kmsg: allow binary characters

* do not touch unprintable characters. This is so that logs can have formatting
  such as newlines, tabulation, or colours.
* the textual part is now delimited by \0. This is because \n which used to be
  the delimiter is now available for logs.
* NOTE: requires corresponding changes in dlogutil.

Signed-off-by: Michal Bloch <m.bloch@samsung.com>
Change-Id: Ib7a83241e7a72b2ba527f52801a8bae0698d18f4

1 files changed, 9 insertions, 10 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d6b96136deb4..20ebf827e858 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -989,15 +989,19 @@ static ssize_t kmsg_read(struct log_buffer *log_b, struct file *file,
 		       user->seq, ts_usec, cont);
 	user->prev = msg->flags;
 
-	/* escape non-printable characters */
 	for (i = 0; i < msg->text_len; i++) {
 		unsigned char c = log_text(msg)[i];
 
-		if (c < ' ' || c >= 127 || c == '\\')
-			p += scnprintf(p, e - p, "\\x%02x", c);
-		else
-			append_char(&p, e, c);
+		append_char(&p, e, c);
 	}
+
+	/*
+	 * The \0 is delimits the text part, while the newline is for formatting
+	 * when catting the device directly. We cannot use \n for delimiting due
+	 * to security: else one could forge dictionary tags through the message
+	 * such as "text\n _PID=123"
+	 */
+	append_char(&p, e, '\0');
 	append_char(&p, e, '\n');
 
 	if (msg->dict_len) {
@@ -1017,11 +1021,6 @@ static ssize_t kmsg_read(struct log_buffer *log_b, struct file *file,
 				continue;
 			}
 
-			if (c < ' ' || c >= 127 || c == '\\') {
-				p += scnprintf(p, e - p, "\\x%02x", c);
-				continue;
-			}
-
 			append_char(&p, e, c);
 		}
 		append_char(&p, e, '\n');