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