ptrace: Fix to use new (final) SEIZE functionality

Since 3.4-rc the seize-devel flag is removed, the stop event
is renamed (great) and the way si_code should be parsed has
been fixed.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/ptrace.h

@@ -22,7 +22,7 @@
 #define PTRACE_EVENT_EXEC	4
 #define PTRACE_EVENT_VFORK_DONE	5
 #define PTRACE_EVENT_EXIT	6
-#define PTRACE_EVENT_STOP	7
+#define PTRACE_EVENT_STOP	128
 
 #define PTRACE_O_TRACESYSGOOD	0x00000001
 #define PTRACE_O_TRACEFORK	0x00000002

parasite-syscall.c

@@ -171,7 +171,7 @@ retry_signal:
 			goto err;
 		}
 
-		if (siginfo.si_code >> 8 != PTRACE_EVENT_STOP)
+		if (((siginfo.si_code & 0xffff) >> 8) != PTRACE_EVENT_STOP)
 			goto retry_signal;
 
 		/*
@@ -218,7 +218,7 @@ retry_signal:
 		goto err;
 	}
 
-	if (siginfo.si_code >> 8 != PTRACE_EVENT_STOP) {
+	if (((siginfo.si_code & 0xffff) >> 8) != PTRACE_EVENT_STOP) {
 		pr_err("si_code doesn't match (pid: %d si_code: %d)\n",
 			pid, siginfo.si_code);
 		goto err;

ptrace.c

@@ -51,8 +51,7 @@ int seize_task(pid_t pid, pid_t ppid, pid_t *pgid, pid_t *sid)
 	int ret, ret2;
 	struct proc_pid_stat_small ps;
 
-	ret = ptrace(PTRACE_SEIZE, pid, NULL,
-		       (void *)(unsigned long)PTRACE_SEIZE_DEVEL);
+	ret = ptrace(PTRACE_SEIZE, pid, NULL, 0);
 
 	/*
 	 * It's ugly, but the ptrace API doesn't allow to distinguish
@@ -114,7 +113,7 @@ try_again:
 		goto err;
 	}
 
-	if ((si.si_code >> 8) != PTRACE_EVENT_STOP) {
+	if (((si.si_code & 0xffff)>> 8) != PTRACE_EVENT_STOP) {
 		/*
 		 * Kernel notifies us about the task being seized received some
 		 * event other than the STOP, i.e. -- a signal. Let the task