On 09/11/18 07:56, Rob Herring wrote:
> With commit 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of
> of_find_node_by_phandle()"), a G3 PowerMac fails to boot. The root cause
> is the DT for this system has no phandle properties when booted with
> BootX. of_populate_phandle_cache() does not handle the case of no
> phandles correctly. The problem is roundup_pow_of_two() for 0 is
> undefined. The implementation subtracts 1 underflowing and then things
> are in the weeds.
>
> Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()")
> Cc: stable@xxxxxxxxxxxxxxx # 4.17+
> Reported-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
> Tested-by: Stan Johnson <userm57@xxxxxxxxx>
> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> ---
> Here's a formal patch of what Stan tested. Will send to Linus this week.
>
> Rob
>
> drivers/of/base.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index a055cd1ef96d..17ae594b7014 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -140,6 +140,9 @@ void of_populate_phandle_cache(void)
> if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL)
> phandles++;
>
> + if (!phandles)
> + goto out;
> +
> cache_entries = roundup_pow_of_two(phandles);
> phandle_cache_mask = cache_entries - 1;
>
>
Reviewed-by: Frank Rowand <frank.rowand@xxxxxxxx>
