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loader: disk_open() should honor D_PARTNONE

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The D_PARTNONE is documented to make it possible to open raw MBR
partition, but the current disk_open() does not really implement this
statement.

The current code is checking partition against -1 (D_PARTNONE) but does
attempt to open partition table in case we do have FreeBSD MBR partition type.
Instead, we should check -2 (D_PARTWILD).

In case we do have MBR + BSD label, this code is only working because
by default, the first BSD partiton is created starting with relative sector
0, and we can still access the BSD table from that MBR slice.

Reviewed by:	imp
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D20501
This commit is contained in:
Toomas Soome 2019-06-06 16:27:05 +00:00
parent fbd9585915
commit ed29b75ca3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=348748
1 changed files with 16 additions and 8 deletions
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24
stand/common/disk.c
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@ -263,8 +263,8 @@ disk_open(struct disk_devdesc *dev, uint64_t mediasize, u_int sectorsize)
slice = dev->d_slice;
partition = dev->d_partition;
DPRINTF("%s unit %d, slice %d, partition %d => %p",
disk_fmtdev(dev), dev->dd.d_unit, dev->d_slice, dev->d_partition, od);
DPRINTF("%s unit %d, slice %d, partition %d => %p", disk_fmtdev(dev),
dev->dd.d_unit, dev->d_slice, dev->d_partition, od);
/* Determine disk layout. */
od->table = ptable_open(&partdev, mediasize / sectorsize, sectorsize,
@ -309,17 +309,25 @@ disk_open(struct disk_devdesc *dev, uint64_t mediasize, u_int sectorsize)
} else if (partition == D_PARTISGPT) {
/*
* When we try to open GPT partition, but partition
* table isn't GPT, reset d_partition value to -1
* and try to autodetect appropriate value.
* table isn't GPT, reset partition value to
* D_PARTWILD and try to autodetect appropriate value.
*/
partition = -1;
partition = D_PARTWILD;
}
/*
* If d_partition < 0 and we are looking at a BSD slice,
* If partition is D_PARTNONE, then disk_open() was called
* to open raw MBR slice.
*/
if (partition == D_PARTNONE)
goto out;
/*
* If partition is D_PARTWILD and we are looking at a BSD slice,
* then try to read BSD label, otherwise return the
* whole MBR slice.
*/
if (partition == -1 &&
if (partition == D_PARTWILD &&
part.type != PART_FREEBSD)
goto out;
/* Try to read BSD label */
@ -331,7 +339,7 @@ disk_open(struct disk_devdesc *dev, uint64_t mediasize, u_int sectorsize)
goto out;
}
/*
* If slice contains BSD label and d_partition < 0, then
* If slice contains BSD label and partition < 0, then
* assume the 'a' partition. Otherwise just return the
* whole MBR slice, because it can contain ZFS.
*/