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SubjectRE: [PATCH 0/5] cramfs refresh for embedded usage
On Mon, 14 Aug 2017, Chris Brandt wrote:

> On Friday, August 11, 2017, Nicolas Pitre wrote:
> > This series brings a nice refresh to the cramfs filesystem, adding the
> > following capabilities:
> >
> > - Direct memory access, bypassing the block and/or MTD layers entirely.
> >
> > - Ability to store individual data blocks uncompressed.
> >
> > - Ability to locate individual data blocks anywhere in the filesystem.
> >
> > The end result is a very tight filesystem that can be accessed directly
> > from ROM without any other subsystem underneath. Also this allows for
> > user space XIP which is a very important feature for tiny embedded
> > systems.
>
>
>
> I just applied the patches tried this simple test:
> - tested with a Renesas RZ/A1 (Cortex-A9...so it has an MMU).
> - I set the sticky bit for busybox before using mkcramfs

You need the newer mkcramfs I linked to in the documentation. With it
you don't need to play tricks with the sticky bit anymore. However you
need to specify -X twice (or just once for no-MMU targets) and it will
make every ELF files XIPable automatically.

> - booted (with squashfs) and mounted the cramfs image
> - confirmed that the sticky bit was still set on busybox
> - was able to execute busybox in the cramfs image
>
>
> However, at this point I'm not sure how I can confirm that the XIP
> busybox actually executed as XIP or not.

Just use busybox's built-in cat command and dump the content of
/proc/self/maps. You should see an offset that refers to a physical
address within your cramfs image for those segments marked read-only and
executable.


Nicolas

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