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Date: Mon, 17 Jun 2024 18:03:11 +0200
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
rust-for-linux@...r.kernel.org
Cc: Miguel Ojeda <ojeda@...nel.org>, Jamie Cunliffe <Jamie.Cunliffe@....com>,
Sven Van Asbroeck <thesven73@...il.com>,
Geert Stappers <stappers@...ppers.nl>, Andrew Lunn <andrew@...n.ch>
Subject: [PATCH v2] arm: rust: Enable Rust support for ARMv7
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 AArch64 version by Jamie Cunliffe.
I have tested the rust samples and a custom simple MMIO module
on hardware (De1SoC FPGA + Arm A9 CPU).
This only includes support for ARMv7, but supporting other
sub-architectures in the future should be as simple as setting
the correct rustc target.
Signed-off-by: Christian Schrefl <chrisi.schrefl@...il.com>
---
Changes since V1 [1]:
- Removed unrelated whitespace change.
- Added target name to panic message in scripts/generate_rust_target.rs.
- Fixed the comment in rust/bindgen_parameters.
[1]: https://lore.kernel.org/rust-for-linux/4e0f5932-c7bc-4878-862c-1186cbecd71d@gmail.com
--
Documentation/rust/arch-support.rst | 1 +
arch/arm/Kconfig | 1 +
arch/arm/Makefile | 1 +
rust/Makefile | 8 ++++++++
rust/bindgen_parameters | 4 ++++
rust/compiler_builtins.rs | 24 ++++++++++++++++++++++++
scripts/generate_rust_target.rs | 4 +++-
7 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
index b13e19d84744..4bf5205f526d 100644
--- a/Documentation/rust/arch-support.rst
+++ b/Documentation/rust/arch-support.rst
@@ -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`` only.
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ee5115252aac..f07149fe078b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -126,6 +126,7 @@ 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
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 71afdd98ddf2..9cc10e32e8be 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -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__
diff --git a/rust/Makefile b/rust/Makefile
index f70d5e244fee..8214a6f378e3 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -287,6 +287,7 @@ 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,
@@ -413,6 +414,13 @@ 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 += \
diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index a721d466bee4..83f28ae4bb2b 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -24,3 +24,7 @@
# These functions use the `__preserve_most` calling convention, which neither bindgen
# nor Rust currently understand, and which Clang currently declares to be unstable.
--blocklist-function __list_.*_report
+
+# Depending on how the architecture defines `ARCH_SLAB_MINALIGN`, `bindgen` might generate a binding.
+# Disable this here as there is a `const` item that will always be generated in `bindings_helper.h`
+--blocklist-item ARCH_SLAB_MINALIGN
diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs
index bba2922c6ef7..c37142b16a45 100644
--- a/rust/compiler_builtins.rs
+++ b/rust/compiler_builtins.rs
@@ -70,5 +70,29 @@ pub extern "C" fn $ident() {
__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`.
diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index 641b713a033a..c3a6058fdf30 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -148,7 +148,9 @@ 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 arm-unknown-linux-gnueabi 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") {
base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0
--
2.45.2
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