Messages in this thread | | | Date | Thu, 21 Feb 2013 16:48:22 +0530 | From | Vineet Gupta <> | Subject | Re: [PATCH 1/2] metag: copy devicetree to non-init memory |
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On Thursday 21 February 2013 03:04 PM, James Hogan wrote: > Hi Vineet, > > On 21/02/13 09:08, Vineet Gupta wrote: >> On Wednesday 20 February 2013 08:22 PM, James Hogan wrote: >>> Make a copy of the device tree blob in non-init memory. It is required >>> when using built-in device tree files that the platform code copies the >>> blob to non-init memory prior to calling unflatten_device_tree(), >>> otherwise the strings that the device tree refer to will get poisoned >>> and potentially reused, breaking later reading of the device tree >>> post-init (such as compatible matching in modules, debugfs, and the >>> procfs interface). >> While the patch conceptually looks correct, I'm not sure why any user of DT - >> post-init would refer to DT bindings using of_fdt_* API which use the flat tree, >> instead of the binary tree (more efficient in space/usage). Is this to support >> some in-transition drivers and other code. > The strings aren't copied when the devicetree is unflattened, so the > unflattened version still points into initdata, so all the strings "in" > the unflattened version are wiped when it's freed too.
You are absolutely right, so ARC port is infested with same ticking time bomb ! Thanks for the heads up - I'll queue up a fix - but that will go in after the first pull request as I want any change, however minimal/local to cook in -next for some time (for paranoid sake at this stage)
> Documentation/kbuild/makefiles.txt has this to say: >> dtc >> Create flattend device tree blob object suitable for linking >> into vmlinux. Device tree blobs linked into vmlinux are placed >> in an init section in the image. Platform code *must* copy the >> blob to non-init memory prior to calling unflatten_device_tree(). > Other architectures using the builtin dtb also do the copy. I presume > it's in initdata in the first place to avoid keeping the built-in one > around if one is provided by the bootloader instead.
Makes sense !
-Vineet
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