[PATCH] arm64: defer __va() translations of initrd_start and initrd_end

[Laurentiu Tudor]

Hi Ard,

On 02/11/2016 04:41 PM, Ard Biesheuvel wrote:
> Commit 66f51676a095 ("arm64: allow kernel Image to be loaded anywhere in
> physical memory") defers the assignment of memstart_addr to the point where
> all memory has been discovered and possibly clipped based on the size of
> the linear region and the presence of a mem= command line parameter.
> 
> However, this results in __va() translations that have been performed up
> to this point to have been carried out with a preliminary, incorrect value
> of memstart_addr, and these values need to be fixed up.
> 
> To make this more transparent, change the initial value of memstart_addr to
> PAGE_OFFSET so that __va() translations are effectively identity functions,
> and fix up the values of initrd_start and initrd_end before use.
> 
> Tested-by: Laurentiu Tudor <laurentiu.tudor at nxp.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
> 
> This is the least ugly way to address this issue in the short term (since the
> offending patch is already in -next). The preferred way of dealing with this
> would be to parametrise early_init_dt_check_for_initrd() in such a way that
> we can decide per-arch whether it should perform the __va() translation or
> not. If this is the preferred approach also for the short term, I am happy
> to code that up as well.
> 
>  arch/arm64/mm/init.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 3a9fc46cbf80..bb53236e54d9 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -48,7 +48,13 @@
>  
>  #include "mm.h"
>  
> -phys_addr_t memstart_addr __read_mostly = 0;
> +/*
> + * Initialize memstart_addr to PAGE_OFFSET so that __va() translations
> + * performed before arm64_memblock_init() executes (i.e., assignments
> + * of initrd_start and initrd_end in the early FDT parsing code) are
> + * effectively identity functions.
> + */
> +phys_addr_t memstart_addr __read_mostly = PAGE_OFFSET;
>  phys_addr_t arm64_dma_phys_limit __read_mostly;
>  
>  #ifdef CONFIG_BLK_DEV_INITRD
> @@ -61,8 +67,8 @@ static int __init early_initrd(char *p)
>  	if (*endp == ',') {
>  		size = memparse(endp + 1, NULL);
>  
> -		initrd_start = (unsigned long)__va(start);
> -		initrd_end = (unsigned long)__va(start + size);
> +		initrd_start = start;
> +		initrd_end = start + size;
>  	}
>  	return 0;
>  }
> @@ -213,8 +219,12 @@ void __init arm64_memblock_init(void)
>  	 */
>  	memblock_reserve(__pa(_text), _end - _text);
>  #ifdef CONFIG_BLK_DEV_INITRD
> -	if (initrd_start)
> -		memblock_reserve(__virt_to_phys(initrd_start), initrd_end - initrd_start);
> +	if (initrd_start) {
> +		memblock_reserve(initrd_start, initrd_end - initrd_start);
> +
> +		initrd_start = phys_to_virt(initrd_start);
> +		initrd_end = phys_to_virt(initrd_end);

There are some warnings here so I think you need to cast these to 'unsigned long'.

arch/arm64/mm/init.c: In function 'arm64_memblock_init':
arch/arm64/mm/init.c:225:16: warning: assignment makes integer from pointer without a cast [enabled by default]
   initrd_start = phys_to_virt(initrd_start);
                ^
arch/arm64/mm/init.c:226:14: warning: assignment makes integer from pointer without a cast [enabled by default]
   initrd_end = phys_to_virt(initrd_end);
              ^
---
Thanks & Best Regards, Laurentiu