Re: [POC][RFC][PATCH 2/2] pstore/ramoops: Add ramoops.mem_name= command line option

Kees Cook
2024-04-09T22:18:47Z

On Tue, Apr 09, 2024 at 05:02:56PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
>
> Add a method to find a region specified by memmap=nn*align:name for
> ramoops. Adding a kernel command line parameter:
>
> memmap=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.
>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> fs/pstore/ram.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index b1a455f42e93..c200388399fb 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -50,6 +50,11 @@ 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 (builtin only)");
> +
> static ulong mem_size;
> module_param(mem_size, ulong, 0400);
> MODULE_PARM_DESC(mem_size,
> @@ -914,6 +919,19 @@ static void __init ramoops_register_dummy(void)
> {
> struct ramoops_platform_data pdata;
>
> +#ifndef MODULE
> + /* Only allowed when builtin */

Why only when builtin?

> + if (mem_name) {
> + u64 start;
> + u64 size;
> +
> + if (memmap_named(mem_name, &start, &size)) {
> + mem_address = start;
> + mem_size = size;
> + }
> + }
> +#endif

Otherwise this looks good, though I'd prefer some comments about what's
happening here.

(And in retrospect, separately, I probably need to rename "dummy" to
"commandline" or something, since it's gathering valid settings here...)

--
Kees Cook