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author | David S. Miller <davem@davemloft.net> | 2011-09-22 03:23:13 -0400 |
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committer | David S. Miller <davem@davemloft.net> | 2011-09-22 03:23:13 -0400 |
commit | 8decf868790b48a727d7e7ca164f2bcd3c1389c0 (patch) | |
tree | b759a5f861f842af7ea76f9011b579d06e9d5508 /Documentation/ramoops.txt | |
parent | 3fc72370186be2f9d4d6ef06d99e1caa5d92c564 (diff) | |
parent | d93dc5c4478c1fd5de85a3e8aece9aad7bbae044 (diff) | |
download | linux-8decf868790b48a727d7e7ca164f2bcd3c1389c0.tar.gz linux-8decf868790b48a727d7e7ca164f2bcd3c1389c0.tar.bz2 linux-8decf868790b48a727d7e7ca164f2bcd3c1389c0.zip |
Merge branch 'master' of github.com:davem330/net
Conflicts:
MAINTAINERS
drivers/net/Kconfig
drivers/net/ethernet/broadcom/bnx2x/bnx2x_link.c
drivers/net/ethernet/broadcom/tg3.c
drivers/net/wireless/iwlwifi/iwl-pci.c
drivers/net/wireless/iwlwifi/iwl-trans-tx-pcie.c
drivers/net/wireless/rt2x00/rt2800usb.c
drivers/net/wireless/wl12xx/main.c
Diffstat (limited to 'Documentation/ramoops.txt')
-rw-r--r-- | Documentation/ramoops.txt | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt new file mode 100644 index 000000000000..8fb1ba7fe7bf --- /dev/null +++ b/Documentation/ramoops.txt @@ -0,0 +1,76 @@ +Ramoops oops/panic logger +========================= + +Sergiu Iordache <sergiu@chromium.org> + +Updated: 8 August 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). + +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). + 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/ramoops.h> +[...] + +static struct ramoops_platform_data ramoops_data = { + .mem_size = <...>, + .mem_address = <...>, + .record_size = <...>, + .dump_oops = <...>, +}; + +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; +} + +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 memory (through /dev/mem or other means). +Getting the module parameters, which are needed in order to parse the data, can +be done through /sys/module/ramoops/parameters/* . |