linux-kernel - Re: [POC][RFC][PATCH 0/2] pstore/mm/x86: Add wildcard memmap to map pstore consistently

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Message-ID: <202404091628.BEC1FAC8@keescook>
Date: Tue, 9 Apr 2024 16:37:10 -0700
From: Kees Cook <keescook@...omium.org>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-trace-kernel@...r.kernel.org" <linux-trace-kernel@...r.kernel.org>,
	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" <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" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Ross Zwisler <zwisler@...gle.com>,
	"wklin@...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>
Subject: Re: [POC][RFC][PATCH 0/2] pstore/mm/x86: Add wildcard memmap to map
 pstore consistently

On Tue, Apr 09, 2024 at 10:25:33PM +0000, Luck, Tony wrote:
> >> I forgot to mention that this makes it trivial for any machine that doesn't
> >> clear memory on soft-reboot, to enable console ramoops (to have access to
> >> the last boot dmesg without needing serial).
> >> 
> >> I tested this on a couple of my test boxes and on QEMU, and it works rather
> >> well.
> >
> > I've long wanted a "stable for this machine and kernel" memory region
> > like this for pstore. It would make testing much easier.
> 
> Which systems does this work on? I'd assume that servers (and anything
> else with ECC memory) would nuke contents while resetting ECC to clean
> state.

Do ECC servers wipe their RAM by default? I know that if you build with
CONFIG_RESET_ATTACK_MITIGATION=y on an EFI system that supports the
MemoryOverwriteRequestControl EFI variable you'll get a RAM wipe...

-- 
Kees Cook