dump: Add should_ignore_fd helper

We should ignore tty devices for a while.
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

cr-dump.c

@@ -221,6 +221,34 @@ err:
 	return ret;
 }
 
+static bool should_ignore_fd(char *pid_fd_dir, int dir, char *fd_name)
+{
+	if (!strcmp(fd_name, "0")) {
+		pr_info("... Skipping stdin ...\n");
+		return true;
+	} else if (!strcmp(fd_name, "1")) {
+		pr_info("... Skipping stdout ...\n");
+		return true;
+	} else if (!strcmp(fd_name, "2")) {
+		pr_info("... Skipping stderr ...\n");
+		return true;
+	} else {
+		char ttybuf[32];
+
+		if (readlinkat(dir, fd_name, ttybuf, sizeof(ttybuf)) > 0) {
+			if (!strncmp(ttybuf, "/dev/tty", 8)) {
+				pr_info("... Skipping tty ...\n");
+				return true;
+			}
+		} else {
+			pr_perror("Failed to readlink %s/%d %s\n", pid_fd_dir, dir, fd_name);
+			return false;
+		}
+	}
+
+	return false;
+}
+
 static int dump_one_fd(char *pid_fd_dir, int dir, char *fd_name, unsigned long pos,
 		       unsigned int flags, struct cr_fdset *cr_fdset)
 {
@@ -228,6 +256,9 @@ static int dump_one_fd(char *pid_fd_dir, int dir, char *fd_name, unsigned long p
 	struct stat st_buf;
 	int fd;
 
+	if (should_ignore_fd(pid_fd_dir, dir, fd_name))
+		return 0;
+
 	fd = openat(dir, fd_name, O_RDONLY);
 	if (fd < 0) {
 		pr_perror("Failed to openat %s/%d %s\n", pid_fd_dir, dir, fd_name);
@@ -254,26 +285,6 @@ static int dump_one_fd(char *pid_fd_dir, int dir, char *fd_name, unsigned long p
 					     st_buf.st_ino, flags, cr_fdset);
 	}
 
-	if (!strcmp(fd_name, "0")) {
-		pr_info("... Skipping stdin ...\n");
-		return 0;
-	}
-
-	if (!strcmp(fd_name, "1")) {
-		pr_info("... Skipping stdout ...\n");
-		return 0;
-	}
-
-	if (!strcmp(fd_name, "2")) {
-		pr_info("... Skipping stderr ...\n");
-		return 0;
-	}
-
-	if (!strcmp(fd_name, "3")) {
-		pr_info("... Skipping tty ...\n");
-		return 0;
-	}
-
 	pr_err("Can't dump file %s of that type [%x]\n", fd_name, st_buf.st_mode);
 	return 1;
 }