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mkimg: Ensure GPT Entry Array is at least 16k

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UEFI v2.10 Section 5.3 documentes that the minimum reserved space after
the GPT header be at least 16kB. Enforce this minimum. Before, we'd only
set the number of entries to be the unpadded size. gpart's selective
enforcement of aspects of the GPT standard meant that these images would
work, but couldn't be changed (to add a partition or grow the size of a
partition). This ensures that gpart's overly picky standards don't cause
problems for people wishing to, for example, resize release images.

MFC after:		1 day (we want this in 14.0)
PR:			274312
Sponsored by:		Netflix
Reviewed by:		emaste
Differential Revision:	https://reviews.freebsd.org/D42245
This commit is contained in:
Warner Losh 2023-10-17 11:14:14 -06:00
parent 56c44bd92e
commit 9b42d3e12f
2 changed files with 19 additions and 4 deletions
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7
sys/sys/disk/gpt.h
View file

@ -82,6 +82,13 @@ struct gpt_hdr {
CTASSERT(offsetof(struct gpt_hdr, padding) == 92);
#endif
/*
* The GPT standard (section 5.3 of UEFI standard version 2.10) requires
* we reserve at least 16k after the PMBR and the GPT header for the GPT
* Array Entries.
*/
#define GPT_MIN_RESERVED 16384
struct gpt_ent {
gpt_uuid_t ent_type;
gpt_uuid_t ent_uuid;

16
usr.bin/mkimg/gpt.c
View file

@ -24,7 +24,7 @@
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <stddef.h>
#include <stdint.h>
@ -124,13 +124,21 @@ crc32(const void *buf, size_t sz)
return (crc ^ ~0U);
}
/*
* Return the number of sectors needed to store the partition table.
*/
static u_int
gpt_tblsz(void)
{
u_int ents;
u_int eps; /* Entries per Sector */
ents = secsz / sizeof(struct gpt_ent);
return ((nparts + ents - 1) / ents);
/*
* Count the number of sectors needed for the GPT Entry Array to store
* the number of partitions defined for this image. Enforce the 16kB
* minimum space for the GPT Entry Array per UEFI v2.10 Section 5.3.
*/
eps = secsz / sizeof(struct gpt_ent);
return (MAX(howmany(GPT_MIN_RESERVED, secsz), howmany(nparts, eps)));
}
static lba_t