[PATCH 16] introduce the empty struct ptrace_context

[Oleg Nesterov]

(relies on 471d6f49e9b9be7830adf1a47f18f5ba90a05041
 "utrace_engine_ops: add release hook" in utrace-dtor)

Introduce the empty struct ptrace_context, change ptrace_attach_task()
to setup engine->data.

It should be used for ptrace_set_action() and ptrace_set_stop_event(),
the current usage of ->ptrace is racy.

Also, ->exit_code and ->last_siginfo should live in engine->data too.

Eventually, all ptrace-related members should be moved from task_struct.

---

 kernel/ptrace.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

--- PU/kernel/ptrace.c~16_PTRACE_CONTEXT	2009-09-02 17:50:58.000000000 +0200
+++ PU/kernel/ptrace.c	2009-09-02 19:48:53.000000000 +0200
@@ -24,6 +24,8 @@
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 
+struct ptrace_context {
+};
 
 /*
  * ptrace a task: make the debugger its new parent and
@@ -467,6 +469,11 @@ static u32 ptrace_report_quiesce(u32 act
 	return ptrace_resume_action(task);
 }
 
+static void ptrace_release(void *data)
+{
+	kfree(data);
+}
+
 static const struct utrace_engine_ops ptrace_utrace_ops = {
 	.report_signal = ptrace_report_signal,
 	.report_quiesce = ptrace_report_quiesce,
@@ -475,6 +482,7 @@ static const struct utrace_engine_ops pt
 	.report_clone = ptrace_report_clone,
 	.report_syscall_entry = ptrace_report_syscall_entry,
 	.report_syscall_exit = ptrace_report_syscall_exit,
+	.release = ptrace_release,
 };
 
 /*
@@ -483,18 +491,24 @@ static const struct utrace_engine_ops pt
  */
 static int ptrace_attach_task(struct task_struct *tracee)
 {
+	struct ptrace_context *context;
 	struct utrace_engine *engine;
 	unsigned long events;
 	int err;
 
+	context = kzalloc(sizeof(*context), GFP_KERNEL);
+	if (unlikely(!context))
+		return -ENOMEM;
+
 	engine = utrace_attach_task(tracee, UTRACE_ATTACH_CREATE |
 						UTRACE_ATTACH_EXCLUSIVE |
 						UTRACE_ATTACH_MATCH_OPS,
-						&ptrace_utrace_ops, NULL);
+						&ptrace_utrace_ops, context);
 	if (unlikely(IS_ERR(engine))) {
 		err = PTR_ERR(engine);
 		if (err != -ESRCH && err != -ERESTARTNOINTR)
 			err = -EPERM;
+		kfree(context);
 		return err;
 	}
 	/*