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.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Samuel Holland <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Acked-by: Christian König <[email protected]> 
Cc: Alex Deucher <[email protected]>
Cc: Borislav Petkov (AMD) <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Nicolas Schier <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Russell King <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: WANG Xuerui <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: SiFiveHolland

lib/Kconfig.debug

@@ -2926,7 +2926,7 @@ 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

lib/Makefile

@@ -110,31 +110,10 @@ 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)
 
 # Some KUnit files (hooks.o) need to be built-in even when KUnit is a module,
 # so we can't just use obj-$(CONFIG_KUNIT).

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 <linux/fpu.h>
 
 #include "test_fpu.h"
 
@@ -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;