Re: [PATCH 09/16] of: overlay: validate overlay properties #address-cells and #size-cells

[Alan Tull <atull@kernel.org>]

On Thu, Oct 4, 2018 at 11:14 PM <frowand.list@gmail.com> wrote:
>
> From: Frank Rowand <frank.rowand@sony.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.

Hi Frank,

I'm starting some FPGA testing on this patchset applied to v4.19-rc7.
That applied cleanly; if that's not the best base to test against,
please let me know.

On a very simple overlay, I'm seeing this patch's warning catching
things other than #address-cells or #size-cells.  I'm just getting
started looking at this, will spend time understanding this better and
I'll test other overlays.  The warnings were:

Applying dtbo: socfpga_overlay.dtb
[   33.117881] fpga_manager fpga0: writing soc_system.rbf to Altera
SOCFPGA FPGA Manager
[   33.575223] OF: overlay: WARNING: add_changeset_property(), memory
leak will occur if overlay removed.  Property:
/soc/base-fpga-region/firmware-name
[   33.588584] OF: overlay: WARNING: add_changeset_property(), memory
leak will occur if overlay removed.  Property:
/soc/base-fpga-region/fpga-bridges
[   33.601856] OF: overlay: WARNING: add_changeset_property(), memory
leak will occur if overlay removed.  Property:
/soc/base-fpga-region/ranges

Here's part of that overlay including the properties it's complaining about:

/dts-v1/;
/plugin/;
/ {
        fragment@0 {
                target = <&base_fpga_region>;
                #address-cells = <1>;
                #size-cells = <1>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <1>;

                        firmware-name = "soc_system.rbf";
                        fpga-bridges = <&fpga_bridge1>;
                        ranges = <0x20000 0xff200000 0x100000>,
                        <0x0 0xc0000000 0x20000000>;

                        gpio@10040 {
so on...

By the way, I didn't get any warnings when I subsequently removed this overlay.

Alan

>
> 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@sony.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 29c33a5c533f..e6fb3ffe9d93 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")) {
> +
> +               if (prop->length != 4 || new_prop->length != 4 ||
> +                   *(u32 *)prop->value != *(u32 *)new_prop->value)
> +                       pr_err("ERROR: overlay and/or live tree #address-cells invalid in node %pOF\n",
> +                              target->np);
> +
> +       } 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);
> +
> +       } 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@sony.com>
>