Starting with Rust 1.85.0 (to be released 2025-02-20), `rustc` warns
[1] about disabling neon in the aarch64 hardfloat target:
warning: target feature `neon` cannot be toggled with
`-Ctarget-feature`: unsound on hard-float targets
because it changes float ABI
|
= note: this was previously accepted by the compiler but
is being phased out; it will become a hard error
in a future release!
= note: for more information, see issue #116344
<https://github.com/rust-lang/rust/issues/116344>
Thus, instead, use the softfloat target instead.
While trying it out, I found that the kernel sanitizers were not enabled
for that built-in target [2]. Upstream Rust agreed to backport
the enablement for the current beta so that it is ready for
the 1.85.0 release [3] -- thanks!
However, that still means that before Rust 1.85.0, we cannot switch
since sanitizers could be in use. Thus conditionally do so.
Cc: <stable@xxxxxxxxxxxxxxx> # Needed in 6.12.y and 6.13.y only (Rust is pinned in older LTSs).
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Matthew Maurer <mmaurer@xxxxxxxxxx>
Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Cc: Ralf Jung <post@xxxxxxxx>
Cc: Jubilee Young <workingjubilee@xxxxxxxxx>
Link: https://github.com/rust-lang/rust/pull/133417 [1]
Link: https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/arm64.20neon.20.60-Ctarget-feature.60.20warning/near/495358442 [2]
Link: https://github.com/rust-lang/rust/pull/135905 [3]
Link: https://github.com/rust-lang/rust/issues/116344
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
---
Matthew: if you could please give this a go and confirm that it is fine
for Android (with sanitizers enabled, for 1.84.1 and 1.85.0), then a
Tested-by tag would be great. Thanks!
I would like to get this one into -rc3 if possible so that by the time
the compiler releases we are already clean.
I am sending another patch to introduce `rustc-min-version` and use it
here, but I am doing so after this one rather than before so that this
fix can be as simple as possible.
arch/arm64/Makefile | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 358c68565bfd..2b25d671365f 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -48,7 +48,11 @@ KBUILD_CFLAGS += $(CC_FLAGS_NO_FPU) \
KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
KBUILD_AFLAGS += $(compat_vdso)
+ifeq ($(call test-ge, $(CONFIG_RUSTC_VERSION), 108500),y)
+KBUILD_RUSTFLAGS += --target=aarch64-unknown-none-softfloat
+else
KBUILD_RUSTFLAGS += --target=aarch64-unknown-none -Ctarget-feature="-neon"
+endif
KBUILD_CFLAGS += $(call cc-option,-mabi=lp64)
KBUILD_AFLAGS += $(call cc-option,-mabi=lp64)
base-commit: a64dcfb451e254085a7daee5fe51bf22959d52d3
--
2.48.1
