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ARM: 9441/1: rust: Enable Rust support for ARMv7

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This commit allows building ARMv7 kernels with Rust support.

The rust core library expects some __eabi_... functions
that are not implemented in the kernel.
Those functions are some float operations and __aeabi_uldivmod.
For now those are implemented with define_panicking_intrinsics!.

This is based on the code by Sven Van Asbroeck from the original
rust branch and inspired by the AArch version by Jamie Cunliffe.

I have tested the rust samples and a custom simple MMIO module
on hardware (De1SoC FPGA + Arm A9 CPU).

Tested-by: Rudraksha Gupta <guptarud@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Christian Schrefl <chrisi.schrefl@gmail.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Christian Schrrefl 2025-01-31 00:03:45 +01:00 • committed by Russell King (Oracle)
parent f9733aa925
commit ccb8ce5268
6 changed files with 38 additions and 1 deletions
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1
Documentation/rust/arch-support.rst
View file

@ -15,6 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
============= ================ ==============================================
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.

1
arch/arm/Kconfig
View file

@ -133,6 +133,7 @@ config ARM
select MMU_GATHER_RCU_TABLE_FREE if SMP && ARM_LPAE
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RSEQ
select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7
select HAVE_STACKPROTECTOR
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UID16

1
arch/arm/Makefile
View file

@ -150,6 +150,7 @@ endif
KBUILD_CPPFLAGS +=$(cpp-y)
KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm
KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) -Wa,$(arch-y) $(tune-y) -include asm/unified.h -msoft-float
KBUILD_RUSTFLAGS += --target=arm-unknown-linux-gnueabi
CHECKFLAGS += -D__arm__

8
rust/Makefile
View file

@ -245,6 +245,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
# Derived from `scripts/Makefile.clang`.
BINDGEN_TARGET_x86 := x86_64-linux-gnu
BINDGEN_TARGET_arm64 := aarch64-linux-gnu
BINDGEN_TARGET_arm := arm-linux-gnueabi
BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
# All warnings are inhibited since GCC builds are very experimental,
@ -397,6 +398,13 @@ redirect-intrinsics = \
__muloti4 __multi3 \
__udivmodti4 __udivti3 __umodti3
ifdef CONFIG_ARM
# Add eabi initrinsics for ARM 32-bit
redirect-intrinsics += \
__aeabi_fadd __aeabi_fmul __aeabi_fcmpeq __aeabi_fcmple __aeabi_fcmplt __aeabi_fcmpun \
__aeabi_dadd __aeabi_dmul __aeabi_dcmple __aeabi_dcmplt __aeabi_dcmpun \
__aeabi_uldivmod
endif
ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
# These intrinsics are defined for ARM64 and RISCV64
redirect-intrinsics += \

24
rust/compiler_builtins.rs
View file

@ -73,5 +73,29 @@ define_panicking_intrinsics!("`u128` should not be used", {
__umodti3,
});
#[cfg(target_arch = "arm")]
define_panicking_intrinsics!("`f32` should not be used", {
__aeabi_fadd,
__aeabi_fmul,
__aeabi_fcmpeq,
__aeabi_fcmple,
__aeabi_fcmplt,
__aeabi_fcmpun,
});
#[cfg(target_arch = "arm")]
define_panicking_intrinsics!("`f64` should not be used", {
__aeabi_dadd,
__aeabi_dmul,
__aeabi_dcmple,
__aeabi_dcmplt,
__aeabi_dcmpun,
});
#[cfg(target_arch = "arm")]
define_panicking_intrinsics!("`u64` division/modulo should not be used", {
__aeabi_uldivmod,
});
// NOTE: if you are adding a new intrinsic here, you should also add it to
// `redirect-intrinsics` in `rust/Makefile`.

4
scripts/generate_rust_target.rs
View file

@ -172,7 +172,9 @@ fn main() {
let mut ts = TargetSpec::new();
// `llvm-target`s are taken from `scripts/Makefile.clang`.
if cfg.has("ARM64") {
if cfg.has("ARM") {
panic!("arm uses the builtin rustc target");
} else if cfg.has("ARM64") {
panic!("arm64 uses the builtin rustc aarch64-unknown-none target");
} else if cfg.has("RISCV") {
if cfg.has("64BIT") {