lkml.org 
[lkml]   [2022]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH 2/3] rust: arch/um: Disable FP/SIMD instruction to match x86
From
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>
---
arch/x86/Makefile.um | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index b3c1ae084180..d2e95d1d4db7 100644
--- 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

--
2.39.0.314.g84b9a713c41-goog
\
 
 \ /
  Last update: 2022-12-17 05:46    [W:0.066 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site