linux-kernel - [RFC PATCH 12/12] selftests/fpu: Allow building on other architectures

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Date:   Thu,  7 Dec 2023 21:54:42 -0800
From:   Samuel Holland <samuel.holland@...ive.com>
To:     linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-riscv@...ts.infradead.org,
        Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        linux-arch@...r.kernel.org,
        Samuel Holland <samuel.holland@...ive.com>
Subject: [RFC PATCH 12/12] selftests/fpu: Allow building on other architectures

Now that ARCH_HAS_KERNEL_FPU_SUPPORT provides a common way to compile
and run floating-point code, this test is no longer x86-specific.

Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

 lib/Kconfig.debug   |  2 +-
 lib/Makefile        | 25 ++-----------------------
 lib/test_fpu_glue.c |  5 ++++-
 3 files changed, 7 insertions(+), 25 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cc7d53d9dc01..bbab0b054e09 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2933,7 +2933,7 @@ config TEST_FREE_PAGES
 
 config TEST_FPU
 	tristate "Test floating point operations in kernel space"
-	depends on X86 && !KCOV_INSTRUMENT_ALL
+	depends on ARCH_HAS_KERNEL_FPU_SUPPORT && !KCOV_INSTRUMENT_ALL
 	help
 	  Enable this option to add /sys/kernel/debug/selftest_helpers/test_fpu
 	  which will trigger a sequence of floating point operations. This is used
diff --git a/lib/Makefile b/lib/Makefile
index e7cbd54944a2..b9f28558c9bd 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -109,31 +109,10 @@ CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
 obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
 obj-$(CONFIG_TEST_OBJPOOL) += test_objpool.o
 
-#
-# CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns
-# off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
-# get appended last to CFLAGS and thus override those previous compiler options.
-#
-FPU_CFLAGS := -msse -msse2
-ifdef CONFIG_CC_IS_GCC
-# Stack alignment mismatch, proceed with caution.
-# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
-# (8B stack alignment).
-# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
-#
-# The "-msse" in the first argument is there so that the
-# -mpreferred-stack-boundary=3 build error:
-#
-#  -mpreferred-stack-boundary=3 is not between 4 and 12
-#
-# can be triggered. Otherwise gcc doesn't complain.
-FPU_CFLAGS += -mhard-float
-FPU_CFLAGS += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
-endif
-
 obj-$(CONFIG_TEST_FPU) += test_fpu.o
 test_fpu-y := test_fpu_glue.o test_fpu_impl.o
-CFLAGS_test_fpu_impl.o += $(FPU_CFLAGS)
+CFLAGS_test_fpu_impl.o += $(CC_FLAGS_FPU)
+CFLAGS_REMOVE_test_fpu_impl.o += $(CC_FLAGS_NO_FPU)
 
 obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/
 
diff --git a/lib/test_fpu_glue.c b/lib/test_fpu_glue.c
index 2761b51117b0..2e0b4027a5e3 100644
--- a/lib/test_fpu_glue.c
+++ b/lib/test_fpu_glue.c
@@ -17,7 +17,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/debugfs.h>
-#include <asm/fpu/api.h>
+#include <asm/fpu.h>
 
 int test_fpu(void);
 
@@ -38,6 +38,9 @@ static struct dentry *selftest_dir;
 
 static int __init test_fpu_init(void)
 {
+	if (!kernel_fpu_available())
+		return -EINVAL;
+
 	selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
 	if (!selftest_dir)
 		return -ENOMEM;
-- 
2.42.0