FW: Re: Why are ARM kernels not completely relocatable like x86counterparts?

"Inderpal Singh" <inderpal.singh@xxxxxxxxx> · Thu, 3 Jan 2008 14:54:04 +0530

On Sun, Dec 16, 2007 at 01:11:25AM +0530, Indraneel Mukherjee wrote:
> Hi,
> AFAIK the ARM Linux kernel is not completely relocatable. The x86
> counterparts can be loaded and run from any address. But the
> uncompressed ARM Linux kernels run at the address for which they have
> been linked statically (although the zImage De-Compressor is
> Relocatable).
> 
> If i am correct then why the feature has not been implemented? Is it
> useless as ARM mostly runs in Embedded Environment OR it's just that
> s'body's yet to do it?

The zImage decompressor is actually quite a special case - it's more
relocatable than the toolchain normally allows.

Normally, when building with -fpic, it is assumed that there is a fixed
offset between the text and data segments which never changes no matter
where the image is located.  This isn't true of zImage, and we do
hack around the toolchain a bit to achieve that.

That said, I've no desire to build the entire kernel with -fpic; I
don't see any need to do so.  Most people seem happy with working with
a fixed address; at some point you have to decide on a fixed address
to place the kernel.

-------------------------------------------------------------------
List admin: http://lists.arm.linux.org.uk/mailman/listinfo/linux-arm
FAQ:        http://www.arm.linux.org.uk/mailinglists/faq.php
Etiquette:  http://www.arm.linux.org.uk/mailinglists/etiquette.php