another gpt vs mbr (sanity) check

Andriy Gapon avg at icyb.net.ua
Wed Mar 10 11:29:11 UTC 2010


on 07/03/2010 13:10 Andriy Gapon said the following:
> 
> Below is a simplistic patch that adds such a check.
> Ideally it should probably check the whole MBR partition table instead of just a
> type of the first entry.

For what it's worth, here is a new version of the patch.
In this version g_part_gpt recognizes MBR as a valid protective/hybrid MBR if
_any_ of the partitions in MBR partition table has type 0xEE (GPT protective
partition).

--- a/sys/geom/part/g_part_gpt.c
+++ b/sys/geom/part/g_part_gpt.c
@@ -568,7 +568,8 @@ g_part_gpt_probe
 {
 	struct g_provider *pp;
 	char *buf;
-	int error, res;
+	int error, res, typ;
+	int i, has_pmbr;

 	/* We don't nest, which means that our depth should be 0. */
 	if (table->gpt_depth != 0)
@@ -598,10 +599,18 @@ g_part_gpt_probe
 	if (buf == NULL)
 		return (error);
 	res = le16dec(buf + DOSMAGICOFFSET);
+	for (has_pmbr = 0, i = 0; i < NDOSPART; i++) {
+		typ = *(unsigned char*)(buf + DOSPARTOFF + i * DOSPARTSIZE + 4);
+		if (typ == DOSPTYP_PMBR) {
+			has_pmbr = 1;
+			break;
+		}
+	}
 	g_free(buf);
 	if (res != DOSMAGIC)
 		return (ENXIO);
-
+	if (!has_pmbr)
+		return (ENXIO);
 	/* Check that there's a primary header. */
 	buf = g_read_data(cp, pp->sectorsize, pp->sectorsize, &error);
 	if (buf == NULL)


-- 
Andriy Gapon


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