€•®t      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ'/translations/zh_CN/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/zh_TW/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/it_IT/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/ja_JP/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/ko_KR/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ'/translations/sp_SP/admin-guide/ramoops”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒRamoops oops/panic logger”h]”hŒRamoops oops/panic logger”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒA/var/lib/git/docbuild/linux/Documentation/admin-guide/ramoops.rst”h KubhŒ	paragraph”“”)”}”(hŒ%Sergiu Iordache <sergiu@chromium.org>”h]”(hŒSergiu Iordache <”…””}”(hh¹hžhhŸNh NubhŒ	reference”“”)”}”(hŒsergiu@chromium.org”h]”hŒsergiu@chromium.org”…””}”(hhÃhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:sergiu@chromium.org”uh1hÁhh¹ubhŒ>”…””}”(hh¹hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒUpdated: 10 Feb 2021”h]”hŒUpdated: 10 Feb 2021”…””}”(hhÝhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒIntroduction”h]”hŒIntroduction”…””}”(hhîhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhëhžhhŸh¶h K	ubh¸)”}”(hŒûRamoops is an oops/panic logger that writes its logs to RAM before the system
crashes. It works by logging oopses and panics in a circular buffer. Ramoops
needs a system with persistent RAM so that the content of that area can
survive after a restart.”h]”hŒûRamoops is an oops/panic logger that writes its logs to RAM before the system
crashes. It works by logging oopses and panics in a circular buffer. Ramoops
needs a system with persistent RAM so that the content of that area can
survive after a restart.”…””}”(hhühžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khhëhžhubeh}”(h]”Œintroduction”ah ]”h"]”Œintroduction”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K	ubh¢)”}”(hhh]”(h§)”}”(hŒRamoops concepts”h]”hŒRamoops concepts”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h Kubh¸)”}”(hŒ†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:”h]”hŒ†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:”…””}”(hj#  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj  hžhubhŒblock_quote”“”)”}”(hX%  * ``mem_address`` for the start
* ``mem_size`` for the size. The memory size will be rounded down to a
  power of two.
* ``mem_type`` to specify if the memory type (default is pgprot_writecombine).
* ``mem_name`` to specify a memory region defined by ``reserve_mem`` command
  line parameter.
”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒ``mem_address`` for the start”h]”h¸)”}”(hj@  h]”(hŒliteral”“”)”}”(hŒ``mem_address``”h]”hŒmem_address”…””}”(hjG  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjB  ubhŒ for the start”…””}”(hjB  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj>  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j<  hj9  ubj=  )”}”(hŒR``mem_size`` for the size. The memory size will be rounded down to a
power of two.”h]”h¸)”}”(hŒR``mem_size`` for the size. The memory size will be rounded down to a
power of two.”h]”(jF  )”}”(hŒ``mem_size``”h]”hŒmem_size”…””}”(hjm  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hji  ubhŒF for the size. The memory size will be rounded down to a
power of two.”…””}”(hji  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khje  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j<  hj9  ubj=  )”}”(hŒL``mem_type`` to specify if the memory type (default is pgprot_writecombine).”h]”h¸)”}”(hj  h]”(jF  )”}”(hŒ``mem_type``”h]”hŒmem_type”…””}”(hj’  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj  ubhŒ@ to specify if the memory type (default is pgprot_writecombine).”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj‹  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j<  hj9  ubj=  )”}”(hŒ[``mem_name`` to specify a memory region defined by ``reserve_mem`` command
line parameter.
”h]”h¸)”}”(hŒZ``mem_name`` to specify a memory region defined by ``reserve_mem`` command
line parameter.”h]”(jF  )”}”(hŒ``mem_name``”h]”hŒmem_name”…””}”(hj¸  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj´  ubhŒ' to specify a memory region defined by ”…””}”(hj´  hžhhŸNh NubjF  )”}”(hŒ``reserve_mem``”h]”hŒreserve_mem”…””}”(hjÊ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj´  ubhŒ command
line parameter.”…””}”(hj´  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj°  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j<  hj9  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1j7  hŸh¶h Khj3  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j1  hŸh¶h Khj  hžhubh¸)”}”(hXd  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.
Setting ``mem_type=2`` attempts to treat the memory region as normal memory,
