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pstore/ram: Introduce max_reason and convert dump_oops

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Now that pstore_register() can correctly pass max_reason to the kmesg
dump facility, introduce a new "max_reason" module parameter and
"max-reason" Device Tree field.

The "dump_oops" module parameter and "dump-oops" Device
Tree field are now considered deprecated, but are now automatically
converted to their corresponding max_reason values when present, though
the new max_reason setting has precedence.

For struct ramoops_platform_data, the "dump_oops" member is entirely
replaced by a new "max_reason" member, with the only existing user
updated in place.

Additionally remove the "reason" filter logic from ramoops_pstore_write(),
as that is not specifically needed anymore, though technically
this is a change in behavior for any ramoops users also setting the
printk.always_kmsg_dump boot param, which will cause ramoops to behave as
if max_reason was set to KMSG_DUMP_MAX.

Co-developed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/lkml/20200515184434.8470-6-keescook@chromium.org/
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
2020-05-13 14:35:03 -07:00
parent 3524e688b8
commit 791205e3ec
4 changed files with 51 additions and 25 deletions
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14
Documentation/admin-guide/ramoops.rst
View File

@@ -32,11 +32,17 @@ 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
power of two) and each kmesg dump 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.
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.
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).
@@ -90,7 +96,7 @@ Setting the ramoops parameters can be done in several different manners:
.mem_address = <...>,
.mem_type = <...>,
.record_size = <...>,
.dump_oops = <...>,
.max_reason = <...>,
.ecc = <...>,
};