x86, mce: export MCE severities coverage via debugfs

The MCE severity judgement code is data-driven, so code coverage tools
such as gcov can not be used for measuring coverage. Instead a dedicated
coverage mechanism is implemented.  The kernel keeps track of rules
executed and reports them in debugfs.

This is useful for increasing coverage of the mce-test testsuite.

Right now it's unconditionally enabled because it's very little code.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 83 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c
index 4f4d2caf4043..ff0807f97056 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -10,6 +10,9 @@
  * Author: Andi Kleen
  */
 #include <linux/kernel.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/debugfs.h>
 #include <asm/mce.h>
 
 #include "mce-internal.h"
@@ -37,6 +40,7 @@ static struct severity {
         unsigned char mcgres;
         unsigned char ser;
         unsigned char context;
+        unsigned char covered;
         char *msg;
 } severities[] = {
 #define KERNEL .context = IN_KERNEL
@@ -126,6 +130,7 @@ int mce_severity(struct mce *a, int tolerant, char **msg)
                         continue;
                 if (msg)
                         *msg = s->msg;
+                s->covered = 1;
                 if (s->sev >= MCE_UC_SEVERITY && ctx == IN_KERNEL) {
                         if (panic_on_oops || tolerant < 1)
                                 return MCE_PANIC_SEVERITY;
@@ -133,3 +138,81 @@ int mce_severity(struct mce *a, int tolerant, char **msg)
                 return s->sev;
         }
 }
+
+static void *s_start(struct seq_file *f, loff_t *pos)
+{
+        if (*pos >= ARRAY_SIZE(severities))
+                return NULL;
+        return &severities[*pos];
+}
+
+static void *s_next(struct seq_file *f, void *data, loff_t *pos)
+{
+        if (++(*pos) >= ARRAY_SIZE(severities))
+                return NULL;
+        return &severities[*pos];
+}
+
+static void s_stop(struct seq_file *f, void *data)
+{
+}
+
+static int s_show(struct seq_file *f, void *data)
+{
+        struct severity *ser = data;
+        seq_printf(f, "%d\t%s\n", ser->covered, ser->msg);
+        return 0;
+}
+
+static const struct seq_operations severities_seq_ops = {
+        .start  = s_start,
+        .next   = s_next,
+        .stop   = s_stop,
+        .show   = s_show,
+};
+
+static int severities_coverage_open(struct inode *inode, struct file *file)
+{
+        return seq_open(file, &severities_seq_ops);
+}
+
+static ssize_t severities_coverage_write(struct file *file,
+                                         const char __user *ubuf,
+                                         size_t count, loff_t *ppos)
+{
+        int i;
+        for (i = 0; i < ARRAY_SIZE(severities); i++)
+                severities[i].covered = 0;
+        return count;
+}
+
+static const struct file_operations severities_coverage_fops = {
+        .open           = severities_coverage_open,
+        .release        = seq_release,
+        .read           = seq_read,
+        .write          = severities_coverage_write,
+};
+
+static int __init severities_debugfs_init(void)
+{
+        struct dentry *dmce = NULL, *fseverities_coverage = NULL;
+
+        dmce = debugfs_create_dir("mce", NULL);
+        if (dmce == NULL)
+                goto err_out;
+        fseverities_coverage = debugfs_create_file("severities-coverage",
+                                                   0444, dmce, NULL,
+                                                   &severities_coverage_fops);
+        if (fseverities_coverage == NULL)
+                goto err_out;
+
+        return 0;
+
+err_out:
+        if (fseverities_coverage)
+                debugfs_remove(fseverities_coverage);
+        if (dmce)
+                debugfs_remove(dmce);
+        return -ENOMEM;
+}
+late_initcall(severities_debugfs_init);