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Date: Thu, 01 Mar 2018 23:13:52 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: frowand.list@...il.com
Cc: Rob Herring <robh+dt@...nel.org>, pantelis.antoniou@...sulko.com,
Pantelis Antoniou <panto@...oniou-consulting.com>,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
geert@...ux-m68k.org, laurent.pinchart+renesas@...asonboard.com
Subject: Re: [PATCH v4 1/4] of: change overlay apply input data from unflattened to FDT
Hi Frank,
Another comment, please see below.
On Thursday, 1 March 2018 22:59:08 EET Laurent Pinchart wrote:
> On Thursday, 1 March 2018 20:00:53 EET frowand.list@...il.com wrote:
> > From: Frank Rowand <frank.rowand@...y.com>
> >
> > Move duplicating and unflattening of an overlay flattened devicetree
> > (FDT) into the overlay application code. To accomplish this,
> > of_overlay_apply() is replaced by of_overlay_fdt_apply().
> >
> > The copy of the FDT (aka "duplicate FDT") now belongs to devicetree
> > code, which is thus responsible for freeing the duplicate FDT. The
> > caller of of_overlay_fdt_apply() remains responsible for freeing the
> > original FDT.
> >
> > The unflattened devicetree now belongs to devicetree code, which is
> > thus responsible for freeing the unflattened devicetree.
> >
> > These ownership changes prevent early freeing of the duplicated FDT
> > or the unflattened devicetree, which could result in use after free
> > errors.
> >
> > of_overlay_fdt_apply() is a private function for the anticipated
> > overlay loader.
> >
> > Update unittest.c to use of_overlay_fdt_apply() instead of
> > of_overlay_apply().
> >
> > Move overlay fragments from artificial locations in
> > drivers/of/unittest-data/tests-overlay.dtsi into one devicetree
> > source file per overlay. This led to changes in
> > drivers/of/unitest-data/Makefile and drivers/of/unitest.c.
> >
> > - Add overlay directives to the overlay devicetree source files so
> > that dtc will compile them as true overlays into one FDT data
> > chunk per overlay.
> >
> > - Set CFLAGS for drivers/of/unittest-data/testcases.dts so that
> > symbols will be generated for overlay resolution of overlays
> > that are no longer artificially contained in testcases.dts
> >
> > - Unflatten and apply each unittest overlay FDT using
> > of_overlay_fdt_apply().
> >
> > - Enable the of_resolve_phandles() check for whether the unflattened
> > overlay is detached. This check was previously disabled because the
> > overlays from tests-overlay.dtsi were not unflattened into detached
> > trees.
> >
> > - Other changes to unittest.c infrastructure to manage multiple test
> > FDTs built into the kernel image (access by name instead of
> > arbitrary number).
> >
> > - of_unittest_overlay_high_level(): previously unused code to add
> > properties from the overlay_base devicetree to the live tree
> > was triggered by the restructuring of tests-overlay.dtsi and thus
> > testcases.dts. This exposed two bugs: (1) the need to dup a
> > property before adding it, and (2) property 'name' is
> > auto-generated in the unflatten code and thus will be a duplicate
> > in the __symbols__ node - do not treat this duplicate as an error.
> >
> > Signed-off-by: Frank Rowand <frank.rowand@...y.com>
> > ---
> >
> > There are checkpatch warnings. I have reviewed them and feel they
> > can be ignored. They are "line over 80 characters" for either
> > pre-existing long lines, or lines in devicetree source files.
