mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-18 09:44:18 +08:00
Documentation/ramoops.txt: convert it to ReST format
- Fix document title; - use quote blocks where needed; - use monotonic fonts for config options and file names; - adjust whitespaces and blank lines; - add it to the user's book. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
parent
e095f0711b
commit
b2777b650c
@ -5,34 +5,37 @@ Sergiu Iordache <sergiu@chromium.org>
|
||||
|
||||
Updated: 17 November 2011
|
||||
|
||||
0. Introduction
|
||||
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 concepts
|
||||
----------------
|
||||
|
||||
Ramoops uses a predefined memory area to store the dump. The start and size
|
||||
and type of the memory area are set using three variables:
|
||||
* "mem_address" for the start
|
||||
* "mem_size" for the size. The memory size will be rounded down to a
|
||||
power of two.
|
||||
* "mem_type" to specifiy if the memory type (default is pgprot_writecombine).
|
||||
|
||||
Typically the default value of mem_type=0 should be used as that sets the pstore
|
||||
mapping to pgprot_writecombine. Setting mem_type=1 attempts to use
|
||||
pgprot_noncached, which only works on some platforms. This is because pstore
|
||||
* ``mem_address`` for the start
|
||||
* ``mem_size`` for the size. The memory size will be rounded down to a
|
||||
power of two.
|
||||
* ``mem_type`` to specifiy if the memory type (default is pgprot_writecombine).
|
||||
|
||||
Typically the default value of ``mem_type=0`` should be used as that sets the pstore
|
||||
mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use
|
||||
``pgprot_noncached``, which only works on some platforms. This is because pstore
|
||||
depends on atomic operations. At least on ARM, pgprot_noncached causes the
|
||||
memory to be mapped strongly ordered, and atomic operations on strongly ordered
|
||||
memory are implementation defined, and won't work on many ARMs such as omaps.
|
||||
|
||||
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
|
||||
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"
|
||||
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
|
||||
@ -43,7 +46,8 @@ 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 parameters
|
||||
----------------------
|
||||
|
||||
Setting the ramoops parameters can be done in several different manners:
|
||||
|
||||
@ -52,12 +56,13 @@ Setting the ramoops parameters can be done in several different manners:
|
||||
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"
|
||||
ramoops region at 128 MB boundary::
|
||||
|
||||
mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1
|
||||
|
||||
B. Use Device Tree bindings, as described in
|
||||
Documentation/device-tree/bindings/reserved-memory/ramoops.txt.
|
||||
For example:
|
||||
``Documentation/device-tree/bindings/reserved-memory/ramoops.txt``.
|
||||
For example::
|
||||
|
||||
reserved-memory {
|
||||
#address-cells = <2>;
|
||||
@ -73,60 +78,63 @@ Setting the ramoops parameters can be done in several different manners:
|
||||
};
|
||||
|
||||
C. 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:
|
||||
be set through that platform data. An example of doing that is::
|
||||
|
||||
#include <linux/pstore_ram.h>
|
||||
[...]
|
||||
#include <linux/pstore_ram.h>
|
||||
[...]
|
||||
|
||||
static struct ramoops_platform_data ramoops_data = {
|
||||
static struct ramoops_platform_data ramoops_data = {
|
||||
.mem_size = <...>,
|
||||
.mem_address = <...>,
|
||||
.mem_type = <...>,
|
||||
.record_size = <...>,
|
||||
.dump_oops = <...>,
|
||||
.ecc = <...>,
|
||||
};
|
||||
};
|
||||
|
||||
static struct platform_device ramoops_dev = {
|
||||
static struct platform_device ramoops_dev = {
|
||||
.name = "ramoops",
|
||||
.dev = {
|
||||
.platform_data = &ramoops_data,
|
||||
},
|
||||
};
|
||||
};
|
||||
|
||||
[... inside a function ...]
|
||||
int ret;
|
||||
[... inside a function ...]
|
||||
int ret;
|
||||
|
||||
ret = platform_device_register(&ramoops_dev);
|
||||
if (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.:
|
||||
very early in the architecture code, e.g.::
|
||||
|
||||
#include <linux/memblock.h>
|
||||
#include <linux/memblock.h>
|
||||
|
||||
memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);
|
||||
memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);
|
||||
|
||||
3. Dump format
|
||||
Dump format
|
||||
-----------
|
||||
|
||||
The data dump begins with a header, currently defined as "====" followed by a
|
||||
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
|
||||
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
|
||||
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
|
||||
---------------------------
|
||||
|
||||
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:
|
||||
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
|
||||
|
Loading…
Reference in New Issue
Block a user