selftests/fpu: move FP code to a separate translation unit

This ensures no compiler-generated floating-point code can appear outside
kernel_fpu_{begin,end}() sections, and some architectures enforce this
separation.

Link: https://lkml.kernel.org/r/20240329072441.591471-15-samuel.holland@sifive.com
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Xuerui <git@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/Makefile b/lib/Makefile
index 7a1fdd1cce7a08faf110c482b04d13c81fb4f289..87f8803587ae0c0ca32a5b8e167cc0455f3d1ab9 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -133,7 +133,8 @@ FPU_CFLAGS += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-st
 endif
 
 obj-$(CONFIG_TEST_FPU) += test_fpu.o
-CFLAGS_test_fpu.o += $(FPU_CFLAGS)
+test_fpu-y := test_fpu_glue.o test_fpu_impl.o
+CFLAGS_test_fpu_impl.o += $(FPU_CFLAGS)
 
 # 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).

diff --git a/lib/test_fpu.c b/lib/test_fpu.c
deleted file mode 100644 (file)
index e82db19..0000000
--- a/lib/test_fpu.c
+++ /dev/null
@@ -1,89 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Test cases for using floating point operations inside a kernel module.
- *
- * This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
- * when userland has modified the floating point control registers. The kernel
- * state might depend on the state set by the userland thread that was active
- * before a syscall.
- *
- * To facilitate the test, this module registers file
- * /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
- * sequence of floating point operations. If the operations fail, either the
- * read returns error status or the kernel crashes.
- * If the operations succeed, the read returns "1\n".
- */
-
-#include <linux/module.h>
-#include <linux/kernel.h>
-#include <linux/debugfs.h>
-#include <asm/fpu/api.h>
-
-static int test_fpu(void)
-{
-       /*
-        * This sequence of operations tests that rounding mode is
-        * to nearest and that denormal numbers are supported.
-        * Volatile variables are used to avoid compiler optimizing
-        * the calculations away.
-        */
-       volatile double a, b, c, d, e, f, g;
-
-       a = 4.0;
-       b = 1e-15;
-       c = 1e-310;
-
-       /* Sets precision flag */
-       d = a + b;
-
-       /* Result depends on rounding mode */
-       e = a + b / 2;
-
-       /* Denormal and very large values */
-       f = b / c;
-
-       /* Depends on denormal support */
-       g = a + c * f;
-
-       if (d > a && e > a && g > a)
-               return 0;
-       else
-               return -EINVAL;
-}
-
-static int test_fpu_get(void *data, u64 *val)
-{
-       int status = -EINVAL;
-
-       kernel_fpu_begin();
-       status = test_fpu();
-       kernel_fpu_end();
-
-       *val = 1;
-       return status;
-}
-
-DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
-static struct dentry *selftest_dir;
-
-static int __init test_fpu_init(void)
-{
-       selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
-       if (!selftest_dir)
-               return -ENOMEM;
-
-       debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
-                                  &test_fpu_fops);
-
-       return 0;
-}
-
-static void __exit test_fpu_exit(void)
-{
-       debugfs_remove(selftest_dir);
-}
-
-module_init(test_fpu_init);
-module_exit(test_fpu_exit);
-
-MODULE_LICENSE("GPL");

diff --git a/lib/test_fpu.h b/lib/test_fpu.h
new file mode 100644 (file)
index 0000000..4459807
--- /dev/null
+++ b/lib/test_fpu.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef _LIB_TEST_FPU_H
+#define _LIB_TEST_FPU_H
+
+int test_fpu(void);
+
+#endif

diff --git a/lib/test_fpu_glue.c b/lib/test_fpu_glue.c
new file mode 100644 (file)
index 0000000..85963d7
--- /dev/null
+++ b/lib/test_fpu_glue.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Test cases for using floating point operations inside a kernel module.
+ *
+ * This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
+ * when userland has modified the floating point control registers. The kernel
+ * state might depend on the state set by the userland thread that was active
+ * before a syscall.
+ *
+ * To facilitate the test, this module registers file
+ * /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
+ * sequence of floating point operations. If the operations fail, either the
+ * read returns error status or the kernel crashes.
+ * If the operations succeed, the read returns "1\n".
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <asm/fpu/api.h>
+
+#include "test_fpu.h"
+
+static int test_fpu_get(void *data, u64 *val)
+{
+       int status = -EINVAL;
+
+       kernel_fpu_begin();
+       status = test_fpu();
+       kernel_fpu_end();
+
+       *val = 1;
+       return status;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
+static struct dentry *selftest_dir;
+
+static int __init test_fpu_init(void)
+{
+       selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
+       if (!selftest_dir)
+               return -ENOMEM;
+
+       debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
+                                  &test_fpu_fops);
+
+       return 0;
+}
+
+static void __exit test_fpu_exit(void)
+{
+       debugfs_remove(selftest_dir);
+}
+
+module_init(test_fpu_init);
+module_exit(test_fpu_exit);
+
+MODULE_LICENSE("GPL");

diff --git a/lib/test_fpu_impl.c b/lib/test_fpu_impl.c
new file mode 100644 (file)
index 0000000..777894d
--- /dev/null
+++ b/lib/test_fpu_impl.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/errno.h>
+
+#include "test_fpu.h"
+
+int test_fpu(void)
+{
+       /*
+        * This sequence of operations tests that rounding mode is
+        * to nearest and that denormal numbers are supported.
+        * Volatile variables are used to avoid compiler optimizing
+        * the calculations away.
+        */
+       volatile double a, b, c, d, e, f, g;
+
+       a = 4.0;
+       b = 1e-15;
+       c = 1e-310;
+
+       /* Sets precision flag */
+       d = a + b;
+
+       /* Result depends on rounding mode */
+       e = a + b / 2;
+
+       /* Denormal and very large values */
+       f = b / c;
+
+       /* Depends on denormal support */
+       g = a + c * f;
+
+       if (d > a && e > a && g > a)
+               return 0;
+       else
+               return -EINVAL;
+}