alpha: Implement CPU vulnerabilities sysfs functions.

Implement the CPU vulnerabilty show functions for meltdown, spectre_v1
and spectre_v2 on Alpha.

Tests on XP1000 (EV67/667MHz) and ES45 (EV68CB/1.25GHz) show them
to be vulnerable to Meltdown and Spectre V1.  In the case of
Meltdown I saw a 1 to 2% success rate in reading bytes on the
XP1000 and 50 to 60% success rate on the ES45. (This compares to
99.97% success reported for Intel CPUs.)  Report EV6 and later
CPUs as vulnerable.

Tests on PWS600au (EV56/600MHz) for Spectre V1 attack were
unsuccessful (though I did not try particularly hard) so mark EV4
through to EV56 as not vulnerable.
Signed-off-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Matt Turner <mattst88@gmail.com>

arch/alpha/Kconfig

@@ -18,6 +18,7 @@ config ALPHA
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select AUDIT_ARCH
 	select GENERIC_CLOCKEVENTS
+	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER

arch/alpha/kernel/Makefile

@@ -9,7 +9,7 @@ ccflags-y	:= -Wno-sign-compare
 
 obj-y    := entry.o traps.o process.o osf_sys.o irq.o \
 	    irq_alpha.o signal.o setup.o ptrace.o time.o \
-	    systbls.o err_common.o io.o
+	    systbls.o err_common.o io.o bugs.o
 
 obj-$(CONFIG_VGA_HOSE)	+= console.o
 obj-$(CONFIG_SMP)	+= smp.o

arch/alpha/kernel/bugs.c

+
+#include <asm/hwrpb.h>
+#include <linux/device.h>
+
+
+#ifdef CONFIG_SYSFS
+
+static int cpu_is_ev6_or_later(void)
+{
+	struct percpu_struct *cpu;
+        unsigned long cputype;
+
+        cpu = (struct percpu_struct *)((char *)hwrpb + hwrpb->processor_offset);
+        cputype = cpu->type & 0xffffffff;
+        /* Include all of EV6, EV67, EV68, EV7, EV79 and EV69. */
+        return (cputype == EV6_CPU) || ((cputype >= EV67_CPU) && (cputype <= EV69_CPU));
+}
+
+ssize_t cpu_show_meltdown(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	if (cpu_is_ev6_or_later())
+		return sprintf(buf, "Vulnerable\n");
+	else
+		return sprintf(buf, "Not affected\n");
+}
+
+ssize_t cpu_show_spectre_v1(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+	if (cpu_is_ev6_or_later())
+		return sprintf(buf, "Vulnerable\n");
+	else
+		return sprintf(buf, "Not affected\n");
+}
+
+ssize_t cpu_show_spectre_v2(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	if (cpu_is_ev6_or_later())
+		return sprintf(buf, "Vulnerable\n");
+	else
+		return sprintf(buf, "Not affected\n");
+}
+#endif