At present, Rust in the kernel only supports 64-bit x86, so UML has followed suit. However, it's significantly easier to support 32-bit i386 on UML than on bare metal, as UML does not use the -mregparm option (which alters the ABI), which is not yet supported by rustc[1]. Add support for CONFIG_RUST on um/i386, by adding a new target config to generate_rust_target, and replacing various checks on CONFIG_X86_64 to also support CONFIG_X86_32. We still use generate_rust_target, rather than a built-in rustc target, in order to match x86_64, provide a future place for -mregparm, and more easily disable floating point instructions. With these changes, the KUnit tests pass with: kunit.py run --make_options LLVM=1 --kconfig_add CONFIG_RUST=y --kconfig_add CONFIG_64BIT=n --kconfig_add CONFIG_FORTIFY_SOURCE=n An earlier version of these changes was proposed on the Rust-for-Linux github[2]. [1]: https://github.com/rust-lang/rust/issues/116972 [2]: https://github.com/Rust-for-Linux/linux/pull/966 Signed-off-by: David Gow <davidgow@xxxxxxxxxx> --- Documentation/rust/arch-support.rst | 2 +- arch/um/Kconfig | 2 +- rust/Makefile | 2 +- scripts/Makefile | 2 +- scripts/generate_rust_target.rs | 17 +++++++++++++++++ 5 files changed, 21 insertions(+), 4 deletions(-) diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst index b13e19d84744..750ff371570a 100644 --- a/Documentation/rust/arch-support.rst +++ b/Documentation/rust/arch-support.rst @@ -18,7 +18,7 @@ Architecture Level of support Constraints ``arm64`` Maintained Little Endian only. ``loongarch`` Maintained \- ``riscv`` Maintained ``riscv64`` only. -``um`` Maintained ``x86_64`` only. +``um`` Maintained \- ``x86`` Maintained ``x86_64`` only. ============= ================ ============================================== diff --git a/arch/um/Kconfig b/arch/um/Kconfig index 93a5a8999b07..b6ac49fec5bb 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -31,7 +31,7 @@ config UML select TRACE_IRQFLAGS_SUPPORT select TTY # Needed for line.c select HAVE_ARCH_VMAP_STACK - select HAVE_RUST if X86_64 + select HAVE_RUST config MMU bool diff --git a/rust/Makefile b/rust/Makefile index f70d5e244fee..83f675adbfab 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -426,7 +426,7 @@ $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--re $(obj)/core.o: private rustc_target_flags = $(core-cfgs) $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs FORCE +$(call if_changed_dep,rustc_library) -ifdef CONFIG_X86_64 +ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),) $(obj)/core.o: scripts/target.json endif diff --git a/scripts/Makefile b/scripts/Makefile index fe56eeef09dd..dccef663ca82 100644 --- a/scripts/Makefile +++ b/scripts/Makefile @@ -12,7 +12,7 @@ hostprogs-always-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE) += insert-sys-cert hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS) += rustdoc_test_builder hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS) += rustdoc_test_gen -ifdef CONFIG_X86_64 +ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),) always-$(CONFIG_RUST) += target.json filechk_rust_target = $< < include/config/auto.conf diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 641b713a033a..87f34925eb7b 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -169,6 +169,23 @@ fn main() { ts.push("features", features); ts.push("llvm-target", "x86_64-linux-gnu"); ts.push("target-pointer-width", "64"); + } else if cfg.has("X86_32") { + // This only works on UML, as i386 otherwise needs regparm support in rustc + if !cfg.has("UML") { + panic!("32-bit x86 only works under UML"); + } + ts.push("arch", "x86"); + ts.push( + "data-layout", + "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-i128:128-f64:32:64-f80:32-n8:16:32-S128", + ); + let mut features = "-3dnow,-3dnowa,-mmx,+soft-float".to_string(); + if cfg.has("MITIGATION_RETPOLINE") { + features += ",+retpoline-external-thunk"; + } + ts.push("features", features); + ts.push("llvm-target", "i386-unknown-linux-gnu"); + ts.push("target-pointer-width", "32"); } else if cfg.has("LOONGARCH") { panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target"); } else { -- 2.45.1.288.g0e0cd299f1-goog
