From 301eece09b7ea7243dfb9b207e4906f4f01e23f5 Mon Sep 17 00:00:00 2001
From: Eduard Shishkin <edward6@linux.ibm.com>
Date: Mon, 24 Aug 2020 11:36:21 +0200
Subject: [PATCH] zipl: fix Error when title is not the first field in BLS file
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Problem:
zipl implementation (specifically the scan code) implicitly
assumes that title field is always on the top of BLS file,
and this assumption doesn't comply the bootloader standards:
https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/

Solution:
Before parsing in-memory BLS entry, rearrange its lines as
following: search for a line with keyword "title" and move it
to the top. The scan code is invariant against such transform

Fixes: https://github.com/ibm-s390-tools/s390-tools/issues/64
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Eduard Shishkin <edward6@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
---
 zipl/src/scan.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/zipl/src/scan.c b/zipl/src/scan.c
index 064709f4..48260f98 100644
--- a/zipl/src/scan.c
+++ b/zipl/src/scan.c
@@ -21,6 +21,7 @@
 #define _GNU_SOURCE
 #endif
 
+#include <assert.h>
 #include <ctype.h>
 #include <dirent.h>
 #include <errno.h>
@@ -28,6 +29,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdbool.h>
 
 #include <sys/stat.h>
 
@@ -730,6 +732,67 @@ scan_bls_field(struct misc_file_buffer *file, struct scan_token* scan,
 	return 0;
 }
 
+/**
+ * find a line with keyword "title" and move it to the top
+ */
+static int sort_bls_fields(struct misc_file_buffer *file, char *filename)
+{
+	bool is_title = false;
+	size_t title_len = 0;
+	int nr_titles = 0;
+	size_t title_off;
+	char *title;
+	int current;
+	size_t len;
+
+	while (file->length - file->pos > 4 /* for "title" */) {
+		if (strncmp("title", &file->buffer[file->pos], 5) == 0) {
+			is_title = true;
+			nr_titles++;
+			title_off = file->pos;
+		}
+		for (len = 0;; file->pos++, len++) {
+			current = misc_get_char(file, 0);
+			if (current == '\n' || current == EOF)
+				break;
+		}
+		if (is_title == true)
+			title_len = len;
+		if (current == EOF)
+			break;
+		file->pos++;
+	}
+	file->pos = 0;
+
+	if (nr_titles == 0) {
+		error_reason("no title in %s", filename);
+		return -1;
+	}
+	if (nr_titles > 1) {
+		error_reason("more than one title in %s", filename);
+		return -1;
+	}
+	if (title_off == 0)
+		return 0;
+
+	title = misc_malloc(title_len);
+	if (!title)
+		return -1;
+	/*
+	 * copy the title field w/o trailing '\n' to the temporary buffer
+	 */
+	memcpy(title, &file->buffer[title_off], title_len);
+	/*
+	 * shift preceded memory region w/o trailing '\n' to the right
+	 */
+	assert(file->buffer[title_off - 1] == '\n');
+	memmove(&file->buffer[title_len + 1], &file->buffer[0], title_off - 1);
+	file->buffer[title_len] = '\n';
+	memcpy(&file->buffer[0], title, title_len);
+
+	free(title);
+	return 0;
+}
 
 int
 scan_bls(const char* blsdir, struct scan_token** token, int scan_size)
@@ -780,6 +843,10 @@ scan_bls(const char* blsdir, struct scan_token** token, int scan_size)
 		if (rc)
 			goto err;
 
+		rc = sort_bls_fields(&file, filename);
+		if (rc)
+			goto err;
+
 		while ((size_t)file.pos < file.length) {
 			current = misc_get_char(&file, 0);
 			switch (current) {