94 lines
2.8 KiB
ReStructuredText
94 lines
2.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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pstore command
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==============
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Synopsis
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--------
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::
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pstore set <addr> <len> [record-size] [console-size] [ftrace-size] [pmsg_size] [ecc-size]
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pstore display [record-type] [nb]
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pstore save <interface> <dev[:part]> <directory-path>
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Design
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------
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Linux PStore and Ramoops modules (Linux config options PSTORE and PSTORE_RAM)
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allow to use memory to pass data from the dying breath of a crashing kernel to
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its successor. This command allows to read those records from U-Boot command
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line.
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Ramoops is an oops/panic logger that writes its logs to RAM before the system
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crashes. It works by logging oopses and panics in a circular buffer. Ramoops
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needs a system with persistent RAM so that the content of that area can survive
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after a restart.
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Ramoops uses a predefined memory area to store the dump.
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Ramoops parameters can be passed as kernel parameters or through Device Tree,
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i.e.::
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ramoops.mem_address=0x30000000 ramoops.mem_size=0x100000 ramoops.record_size=0x2000 ramoops.console_size=0x2000 memmap=0x100000$0x30000000
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The same values should be set in U-Boot to be able to retrieve the records.
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This values can be set at build time in U-Boot configuration file, or at runtime.
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U-Boot automatically patches the Device Tree to pass the Ramoops parameters to
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the kernel.
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The PStore configuration parameters are:
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======================= ==========
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Name Default
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======================= ==========
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CMD_PSTORE_MEM_ADDR
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CMD_PSTORE_MEM_SIZE 0x10000
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CMD_PSTORE_RECORD_SIZE 0x1000
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CMD_PSTORE_CONSOLE_SIZE 0x1000
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CMD_PSTORE_FTRACE_SIZE 0x1000
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CMD_PSTORE_PMSG_SIZE 0x1000
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CMD_PSTORE_ECC_SIZE 0
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======================= ==========
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Records sizes should be a power of 2.
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The memory size and the record/console size must be non-zero.
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Multiple 'dump' records can be stored in the memory reserved for PStore.
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The memory size has to be larger than the sum of the record sizes, i.e.::
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MEM_SIZE >= RECORD_SIZE * n + CONSOLE_SIZE + FTRACE_SIZE + PMSG_SIZE
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Usage
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-----
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Generate kernel crash
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~~~~~~~~~~~~~~~~~~~~~
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For test purpose, you can generate a kernel crash by setting reboot timeout to
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10 seconds and trigger a panic
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.. code-block:: console
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$ sudo sh -c "echo 1 > /proc/sys/kernel/sysrq"
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$ sudo sh -c "echo 10 > /proc/sys/kernel/panic"
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$ sudo sh -c "echo c > /proc/sysrq-trigger"
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Retrieve logs in U-Boot
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~~~~~~~~~~~~~~~~~~~~~~~
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First of all, unless PStore parameters as been set during U-Boot configuration
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and match kernel ramoops parameters, it needs to be set using 'pstore set', e.g.::
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=> pstore set 0x30000000 0x100000 0x2000 0x2000
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Then all available dumps can be displayed
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using::
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=> pstore display
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Or saved to an existing directory in an Ext2 or Ext4 partition, e.g. on root
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directory of 1st partition of the 2nd MMC::
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=> pstore save mmc 1:1 /
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