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Message-ID: <b07d8b91-d0d7-fbf1-681c-2801fc77f81c@allwinnertech.com>
Date: Sat, 3 Sep 2022 16:54:11 +0800
From: Victor Hassan <victor@...winnertech.com>
To: Rob Herring <robh@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
Russell King <linux@...linux.org.uk>,
Russell King <rmk+kernel@...linux.org.uk>,
Linus Walleij <linus.walleij@...aro.org>,
yanfei.xu@...driver.com, Ard Biesheuvel <ardb@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Michał Mirosław <mirq-linux@...e.qmqm.pl>,
Arnd Bergmann <arnd@...db.de>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: mmu: fix access to illegal address when using
earlycon & memblock=debug
Dear Rob,
On 2022/9/1 21:21, Rob Herring wrote:
> On Thu, Sep 1, 2022 at 7:54 AM Victor Hassan <victor@...winnertech.com> wrote:
>>
>>
>>
>> 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.
>
> How? Due to recent changes in how printk and the consoles work or just
> because create_mapping() can print? In the latter case, the only
> variable input is the phys address. I think most if not all prints
> cannot occur.
>
>>>>> 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
>
> This is always true for CONFIG_MMU and this file is only built for
> CONFIG_MMU. So you don't need it.
Yes, you are right.
>
>> + if (console_drivers)
>> + console_stop(console_drivers);
>
> console_drivers is a list, so you are only stopping the 1st one.
> Couldn't console_lock() be used here?
>
Thanks for the suggestion: console_lock is actually the same as
console_stop in the test, and the code is more compact.
> Also, this should be before pmd_clear().
During the test, I found that the console failed after executing
local_flush_tlb_kernel_page, so I think the pmd_clear function can
output in time if there is printing. This doesn't seem possible, so
before pmd_clear it's not bad either.
>
>> +#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
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Here is the patch-v3. Please review:
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index a49f0b9..57ca77f 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>
@@ -1727,6 +1728,7 @@
unsigned long va = fix_to_virt(__end_of_permanent_fixed_addresses - 1);
pte_offset_fixmap = pte_offset_late_fixmap;
+ console_lock();
pmd_clear(fixmap_pmd(va));
local_flush_tlb_kernel_page(va);
@@ -1748,6 +1750,7 @@
create_mapping(&map);
}
+ console_unlock();
}
Thanks you.
Regards,
Victor
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