RAS, debugfs: Add debugfs interface for RAS subsystem

Implement a new debugfs interface for RAS susbsystem.
A file named daemon_active is added there accordingly.
This file is used to track if user space daemon accesses
perf/trace interface or not. One can track which daemon
opens it via "lsof /path/to/debugfs/ras/daemon_active".

Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1402475691-30045-5-git-send-email-gong.chen@linux.intel.com
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>

3 files changed, 71 insertions, 1 deletions

diff --git a/drivers/ras/Makefile b/drivers/ras/Makefile
index 223e806fa5bf..d7f73341ced3 100644
--- a/drivers/ras/Makefile
+++ b/drivers/ras/Makefile
@@ -1 +1 @@
-obj-$(CONFIG_RAS) += ras.o
+obj-$(CONFIG_RAS) += ras.o debugfs.o
diff --git a/drivers/ras/debugfs.c b/drivers/ras/debugfs.c
new file mode 100644
index 000000000000..0322acf67ea5
--- /dev/null
+++ b/drivers/ras/debugfs.c
@@ -0,0 +1,56 @@
+#include <linux/debugfs.h>
+
+static struct dentry *ras_debugfs_dir;
+
+static atomic_t trace_count = ATOMIC_INIT(0);
+
+int ras_userspace_consumers(void)
+{
+        return atomic_read(&trace_count);
+}
+EXPORT_SYMBOL_GPL(ras_userspace_consumers);
+
+static int trace_show(struct seq_file *m, void *v)
+{
+        return atomic_read(&trace_count);
+}
+
+static int trace_open(struct inode *inode, struct file *file)
+{
+        atomic_inc(&trace_count);
+        return single_open(file, trace_show, NULL);
+}
+
+static int trace_release(struct inode *inode, struct file *file)
+{
+        atomic_dec(&trace_count);
+        return single_release(inode, file);
+}
+
+static const struct file_operations trace_fops = {
+        .open    = trace_open,
+        .read    = seq_read,
+        .llseek  = seq_lseek,
+        .release = trace_release,
+};
+
+int __init ras_add_daemon_trace(void)
+{
+        struct dentry *fentry;
+
+        if (!ras_debugfs_dir)
+                return -ENOENT;
+
+        fentry = debugfs_create_file("daemon_active", S_IRUSR, ras_debugfs_dir,
+                                     NULL, &trace_fops);
+        if (!fentry)
+                return -ENODEV;
+
+        return 0;
+
+}
+
+void __init ras_debugfs_init(void)
+{
+        ras_debugfs_dir = debugfs_create_dir("ras", NULL);
+}
diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
index b0c6ed1d8e77..4cac43a1e25c 100644
--- a/drivers/ras/ras.c
+++ b/drivers/ras/ras.c
@@ -5,8 +5,22 @@
  *      Chen, Gong <gong.chen@linux.intel.com>
  */
 
+#include <linux/init.h>
+#include <linux/ras.h>
+
 #define CREATE_TRACE_POINTS
 #define TRACE_INCLUDE_PATH ../../include/ras
 #include <ras/ras_event.h>
 
+static int __init ras_init(void)
+{
+        int rc = 0;
+
+        ras_debugfs_init();
+        rc = ras_add_daemon_trace();
+
+        return rc;
+}
+subsys_initcall(ras_init);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(mc_event);