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Date: Thu, 30 May 2024 10:00:00 -0700
From: Boqun Feng <boqun.feng@gmail.com>
To: David Gow <davidgow@google.com>
Cc: Rae Moar <rmoar@google.com>, Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [PATCH] arch: um: rust: Use the generated target.json again
Message-ID: <ZliwkPY-psgVNhZY@boqun-archlinux>
References: <20240529093336.4075206-1-davidgow@google.com>
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In-Reply-To: <20240529093336.4075206-1-davidgow@google.com>

On Wed, May 29, 2024 at 05:33:35PM +0800, David Gow wrote:
> 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>

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

Regards,
Boqun

> ---
>  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
>