Add some documentation about behaviour and setup of pstore/RAMOOPS. Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> --- Documentation/filesystems/pstore.rst | 76 ++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 Documentation/filesystems/pstore.rst diff --git a/Documentation/filesystems/pstore.rst b/Documentation/filesystems/pstore.rst new file mode 100644 index 000000000000..2d16753fce7e --- /dev/null +++ b/Documentation/filesystems/pstore.rst @@ -0,0 +1,76 @@ +.. index:: pstore (filesystem) + +pstore filesystem with RAM backend (RAMOOPS) +============================================ + +Barebox supports the pstore filesystem known from the kernel. The main backend +implementation is RAM. All other backends are currently not implemented by +Barebox. + +pstore is a filesystem to store kernel log or kernel panic messages. These +messages are stored by the kernel in a specified RAM area which is never +overwritten by any user. This data can be accessed after a reboot through +/pstore in Barebox or the kernel. The pstore filesystem is automatically mounted +at boot:: + none on / type ramfs + none on /dev type devfs + none on /pstore type pstore + +pstore may add additional warnings during boot due to wrong ECCs (no data +written):: + + persistent_ram: found existing invalid buffer, size 791282217, start 1116786789 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 791282281, start 1133564005 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 791347753, start 1133564005 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 791347753, start 1133572197 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 774505001, start 1133564005 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 791282281, start 1133564005 + persistent_ram: uncorrectable error in header + persistent_ram: found existing invalid buffer, size 791282217, start 1133564005 + pstore: Registered ramoops as persistent store backend + ramoops: attached 0x200000@0x1fdf4000, ecc: 16/0 + +To use pstore/RAMOOPS both Barebox and Kernel have to be compiled with pstore +and RAM backend support. The kernel receives the parameters describing the +layout over the kernel command line. These parameters are automatically +generated by Barebox. You can change these parameters in Barebox menuconfig. The +RAMOOPS parameters for the Kernel are stored in the variable +global.linux.bootargs.ramoops:: + +To see where the RAMOOPS area is located, you can execute iomem in Barebox. The +RAMOOPS area is listed as 'persistent ram':: + + 0x10000000 - 0x1fffffff (size 0x10000000) ram0 + 0x17e7c0c0 - 0x1fcf817f (size 0x07e7c0c0) malloc space + 0x1fcf8180 - 0x1fcfffff (size 0x00007e80) board data + 0x1fd00000 - 0x1fd6eeff (size 0x0006ef00) barebox + 0x1fd6ef00 - 0x1fd88dff (size 0x00019f00) barebox data + 0x1fd88e00 - 0x1fd8c3db (size 0x000035dc) bss + 0x1fdf4000 - 0x1fe13fff (size 0x00020000) persistent ram + 0x1fe14000 - 0x1fe33fff (size 0x00020000) persistent ram + 0x1fe34000 - 0x1fe53fff (size 0x00020000) persistent ram + 0x1fe54000 - 0x1fe73fff (size 0x00020000) persistent ram + 0x1fe74000 - 0x1fe93fff (size 0x00020000) persistent ram + 0x1fe94000 - 0x1feb3fff (size 0x00020000) persistent ram + 0x1feb4000 - 0x1fed3fff (size 0x00020000) persistent ram + 0x1fed4000 - 0x1fef3fff (size 0x00020000) persistent ram + 0x1fef4000 - 0x1ff13fff (size 0x00020000) persistent ram + 0x1ff14000 - 0x1ff33fff (size 0x00020000) persistent ram + 0x1ff34000 - 0x1ff53fff (size 0x00020000) persistent ram + 0x1ff54000 - 0x1ff73fff (size 0x00020000) persistent ram + 0x1ff74000 - 0x1ff93fff (size 0x00020000) persistent ram + 0x1ff94000 - 0x1ffb3fff (size 0x00020000) persistent ram + 0x1ffb4000 - 0x1ffd3fff (size 0x00020000) persistent ram + 0x1ffd4000 - 0x1fff3fff (size 0x00020000) persistent ram + 0x1fff4000 - 0x1fff7fff (size 0x00004000) ttb + 0x1fff8000 - 0x1fffffff (size 0x00008000) stack + +All pstore files that could be found are added to the /pstore directory. This is +a read-only filesystem. If you disable the Kconfig option FS_PSTORE_RAMOOPS_RO, +the RAMOOPS area is reset and its ECC recalculated. But that does not allow any +writes from Barebox into that area. -- 2.6.2 _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
