From 9744d1a547847dea89277b00606fe4c837c1b4ea Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Danis?= Date: Fri, 20 Mar 2020 10:59:22 +0100 Subject: cmd: Add command to display or save Linux PStore dumps MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch adds a new pstore command allowing to display or save ramoops logs (oops, panic, console, ftrace and user) generated by a previous kernel crash. PStore parameters can be set in U-Boot configuration file, or at run-time using "pstore set" command. Records size should be the same as the ones used by kernel, and should be a power of 2. This command allows: - to display uncompressed logs - to save compressed or uncompressed logs, compressed logs are saved as a compressed stream, it may need some work to be able to decompress it, e.g. adding a fake header: "printf "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x00" | cat - dmesg-ramoops-0.enc.z | gzip -dc" - ECC part is not used to check memory corruption - only 1st FTrace log is displayed or saved Signed-off-by: Frédéric Danis [trini: Minor updates for current design, correct spacing in rST] Signed-off-by: Tom Rini Cc: Heinrich Schuchardt Cc: Wolfgang Denk Cc: Heiko Schocher --- doc/index.rst | 7 +++++ doc/pstore.rst | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 87 insertions(+) create mode 100644 doc/pstore.rst (limited to 'doc') diff --git a/doc/index.rst b/doc/index.rst index fd9f10f28e..68a083b16b 100644 --- a/doc/index.rst +++ b/doc/index.rst @@ -109,6 +109,13 @@ Android-specific features available in U-Boot. android/index +Command line +------------ +.. toctree:: + :maxdepth: 2 + + pstore.rst + Indices and tables ================== diff --git a/doc/pstore.rst b/doc/pstore.rst new file mode 100644 index 0000000000..4fceb2dd99 --- /dev/null +++ b/doc/pstore.rst @@ -0,0 +1,80 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +PStore command +============== + +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. + +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:: + + $ 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 / -- cgit v1.2.1