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From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Andrew Donnellan" <ajd@linux.ibm.com>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc: "linux-hardening@vger.kernel.org"
	<linux-hardening@vger.kernel.org>,
	"cmr@bluescreens.de" <cmr@bluescreens.de>
Subject: Re: [RFC PATCH 2/6] powerpc/64s: Helpers to switch between linear and vmapped stack pointers
Date: Mon, 07 Nov 2022 22:38:06 +1000	[thread overview]
Message-ID: <CO62IBK4D7K1.1USN6WO3YDZPY@bobo> (raw)
In-Reply-To: <20c79a09-0b95-bb52-2495-999d2365308d@csgroup.eu>

On Sat Nov 5, 2022 at 6:00 PM AEST, Christophe Leroy wrote:
>
>
> Le 04/11/2022 à 18:27, Andrew Donnellan a écrit :
> > powerpc unfortunately has too many places where we run stuff in real mode.
> > 
> > With CONFIG_VMAP_STACK enabled, this means we need to be able to swap the
> > stack pointer to use the linear mapping when we enter a real mode section,
> > and back afterwards.
> > 
> > Store the top bits of the stack pointer in both the linear map and the
> > vmalloc space in the PACA, and add some helper macros/functions to swap
> > between them.
>
> That may work when pagesize is 64k because stack is on a single page, 
> but I doubt is works with 4k pages, because vmalloc may allocate non 
> contiguous pages.

Yeah. This could be a first-stage though, and depend on 64k page size
and stack size, or !KVM or whatever. When the real-mode code is solved,
that could be relaxed.

Thanks,
Nick

  parent reply	other threads:[~2022-11-07 12:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-04 17:27 [RFC PATCH 0/6] VMAP_STACK support for book3s64 Andrew Donnellan
2022-11-04 17:27 ` [RFC PATCH 1/6] powerpc/64s: Fix assembly to support larger values of THREAD_SIZE Andrew Donnellan
2022-11-04 17:51   ` Christophe Leroy
2023-04-26  7:03     ` Andrew Donnellan
2022-11-04 17:27 ` [RFC PATCH 2/6] powerpc/64s: Helpers to switch between linear and vmapped stack pointers Andrew Donnellan
2022-11-05  8:00   ` Christophe Leroy
2022-11-05 19:28     ` Christophe Leroy
2022-11-07 12:38     ` Nicholas Piggin [this message]
2022-11-04 17:27 ` [RFC PATCH 3/6] powerpc/powernv: Keep MSR in register across OPAL entry/return path Andrew Donnellan
2022-11-04 18:00   ` Christophe Leroy
2022-11-04 17:27 ` [RFC PATCH 4/6] powerpc/powernv: Convert pointers to physical addresses in OPAL call args Andrew Donnellan
2022-11-07  0:00   ` Russell Currey
2022-11-08 16:21   ` Christophe Leroy
2022-11-04 17:27 ` [RFC PATCH 5/6] powerpc/powernv/idle: Convert stack pointer to physical address Andrew Donnellan
2022-11-08 16:17   ` Christophe Leroy
2022-11-04 17:27 ` [RFC PATCH 6/6] powerpc/64s: Enable CONFIG_VMAP_STACK Andrew Donnellan
2022-11-05 17:07   ` Christophe Leroy

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