which enables full cache on it. This can improve the performance.”h]”(hŒTypically the default value of ”…””}”(hjö  hžhhŸNh NubjF  )”}”(hŒ``mem_type=0``”h]”hŒ
mem_type=0”…””}”(hjþ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjö  ubhŒP should be used as that sets the pstore
mapping to pgprot_writecombine. Setting ”…””}”(hjö  hžhhŸNh NubjF  )”}”(hŒ``mem_type=1``”h]”hŒ
mem_type=1”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjö  ubhŒ attempts to use
”…””}”(hjö  hžhhŸNh NubjF  )”}”(hŒ``pgprot_noncached``”h]”hŒpgprot_noncached”…””}”(hj"  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjö  ubhX0  , which only works on some platforms. This is because pstore
depends on atomic operations. At least on ARM, pgprot_noncached causes the
memory to be mapped strongly ordered, and atomic operations on strongly ordered
memory are implementation defined, and wonâ€™t work on many ARMs such as omaps.
Setting ”…””}”(hjö  hžhhŸNh NubjF  )”}”(hŒ``mem_type=2``”h]”hŒ
mem_type=2”…””}”(hj4  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjö  ubhŒx attempts to treat the memory region as normal memory,
which enables full cache on it. This can improve the performance.”…””}”(hjö  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj  hžhubh¸)”}”(hŒThe memory area is divided into ``record_size`` chunks (also rounded down to
power of two) and each kmesg dump writes a ``record_size`` chunk of
information.”h]”(hŒ The memory area is divided into ”…””}”(hjL  hžhhŸNh NubjF  )”}”(hŒ``record_size``”h]”hŒrecord_size”…””}”(hjT  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjL  ubhŒI chunks (also rounded down to
power of two) and each kmesg dump writes a ”…””}”(hjL  hžhhŸNh NubjF  )”}”(hŒ``record_size``”h]”hŒrecord_size”…””}”(hjf  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjL  ubhŒ chunk of
information.”…””}”(hjL  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K&hj  hžhubh¸)”}”(hX  Limiting which kinds of kmsg dumps are stored can be controlled via
the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's
``enum kmsg_dump_reason``. For example, to store both Oopses and Panics,
``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics
``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0
(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the
``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS,
otherwise KMSG_DUMP_MAX.”h]”(hŒHLimiting which kinds of kmsg dumps are stored can be controlled via
the ”…””}”(hj~  hžhhŸNh NubjF  )”}”(hŒ``max_reason``”h]”hŒ
max_reason”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj~  ubhŒ4 value, as defined in include/linux/kmsg_dump.hâ€™s
”…””}”(hj~  hžhhŸNh NubjF  )”}”(hŒ``enum kmsg_dump_reason``”h]”hŒenum kmsg_dump_reason”…””}”(hj˜  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj~  ubhŒ0. For example, to store both Oopses and Panics,
”…””}”(hj~  hžhhŸNh NubjF  )”}”(hŒ``max_reason``”h]”hŒ
max_reason”…””}”(hjª  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj~  ubhŒ; should be set to 2 (KMSG_DUMP_OOPS), to store only Panics
”…””}”(hj~  hžhhŸNh NubjF  )”}”(hŒ``max_reason``”h]”hŒ
max_reason”…””}”(hj¼  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj~  ubhŒ should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0
(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the
”…””}”(hj~  hžhhŸNh NubjF  )”}”(hŒ``printk.always_kmsg_dump``”h]”hŒprintk.always_kmsg_dump”…””}”(hjÎ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj~  ubhŒJ boot param: if unset, itâ€™ll be KMSG_DUMP_OOPS,
otherwise KMSG_DUMP_MAX.”…””}”(hj~  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K*hj  hžhubh¸)”}”(hŒ”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).”h]”hŒ”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).”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K3hj  hžhubh¸)”}”(hX  Ramoops also supports software ECC protection of persistent memory regions.
This might be useful when a hardware reset was used to bring the machine back
to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat
corrupt, but usually it is restorable.”h]”hX  Ramoops also supports software ECC protection of persistent memory regions.
This might be useful when a hardware reset was used to bring the machine back
to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat
corrupt, but usually it is restorable.”…””}”(hjô  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K6hj  hžhubeh}”(h]”Œramoops-concepts”ah ]”h"]”Œramoops concepts”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒSetting the parameters”h]”hŒSetting the parameters”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj
  hžhhŸh¶h K<ubh¸)”}”(hŒHSetting the ramoops parameters can be done in several different manners:”h]”hŒHSetting the ramoops parameters can be done in several different manners:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K>hj
  hžhubj2  )”}”(hXˆ	  A. 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

