98 lines
3.9 KiB
Plaintext
98 lines
3.9 KiB
Plaintext
This directory contains an implementation of a block-device-partition server.
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Behavior
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--------
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The server uses Genode's block-session interfaces as both front and back end,
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leading to the most common use case where this server will reside "between" a
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block-driver server and a higher level component like a file-system server.
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At startup, the partition server will try to parse the master boot record (MBR)
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of its back-end block session. If no partition table is found, the whole block
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device is exported as partition '0'. In the other case, the MBR and possible
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extended boot records (EBRs) are parsed and offered as separate block sessions
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to the front-end clients. The four primary partitions will receive partition
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numbers '1' to '4' whereas the first logical partition will be assigned to '5'.
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The partition server also understands the GUID partition table (GPT). It will
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always try to read the MBR as well as the GPT and will bail out if both are
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considered valid. It is up to the user to choose the right table. To do so,
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the 'ignore_mbr' or 'ignore_gpt' config attribute may be specified. Using both
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at the same time is a configuration error. Apart from that, the server will
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show a warning in case a protective MBR is found but GPT is ignored and abort.
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If valid GPT was encountered without a proper protective MBR it will use the
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GPT but show a diagnostic warning.
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In order to route a client to the right partition, the server parses its
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configuration section looking for 'policy' tags.
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XML Syntax:
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! <policy label="<program name>" partition="<partition number>" writeable="<boolean>"/>
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part_block supports partition reporting, which can be enabled via the
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<report> configuration node. See below for an example. The report
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looks like follows (for MBR resp. GPT).
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! <partitions type="mbr">
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! <partition number="1" type="12" start="2048" length="2048"/>
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! <partition number="2" type="15" start="4096" length="16384"/>
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! <partition number="5" type="12" start="6144" length="4096"/>
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! <partition number="6" type="12" start="12288" length="8192"/>
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! </partitions>
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! <partitions type="gpt">
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! <partition number="1" name="one" type="ebd0a0a2-b9e5-4433-87c0-68b6b72699c7"
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! guid="5f4061cc-8d4a-4e6f-ad15-10b881b79aee" start="2048" length="2048"/>
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! <partition number="2" name="two" type="ebd0a0a2-b9e5-4433-87c0-68b6b72699c7"
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! guid="87199a83-d0f4-4a01-b9e3-6516a8579d61" start="4096" length="16351"/>
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! </partitions>
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Clients have read-only access to partitions unless overriden by a 'writeable'
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policy attribute.
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Usage
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-----
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Configuration snippet with two clients and an (hypothetical) IDE driver:
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!<start name="ata_driver">
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! <resource name="RAM" quantum="1M" />
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! <provides><service name="Block"/></provides>
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! <config ata="yes" />
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!</start>
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!
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!<start name="part_block">
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! <resource name="RAM" quantum="10M" />
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! <provides><service name="Block" /></provides>
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!
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! <!-- route part_block to the ata_driver -->
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! <route>
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! <any-service><child name="ata_driver"/> <parent/><any-child/></any-service>
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! </route>
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!
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! <!-- allow program 'test-part1' to access logical partition '6', while program
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! 'test-part2' receives access to primary partition 1, the buffer between
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! the 'ata_driver' and 'part_block' is 1 MeB ('io_buffer') -->
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! <config io_buffer="1M">
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! <report partitions="yes"/>
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! <policy label_prefix="test-part1" partition="6" writeable="yes"/>
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! <policy label_prefix="test-part2" partition="1" writeable="yes"/>
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! </config>
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!</start>
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!
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!<!-- part_block clients -->
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!<start name="test-part1">
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! <binary name="test-part"/>
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! <resource name="RAM" quantum="10M" />
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! <route>
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! <any-service> <child name="part_block" /> <parent/> <any-child/> </any-service>
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! </route>
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!</start>
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!
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!<start name="test-part2">
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! <binary name="test-part"/>
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! <resource name="RAM" quantum="10M" />
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! <route>
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! <any-service> <child name="part_block" /> <parent/> <any-child/> </any-service>
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! </route>
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!</start>
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