pie: paresite -- Print error codes from syscalls

In case if we hit error returned from syscall, better
to print error code for easier understanding of the
protblem.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

pie/parasite.c

@@ -90,7 +90,7 @@ static int dump_sigact(struct parasite_dump_sa_args *da)
 
 		ret = sys_sigaction(sig, NULL, &da->sas[i], sizeof(k_rtsigset_t));
 		if (ret < 0) {
-			pr_err("sys_sigaction failed\n");
+			pr_err("sys_sigaction failed (%d)\n", ret);
 			break;
 		}
 	}
@@ -109,7 +109,7 @@ static int dump_itimers(struct parasite_dump_itimers_args *args)
 		ret = sys_getitimer(ITIMER_PROF, &args->prof);
 
 	if (ret)
-		pr_err("getitimer failed\n");
+		pr_err("getitimer failed (%d)\n", ret);
 
 	return ret;
 }
@@ -122,13 +122,13 @@ static int dump_posix_timers(struct parasite_dump_posix_timers_args *args)
 	for(i = 0; i < args->timer_n; i++){
 		ret = sys_timer_gettime(args->timer[i].it_id, &args->timer[i].val);
 		if (ret < 0) {
-			pr_err("sys_timer_gettime failed\n");
+			pr_err("sys_timer_gettime failed (%d)\n", ret);
 			return ret;
 		}
 		args->timer[i].overrun = sys_timer_getoverrun(args->timer[i].it_id);
 		ret = args->timer[i].overrun;
 		if (ret < 0) {
-			pr_err("sys_timer_getoverrun failed\n");
+			pr_err("sys_timer_getoverrun failed (%d)\n", ret);
 			return ret;
 		}
 	}
@@ -201,7 +201,7 @@ static int drain_fds(struct parasite_drain_fd *args)
 	ret = send_fds(tsock, NULL, 0,
 		       args->fds, args->nr_fds, true);
 	if (ret)
-		pr_err("send_fds failed\n");
+		pr_err("send_fds failed (%d)\n", ret);
 
 	return ret;
 }
@@ -220,7 +220,7 @@ static int parasite_get_proc_fd()
 
 	ret = sys_readlink("/proc/self", buf, sizeof(buf));
 	if (ret < 0 && ret != -ENOENT) {
-		pr_err("Can't readlink /proc/self\n");
+		pr_err("Can't readlink /proc/self (%d)\n", ret);
 		return ret;
 	}
 
@@ -230,13 +230,15 @@ static int parasite_get_proc_fd()
 		goto out_send_fd;
 	}
 
-	if (sys_mkdir(proc_mountpoint, 0700)) {
-		pr_err("Can't create a directory\n");
+	ret = sys_mkdir(proc_mountpoint, 0700);
+	if (ret) {
+		pr_err("Can't create a directory (%d)\n", ret);
 		return -1;
 	}
 
-	if (sys_mount("proc", proc_mountpoint, "proc", MS_MGC_VAL, NULL)) {
-		pr_err("mount failed\n");
+	ret = sys_mount("proc", proc_mountpoint, "proc", MS_MGC_VAL, NULL);
+	if (ret) {
+		pr_err("mount failed (%d)\n", ret);
 		sys_rmdir(proc_mountpoint);
 		return -1;
 	}