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Subject: Re: [PATCH] powerpc/kasan: fix early boot failure on PPC32
From:   Christophe Leroy <christophe.leroy@c-s.fr>
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <da89670093651437f27d2975224712e0a130b055.1564552796.git.christophe.leroy@c-s.fr>
Message-ID: <2f29b91a-11cd-8385-74b6-d85e515012c3@c-s.fr>
Date:   Wed, 31 Jul 2019 10:02:56 +0200
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Le 31/07/2019 à 08:01, Christophe Leroy a écrit :
> Due to commit 4a6d8cf90017 ("powerpc/mm: don't use pte_alloc_kernel()
> until slab is available on PPC32"), pte_alloc_kernel() cannot be used
> during early KASAN init.
> 
> Fix it by using memblock_alloc() instead.
> 
> Reported-by: Erhard F. <erhard_f@mailbox.org>
> Fixes: 2edb16efc899 ("powerpc/32: Add KASAN support")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Cc: stable@vger.kernel.org

> ---
>   arch/powerpc/mm/kasan/kasan_init_32.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
> index 0d62be3cba47..74f4555a62ba 100644
> --- a/arch/powerpc/mm/kasan/kasan_init_32.c
> +++ b/arch/powerpc/mm/kasan/kasan_init_32.c
> @@ -21,7 +21,7 @@ static void kasan_populate_pte(pte_t *ptep, pgprot_t prot)
>   		__set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
>   }
>   
> -static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
> +static int __ref kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
>   {
>   	pmd_t *pmd;
>   	unsigned long k_cur, k_next;
> @@ -35,7 +35,10 @@ static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_
>   		if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte)
>   			continue;
>   
> -		new = pte_alloc_one_kernel(&init_mm);
> +		if (slab_is_available())
> +			new = pte_alloc_one_kernel(&init_mm);
> +		else
> +			new = memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);
>   
>   		if (!new)
>   			return -ENOMEM;
>