Eliminate a couple of 'XXX' assumptions by calculating the actual

number of sectors a given number of GPT partition entries
require.

No intentional functional change.

diff --git a/sbin/fdisk/gpt.c b/sbin/fdisk/gpt.c
index d802d7a..960b047 100644 (file)
--- a/sbin/fdisk/gpt.c
+++ b/sbin/fdisk/gpt.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: gpt.c,v 1.61 2022/03/16 17:03:13 krw Exp $    */
+/*     $OpenBSD: gpt.c,v 1.62 2022/04/13 15:07:25 krw Exp $    */
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -115,8 +115,7 @@ int
 get_header(const uint64_t sector)
 {
        char                    *secbuf;
-       uint64_t                 partlastlba, partslen, lba_end;
-       int                      partspersec;
+       uint64_t                 gpbytes, gpsectors, lba_end;
        uint32_t                 gh_csum;
 
        secbuf = DISK_readsectors(sector, 1);
@@ -173,10 +172,9 @@ get_header(const uint64_t sector)
                        return -1;
        }
 
-       /* XXX Assume part_num * part_size is multiple of secsize. */
-       partslen = letoh32(gh.gh_part_num) * letoh32(gh.gh_part_size) /
-           dl.d_secsize;
-       lba_end = DL_GETDSIZE(&dl) - partslen - 2;
+       gpbytes = letoh32(gh.gh_part_num) * letoh32(gh.gh_part_size);
+       gpsectors = (gpbytes + dl.d_secsize - 1) / dl.d_secsize;
+       lba_end = DL_GETDSIZE(&dl) - gpsectors - 2;
        if (letoh64(gh.gh_lba_end) > lba_end) {
                DPRINTF("gpt last usable LBA: reduced from %llu to %llu\n",
                    letoh64(gh.gh_lba_end), lba_end);
@@ -197,14 +195,12 @@ get_header(const uint64_t sector)
                return -1;
        }
 
-       partspersec = dl.d_secsize / letoh32(gh.gh_part_size);
-       partlastlba = letoh64(gh.gh_part_lba) +
-           ((letoh32(gh.gh_part_num) + partspersec - 1) / partspersec) - 1;
-       if (partlastlba <= letoh64(gh.gh_lba_end) &&
-           partlastlba >= letoh64(gh.gh_lba_start)) {
+       lba_end = letoh64(gh.gh_part_lba) + gpsectors - 1;
+       if (lba_end <= letoh64(gh.gh_lba_end) &&
+           lba_end >= letoh64(gh.gh_lba_start)) {
                DPRINTF("gpt partition table last LBA: expected < %llu or "
                    "> %llu, got %llu\n", letoh64(gh.gh_lba_start),
-                   letoh64(gh.gh_lba_end), partlastlba);
+                   letoh64(gh.gh_lba_end), lba_end);
                return -1;
        }
 
@@ -234,7 +230,7 @@ get_partition_table(void)
                return -1;
        }
        gpbytes = letoh32(gh.gh_part_num) * letoh32(gh.gh_part_size);
-       gpsectors = gpbytes / dl.d_secsize;
+       gpsectors = (gpbytes + dl.d_secsize - 1) / dl.d_secsize;
        memset(&gp, 0, sizeof(gp));
 
        secbuf = DISK_readsectors(letoh64(gh.gh_part_lba), gpsectors);
@@ -643,11 +639,8 @@ GPT_write(void)
        if (MBR_write(&gmbr))
                return -1;
 
-       /*
-        * XXX Assume size of gp is multiple of sector size.
-        */
        gpbytes = letoh32(gh.gh_part_num) * letoh32(gh.gh_part_size);
-       gpsectors = gpbytes / dl.d_secsize;
+       gpsectors = (gpbytes + dl.d_secsize - 1) / dl.d_secsize;
 
        prigh = GPTSECTOR;
        prigp = prigh + 1;