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

[Victor Hassan]

On 4/18/2022 11:08 PM, Victor Hassan wrote:
> On 18/04/2022 07:21, Linus Walleij wrote:
> > On Wed, Mar 16, 2022 at 3:33 AM Victor Hassan 
> > <victor@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> >
> > 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.
> Hi Linus,
> Thank you for the reply. I used earlycon, in early_fixmap_shutdown, the 
> base address of earlycon is in the critical stage of release and 
> reassignment, so early_fixmap_shutdown -> create_mapping should not call 
> earlycon in this process, and create_mapping has a lot of conditions 
> that trigger print, memblock=debug just makes it easier to expose problems.
>
> > How are you using this on Arm even? What system and what serial
> > driver?
> I'm using serial driver 8250 on arm32, with cmdline: memblock=debug.
> CONFIG_SERIAL_8250=y
> CONFIG_SERIAL_8520_CONSOLE=y
> > That said, it looks correct.
> > Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Hi Linus,
Sorry to disturb. Is there any question about this issue? Thank you :)