> >
> > Changes from v3:
> > - OF_OVERLAY: add select OF_FLATTREE
> >
> > Changes from v1:
> > - rebase on v4.16-rc1
> >
> > drivers/of/Kconfig | 1 +
> > drivers/of/of_private.h | 1 +
> > drivers/of/overlay.c | 107 +++++++++-
> > drivers/of/resolver.c | 6 -
> > drivers/of/unittest-data/Makefile | 28 ++-
> > drivers/of/unittest-data/overlay_0.dts | 14 ++
> > drivers/of/unittest-data/overlay_1.dts | 14 ++
> > drivers/of/unittest-data/overlay_10.dts | 34 ++++
> > drivers/of/unittest-data/overlay_11.dts | 34 ++++
> > drivers/of/unittest-data/overlay_12.dts | 14 ++
> > drivers/of/unittest-data/overlay_13.dts | 14 ++
> > drivers/of/unittest-data/overlay_15.dts | 35 ++++
> > drivers/of/unittest-data/overlay_2.dts | 14 ++
> > drivers/of/unittest-data/overlay_3.dts | 14 ++
> > drivers/of/unittest-data/overlay_4.dts | 23 +++
> > drivers/of/unittest-data/overlay_5.dts | 14 ++
> > drivers/of/unittest-data/overlay_6.dts | 15 ++
> > drivers/of/unittest-data/overlay_7.dts | 15 ++
> > drivers/of/unittest-data/overlay_8.dts | 15 ++
> > drivers/of/unittest-data/overlay_9.dts | 15 ++
> > drivers/of/unittest-data/tests-overlay.dtsi | 213 --------------------
> > drivers/of/unittest.c | 294 +++++++++++------------
> > include/linux/of.h | 7 -
> > 23 files changed, 552 insertions(+), 389 deletions(-)
> > create mode 100644 drivers/of/unittest-data/overlay_0.dts
> > create mode 100644 drivers/of/unittest-data/overlay_1.dts
> > create mode 100644 drivers/of/unittest-data/overlay_10.dts
> > create mode 100644 drivers/of/unittest-data/overlay_11.dts
> > create mode 100644 drivers/of/unittest-data/overlay_12.dts
> > create mode 100644 drivers/of/unittest-data/overlay_13.dts
> > create mode 100644 drivers/of/unittest-data/overlay_15.dts
> > create mode 100644 drivers/of/unittest-data/overlay_2.dts
> > create mode 100644 drivers/of/unittest-data/overlay_3.dts
> > create mode 100644 drivers/of/unittest-data/overlay_4.dts
> > create mode 100644 drivers/of/unittest-data/overlay_5.dts
> > create mode 100644 drivers/of/unittest-data/overlay_6.dts
> > create mode 100644 drivers/of/unittest-data/overlay_7.dts
> > create mode 100644 drivers/of/unittest-data/overlay_8.dts
> > create mode 100644 drivers/of/unittest-data/overlay_9.dts
[snip]
> > diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> > index 3397d7642958..5f6c5569e97d 100644
> > --- a/drivers/of/overlay.c
> > +++ b/drivers/of/overlay.c
[snip]
> > @@ -766,7 +803,59 @@ int of_overlay_apply(struct device_node *tree, int
> > *ovcs_id)
> >
> > return ret;
> >
> > }
> >
> > -EXPORT_SYMBOL_GPL(of_overlay_apply);
> > +
> > +int of_overlay_fdt_apply(void *overlay_fdt, int *ovcs_id)
I find it a bit dangerous that this function doesn't take the size of the FDT
blob. I don't think we will always be able to trust the FDT blob. I'm fine
fixing this in follow-up patches, I don't think it's a blocker as the only
user we have today passes an FDT compiled in the kernel sources.
> > +{
> > + const void *new_fdt;
> > + int ret;
> > + u32 size;
> > + struct device_node *overlay_root;
> > +
> > + *ovcs_id = 0;
> > + ret = 0;
> > +
> > + if (fdt_check_header(overlay_fdt)) {
> > + pr_err("Invalid overlay_fdt header\n");
> > + return -EINVAL;
> > + }
> > +
> > + size = fdt_totalsize(overlay_fdt);
> > +
> > + /*
> > + * Must create permanent copy of FDT because of_fdt_unflatten_tree()
> > + * will create pointers to the passed in FDT in the unflattened tree.
> > + */
> > + new_fdt = kmemdup(overlay_fdt, size, GFP_KERNEL);
> > + if (!new_fdt)
> > + return -ENOMEM;
> > +
> > + of_fdt_unflatten_tree(new_fdt, NULL, &overlay_root);
> > + if (!overlay_root) {
> > + pr_err("unable to unflatten overlay_fdt\n");
> > + ret = -EINVAL;
> > + goto out_free_new_fdt;
> > + }
> > +
> > + ret = of_overlay_apply(new_fdt, overlay_root, ovcs_id);
> > + if (ret < 0) {
> > + /*
> > + * new_fdt and overlay_root now belong to the overlay
> > + * changeset.
> > + * overlay changeset code is responsible for freeing them.
> > + */
> > + goto out;
> > + }
> > +
> > + return 0;
> > +
> > +
> > +out_free_new_fdt:
> > + kfree(new_fdt);
> > +
> > +out:
> > + return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(of_overlay_fdt_apply);
> >
> > /*
> > * Find @np in @tree.
--
Regards,
Laurent Pinchart
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