Date: Sun, 10 Jul 2022 14:55:28 -0700 From: Mark Millard <marklmi@yahoo.com> To: "Dr. Rolf Jansen" <freebsd-rj@cyclaero.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Partition layout of ARM SD card images Message-ID: <97AEE0AA-7EB1-44B6-9175-841425077974@yahoo.com> In-Reply-To: <C1AA808B-8B0F-4D47-A6CE-DF1136787F3F@cyclaero.com> References: <1F42EED0-B39F-4E33-986A-FB70A3AA4362@cyclaero.com> <FA446115-E78D-42C9-B5B0-21EF88075FC1@yahoo.com> <C1AA808B-8B0F-4D47-A6CE-DF1136787F3F@cyclaero.com>
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On 2022-Jul-10, at 14:34, Dr. Rolf Jansen <freebsd-rj@cyclaero.com> =
wrote:
>> Am 10.07.2022 um 17:48 schrieb Mark Millard <marklmi@yahoo.com>:
>>=20
>> On 2022-Jul-10, at 12:26, Dr. Rolf Jansen <freebsd-rj@cyclaero.com> =
wrote:
>>=20
>>> For example let's have a llok on the partition layout of, =
FreeBSD-13.1-RELEASE-arm64-aarch64-RPI.img (the others are similar):
>>>=20
>>> # mdconfig -a -u 0 -t vnode -f =
diskimg/FreeBSD-13.1-RELEASE-arm64-aarch64-RPI.img
>>> # gpart show md0 md0s2
>>>=20
>>> =3D> 63 6291393 md0 MBR (3.0G)
>>> 63 2016 - free - (1.0M)
>>> 2079 102312 1 fat32lba [active] (50M)
>>> 104391 6187041 2 freebsd (3.0G)
>>> 6291432 24 - free - (12K)
>>>=20
>>> =3D> 0 6187041 md0s2 BSD (3.0G)
>>> 0 57 - free - (29K)
>>> 57 6186880 1 freebsd-ufs (2.9G)
>>> 6186937 104 - free - (52K)
>>>=20
>>> The start of the fat32 boot slice s1 (containing the u-boot) stuff =
is neither aligned to 1M nor to 4k, it starts on an odd base. The start =
of the BSD payload slice s2 and its size are odd as well. The padding of =
57 blocks within s2 lets the UFS partition start on a globally even =
base, namely 104391+57 =3D 104448, which as a matter of fact is 4k =
aligned (104448*512/4096 =3D 13056) and 1M aligned as well =
(104448*512/1024/1024 =3D 51), however all this keeps looking strange.
>>>=20
>>> Are there reasons for this partition layout besides making it look =
more interesting? If yes, some insights would be good.
>>=20
>> The layout details are more specific to the aarch64 RPi* context
>> than to general aarch64 SD card images. For example, the Rock64
>> image is different:
>>=20
>> # mdconfig -a -u 0 -t vnode -f =
FreeBSD-14.0-CURRENT-arm64-aarch64-ROCK64-20220708-a0b956f5ac5-256605.img
>> # gpart show md0
>> =3D> 40 6291376 md0 GPT (3.0G)
>> 40 32728 - free - (16M)
>> 32768 102400 1 efi (50M)
>> 135168 6156160 2 freebsd-ufs (2.9G)
>> 6291328 88 - free - (44K)
>=20
> This is a GPT table, while the others are still MBR. Images which come =
with u-boot must have a different layout.
I know it is a GPT table. That is part of the point about
the variety of contexts that there are across the Small
Board Computers.
No SBC that has a U-Boot/whatever needing more space
than is provided below is going to use the same
2079 figure:
=3D> 63 ??? md0 ??? (?)
63 2016 - free - (1.0M)
2079 ?????? 1 fat32lba [active] (?)
MBR vs. GPT is not the fundamental issue for that.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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