linux-hardening - Re: [POC][RFC][PATCH 1/2] mm/x86: Add wildcard * option as memmap=nn*align:name

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Date: Tue, 9 Apr 2024 16:41:24 -0700
From: Kees Cook <keescook@...omium.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-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,
	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>,
	Tony Luck <tony.luck@...el.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	linux-hardening@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
	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>
Subject: Re: [POC][RFC][PATCH 1/2] mm/x86: Add wildcard * option as
 memmap=nn*align:name

On Tue, Apr 09, 2024 at 07:11:56PM -0400, Steven Rostedt wrote:
> On Tue, 9 Apr 2024 15:23:07 -0700
> Kees Cook <keescook@...omium.org> wrote:
> 
> > Do we need to involve e820 at all? I think it might be possible to just
> > have pstore call request_mem_region() very early? Or does KASLR make
> > that unstable?
> 
> Yeah, would that give the same physical memory each boot, and can we
> guarantee that KASLR will not map the kernel over the previous location?

Hm, no, for physical memory it needs to get excluded very early, which
means e820. So, yeah, your proposal makes sense. I'm not super excited
about this be x86-only though. What does arm64 for for memmap?

-- 
Kees Cook