From: krw <krw@openbsd.org>
Date: Fri, 14 May 2021 15:31:01 +0000 (+0000)
Subject: Tweak the two copies of gpt_chk_mbr() to return the index of the MBR
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=17eb2d2cf329a5c5d84377ceb5d54a0f9bf2a38b;p=openbsd

Tweak the two copies of gpt_chk_mbr() to return the index of the MBR
0xEE (DOSPTYP_EFI) partition, or -1 no usable such partition is found.

Adopt a consistent idiom to capture the index for future use.

Clean up the gpt_chk_mbr() logic to make it clearer what constraints
are being applied when looking for the DOSTYP_EFI partition.

No intentional functional change.
---

diff --git a/sbin/fdisk/cmd.c b/sbin/fdisk/cmd.c
index 0ee22c37c3b..8ba7f5e6fd3 100644
--- a/sbin/fdisk/cmd.c
+++ b/sbin/fdisk/cmd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cmd.c,v 1.102 2021/05/10 17:16:01 krw Exp $	*/
+/*	$OpenBSD: cmd.c,v 1.103 2021/05/14 15:31:01 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -45,7 +45,9 @@ int
 Xreinit(char *args, struct mbr *mbr)
 {
 	struct dos_mbr dos_mbr;
-	int dogpt;
+	int efi, dogpt;
+
+	efi = MBR_protective_mbr(mbr);
 
 	if (strncasecmp(args, "gpt", 3) == 0)
 		dogpt = 1;
@@ -54,7 +56,7 @@ Xreinit(char *args, struct mbr *mbr)
 	else if (strlen(args) > 0) {
 		printf("Unrecognized modifier '%s'\n", args);
 		return (CMD_CONT);
-	} else if (MBR_protective_mbr(mbr) == 0)
+	} else if (efi != -1)
 		dogpt = 1;
 	else
 		dogpt = 0;
@@ -393,8 +395,10 @@ Xselect(char *args, struct mbr *mbr)
 int
 Xprint(char *args, struct mbr *mbr)
 {
+	int efi;
 
-	if (MBR_protective_mbr(mbr) == 0 && letoh64(gh.gh_sig) == GPTSIGNATURE)
+	efi = MBR_protective_mbr(mbr);
+	if (efi != -1 && letoh64(gh.gh_sig) == GPTSIGNATURE)
 		GPT_print(args, VERBOSE);
 	else
 		MBR_print(mbr, args);
diff --git a/sbin/fdisk/fdisk.c b/sbin/fdisk/fdisk.c
index 55ad12d7eee..9fc0abb344f 100644
--- a/sbin/fdisk/fdisk.c
+++ b/sbin/fdisk/fdisk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fdisk.c,v 1.106 2021/05/10 17:16:01 krw Exp $	*/
+/*	$OpenBSD: fdisk.c,v 1.107 2021/05/14 15:31:01 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -71,7 +71,7 @@ int
 main(int argc, char *argv[])
 {
 	ssize_t len;
-	int ch, fd, error;
+	int ch, fd, efi, error;
 	int e_flag = 0, g_flag = 0, i_flag = 0, u_flag = 0;
 	int verbosity = TERSE;
 	int c_arg = 0, h_arg = 0, s_arg = 0;
@@ -175,7 +175,8 @@ main(int argc, char *argv[])
 	MBR_parse(&dos_mbr, 0, 0, &mbr);
 
 	/* Get the GPT if present. Either primary or secondary is ok. */
-	if (MBR_protective_mbr(&mbr) == 0)
+	efi = MBR_protective_mbr(&mbr);
+	if (efi != -1)
 		GPT_read(ANYGPT);
 
 	if (!(i_flag || u_flag || e_flag)) {
diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 9ae252354e4..e833989422d 100644
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mbr.c,v 1.68 2021/05/07 22:15:13 krw Exp $	*/
+/*	$OpenBSD: mbr.c,v 1.69 2021/05/14 15:31:01 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -289,39 +289,36 @@ MBR_zapgpt(struct dos_mbr *dos_mbr, uint64_t lastsec)
 }
 
 /*
- * Returns 0 if the MBR with the provided partition array is a GPT protective
- * MBR, and returns 1 otherwise. A GPT protective MBR would have one and only
- * one MBR partition, an EFI partition that either covers the whole disk or as
- * much of it as is possible with a 32bit size field.
+ * Return the index into dp[] of the EFI GPT (0xEE) partition, or -1 if no such
+ * partition exists.
  *
  * Taken from kern/subr_disk.c.
  *
- * NOTE: MS always uses a size of UINT32_MAX for the EFI partition!**
  */
 int
-gpt_chk_mbr(struct dos_partition *dp, uint64_t dsize)
+gpt_chk_mbr(struct dos_partition *dp, u_int64_t dsize)
 {
 	struct dos_partition *dp2;
-	int efi, found, i;
-	uint32_t psize;
+	int efi, eficnt, found, i;
+	u_int32_t psize;
 
-	found = efi = 0;
+	found = efi = eficnt = 0;
 	for (dp2=dp, i=0; i < NDOSPART; i++, dp2++) {
 		if (dp2->dp_typ == DOSPTYP_UNUSED)
 			continue;
 		found++;
 		if (dp2->dp_typ != DOSPTYP_EFI)
 			continue;
+		if (letoh32(dp2->dp_start) != GPTSECTOR)
+			continue;
 		psize = letoh32(dp2->dp_size);
-		if (psize == (dsize - 1) ||
-		    psize == UINT32_MAX) {
-			if (letoh32(dp2->dp_start) == 1)
-				efi++;
+		if (psize == (dsize - 1) || psize == UINT32_MAX) {
+			efi = i;
+			eficnt++;
 		}
 	}
-	if (found == 1 && efi == 1)
-		return (0);
+	if (found == 1 && eficnt == 1)
+		return (efi);
 
