NAME¶
geom_map
—
GEOM module that maps defined items as separate
partitions
SYNOPSIS¶
To compile this driver into the kernel, place the following line in your kernel
configuration file:
device
geom_map
DESCRIPTION¶
The
geom_map
framework provides support for
mapping defined parts of the media. Basically it is helpful for embedded
devices where in the one continuous flash are loader, kernel and rootfs parts.
geom_map
allows making them available as
separate parts and protects the loader from being overwritten.
At boot time
geom_map
partitions are listed
(only with bootverbose) as:
MAP: 0x30000, data=0x30000 "/dev/map/bootloader"
MAP: 30000x10000, data=0x10000 "/dev/map/factory"
MAP: 40000x7a0000, data=0x7a0000 "/dev/map/upgrade"
MAP: search key ".!/bin/sh" from 0x100000, step 0x10000
MAP: 40000x110000, data=0x110000 "/dev/map/kernel"
MAP: search key ".!/bin/sh" from 0x100000, step 0x10000
MAP: 150000x690000, data=0x690000 "/dev/map/rootfs"
MAP: 7e0000x20000, data=0x20000 "/dev/map/config"
The current
geom_map
configuration can be
accessed with the following
sysctl(8) nodes:
kern.geom.conftxt,
kern.geom.confxml, and
kern.geom.confdot or by using
“
geom map list
”.
# sysctl -n kern.geom.conftxt
0 MD md0 10485760 512 u 0 s 512 f 0 fs 0 l 10485760 t malloc
0 DISK cfid0 8388608 4 hd 0 sc 0
1 MAP map/config 131072 4 i 5 o 8257536 entry 0 dsize 131072
1 MAP map/rootfs 6881280 4 i 4 o 1376256 entry 0 dsize 6881280
2 UNCOMPRESS map/rootfs.uncompress 18677760 512
1 MAP map/kernel 1114112 4 i 3 o 262144 entry 0 dsize 1114112
1 MAP map/upgrade 7995392 4 i 2 o 262144 entry 0 dsize 7995392
1 MAP map/factory 65536 4 i 1 o 196608 entry 0 dsize 65536
1 MAP map/bootloader 196608 4 i 0 o 0 entry 0 dsize 196608
Driver configuration can be done in
device.hints(5). List of used parameters:
- at
- select media to attach
- name
- name of partition (will create device
/dev/map/that_name)
- start
- offset from the beginning of the parent media to start of the mapped
partition. This field can also have a special value
“
search:
searchstart:searchstep:searchkey”,
where:
- searchstart
- offset from the beginning of the parent media where search will be
started
- searchstep
- value of the increment used while searching for the partition boundary
markers
- searchkey
- key which will be used to find partition boundary markers. The
wildcard ‘
.
’ can be used to
match any character on that position
- end
- offset from the beginning of the parent media to the end of the mapped
partition. This field can also have the special value
“
search:
searchstart:searchstep:searchkey”,
as described above.
- offset
- offset where the data of the mapped partition begins
Each record contains the start address (in bytes) from the media begin, size (in
bytes), offset where the data of mapped partition begins, and the name of new
device.
MAP: 150000x690000, data=0x690000 "/dev/map/rootfs"
00150000 - start address
00690000 - size
00000000 - data begin from zero offset
00690000 - data size
"map/rootfs" - new media will be accessible via /dev/map/rootfs dev.
EXAMPLES¶
If we need to implement layout shown above, we need to define the following
hints:
hint.map.0.at="cfid0"
hint.map.0.start=0x00000000
hint.map.0.end=0x00030000
hint.map.0.name="bootloader"
hint.map.0.readonly=1
This defines
/dev/map/bootloader at disk
cfid0 starting at
0x00000000
and ending at
0x00030000
, it is also marked as readonly.
hint.map.1.at="cfid0"
hint.map.1.start=0x00030000
hint.map.1.end=0x00040000
hint.map.1.name="factory"
hint.map.2.at="cfid0"
hint.map.2.start=0x00040000
hint.map.2.end=0x007e0000
hint.map.2.name="upgrade"
hint.map.3.at="cfid0"
hint.map.3.name="kernel"
hint.map.3.start=0x00040000
hint.map.3.end="search:0x00100000:0x10000:.!/bin/sh"
This defines
/dev/map/kernel at disk
cfid0 starting at
0x00040000
, but the end position must be searched by
finding the key “
.!/bin/sh
”, from offset
0x00100000
to the end of media with step
0x10000
. The real marker in this case is
“
#!/bin/sh
”, but
‘
#
’ terminates the line when the hints
file is parsed, so we need to use wildcard
‘
.
’ instead of
‘
#
’.
hint.map.4.at="cfid0"
hint.map.4.name="rootfs"
hint.map.4.start="search:0x00100000:0x10000:.!/bin/sh"
hint.map.4.end=0x007e0000
hint.map.5.at="cfid0"
hint.map.5.start=0x007e0000
hint.map.5.end=0x00800000
hint.map.5.name="config"
SEE ALSO¶
geom(4),
geom(8),
sysctl(8)
AUTHORS¶
The
geom_map
driver was written by
Aleksandr Rybalko
⟨ray@ddteam.net⟩.