On Sat, Aug 17, 2019 at 11:00:13AM +0800, Zhaoyang Huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> pfn_valid can be wrong while the MSB of physical address be trimed as pfn
> larger than the max_pfn.
How the overflow of __pfn_to_phys() is related to max_pfn?
Where is the guarantee that __pfn_to_phys(max_pfn) won't overflow?
> Signed-off-by: Zhaoyang Huang <huangzhaoyang@xxxxxxxxx>
> ---
> arch/arm/mm/init.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index c2daabb..9c4d938 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -177,7 +177,8 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
> #ifdef CONFIG_HAVE_ARCH_PFN_VALID
> int pfn_valid(unsigned long pfn)
> {
> - return memblock_is_map_memory(__pfn_to_phys(pfn));
> + return (pfn > max_pfn) ?
> + false : memblock_is_map_memory(__pfn_to_phys(pfn));
> }
> EXPORT_SYMBOL(pfn_valid);
> #endif
> --
> 1.9.1
>
--
Sincerely yours,
Mike.
