Add [start]wait command to ctl, first iteration

[currently only wakes up the debugger(s) when the child exits]

Author: igorcanadi

fs/proc/base.c

@@ -1024,7 +1024,24 @@ static int ctl_get_sigmask(const char __user *buf, int count) {
 return retval;
 }
 
-static ssize_t ctl_write(struct file * file, const char __user *buf,
+
+static int ctl_wait(struct task_struct *task, int start_the_task) {
+DEFINE_WAIT(wait);
+
+printk("PROCTRACE waiting %d task with %d\n", task->pid, current->pid);
+
+if (start_the_task) {
+wake_up_process(task);
+}
+
+prepare_to_wait(&task->wq_for_stop, &wait, TASK_INTERRUPTIBLE);
+schedule();
+finish_wait(&task->wq_for_stop, &wait);
+
+return 0;
+}
+
+static ssize_t ctl_write(struct file *file, const char __user *buf,
  size_t count, loff_t *ppos)
 {
 struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
@@ -1033,10 +1050,14 @@ static ssize_t ctl_write(struct file * file, const char __user *buf,
 ctl_waitsignal(task, ctl_get_sigmask(buf + 11, count - 11), 0);
 } else if (strncmp(buf, "startwaitsignal", 15) == 0) {
 ctl_waitsignal(task, ctl_get_sigmask(buf + 16, count - 16), 1);
+} else if (strncmp(buf, "startwait", 9) == 0) {
+ctl_wait(task, 1);
 } else if (strncmp(buf, "stop", 4) == 0) {
 ctl_stop(task);
 } else if (strncmp(buf, "start", 5) == 0) {
 ctl_start(task);
+} else if (strncmp(buf, "wait", 4) == 0) {
+ctl_wait(task, 0);
 }
 
 return count;

include/linux/init_task.h

@@ -155,6 +155,7 @@ extern struct cred init_cred;
 INIT_PUSHABLE_TASKS(tsk)	\
 .ptraced	= LIST_HEAD_INIT(tsk.ptraced),	\
 .ptrace_entry	= LIST_HEAD_INIT(tsk.ptrace_entry),	\
+.wq_for_stop	= __WAIT_QUEUE_HEAD_INITIALIZER(tsk.wq_for_stop),\
 .sig_wait_list = LIST_HEAD_INIT(tsk.sig_wait_list),	\
 .real_parent	= &tsk,	\
 .parent	= &tsk,	\

include/linux/sched.h

@@ -1343,6 +1343,9 @@ struct task_struct {
 struct list_head ptraced;
 struct list_head ptrace_entry;
 
+/* Debuggers waiting for child to stop or exit */
+wait_queue_head_t wq_for_stop;
+/* Debuggers waiting for child to get a signal or exit */
 struct list_head sig_wait_list;
 
 /* PID/PID hash table linkage. */

kernel/fork.c

@@ -1302,7 +1302,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 p->pdeath_signal = 0;
 p->exit_state = 0;
 
-/* Initialize signal wait queue list */
+/* Initialize proctrace data structures */
+init_waitqueue_head(&p->wq_for_stop);
 INIT_LIST_HEAD(&p->sig_wait_list);
 
 /*

kernel/signal.c

@@ -1666,6 +1666,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 __wake_up_parent(tsk, tsk->parent);
 
 /* also notify all the proctraces */
+wake_up(&tsk->wq_for_stop);
 list_for_each(p, &tsk->sig_wait_list) {
 printk("PROCTRACE budim frajera jer je child umro\n");
 wake_up(&list_entry(