linux-hardening - Re: [PATCH v4 2/2] pstore/ramoops: Add ramoops.mem

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Message-ID: <c237c185-dbf3-49dc-a849-058d9093570b@roeck-us.net>
Date: Tue, 11 Jun 2024 15:30:50 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Lorenzo Stoakes <lstoakes@...il.com>, linux-mm@...ck.org,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Peter Zijlstra <peterz@...radead.org>, Kees Cook <keescook@...omium.org>,
 Tony Luck <tony.luck@...el.com>, "Guilherme G. Piccoli"
 <gpiccoli@...lia.com>, linux-hardening@...r.kernel.org,
 Ross Zwisler <zwisler@...gle.com>, wklin@...gle.com,
 Vineeth Remanan Pillai <vineeth@...byteword.org>,
 Joel Fernandes <joel@...lfernandes.org>,
 Suleiman Souhlal <suleiman@...gle.com>,
 Linus Torvalds <torvalds@...uxfoundation.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Ard Biesheuvel <ardb@...nel.org>, Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH v4 2/2] pstore/ramoops: Add ramoops.mem_name= command line
 option

On 6/11/24 14:56, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> 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.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
> Changes since v3: https://lore.kernel.org/linux-trace-kernel/20240606150316.916395285@goodmis.org
> 
> - Change type of start and size to phys_addr_t
> 
>   fs/pstore/ram.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index b1a455f42e93..4311fcbc84f2 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -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