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Date:      Tue, 28 Dec 2010 08:36:45 +0000 (UTC)
From:      "Andrey V. Elsukov" <ae@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r216754 - head/sys/geom/part
Message-ID:  <201012280836.oBS8ajBX051560@svn.freebsd.org>
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Author: ae
Date: Tue Dec 28 08:36:44 2010
New Revision: 216754
URL: http://svn.freebsd.org/changeset/base/216754

Log:
  Make EBR probe method less strictly to be able detect EBRs with
  small non fatal inconsistency. EBR may contain boot loader and sometimes
  it just has some garbage data. Now this does not prevent FreeBSD to use
  extended partitions. But since we do not support bootcode for EBR we mark
  tables which have non empty boot area as corrupt. This does make them
  readonly and we can not damage this data.
  
  PR:		kern/141235
  MFC after:	1 month

Modified:
  head/sys/geom/part/g_part_ebr.c

Modified: head/sys/geom/part/g_part_ebr.c
==============================================================================
--- head/sys/geom/part/g_part_ebr.c	Tue Dec 28 03:27:20 2010	(r216753)
+++ head/sys/geom/part/g_part_ebr.c	Tue Dec 28 08:36:44 2010	(r216754)
@@ -377,7 +377,7 @@ g_part_ebr_probe(struct g_part_table *ta
 	char psn[8];
 	struct g_provider *pp;
 	u_char *buf, *p;
-	int error, index, res, sum;
+	int error, index, res;
 	uint16_t magic;
 
 	pp = cp->provider;
@@ -409,29 +409,11 @@ g_part_ebr_probe(struct g_part_table *ta
 	if (magic != DOSMAGIC)
 		goto out;
 
-	/*
-	 * The sector is all zeroes, except for the partition entries,
-	 * pseudo boot code and some signatures or disk serial number.
-	 * The latter can be found in the 9 bytes immediately in front
-	 * of the partition table.
-	 */
-	sum = 0;
-	for (index = 96; index < DOSPARTOFF - 9; index++)
-		sum += buf[index];
-	if (sum != 0)
-		goto out;
-
-	for (index = 0; index < NDOSPART; index++) {
+	for (index = 0; index < 2; index++) {
 		p = buf + DOSPARTOFF + index * DOSPARTSIZE;
 		if (p[0] != 0 && p[0] != 0x80)
 			goto out;
-		if (index < 2)
-			continue;
-		/* The 3rd & 4th entries are always zero. */
-		if ((le64dec(p+0) + le64dec(p+8)) != 0)
-			goto out;
 	}
-
 	res = G_PART_PROBE_PRI_NORM;
 
  out:
@@ -450,7 +432,7 @@ g_part_ebr_read(struct g_part_table *bas
 	u_char *buf;
 	off_t ofs, msize;
 	u_int lba;
-	int error, index;
+	int error, index, sum;
 
 	pp = cp->provider;
 	table = (struct g_part_ebr_table *)basetable;
@@ -465,6 +447,28 @@ g_part_ebr_read(struct g_part_table *bas
 
 		ebr_entry_decode(buf + DOSPARTOFF + 0 * DOSPARTSIZE, ent + 0);
 		ebr_entry_decode(buf + DOSPARTOFF + 1 * DOSPARTSIZE, ent + 1);
+
+		/* The 3rd & 4th entries should be zeroes. */
+		if (le64dec(buf + DOSPARTOFF + 2 * DOSPARTSIZE) +
+		    le64dec(buf + DOSPARTOFF + 3 * DOSPARTSIZE) != 0) {
+			basetable->gpt_corrupt = 1;
+			printf("GEOM: %s: invalid entries in the EBR ignored.\n",
+			    pp->name);
+		}
+		/* We do not support bootcode for EBR. If bootcode area is
+		 * not zeroes, then mark this EBR as corrupt to do not break
+		 * anything for another OS'es.
+		 */
+		if (lba == 0) {
+			sum = 0;
+			for (index = 0; index < DOSPARTOFF; index++)
+				sum += buf[index];
+			if (sum != 0) {
+				basetable->gpt_corrupt = 1;
+				printf("GEOM: %s: EBR has non empty bootcode.\n",
+				    pp->name);
+			}
+		}
 		g_free(buf);
 
 		if (ent[0].dp_typ == 0)

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