EBR could contain an early stage of boot code. But we do not support it.

Remove message about non empty bootcode, we can not break something
while GEOM_PART_EBR_COMPAT is defined.

But without GEOM_PART_EBR_COMPAT any changes in EBR are allowed and we
can accidentally wipe the boot code. To do not break anything save
the first EBR chunk and keep it untouched each time when we are
changing EBR. Note that we are still not support boot code for EBR.

PR:		kern/141235
MFC after:	1 month

1 files changed, 20 insertions, 16 deletions

diff --git a/sys/geom/part/g_part_ebr.c b/sys/geom/part/g_part_ebr.c
index 8ea9b47..85b8a8a 100644
--- a/sys/geom/part/g_part_ebr.c
+++ b/sys/geom/part/g_part_ebr.c
@@ -59,6 +59,9 @@ FEATURE(geom_part_ebr_compat,
 
 struct g_part_ebr_table {
 	struct g_part_table	base;
+#ifndef GEOM_PART_EBR_COMPAT
+	u_char		ebr[EBRSIZE];
+#endif
 };
 
 struct g_part_ebr_entry {
@@ -459,7 +462,7 @@ g_part_ebr_read(struct g_part_table *basetable, struct g_consumer *cp)
 	u_char *buf;
 	off_t ofs, msize;
 	u_int lba;
-	int error, index, sum;
+	int error, index;
 
 	pp = cp->provider;
 	table = (struct g_part_ebr_table *)basetable;
@@ -482,20 +485,11 @@ g_part_ebr_read(struct g_part_table *basetable, struct g_consumer *cp)
 			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);
-			}
-		}
+#ifndef GEOM_PART_EBR_COMPAT
+		/* Save the first EBR, it can contain a boot code */
+		if (lba == 0)
+			bcopy(buf, table->ebr, sizeof(table->ebr));
+#endif
 		g_free(buf);
 
 		if (ent[0].dp_typ == 0)
@@ -583,6 +577,9 @@ g_part_ebr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
 static int
 g_part_ebr_write(struct g_part_table *basetable, struct g_consumer *cp)
 {
+#ifndef GEOM_PART_EBR_COMPAT
+	struct g_part_ebr_table *table;
+#endif
 	struct g_provider *pp;
 	struct g_part_entry *baseentry, *next;
 	struct g_part_ebr_entry *entry;
@@ -592,6 +589,10 @@ g_part_ebr_write(struct g_part_table *basetable, struct g_consumer *cp)
 
 	pp = cp->provider;
 	buf = g_malloc(pp->sectorsize, M_WAITOK | M_ZERO);
+#ifndef GEOM_PART_EBR_COMPAT
+	table = (struct g_part_ebr_table *)basetable;
+	bcopy(table->ebr, buf, DOSPARTOFF);
+#endif
 	le16enc(buf + DOSMAGICOFFSET, DOSMAGIC);
 
 	baseentry = LIST_FIRST(&basetable->gpt_entry);
@@ -644,7 +645,10 @@ g_part_ebr_write(struct g_part_table *basetable, struct g_consumer *cp)
 
 		error = g_write_data(cp, baseentry->gpe_start * pp->sectorsize,
 		    buf, pp->sectorsize);
-
+#ifndef GEOM_PART_EBR_COMPAT
+		if (baseentry->gpe_start == 0)
+			bzero(buf, DOSPARTOFF);
+#endif
 		baseentry = next;
 	} while (!error && baseentry != NULL);