>> rust/bindings.o:(::default) in archive vmlinux.a >>> referenced by bindings.4cab29b7397d35cb-cgu.0 >>> rust/bindings.o:(::default) in archive vmlinux.a >>> referenced by uapi.fe46408b8870a0f6-cgu.0 >>> rust/uapi.o:(::default) in archive vmlinux.a >>> referenced 95 more times ld.lld: error: undefined symbol: __aeabi_memset >>> referenced by core.64aa0a46a0f8f964-cgu.0 >>> rust/core.o:(::write) in archive vmlinux.a >>> referenced by core.64aa0a46a0f8f964-cgu.0 >>> rust/core.o:(core::fmt::num::fmt_u128) in archive vmlinux.a ld.lld: error: undefined symbol: __aeabi_memcpy4 >>> referenced by kernel.2bb770ae1dba3d33-cgu.0 >>> rust/kernel.o:(::new) in archive vmlinux.a >>> referenced by core.64aa0a46a0f8f964-cgu.0 >>> rust/core.o:(::fmt) in archive vmlinux.a ld.lld: error: undefined symbol: __aeabi_memclr >>> referenced by kernel.2bb770ae1dba3d33-cgu.0 >>> rust/kernel.o:(::fill_zero_raw) in archive vmlinux.a >>> referenced by uapi.fe46408b8870a0f6-cgu.0 >>> rust/uapi.o:(::default) in archive vmlinux.a >>> referenced by uapi.fe46408b8870a0f6-cgu.0 >>> rust/uapi.o:(::default) in archive vmlinux.a >>> referenced 16 more times ld.lld: error: undefined symbol: __aeabi_memset4 >>> referenced by core.64aa0a46a0f8f964-cgu.0 >>> rust/core.o:(core::fmt::num::fmt_u128) in archive vmlinux.a make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1 make[1]: *** [/home/chrisi/Documents/code/rust-arm32/Makefile:1242: vmlinux] Error 2 make: *** [Makefile:248: __sub-make] Error 2 ``` With define_panicking_intrinsics! for these an empty sample works (not yet tested as module), but even printing a non formatted string (with `pr_info!("Hi rust\n");`) fails because rust tries to use __adddf3: `` Hardware name: ARM-Versatile (Device Tree Support) PC is at __rust__adddf3+0x0/0x4 LR is at _RNvXsg_NtCs3KHxpmQFgFb_6kernel3strNtB5_12RawFormatterNtNtCs8DPF7ip8WBQ_4core3fmt5Write9write_str+0x34/0x40 pc : [] lr : [] psr: 20000193 sp : c8811a78 ip : c8811ae8 fp : c058e44e r10: 00000000 r9 : c058e450 r8 : c07ac118 r7 : 00000000 r6 : 00000000 r5 : c07ac120 r4 : c8811adc r3 : c07ac120 r2 : 00000008 r1 : c0667f60 r0 : c07ac118 Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none ``` I'm not sure how to proceed from here and I most likely won't find time to continue working on this anytime soon. My very hacky changes are available on Github at: https://github.com/onestacked/linux/commit/edddb388267ab1afe5255bea4d84f96cbdb37978 Cheers, Christian