ftrace: use struct pid

Impact: clean up, extend PID filtering to PID namespaces

Eric Biederman suggested using the struct pid for filtering on
pids in the kernel. This patch is based off of a demonstration
of an implementation that Eric sent me in an email.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 46 insertions, 34 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 57592a9dd630..10b1d7c1b1dd 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -48,7 +48,7 @@ int ftrace_enabled __read_mostly;
 static int last_ftrace_enabled;
 
 /* set when tracing only a pid */
-int ftrace_pid_trace = -1;
+struct pid *ftrace_pid_trace;
 
 /* Quick disabling of function tracer. */
 int function_trace_stop;
@@ -153,7 +153,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
                 else
                         func = ftrace_list_func;
 
-                if (ftrace_pid_trace >= 0) {
+                if (ftrace_pid_trace) {
                         set_ftrace_pid_function(func);
                         func = ftrace_pid_func;
                 }
@@ -209,7 +209,7 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
                 if (ftrace_list->next == &ftrace_list_end) {
                         ftrace_func_t func = ftrace_list->func;
 
-                        if (ftrace_pid_trace >= 0) {
+                        if (ftrace_pid_trace) {
                                 set_ftrace_pid_function(func);
                                 func = ftrace_pid_func;
                         }
@@ -239,7 +239,7 @@ static void ftrace_update_pid_func(void)
 
         func = ftrace_trace_function;
 
-        if (ftrace_pid_trace >= 0) {
+        if (ftrace_pid_trace) {
                 set_ftrace_pid_function(func);
                 func = ftrace_pid_func;
         } else {
@@ -1678,18 +1678,40 @@ ftrace_pid_read(struct file *file, char __user *ubuf,
         char buf[64];
         int r;
 
-        if (ftrace_pid_trace >= 0)
-                r = sprintf(buf, "%u\n", ftrace_pid_trace);
+        if (ftrace_pid_trace)
+                r = sprintf(buf, "%u\n", pid_nr(ftrace_pid_trace));
         else
                 r = sprintf(buf, "no pid\n");
 
         return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 }
 
+static void clear_ftrace_pid_task(struct pid **pid)
+{
+        struct task_struct *p;
+
+        do_each_pid_task(*pid, PIDTYPE_PID, p) {
+                clear_tsk_trace_trace(p);
+        } while_each_pid_task(*pid, PIDTYPE_PID, p);
+        put_pid(*pid);
+
+        *pid = NULL;
+}
+
+static void set_ftrace_pid_task(struct pid *pid)
+{
+        struct task_struct *p;
+
+        do_each_pid_task(pid, PIDTYPE_PID, p) {
+                set_tsk_trace_trace(p);
+        } while_each_pid_task(pid, PIDTYPE_PID, p);
+}
+
 static ssize_t
 ftrace_pid_write(struct file *filp, const char __user *ubuf,
                    size_t cnt, loff_t *ppos)
 {
+        struct pid *pid;
         char buf[64];
         long val;
         int ret;
@@ -1707,40 +1729,30 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
                 return ret;
 
         mutex_lock(&ftrace_start_lock);
-        if (ret < 0) {
+        if (val < 0) {
                 /* disable pid tracing */
-                if (ftrace_pid_trace < 0)
+                if (!ftrace_pid_trace)
                         goto out;
-                ftrace_pid_trace = -1;
+
+                clear_ftrace_pid_task(&ftrace_pid_trace);
 
         } else {
-                struct task_struct *p;
-                int found = 0;
+                pid = find_get_pid(val);
 
-                if (ftrace_pid_trace == val)
+                if (pid == ftrace_pid_trace) {
+                        put_pid(pid);
                         goto out;
-
-                /*
-                 * Find the task that matches this pid.
-                 * TODO: use pid namespaces instead.
-                 */
-                rcu_read_lock();
-                for_each_process(p) {
-                        if (p->pid == val) {
-                                found = 1;
-                                set_tsk_trace_trace(p);
-                        } else if (test_tsk_trace_trace(p))
-                                clear_tsk_trace_trace(p);
                 }
-                rcu_read_unlock();
 
-                if (found)
-                        ftrace_pid_trace = val;
-                else {
-                        if (ftrace_pid_trace < 0)
-                                goto out;
-                        ftrace_pid_trace = -1;
-                }
+                if (ftrace_pid_trace)
+                        clear_ftrace_pid_task(&ftrace_pid_trace);
+
+                if (!pid)
+                        goto out;
+
+                ftrace_pid_trace = pid;
+
+                set_ftrace_pid_task(ftrace_pid_trace);
         }
 
         /* update the function call */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 95fff37ed970..8b81b4d727bd 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -541,11 +541,11 @@ print_graph_function(struct trace_iterator *iter)
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
-extern int ftrace_pid_trace;
+extern struct pid *ftrace_pid_trace;
 
 static inline int ftrace_trace_task(struct task_struct *task)
 {
-        if (ftrace_pid_trace < 0)
+        if (ftrace_pid_trace)
                 return 1;
 
         return test_tsk_trace_trace(task);