This is a note to let you know that I've just added the patch titled
rust: arch/um: Disable FP/SIMD instruction to match x86
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rust-arch-um-disable-fp-simd-instruction-to-match-x86.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8849818679478933dd1d9718741f4daa3f4e8b86 Mon Sep 17 00:00:00 2001
From: David Gow <davidgow@xxxxxxxxxx>
Date: Sat, 17 Dec 2022 12:44:35 +0800
Subject: rust: arch/um: Disable FP/SIMD instruction to match x86
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From: David Gow <davidgow@xxxxxxxxxx>
commit 8849818679478933dd1d9718741f4daa3f4e8b86 upstream.
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@xxxxxxxxxx>
Reviewed-by: Sergio González Collado <sergio.collado@xxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/Makefile.um | 6 ++++++
1 file changed, 6 insertions(+)
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -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
Patches currently in stable-queue which might be from davidgow@xxxxxxxxxx are
queue-6.2/um-only-disable-sse-on-clang-to-work-around-old-gcc-bugs.patch
queue-6.2/rust-arch-um-disable-fp-simd-instruction-to-match-x86.patch
