linux-kernel - Re: [PATCH 1/1] initrd: move initrd_start calculate within linear mapping range check

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Date:   Wed, 13 Mar 2019 11:45:01 +0000
From:   Steven Price <steven.price@....com>
To:     pierre Kuo <vichy.kuo@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] initrd: move initrd_start calculate within linear
 mapping range check

On 12/03/2019 03:17, pierre Kuo wrote:
> in the previous case, initrd_start and initrd_end can be successfully
> returned even (base < memblock_start_of_DRAM()) or (base + size >
> memblock_start_of_DRAM() + linear_region_size).
> 
> That means even linear mapping range check fail for initrd_start and
> initrd_end, it still can get virtual address. Here we put
> initrd_start/initrd_end to be calculated only when linear mapping check
> pass.

>From what I can see this was broken in commit c756c592e442ba101c91daed3524ba5b3a784ba6 ("arm64: Utilize phys_initrd_start/phys_initrd_size") which switched the condition for setting initrd_start/initrd_end to depending on phys_initrd_size (rather than initrd_start). This means that when the code detects the initrd is not fully accessible sets initrd_start = 0 it no longer has the desired effect.

So you might want to add a Fixes tag. Otherwise FWIW:

Reviewed-by: Steven Price <steven.price@....com>

Thanks,

Steve

> Signed-off-by: pierre Kuo <vichy.kuo@...il.com>
> ---
>  arch/arm64/mm/init.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 7205a9085b4d..1adf418de685 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -425,6 +425,9 @@ void __init arm64_memblock_init(void)
>  			memblock_remove(base, size); /* clear MEMBLOCK_ flags */
>  			memblock_add(base, size);
>  			memblock_reserve(base, size);
> +			/* the generic initrd code expects virtual addresses */
> +			initrd_start = __phys_to_virt(phys_initrd_start);
> +			initrd_end = initrd_start + phys_initrd_size;
>  		}
>  	}
>  
> @@ -450,11 +453,6 @@ void __init arm64_memblock_init(void)
>  	 * pagetables with memblock.
>  	 */
>  	memblock_reserve(__pa_symbol(_text), _end - _text);
> -	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
> -		/* the generic initrd code expects virtual addresses */
> -		initrd_start = __phys_to_virt(phys_initrd_start);
> -		initrd_end = initrd_start + phys_initrd_size;
> -	}
>  
>  	early_init_fdt_scan_reserved_mem();
>  
>