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Date: Wed, 29 May 2024 17:33:35 +0800
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Message-ID: <20240529093336.4075206-1-davidgow@google.com>
Subject: [PATCH] arch: um: rust: Use the generated target.json again
From: David Gow <davidgow@google.com>
To: Rae Moar <rmoar@google.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, 
	Miguel Ojeda <ojeda@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>, Masahiro Yamada <masahiroy@kernel.org>, 
	Jamie Cunliffe <Jamie.Cunliffe@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, 
	Richard Weinberger <richard@nod.at>, Anton Ivanov <anton.ivanov@cambridgegreys.com>, 
	Johannes Berg <johannes@sipsolutions.net>
Cc: David Gow <davidgow@google.com>, kunit-dev@googlegroups.com, 
	linux-kernel@vger.kernel.org, linux-um@lists.infradead.org, 
	rust-for-linux@vger.kernel.org, x86@kernel.org, 
	Wedson Almeida Filho <wedsonaf@gmail.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, Alex Gaynor <alex.gaynor@gmail.com>, 
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
	"=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" <bjorn3_gh@protonmail.com>, Benno Lossin <benno.lossin@proton.me>, 
	Andreas Hindborg <a.hindborg@samsung.com>, Alice Ryhl <aliceryhl@google.com>
Content-Type: text/plain; charset="UTF-8"

The Rust compiler can take a target config from 'target.json', which is
generated by scripts/generate_rust_target.rs. It used to be that all
Linux architectures used this to generate a target.json, but now
architectures must opt-in to this, or they will default to the Rust
compiler's built-in target definition.

This is mostly okay for (64-bit) x86 and UML, except that it can
generate SSE instructions, which we can't use in the kernel. So
re-instate the custom target.json, which disables SSE (and generally
enables the 'soft-float' feature). This fixes the following compile
error:

error: <unknown>:0:0: in function _RNvMNtCs5QSdWC790r4_4core3f32f7next_up float (float): SSE register return with SSE disabled

Fixes: f82811e22b48 ("rust: Refactor the build target to allow the use of builtin targets")
Signed-off-by: David Gow <davidgow@google.com>
---
 arch/x86/Makefile.um | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index 2106a2bd152b..a46b1397ad01 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -9,6 +9,7 @@ core-y += arch/x86/crypto/
 #
 ifeq ($(CONFIG_CC_IS_CLANG),y)
 KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
+KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
 KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
 endif
 
-- 
2.45.1.288.g0e0cd299f1-goog