On 06/23/2014 12:13 PM, Pantelis Antoniou wrote:
Hi Ioan,
I'm going to let Grant answer that but the code in question doesn't look right.
On Jun 23, 2014, at 9:33 PM, Ioan Nicu wrote:
Hi Pantelis,
On Mon, Jun 23, 2014 at 07:57:24PM +0300, ext Pantelis Antoniou wrote:
Hi Alexander,
On Jun 23, 2014, at 7:26 PM, Alexander Sverdlin wrote:
Hello Pantelis!
On 22/06/14 11:40, ext Pantelis Antoniou wrote:
Introduce helper functions for working with the live DT tree,
all of them related to dynamically adding/removing nodes and
properties.
__of_copy_property() copies a property dynamically
__of_create_empty_node() creates an empty node
Bug fix about prop->len == 0 by Ionut Nicu <ioan.nicu.ext@xxxxxxx>
Are you sure about this? (see below...)
Alexander is right, my fix was lost even though it's mentioned in this patch.
I'm sorry, I didn't understand that the intention of the fix was to address
the issue below.
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
---
[snip]
+
+ if (prop->length > 0) {
^^^^^^^^^^^^^^^^^^^^^
Seems, that length==0 case will still produce value==NULL results,
which will brake some checks in the kernel... Or am I missing something in
the new version?
prop->value will be set to NULL, and length will be set to zero (kzalloc).
This is a normal zero length property.
I don't know of any place in the kernel accessing the value if prop->length==0
We have a simple use case. We have an overlay which adds an interrupt controller.
If you look in drivers/of/irq.c, in of_irq_parse_raw():
[...]
/* Now start the actual "proper" walk of the interrupt tree */
while (ipar != NULL) {
/* Now check if cursor is an interrupt-controller and if it is
* then we are done
*/
if (of_get_property(ipar, "interrupt-controller", NULL) !=
NULL) {
pr_debug(" -> got it !\n");
return 0;
}
[...]
A node is identified as an interrupt controller if it has a zero-length property
called "interrupt-controller" but with a non-NULL value.
My proposed fix for this was to remove the if () condition. propn->value will be
allocated with kmalloc(0) which returns ZERO_SIZE_PTR which is != NULL.
If that's the case, the code in irq.c is wrong.
interrupt-controller is a bool property; the correct call to use is of_property_read_bool()
which returns true or false when the value is defined.
The use of of_get_property is a bug here. It is perfectly valid for a property to have a
NULL value when length = 0.
That usage is spread throughout the code though. There are three or four similar checks
for interrupt-controller in the code, and many others using of_get_property() to check
for booleans.
Some examples:
s5m8767,pmic-buck2-ramp-enable
s5m8767,pmic-buck3-ramp-enable
s5m8767,pmic-buck4-ramp-enable
d7s-flipped?
atmel,use-dma-rx
linux,rs485-enabled-at-boot-time
marvell,enable-port1 (and many others)
linux,bootx-noscreen
linux,opened
and many many others.
Maybe people meant to use of_find_property() ?
Either case, if the new code depends on proper use of of_get_property(), we may have
a problem unless all those bad use cases are fixed.
Guenter
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