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

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Date:   Thu, 1 Sep 2022 20:53:19 +0800
From:   Victor Hassan <victor@...winnertech.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>, linux@...linux.org.uk,
        rmk+kernel@...linux.org.uk, linus.walleij@...aro.org,
        yanfei.xu@...driver.com, ardb@...nel.org, tglx@...utronix.de,
        mirq-linux@...e.qmqm.pl, arnd@...db.de
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: mmu: fix access to illegal address when using
 earlycon & memblock=debug



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@...winnertech.com>
>>
>> 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