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

[Victor Hassan]

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 at allwinnertech.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