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pstore/ramoops: Add ramoops.mem_name= command line option

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Add a method to find a region specified by reserve_mem=nn:align:name for
ramoops. Adding a kernel command line parameter:

  reserve_mem=12M:4096:oops ramoops.mem_name=oops

Will use the size and location defined by the memmap parameter where it
finds the memory and labels it "oops". The "oops" in the ramoops option
is used to search for it.

This allows for arbitrary RAM to be used for ramoops if it is known that
the memory is not cleared on kernel crashes or soft reboots.

Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20240613155527.591647061@goodmis.org
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
This commit is contained in:
Steven Rostedt (Google) 2024-06-13 11:55:08 -04:00 committed by Mike Rapoport (IBM)
parent 1e4c64b71c
commit d9d814eebb
2 changed files with 27 additions and 0 deletions
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13
Documentation/admin-guide/ramoops.rst
View File

@ -23,6 +23,8 @@ and type of the memory area are set using three variables:
* ``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.
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
@ -118,6 +120,17 @@ Setting the ramoops parameters can be done in several different manners:
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.
reserver_mem=2M:4096:oops ramoops.mem_name=oops
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.::

14
fs/pstore/ram.c
View File

@ -50,6 +50,10 @@ module_param_hw(mem_address, ullong, other, 0400);
MODULE_PARM_DESC(mem_address,
"start of reserved RAM used to store oops/panic logs");
static char *mem_name;
module_param_named(mem_name, mem_name, charp, 0400);
MODULE_PARM_DESC(mem_name, "name of kernel param that holds addr");
static ulong mem_size;
module_param(mem_size, ulong, 0400);
MODULE_PARM_DESC(mem_size,
@ -914,6 +918,16 @@ static void __init ramoops_register_dummy(void)
{
struct ramoops_platform_data pdata;
if (mem_name) {
phys_addr_t start;
phys_addr_t size;
if (reserve_mem_find_by_name(mem_name, &start, &size)) {
mem_address = start;
mem_size = size;
}
}
/*
* Prepare a dummy platform data structure to carry the module
* parameters. If mem_size isn't set, then there are no module