tracing: Add syscall tracepoints

add two tracepoints in syscall exit and entry path, conditioned on
TIF_SYSCALL_FTRACE. Supports the syscall trace event code.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 1ef5d3a601c7..070a42bb8920 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -24,6 +24,7 @@
 #include <linux/tracepoint.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/sched.h>
 
 extern struct tracepoint __start___tracepoints[];
 extern struct tracepoint __stop___tracepoints[];
@@ -577,3 +578,40 @@ static int init_tracepoints(void)
 __initcall(init_tracepoints);
 
 #endif /* CONFIG_MODULES */
+
+static DEFINE_MUTEX(regfunc_mutex);
+static int sys_tracepoint_refcount;
+
+void syscall_regfunc(void)
+{
+        unsigned long flags;
+        struct task_struct *g, *t;
+
+        mutex_lock(&regfunc_mutex);
+        if (!sys_tracepoint_refcount) {
+                read_lock_irqsave(&tasklist_lock, flags);
+                do_each_thread(g, t) {
+                        set_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
+                } while_each_thread(g, t);
+                read_unlock_irqrestore(&tasklist_lock, flags);
+        }
+        sys_tracepoint_refcount++;
+        mutex_unlock(&regfunc_mutex);
+}
+
+void syscall_unregfunc(void)
+{
+        unsigned long flags;
+        struct task_struct *g, *t;
+
+        mutex_lock(&regfunc_mutex);
+        sys_tracepoint_refcount--;
+        if (!sys_tracepoint_refcount) {
+                read_lock_irqsave(&tasklist_lock, flags);
+                do_each_thread(g, t) {
+                        clear_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
+                } while_each_thread(g, t);
+                read_unlock_irqrestore(&tasklist_lock, flags);
+        }
+        mutex_unlock(&regfunc_mutex);
+}