Re: [XEN v4] xen/arm: Probe the load/entry point address of an uImage correctly

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On 08.01.23 18:06, Julien Grall wrote:

Hello Julien, Ayan, all

> Hi Ayan,
>
> On 21/12/2022 18:53, Ayan Kumar Halder wrote:
> > Currently, kernel_uimage_probe() does not read the load/entry point 
> > address
> > set in the uImge header. Thus, info->zimage.start is 0 (default 
> > value). This
> > causes, kernel_zimage_place() to treat the binary (contained within 
> > uImage)
> > as position independent executable. Thus, it loads it at an incorrect
> > address.
> >
> > The correct approach would be to read "uimage.load" and set
> > info->zimage.start. This will ensure that the binary is loaded at the
> > correct address. Also, read "uimage.ep" and set info->entry (ie kernel 
> > entry
> > address).
> >
> > If user provides load address (ie "uimage.load") as 0x0, then the 
> > image is
> > treated as position independent executable. Xen can load such an image at
> > any address it considers appropriate. A position independent executable
> > cannot have a fixed entry point address.
> >
> > This behavior is applicable for both arm32 and arm64 platforms.
> >
> > Earlier for arm32 and arm64 platforms, Xen was ignoring the load and 
> > entry
> > point address set in the uImage header. With this commit, Xen will use 
> > them.
> > This makes the behavior of Xen consistent with uboot for uimage headers.
> The changes look good to me (with a few of comments below). That said, 
> before acking the code, I would like an existing user of uImage (maybe 
> EPAM or Arm?) to confirm they are happy with the change.

I have just re-checked current patch in our typical Xen based 
environment (no dom0less, Linux in Dom0) and didn't notice issues with 
it. But we use zImage for Dom0's kernel, so kernel_uimage_probe() is not 
called.


I CCed Dmytro Firsov who is playing with Zephyr in Dom0 and *might* use 
uImage.

[snip]