s390: move spectre sysfs attribute code

BugLink: https://bugs.launchpad.net/bugs/1775477

[ Upstream commit 4253b0e0 ]

The nospec-branch.c file is compiled without the gcc options to
generate expoline thunks. The return branch of the sysfs show
functions cpu_show_spectre_v1 and cpu_show_spectre_v2 is an indirect
branch as well. These need to be compiled with expolines.

Move the sysfs functions for spectre reporting to a separate file
and loose an '.' for one of the messages.

Cc: stable@vger.kernel.org # 4.16
Fixes: d424986f ("s390: add sysfs attributes for spectre")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/s390/kernel/Makefile

@@ -49,6 +49,7 @@ obj-y	+= nospec-branch.o
 
 extra-y				+= head.o head64.o vmlinux.lds
 
+obj-$(CONFIG_SYSFS)		+= nospec-sysfs.o
 CFLAGS_REMOVE_nospec-branch.o	+= $(CC_FLAGS_EXPOLINE)
 
 obj-$(CONFIG_MODULES)		+= s390_ksyms.o module.o

arch/s390/kernel/nospec-branch.c

@@ -44,24 +44,6 @@ static int __init nospec_report(void)
 }
 arch_initcall(nospec_report);
 
-#ifdef CONFIG_SYSFS
-ssize_t cpu_show_spectre_v1(struct device *dev,
-			    struct device_attribute *attr, char *buf)
-{
-	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
-}
-
-ssize_t cpu_show_spectre_v2(struct device *dev,
-			    struct device_attribute *attr, char *buf)
-{
-	if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
-		return sprintf(buf, "Mitigation: execute trampolines\n");
-	if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
-		return sprintf(buf, "Mitigation: limited branch prediction.\n");
-	return sprintf(buf, "Vulnerable\n");
-}
-#endif
-
 #ifdef CONFIG_EXPOLINE
 
 int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);

arch/s390/kernel/nospec-sysfs.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/device.h>
+#include <linux/cpu.h>
+#include <asm/facility.h>
+#include <asm/nospec-branch.h>
+
+ssize_t cpu_show_spectre_v1(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+}
+
+ssize_t cpu_show_spectre_v2(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
+		return sprintf(buf, "Mitigation: execute trampolines\n");
+	if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
+		return sprintf(buf, "Mitigation: limited branch prediction\n");
+	return sprintf(buf, "Vulnerable\n");
+}