git: 2cbda736cea8 - main - gpart: Add warning when the start sector is too low.

The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=2cbda736cea8f82cfc5caab0f6099f0fbfe28537

commit 2cbda736cea8f82cfc5caab0f6099f0fbfe28537
Author:     Warner Losh <imp@FreeBSD.org>
AuthorDate: 2024-10-16 00:03:03 +0000
Commit:     Warner Losh <imp@FreeBSD.org>
CommitDate: 2024-10-16 00:15:16 +0000

    gpart: Add warning when the start sector is too low.
    
    Add a warning if the starting sector is too low. The standard requires
    that at least 16k is reserved for the GPT Partition Array, but some
    tools produce GPT images with fewer than the required number of reserved
    sectors.
    
    PR: 274312
    Sponsored by:           Netflix
    Differential Revision:  https://reviews.freebsd.org/D42247
---
 sys/geom/part/g_part_gpt.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/sys/geom/part/g_part_gpt.c b/sys/geom/part/g_part_gpt.c
index 022337bd6575..4733631c4b20 100644
--- a/sys/geom/part/g_part_gpt.c
+++ b/sys/geom/part/g_part_gpt.c
@@ -1045,6 +1045,20 @@ g_part_gpt_read(struct g_part_table *basetable, struct g_consumer *cp)
 		g_free(sectbl);
 	}
 
+	/*
+	 * The reserved area preceeds the valid area for partitions. Warn when
+	 * the lba_start doesn't meet the standard's minimum size for the gpt
+	 * entry array. UEFI 2.10 section 5.3 specifies that the LBA must be 32
+	 * (for 512 byte sectors) or 6 (4k sectors) or larger. This is different
+	 * than the number of valid entries in the GPT entry array, which can be
+	 * smaller.
+	 */
+	if (table->hdr->hdr_lba_start < GPT_MIN_RESERVED / pp->sectorsize + 2) {
+		printf("GEOM: warning: %s lba_start %llu < required min %d\n",
+		    pp->name, (unsigned long long)table->hdr->hdr_lba_start,
+		    GPT_MIN_RESERVED / pp->sectorsize + 2);
+	}
+
 	basetable->gpt_first = table->hdr->hdr_lba_start;
 	basetable->gpt_last = table->hdr->hdr_lba_end;
 	basetable->gpt_entries = table->hdr->hdr_entries;