xids: Save pgid and sid on pstree_Item and pstree_entry

I store them on _entry since sids can only be inherited or
set to current's pid. Thus the best we can do it restore sids
at fork time, thus save them in the image we use to fork.

Maybe when we submit patches that will give us ability to set
arbitrary pgid and sid we'll change this, but this is in the
future.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -1105,7 +1105,7 @@ static int seize_threads(const struct pstree_item *item)
 			continue;
 
 		pr_info("\tSeizing %d's %d thread\n", item->pid, item->threads[i]);
-		ret = seize_task(item->threads[i], item_ppid(item));
+		ret = seize_task(item->threads[i], item_ppid(item), NULL, NULL);
 		if (ret < 0)
 			goto err;
 
@@ -1159,7 +1159,7 @@ static struct pstree_item *collect_task(pid_t pid, struct pstree_item *parent,
 	item->pid = pid;
 	item->parent = parent;
 
-	ret = seize_task(pid, item_ppid(item));
+	ret = seize_task(pid, item_ppid(item), &item->pgid, &item->sid);
 	if (ret < 0)
 		goto err_free;
 
@@ -1327,6 +1327,8 @@ static int dump_pstree(pid_t pid, const struct list_head *pstree_list)
 			item->pid, item->nr_children);
 
 		e.pid		= item->pid;
+		e.pgid		= item->pgid;
+		e.sid		= item->sid;
 		e.nr_children	= item->nr_children;
 		e.nr_threads	= item->nr_threads;
 

cr-restore.c

@@ -230,6 +230,8 @@ static int prepare_pstree(void)
 			break;
 
 		pi->pid = e.pid;
+		pi->pgid = e.pgid;
+		pi->sid = e.sid;
 
 		ret = -1;
 		pi->nr_children = e.nr_children;

cr-show.c

@@ -358,8 +358,8 @@ static int show_collect_pstree(int fd_pstree, struct list_head *collect)
 		ret = read_img_eof(fd_pstree, &e);
 		if (ret <= 0)
 			goto out;
-		pr_msg("pid: %8d nr_children: %8d nr_threads: %8d\n",
-		       e.pid, e.nr_children, e.nr_threads);
+		pr_msg("pid: %8d pgid: %8d sid %8d  nr_children: %8d nr_threads: %8d\n",
+		       e.pid, e.pgid, e.sid, e.nr_children, e.nr_threads);
 
 		if (collect) {
 			item = xzalloc(sizeof(struct pstree_item));

include/crtools.h

@@ -177,6 +177,8 @@ struct pstree_item {
 	struct list_head	list;
 	pid_t			pid;		/* leader pid */
 	struct pstree_item	*parent;
+	pid_t			pgid;
+	pid_t			sid;
 	int			state;		/* TASK_XXX constants */
 	int			nr_children;	/* number of children */
 	int			nr_threads;	/* number of threads */

include/image.h

@@ -69,6 +69,8 @@ struct fs_entry {
 
 struct pstree_entry {
 	u32	pid;
+	u32	pgid;
+	u32	sid;
 	u32	nr_children;
 	u32	nr_threads;
 } __packed;

include/ptrace.h

@@ -32,7 +32,7 @@
 #define PTRACE_O_TRACEVFORKDONE	0x00000020
 #define PTRACE_O_TRACEEXIT	0x00000040
 
-extern int seize_task(pid_t pid, pid_t ppid);
+extern int seize_task(pid_t pid, pid_t ppid, pid_t *pgid, pid_t *sid);
 extern int unseize_task(pid_t pid, int state);
 extern int ptrace_peek_area(pid_t pid, void *dst, void *addr, long bytes);
 extern int ptrace_poke_area(pid_t pid, void *src, void *addr, long bytes);

ptrace.c

@@ -44,7 +44,7 @@ int unseize_task(pid_t pid, int st)
  * up with someone else.
  */
 
-int seize_task(pid_t pid, pid_t ppid)
+int seize_task(pid_t pid, pid_t ppid, pid_t *pgid, pid_t *sid)
 {
 	siginfo_t si;
 	int status;
@@ -53,10 +53,23 @@ int seize_task(pid_t pid, pid_t ppid)
 
 	ret = ptrace(PTRACE_SEIZE, pid, NULL,
 		       (void *)(unsigned long)PTRACE_SEIZE_DEVEL);
+
+	/*
+	 * It's ugly, but the ptrace API doesn't allow to distinguish
+	 * attaching to zombie from other errors. Thus we have to parse
+	 * the target's /proc/pid/stat. Sad, but parse whatever else
+	 * we might nead at that early point.
+	 */
+
 	ret2 = parse_pid_stat_small(pid, &ps);
 	if (ret2 < 0)
 		return -1;
 
+	if (pgid)
+		*pgid = ps.pgid;
+	if (sid)
+		*sid = ps.sid;
+
 	if (ret < 0) {
 		if (ps.state != 'Z') {
 			pr_err("Unseizeable non-zombie %d found, state %c\n",