B. Use Device Tree bindings, as described in
``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``.
For example::

       reserved-memory {
               #address-cells = <2>;
               #size-cells = <2>;
               ranges;

               ramoops@8f000000 {
                       compatible = "ramoops";
                       reg = <0 0x8f000000 0 0x100000>;
                       record-size = <0x4000>;
                       console-size = <0x4000>;
               };
       };

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:

.. code-block:: c

 #include <linux/pstore_ram.h>
 [...]

 static struct ramoops_platform_data ramoops_data = {
       .mem_size               = <...>,
       .mem_address            = <...>,
       .mem_type               = <...>,
       .record_size            = <...>,
       .max_reason             = <...>,
       .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;
 }

D. Using a region of memory reserved via ``reserve_mem`` command line
   parameter. The address and size will be defined by the ``reserve_mem``
   parameter. Note, that ``reserve_mem`` may not always allocate memory
   in the same location, and cannot be relied upon. Testing will need
   to be done, and it may not work on every machine, nor every kernel.
   Consider this a "best effort" approach. The ``reserve_mem`` option
   takes a size, alignment and name as arguments. The name is used
   to map the memory to a label that can be retrieved by ramoops.

       reserve_mem=2M:4096:oops  ramoops.mem_name=oops
”h]”(h¸)”}”(hX¡  A. 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::”h]”hX   A. 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:”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K@hj)  ubhŒliteral_block”“”)”}”(hŒ4mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1”h]”hŒ4mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1”…””}”hj=  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j;  hŸh¶h KGhj)  ubh¸)”}”(hŒ~B. Use Device Tree bindings, as described in
``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``.
For example::”h]”(hŒ-B. Use Device Tree bindings, as described in
”…””}”(hjM  hžhhŸNh NubjF  )”}”(hŒB``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``”h]”hŒ>Documentation/devicetree/bindings/reserved-memory/ramoops.yaml”…””}”(hjU  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjM  ubhŒ.
For example:”…””}”(hjM  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KIhj)  ubj<  )”}”(hX.  reserved-memory {
        #address-cells = <2>;
        #size-cells = <2>;
        ranges;

        ramoops@8f000000 {
                compatible = "ramoops";
                reg = <0 0x8f000000 0 0x100000>;
                record-size = <0x4000>;
                console-size = <0x4000>;
        };
};”h]”hX.  reserved-memory {
        #address-cells = <2>;
        #size-cells = <2>;
        ranges;

        ramoops@8f000000 {
                compatible = "ramoops";
                reg = <0 0x8f000000 0 0x100000>;
                record-size = <0x4000>;
                console-size = <0x4000>;
        };
};”…””}”hjm  sbah}”(h]”h ]”h"]”h$]”h&]”jK  jL  uh1j;  hŸh¶h KMhj)  ubh¸)”}”(hŒ‹C. Use a platform device and set the platform data. The parameters can then
be set through that platform data. An example of doing that is:”h]”hŒ‹C. Use a platform device and set the platform data. The parameters can then
be set through that platform data. An example of doing that is:”…””}”(hj{  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KZhj)  ubj<  )”}”(hXŠ  #include <linux/pstore_ram.h>
[...]

