linux-kernel - Re: [PATCH] ARM: mmu: fix access to illegal address when using earlycon & memblock=debug

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Date:   Mon, 18 Apr 2022 01:21:10 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Victor Hassan <victor@...winnertech.com>
Cc:     linux@...linux.org.uk, rmk+kernel@...linux.org.uk,
        yanfei.xu@...driver.com, ardb@...nel.org, tglx@...utronix.de,
        mirq-linux@...e.qmqm.pl, arnd@...db.de,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        allwinner-opensource-support@...winnertech.com
Subject: Re: [PATCH] ARM: mmu: fix access to illegal address when using
 earlycon & memblock=debug

On Wed, Mar 16, 2022 at 3:33 AM Victor Hassan <victor@...winnertech.com> wrote:

> earlycon uses fixmap to create a memory map,
> So we need to close earlycon before closing fixmap,
> otherwise printk will access illegal addresses.
> After creating a new memory map, we open earlycon again.
>
> Signed-off-by: Victor Hassan <victor@...winnertech.com>

I think noone really noticed this because everyone on Arm systems
use CONFIG_DEBUG_LL, and that makes printascii hammer out
stuff on the console very early, it even accounts for whether we have
MMU on or not.

How are you using this on Arm even? What system and what serial
driver?

That said, it looks correct.
Acked-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij