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diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt deleted file mode 100644 index 69b3cac4749d..000000000000 --- a/Documentation/ramoops.txt +++ /dev/null @@ -1,119 +0,0 @@ -Ramoops oops/panic logger -========================= - -Sergiu Iordache <sergiu@chromium.org> - -Updated: 17 November 2011 - -0. Introduction - -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. - -1. Ramoops concepts - -Ramoops uses a predefined memory area to store the dump. The start and size of -the memory area are set using two variables: - * "mem_address" for the start - * "mem_size" for the size. The memory size will be rounded down to a - power of two. - -The memory area is divided into "record_size" chunks (also rounded down to -power of two) and each oops/panic writes a "record_size" chunk of -information. - -Dumping both oopses and panics can be done by setting 1 in the "dump_oops" -variable while setting 0 in that variable dumps only the panics. - -The module uses a counter to record multiple dumps but the counter gets reset -on restart (i.e. new dumps after the restart will overwrite old ones). - -Ramoops also supports software ECC protection of persistent memory regions. -This might be useful when a hardware reset was used to bring the machine back -to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat -corrupt, but usually it is restorable. - -2. Setting the parameters - -Setting the ramoops parameters can be done in 2 different manners: - 1. Use the module parameters (which have the names of the variables described - as before). - For quick debugging, you can also reserve parts of memory during boot - and then use the reserved memory for ramoops. For example, assuming a machine - with > 128 MB of memory, the following kernel command line will tell the - kernel to use only the first 128 MB of memory, and place ECC-protected ramoops - region at 128 MB boundary: - "mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1" - 2. Use a platform device and set the platform data. The parameters can then - be set through that platform data. An example of doing that is: - -#include <linux/pstore_ram.h> -[...] - -static struct ramoops_platform_data ramoops_data = { - .mem_size = <...>, - .mem_address = <...>, - .record_size = <...>, - .dump_oops = <...>, - .ecc = <...>, -}; - -static struct platform_device ramoops_dev = { - .name = "ramoops", - .dev = { - .platform_data = &ramoops_data, - }, -}; - -[... inside a function ...] -int ret; - -ret = platform_device_register(&ramoops_dev); -if (ret) { - printk(KERN_ERR "unable to register platform device\n"); - return ret; -} - -You can specify either RAM memory or peripheral devices' memory. However, when -specifying RAM, be sure to reserve the memory by issuing memblock_reserve() -very early in the architecture code, e.g.: - -#include <linux/memblock.h> - -memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size); - -3. Dump format - -The data dump begins with a header, currently defined as "====" followed by a -timestamp and a new line. The dump then continues with the actual data. - -4. Reading the data - -The dump data can be read from the pstore filesystem. The format for these -files is "dmesg-ramoops-N", where N is the record number in memory. To delete -a stored record from RAM, simply unlink the respective pstore file. - -5. Persistent function tracing - -Persistent function tracing might be useful for debugging software or hardware -related hangs. The functions call chain log is stored in a "ftrace-ramoops" -file. Here is an example of usage: - - # mount -t debugfs debugfs /sys/kernel/debug/ - # echo 1 > /sys/kernel/debug/pstore/record_ftrace - # reboot -f - [...] - # mount -t pstore pstore /mnt/ - # tail /mnt/ftrace-ramoops - 0 ffffffff8101ea64 ffffffff8101bcda native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0 - 0 ffffffff8101ea44 ffffffff8101bcf6 native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0 - 0 ffffffff81020084 ffffffff8101a4b5 hpet_disable <- native_machine_shutdown+0x75/0x90 - 0 ffffffff81005f94 ffffffff8101a4bb iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90 - 0 ffffffff8101a6a1 ffffffff8101a437 native_machine_emergency_restart <- native_machine_restart+0x37/0x40 - 0 ffffffff811f9876 ffffffff8101a73a acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0 - 0 ffffffff8101a514 ffffffff8101a772 mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0 - 0 ffffffff811d9c54 ffffffff8101a7a0 __const_udelay <- native_machine_emergency_restart+0x110/0x1e0 - 0 ffffffff811d9c34 ffffffff811d9c80 __delay <- __const_udelay+0x30/0x40 - 0 ffffffff811d9d14 ffffffff811d9c3f delay_tsc <- __delay+0xf/0x20 |