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rust: arch/um: Disable FP/SIMD instruction to match x86 

The kernel disables all SSE and similar FP/SIMD instructions on
x86-based architectures (partly because we shouldn't be using floats in
the kernel, and partly to avoid the need for stack alignment, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383 )

UML does not do the same thing, which isn't in itself a problem, but
does add to the list of differences between UML and "normal" x86 builds.

In addition, there was a crash bug with LLVM < 15 / rustc < 1.65 when
building with SSE, so disabling it fixes rust builds with earlier
compiler versions, see:
https://github.com/Rust-for-Linux/linux/pull/881

Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Sergio González Collado <sergio.collado@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
David Gow 2022-12-17 12:44:35 +08:00 committed by Richard Weinberger
parent 905a770775
commit 8849818679
1 changed files with 6 additions and 0 deletions
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6
arch/x86/Makefile.um
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@ -1,6 +1,12 @@
# SPDX-License-Identifier: GPL-2.0
core-y += arch/x86/crypto/
#
# Disable SSE and other FP/SIMD instructions to match normal x86
#
KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
ifeq ($(CONFIG_X86_32),y)
START := 0x8048000