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>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index bdaf60d3d33730038333da63962bc01b10a516a1..40e983ed994f5338a1a7fef1eb8bff3cf2698910 100644 (file)
--- 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)