-	return (1);
+	return (-1);
 }
-
diff --git a/sbin/fdisk/user.c b/sbin/fdisk/user.c
index 409ff366711..1f721a89335 100644
--- a/sbin/fdisk/user.c
+++ b/sbin/fdisk/user.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: user.c,v 1.53 2021/05/10 17:16:01 krw Exp $	*/
+/*	$OpenBSD: user.c,v 1.54 2021/05/14 15:31:01 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -63,7 +63,7 @@ USER_edit(off_t offset, off_t reloff)
 	struct dos_mbr dos_mbr;
 	struct mbr mbr;
 	char *cmd, *args;
-	int i, st, error;
+	int i, st, efi, error;
 
 	/* One level deeper */
 	editlevel += 1;
@@ -79,7 +79,8 @@ USER_edit(off_t offset, off_t reloff)
 	if (editlevel == 1) {
 		memset(&gh, 0, sizeof(gh));
 		memset(&gp, 0, sizeof(gp));
-		if (MBR_protective_mbr(&mbr) == 0)
+		efi = MBR_protective_mbr(&mbr);
+		if (efi != -1)
 			GPT_read(ANYGPT);
 	}
 
@@ -141,7 +142,7 @@ void
 USER_print_disk(int verbosity)
 {
 	off_t offset, firstoff;
-	int i, error;
+	int i, efi, error;
 	struct dos_mbr dos_mbr;
 	struct mbr mbr;
 
@@ -153,8 +154,8 @@ USER_print_disk(int verbosity)
 			break;
 		MBR_parse(&dos_mbr, offset, firstoff, &mbr);
 		if (offset == 0) {
-			if (verbosity == VERBOSE || MBR_protective_mbr(&mbr) ==
-			    0) {
+			efi = MBR_protective_mbr(&mbr);
+			if (verbosity == VERBOSE || efi != -1) {
 				if (verbosity == VERBOSE) {
 					printf("Primary GPT:\n");
 					GPT_read(PRIMARYGPT);
diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index 40397a92626..21c61e7074b 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_disk.c,v 1.239 2021/05/08 16:41:24 krw Exp $	*/
+/*	$OpenBSD: subr_disk.c,v 1.240 2021/05/14 15:31:01 krw Exp $	*/
 /*	$NetBSD: subr_disk.c,v 1.17 1996/03/16 23:17:08 christos Exp $	*/
 
 /*
@@ -330,13 +330,13 @@ int
 readdoslabel(struct buf *bp, void (*strat)(struct buf *),
     struct disklabel *lp, daddr_t *partoffp, int spoofonly)
 {
+	struct dos_partition dp[NDOSPART], *dp2;
 	struct disklabel *gptlp;
 	u_int64_t dospartoff = 0, dospartend = DL_GETBEND(lp);
-	int i, ourpart = -1, wander = 1, n = 0, loop = 0, offset;
-	struct dos_partition dp[NDOSPART], *dp2;
 	u_int64_t sector = DOSBBSECTOR;
 	u_int32_t extoff = 0;
-	int error;
+	int ourpart = -1, wander = 1, n = 0, loop = 0;
+	int efi, error, i, offset;
 
 	if (lp->d_secpercyl == 0)
 		return (EINVAL);	/* invalid label */
@@ -374,7 +374,8 @@ readdoslabel(struct buf *bp, void (*strat)(struct buf *),
 			if (mbrtest != 0x55aa)
 				goto notmbr;
 
-			if (gpt_chk_mbr(dp, DL_GETDSIZE(lp)) != 0)
+			efi = gpt_chk_mbr(dp, DL_GETDSIZE(lp));
+			if (efi == -1)
 				goto notgpt;
 
 			gptlp = malloc(sizeof(struct disklabel), M_DEVBUF,
@@ -584,38 +585,37 @@ notfat:
 }
 
 /*
- * Returns 0 if the MBR with the provided partition array is a GPT protective
- * MBR, and returns 1 otherwise. A GPT protective MBR would have one and only
- * one MBR partition, an EFI partition that either covers the whole disk or as
- * much of it as is possible with a 32bit size field.
+ * Return the index into dp[] of the EFI GPT (0xEE) partition, or -1 if no such
+ * partition exists.
  *
- * NOTE: MS always uses a size of UINT32_MAX for the EFI partition!**
+ * Copied into sbin/fdisk/mbr.c.
  */
 int
 gpt_chk_mbr(struct dos_partition *dp, u_int64_t dsize)
 {
 	struct dos_partition *dp2;
-	int efi, found, i;
+	int efi, eficnt, found, i;
 	u_int32_t psize;
 
-	found = efi = 0;
+	found = efi = eficnt = 0;
 	for (dp2=dp, i=0; i < NDOSPART; i++, dp2++) {
 		if (dp2->dp_typ == DOSPTYP_UNUSED)
 			continue;
 		found++;
 		if (dp2->dp_typ != DOSPTYP_EFI)
 			continue;
+		if (letoh32(dp2->dp_start) != GPTSECTOR)
+			continue;
 		psize = letoh32(dp2->dp_size);
-		if (psize == (dsize - 1) ||
-		    psize == UINT32_MAX) {
-			if (letoh32(dp2->dp_start) == 1)
-				efi++;
+		if (psize == (dsize - 1) || psize == UINT32_MAX) {
+			efi = i;
+			eficnt++;
 		}
 	}
-	if (found == 1 && efi == 1)
-		return (0);
+	if (found == 1 && eficnt == 1)
+		return (efi);
 
-	return (1);
+	return (-1);
 }
 
 int