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

[Victor Hassan]

On 2022/8/31 20:37, Victor Hassan wrote:
> On 8/31/2022 7:52 PM, Marek Szyprowski wrote:
> > Hi Victor,
> >
> > On 16.03.2022 03:33, Victor Hassan 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>
> >
> > This patch landed in linux next-20220831 as commit a76886d117cb ("ARM:
> > 9223/1: mmu: fix access to illegal address when using earlycon &
> > memblock=debug"). Unfortunately it breaks booting of all my test boards
> > which *do not* use earlycon. It can be easily reproduced even with QEMU.
> >
> > With kernel compiled from multi_v7_defconfig the following setup boots:
> >
> > $ qemu-system-arm -nographic -kernel arch/arm/boot/zImage -append
> > "console=ttyAMA0 earlycon" -M virt -smp 2 -m 512
> >
> > while this one doesn't:
> >
> > $ qemu-system-arm -nographic -kernel arch/arm/boot/zImage -append
> > "console=ttyAMA0" -M virt -smp 2 -m 512
> >
> >
> > > ---
> > >    arch/arm/mm/mmu.c | 7 +++++++
> > >    1 file changed, 7 insertions(+)
> > >
> > > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > > index 274e4f73fd33..f3511f07a7d0 100644
> > > --- a/arch/arm/mm/mmu.c
> > > +++ b/arch/arm/mm/mmu.c
> > > @@ -14,6 +14,7 @@
> > >    #include <linux/fs.h>
> > >    #include <linux/vmalloc.h>
> > >    #include <linux/sizes.h>
> > > +#include <linux/console.h>
> > >    #include <asm/cp15.h>
> > >    #include <asm/cputype.h>
> > > @@ -1695,6 +1696,9 @@ static void __init early_fixmap_shutdown(void)
> > >        pmd_clear(fixmap_pmd(va));
> > >        local_flush_tlb_kernel_page(va);
> > > +#ifdef CONFIG_FIX_EARLYCON_MEM
> > > +    console_stop(console_drivers);
> > > +#endif
> > >        for (i = 0; i < __end_of_permanent_fixed_addresses; i++) {
> > >            pte_t *pte;
> > >            struct map_desc map;
> > > @@ -1713,6 +1717,9 @@ static void __init early_fixmap_shutdown(void)
> > >            create_mapping(&map);
> > >        }
> > > +#ifdef CONFIG_FIX_EARLYCON_MEM
> > > +    console_start(console_drivers);
> > > +#endif
> > >    }
> > >    /*
> >
> > Best regards
>
> Dear Marek,
> Thank you for the notice. I'll figure it out and feed back to you as 
> soon as possible.
>
> Regards,
> Victor

Hi Marek,

Sorry, didn't take into account that console_drivers is NULL when 
earlycon is not used.

Here is the patch-v2. Please review:

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index a49f0b9..a240f38 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -14,6 +14,7 @@
 #include <linux/fs.h>
 #include <linux/vmalloc.h>
 #include <linux/sizes.h>
+#include <linux/console.h>

 #include <asm/cp15.h>
 #include <asm/cputype.h>
@@ -1730,6 +1731,10 @@
 	pmd_clear(fixmap_pmd(va));
 	local_flush_tlb_kernel_page(va);

+#ifdef CONFIG_FIX_EARLYCON_MEM
+	if (console_drivers)
+		console_stop(console_drivers);
+#endif
 	for (i = 0; i < __end_of_permanent_fixed_addresses; i++) {
 		pte_t *pte;
 		struct map_desc map;
@@ -1748,6 +1753,10 @@

 		create_mapping(&map);
 	}
+#ifdef CONFIG_FIX_EARLYCON_MEM
+	if (console_drivers)
+		console_start(console_drivers);
+#endif
 }

BTW, should I resend the patch-v2 through the site 
(https://www.armlinux.org.uk/developer/patches/add.php), or should I 
send the patch-v2 through E-mail to Linux-Mainline?

Thanks you.

Regards,
Victor