static struct ramoops_platform_data ramoops_data = {
      .mem_size               = <...>,
      .mem_address            = <...>,
      .mem_type               = <...>,
      .record_size            = <...>,
      .max_reason             = <...>,
      .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;
}”h]”hXŠ  #include <linux/pstore_ram.h>
[...]

static struct ramoops_platform_data ramoops_data = {
      .mem_size               = <...>,
      .mem_address            = <...>,
      .mem_type               = <...>,
      .record_size            = <...>,
      .max_reason             = <...>,
      .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;
}”…””}”hj‰  sbah}”(h]”h ]”h"]”h$]”h&]”jK  jL  Œforce”‰Œlanguage”Œc”Œhighlight_args”}”uh1j;  hŸh¶h K]hj)  ubhŒenumerated_list”“”)”}”(hhh]”j=  )”}”(hXM  Using a region of memory reserved via ``reserve_mem`` command line
parameter. The address and size will be defined by the ``reserve_mem``
parameter. Note, that ``reserve_mem`` may not always allocate memory
in the same location, and cannot be relied upon. Testing will need
to be done, and it may not work on every machine, nor every kernel.
Consider this a "best effort" approach. The ``reserve_mem`` option
takes a size, alignment and name as arguments. The name is used
to map the memory to a label that can be retrieved by ramoops.

    reserve_mem=2M:4096:oops  ramoops.mem_name=oops
”h]”(h¸)”}”(hX  Using a region of memory reserved via ``reserve_mem`` command line
parameter. The address and size will be defined by the ``reserve_mem``
parameter. Note, that ``reserve_mem`` may not always allocate memory
in the same location, and cannot be relied upon. Testing will need
to be done, and it may not work on every machine, nor every kernel.
Consider this a "best effort" approach. The ``reserve_mem`` option
takes a size, alignment and name as arguments. The name is used
to map the memory to a label that can be retrieved by ramoops.”h]”(hŒ&Using a region of memory reserved via ”…””}”(hj¥  hžhhŸNh NubjF  )”}”(hŒ``reserve_mem``”h]”hŒreserve_mem”…””}”(hj­  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj¥  ubhŒE command line
parameter. The address and size will be defined by the ”…””}”(hj¥  hžhhŸNh NubjF  )”}”(hŒ``reserve_mem``”h]”hŒreserve_mem”…””}”(hj¿  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj¥  ubhŒ
parameter. Note, that ”…””}”(hj¥  hžhhŸNh NubjF  )”}”(hŒ``reserve_mem``”h]”hŒreserve_mem”…””}”(hjÑ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj¥  ubhŒ× may not always allocate memory
in the same location, and cannot be relied upon. Testing will need
to be done, and it may not work on every machine, nor every kernel.
Consider this a â€œbest effortâ€ approach. The ”…””}”(hj¥  hžhhŸNh NubjF  )”}”(hŒ``reserve_mem``”h]”hŒreserve_mem”…””}”(hjã  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj¥  ubhŒ† option
takes a size, alignment and name as arguments. The name is used
to map the memory to a label that can be retrieved by ramoops.”…””}”(hj¥  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K{hj¡  ubj2  )”}”(hŒ0reserve_mem=2M:4096:oops  ramoops.mem_name=oops
”h]”h¸)”}”(hŒ/reserve_mem=2M:4096:oops  ramoops.mem_name=oops”h]”hŒ/reserve_mem=2M:4096:oops  ramoops.mem_name=oops”…””}”(hjÿ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K„hjû  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j1  hŸh¶h K„hj¡  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j<  hjž  ubah}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œ
upperalpha”Œprefix”hŒsuffix”Œ.”Œstart”Kuh1jœ  hj)  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j1  hŸh¶h K@hj
  hžhubh¸)”}”(hŒÆYou 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.::”h]”hŒÇYou can specify either RAM memory or peripheral devicesâ€™ memory. However, when
specifying RAM, be sure to reserve the memory by issuing memblock_reserve()
very early in the architecture code, e.g.:”…””}”(hj+  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K†hj
  hžhubj<  )”}”(hŒ_#include <linux/memblock.h>

memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);”h]”hŒ_#include <linux/memblock.h>

memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);”…””}”hj9  sbah}”(h]”h ]”h"]”h$]”h&]”jK  jL  uh1j;  hŸh¶h KŠhj
  hžhubeh}”(h]”Œsetting-the-parameters”ah ]”h"]”Œsetting the parameters”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K<ubh¢)”}”(hhh]”(h§)”}”(hŒDump format”h]”hŒDump format”…””}”(hjR  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjO  hžhhŸh¶h Kubh¸)”}”(hŒ—The data dump begins with a header, currently defined as ``====`` followed by a
timestamp and a new line. The dump then continues with the actual data.”h]”(hŒ9The data dump begins with a header, currently defined as ”…””}”(hj`  hžhhŸNh NubjF  )”}”(hŒ``====``”h]”hŒ====”…””}”(hjh  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj`  ubhŒV followed by a
timestamp and a new line. The dump then continues with the actual data.”…””}”(hj`  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‘hjO  hžhubeh}”(h]”Œdump-format”ah ]”h"]”Œdump format”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒReading the data”h]”hŒReading the data”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjˆ  hžhhŸh¶h K•ubh¸)”}”(hŒÞThe dump data can be read from the pstore filesystem. The format for these
files is ``dmesg-ramoops-N``, where N is the record number in memory. To delete
a stored record from RAM, simply unlink the respective pstore file.”h]”(hŒTThe dump data can be read from the pstore filesystem. The format for these
files is ”…””}”(hj™  hžhhŸNh NubjF  )”}”(hŒ``dmesg-ramoops-N``”h]”hŒdmesg-ramoops-N”…””}”(hj¡  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hj™  ubhŒw, where N is the record number in memory. To delete
a stored record from RAM, simply unlink the respective pstore file.”…””}”(hj™  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K—hjˆ  hžhubeh}”(h]”Œreading-the-data”ah ]”h"]”Œreading the data”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K•ubh¢)”}”(hhh]”(h§)”}”(hŒPersistent function tracing”h]”hŒPersistent function tracing”…””}”(hjÄ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÁ  hžhhŸh¶h Kœubh¸)”}”(hŒÀPersistent function tracing might be useful for debugging software or hardware
related hangs. The functions call chain log is stored in a ``ftrace-ramoops``
file. Here is an example of usage::”h]”(hŒŠPersistent function tracing might be useful for debugging software or hardware
related hangs. The functions call chain log is stored in a ”…””}”(hjÒ  hžhhŸNh NubjF  )”}”(hŒ``ftrace-ramoops``”h]”hŒftrace-ramoops”…””}”(hjÚ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jE  hjÒ  ubhŒ#
file. Here is an example of usage:”…””}”(hjÒ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KžhjÁ  hžhubj<  )”}”(hXB  # 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”h]”hXB  # 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”…””}”hjò  sbah}”(h]”h ]”h"]”h$]”h&]”jK  jL  uh1j;  hŸh¶h K¢hjÁ  hžhubeh}”(h]”Œpersistent-function-tracing”ah ]”h"]”Œpersistent function tracing”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kœubeh}”(h]”Œramoops-oops-panic-logger”ah ]”h"]”Œramoops oops/panic logger”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j3  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j
  j  j  j  j  jL  jI  j…  j‚  j¾  j»  j  j  uŒ	nametypes”}”(j  ‰j  ‰j  ‰jL  ‰j…  ‰j¾  ‰j  ‰uh}”(j
  h£j  hëj  j  jI  j
  j‚  jO  j»  jˆ  j  jÁ  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”hŒsystem_message”“”)”}”(hhh]”h¸)”}”(hŒ:Enumerated list start value not ordinal-1: "D" (ordinal 4)”h]”hŒ>Enumerated list start value not ordinal-1: â€œDâ€ (ordinal 4)”…””}”(hjš  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hj—  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”ŒINFO”Œsource”h¶Œline”Kuh1j•  hj)  ubaŒtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.