tracing: add options directory and core option files

This patch creates an options directory in the debugfs, that contains
the available tracing options. These files contain 1 or 0, where 1
is the option is enabled and 0 it is disabled.

Simply echoing in 1 will enable the option and 0 will disable it.
This patch only contains the core options, not the tracer options.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bdaf60d3d337..40e983ed994f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3093,6 +3093,121 @@ static void tracing_init_debugfs_percpu(long cpu)
 #include "trace_selftest.c"
 #endif
 
+static ssize_t
+trace_options_core_read(struct file *filp, char __user *ubuf, size_t cnt,
+                        loff_t *ppos)
+{
+        long index = (long)filp->private_data;
+        char *buf;
+
+        if (trace_flags & (1 << index))
+                buf = "1\n";
+        else
+                buf = "0\n";
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
+}
+
+static ssize_t
+trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
+                         loff_t *ppos)
+{
+        long index = (long)filp->private_data;
+        char buf[64];
+        unsigned long val;
+        int ret;
+
+        if (cnt >= sizeof(buf))
+                return -EINVAL;
+
+        if (copy_from_user(&buf, ubuf, cnt))
+                return -EFAULT;
+
+        buf[cnt] = 0;
+
+        ret = strict_strtoul(buf, 10, &val);
+        if (ret < 0)
+                return ret;
+
+        switch (val) {
+        case 0:
+                trace_flags &= ~(1 << index);
+                break;
+        case 1:
+                trace_flags |= 1 << index;
+                break;
+
+        default:
+                return -EINVAL;
+        }
+
+        *ppos += cnt;
+
+        return cnt;
+}
+
+
+static const struct file_operations trace_options_core_fops = {
+        .open = tracing_open_generic,
+        .read = trace_options_core_read,
+        .write = trace_options_core_write,
+};
+
+static struct dentry *trace_options_init_dentry(void)
+{
+        struct dentry *d_tracer;
+        static struct dentry *t_options;
+
+        if (t_options)
+                return t_options;
+
+        d_tracer = tracing_init_dentry();
+        if (!d_tracer)
+                return NULL;
+
+        t_options = debugfs_create_dir("options", d_tracer);
+        if (!t_options) {
+                pr_warning("Could not create debugfs directory 'options'\n");
+                return NULL;
+        }
+
+        return t_options;
+}
+
+static struct dentry *
+create_trace_option_core_file(const char *option, long index)
+{
+        struct dentry *t_options;
+        struct dentry *entry;
+
+        t_options = trace_options_init_dentry();
+        if (!t_options)
+                return NULL;
+
+        entry = debugfs_create_file(option, 0644, t_options, (void *)index,
+                                    &trace_options_core_fops);
+
+        return entry;
+}
+
+static __init void create_trace_options_dir(void)
+{
+        struct dentry *t_options;
+        struct dentry *entry;
+        int i;
+
+        t_options = trace_options_init_dentry();
+        if (!t_options)
+                return;
+
+        for (i = 0; trace_options[i]; i++) {
+                entry = create_trace_option_core_file(trace_options[i], i);
+                if (!entry)
+                        pr_warning("Could not create debugfs %s entry\n",
+                                   trace_options[i]);
+        }
+}
+
 static __init int tracer_init_debugfs(void)
 {
         struct dentry *d_tracer;
@@ -3111,6 +3226,8 @@ static __init int tracer_init_debugfs(void)
         if (!entry)
                 pr_warning("Could not create debugfs 'trace_options' entry\n");
 
+        create_trace_options_dir();
+
         entry = debugfs_create_file("tracing_cpumask", 0644, d_tracer,
                                     NULL, &tracing_cpumask_fops);
         if (!entry)