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Message-ID: <87525c4a-6c7d-5c1d-1f99-6784f315b89c@gmail.com>
Date: Mon, 15 Oct 2018 13:16:50 -0700
From: Frank Rowand <frowand.list@...il.com>
To: Alan Tull <atull@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Moritz Fischer <mdf@...nel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>, linux-fpga@...r.kernel.org
Subject: Re: [PATCH v3 09/18] of: overlay: validate overlay properties
#address-cells and #size-cells
On 10/15/18 12:01, Alan Tull wrote:
> On Sun, Oct 14, 2018 at 7:26 PM <frowand.list@...il.com> wrote:
>>
>> From: Frank Rowand <frank.rowand@...y.com>
>>
>> If overlay properties #address-cells or #size-cells are already in
>> the live devicetree for any given node, then the values in the
>> overlay must match the values in the live tree.
>>
>> If the properties are already in the live tree then there is no
>> need to create a changeset entry to add them since they must
>> have the same value. This reduces the memory used by the
>> changeset and eliminates a possible memory leak. This is
>> verified by 12 fewer warnings during the devicetree unittest,
>> as the possible memory leak warnings about #address-cells and
>>
>> Signed-off-by: Frank Rowand <frank.rowand@...y.com>
>> ---
>> drivers/of/overlay.c | 38 +++++++++++++++++++++++++++++++++++---
>> 1 file changed, 35 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index 272a0d1a5e18..ee66651db553 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -287,7 +287,12 @@ static struct property *dup_and_fixup_symbol_prop(
>> * @target may be either in the live devicetree or in a new subtree that
>> * is contained in the changeset.
>> *
>> - * Some special properties are not updated (no error returned).
>> + * Some special properties are not added or updated (no error returned):
>> + * "name", "phandle", "linux,phandle".
>> + *
>> + * Properties "#address-cells" and "#size-cells" are not updated if they
>> + * are already in the live tree, but if present in the live tree, the values
>> + * in the overlay must match the values in the live tree.
>> *
>> * Update of property in symbols node is not allowed.
>> *
>> @@ -300,6 +305,7 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
>> {
>> struct property *new_prop = NULL, *prop;
>> int ret = 0;
>> + bool check_for_non_overlay_node = false;
>>
>> if (!of_prop_cmp(overlay_prop->name, "name") ||
>> !of_prop_cmp(overlay_prop->name, "phandle") ||
>> @@ -322,13 +328,39 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
>> if (!new_prop)
>> return -ENOMEM;
>>
>> - if (!prop)
>> + if (!prop) {
>> +
>> + check_for_non_overlay_node = true;
>> ret = of_changeset_add_property(&ovcs->cset, target->np,
>> new_prop);
>> - else
>> +
>> + } else if (!of_prop_cmp(prop->name, "#address-cells")) {
>> +
>
> Hi Frank,
>
> If we get these ERROR messages, I suggest that this function should
> return an error so the overlay will be rejected.
>
>> + if (prop->length != 4 || new_prop->length != 4 ||
>> + *(u32 *)prop->value != *(u32 *)new_prop->value)
>
> *(u32 *)prop->value != *(u32 *)new_prop->value) {
>
>> + pr_err("ERROR: overlay and/or live tree #address-cells invalid in node %pOF\n",
>> + target->np);
>
> ret = -EINVAL;
> }
>
> Otherwise there is an ERROR message, but it continues trying to apply
> the invalid overlay anyway and I get an oops. By adding the ret =
> -EINVAL, the overlay gets rejected and the oops is avoided.
Yes, that sounds good.
>> +
>> + } else if (!of_prop_cmp(prop->name, "#size-cells")) {
>> +
>> + if (prop->length != 4 || new_prop->length != 4 ||
>> + *(u32 *)prop->value != *(u32 *)new_prop->value)
>> + pr_err("ERROR: overlay and/or live tree #size-cells invalid in node %pOF\n",
>> + target->np);
>
> Add the ret = -EINVAL here also. This give me the following (if my
> overlay changes #address-cells):
Yes.
> [ 21.167551] OF: overlay: ERROR: overlay and/or live tree
> #address-cells invalid in node /soc/base_fpga_region
> [ 21.177442] OF: overlay: add_changeset_property ret=-22
> [ 21.182656] create_overlay: Failed to create overlay (err=-22)
>
> Also, I wonder if the ERROR message could be more direct. Currently
> it says the #address-cells property is invalid but that doesn't say
> anything about why it's invalid. How about something like:
>
> OF: overlay: ERROR: changing #address-cells not allowed (/soc/base_fpga_region)
That sounds like a more useful message, maybe a slight change
s/changing #address-cells/changing value of #address-cells/
> The 'OF: overlay' part still makes it clear it's overlay related. The
> rest of it makes it clear *why* it's invalid. This ERROR will be a
> surprise for people who have been using overlays, so that could be
> helpful to light the way a bit.
>
> Alan
>
>> +
>> + } else {
>> +
>> + check_for_non_overlay_node = true;
>> ret = of_changeset_update_property(&ovcs->cset, target->np,
>> new_prop);
>>
>> + }
>> +
>> + if (check_for_non_overlay_node &&
>> + !of_node_check_flag(target->np, OF_OVERLAY))
>> + pr_err("WARNING: %s(), memory leak will occur if overlay removed. Property: %pOF/%s\n",
>> + __func__, target->np, new_prop->name);
>> +
>> if (ret) {
>> kfree(new_prop->name);
>> kfree(new_prop->value);
>> --
>> Frank Rowand <frank.rowand@...y.com>
>>
>
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