[CRIU] [PATCH 6/8] restore: catch task on the exit from sigreturn (v2)

[Andrey Vagin]

A task is stopped here for unmaping restorer blob and restoring a state.

The method is the same as for parasite. CRIU attaches to processes via
ptrace and start to trace all syscalls.

v2: don't use a software breakpoint
Signed-off-by: Andrey Vagin <avagin at openvz.org>
---
 cr-restore.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/cr-restore.c b/cr-restore.c
index 8517672..ddfb9f9 100644
--- a/cr-restore.c
+++ b/cr-restore.c
@@ -64,6 +64,8 @@
 #include "stats.h"
 #include "tun.h"
 
+#include "parasite-syscall.h"
+
 #include "protobuf.h"
 #include "protobuf/sa.pb-c.h"
 #include "protobuf/timer.pb-c.h"
@@ -1321,6 +1323,65 @@ static int restore_switch_stage(int next_stage)
 	return restore_wait_inprogress_tasks();
 }
 
+static int attach_to_tasks()
+{
+	struct pstree_item *item;
+	int nr = 0;
+
+	for_each_pstree_item(item) {
+		pid_t pid = item->pid.real;
+		int status;
+
+		if (item->state == TASK_DEAD)
+			continue;
+
+		if (item->state == TASK_HELPER)
+			continue;
+
+		if (ptrace(PTRACE_ATTACH, pid, NULL, PTRACE_O_TRACEFORK)) {
+			pr_perror("Can't attach to %d", pid);
+			return -1;
+		}
+
+		if (waitpid(pid, &status, 0) < 0) {
+			pr_perror("waitpid() failed");
+			return -1;
+		}
+
+		if (ptrace(PTRACE_SYSCALL, pid, NULL, NULL)) {
+			pr_perror("ptrace");
+			return -1;
+		}
+
+		nr++;
+	}
+
+	return nr;
+}
+
+static void finalize_restore(int status)
+{
+	struct pstree_item *item;
+
+	for_each_pstree_item(item) {
+		pid_t pid = item->pid.real;
+
+		if (item->state == TASK_DEAD)
+			continue;
+
+		if (item->state == TASK_HELPER)
+			continue;
+
+		if (status  < 0)
+			goto detach;
+
+		/* TODO Unmap the restorer blob and restore the process state */
+detach:
+		if (ptrace(PTRACE_DETACH, pid, NULL, 0))
+			pr_perror("Unable to execute %d", pid);
+	}
+}
+
 static int restore_root_task(struct pstree_item *init)
 {
 	int ret, fd;
@@ -1433,9 +1494,16 @@ static int restore_root_task(struct pstree_item *init)
 
 	timing_stop(TIME_RESTORE);
 
+	ret = attach_to_tasks();
+
 	pr_info("Restore finished successfully. Resuming tasks.\n");
 	futex_set_and_wake(&task_entries->start, CR_STATE_COMPLETE);
 
+	if (ret > 0)
+		ret = parasite_stop_on_syscall(ret, __NR_rt_sigreturn);
+
+	finalize_restore(ret);
+
 	write_stats(RESTORE_STATS);
 
 	if (!opts.restore_detach)
-- 
1.8.3.1