On Wed, Apr 4, 2018 at 5:35 PM, Jan Kiszka <jan.kiszka@xxxxxx> wrote: > Hi Frank, > > On 2018-03-04 01:17, frowand.list@xxxxxxxxx wrote: >> From: Frank Rowand <frank.rowand@xxxxxxxx> >> >> 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. > > We are using of_fdt_unflatten_tree + of_overlay_apply in the > (out-of-tree) Jailhouse loader driver in order to register a virtual > device during hypervisor activation with Linux. The DT overlay is > created from a a template but modified prior to application to account > for runtime-specific parameters. See [1] for the current implementation. > > I'm now wondering how to model that scenario best with the new API. > Given that the loader lost ownership of the unflattened tree but the > modification API exist only for the that DT state, I'm not yet seeing a > clear solution. Should we apply the template in disabled form (status = > "disabled"), modify it, and then activate it while it is already applied? No. I don't think that will work. The of_overlay_apply() function is still there, but static. We can export it again if the need arises. Another option is there is a notifier callback OF_OVERLAY_PRE_APPLY, but I'm not sure we want to make that be the normal interface to make modifications. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
