linux-kernel - Re: [PATCH] arm64/mm: Poison initmem while freeing with free_reserved

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Message-ID: <50d88564-c645-62f4-b5b3-3ce7a4425b0a@arm.com>
Date:   Fri, 4 Oct 2019 16:18:01 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Steven Price <steven.price@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/mm: Poison initmem while freeing with
 free_reserved_area()



On 10/04/2019 03:49 PM, Steven Price wrote:
> On 04/10/2019 05:23, Anshuman Khandual wrote:
>> Platform implementation for free_initmem() should poison the memory while
>> freeing it up. Hence pass across POISON_FREE_INITMEM while calling into
>> free_reserved_area(). The same is being followed in the generic fallback
>> for free_initmem() and some other platforms overriding it.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> 
> Is there a good reason you haven't made a similar change to
> free_initrd_mem() - the same logic seems to apply. However this change
> looks fine to me.

We will use generic free_initrd_mem() going forward as proposed in a recent
patch which does call free_reserved_area() with POISON_FREE_INITMEM.

https://patchwork.kernel.org/patch/11165379/

> 
> Reviewed-by: Steven Price <steven.price@....com>
> 
>> ---
>>  arch/arm64/mm/init.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 45c00a54909c..ea7d38011e83 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -571,7 +571,7 @@ void free_initmem(void)
>>  {
>>  	free_reserved_area(lm_alias(__init_begin),
>>  			   lm_alias(__init_end),
>> -			   0, "unused kernel");
>> +			   POISON_FREE_INITMEM, "unused kernel");
>>  	/*
>>  	 * Unmap the __init region but leave the VM area in place. This
>>  	 * prevents the region from being reused for kernel modules, which
>>
> 
>