2018-09-11 14:57:50

by Rob Herring (Arm)

Subject: [PATCH] of: fix phandle cache creation for DTs with no phandles

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: [email protected] # 4.17+
Reported-by: Finn Thain <[email protected]>
Tested-by: Stan Johnson <[email protected]>
Cc: Frank Rowand <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Rob Herring <[email protected]>
---
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;

--
2.17.1

2018-09-11 16:03:24

by Frank Rowand

Subject: Re: [PATCH] of: fix phandle cache creation for DTs with no phandles

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: [email protected] # 4.17+
> Reported-by: Finn Thain <[email protected]>
> Tested-by: Stan Johnson <[email protected]>
> Cc: Frank Rowand <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Signed-off-by: Rob Herring <[email protected]>
> ---
> 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 <[email protected]>