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@vger.kernel.org # 4.17+ Reported-by: Finn Thain fthain@telegraphics.com.au Tested-by: Stan Johnson userm57@yahoo.com Cc: Frank Rowand frowand.list@gmail.com Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Signed-off-by: Rob Herring robh@kernel.org

---

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@sony.com