MPC8260 strange virtual addresses returned by kmalloc()

Eugene Surovegin ebs at
Thu Jan 6 04:41:54 EST 2005

On Wed, Jan 05, 2005 at 02:38:12PM +0100, Laurent Lagrange wrote:
> Hi and Happy New Year to all,
> I use a Linux 2.4.25 kernel on a MPC8260 custom board with 128MB of RAM.
> PCI is activated and my drivers are loaded as modules.
> The RAM is mapped at 0xC0000000 as usual.
> On MPC8XX I used kmalloc and iopa to get the physical addresses of the
> allocated buffers.
> On MPC82XX I used kmalloc and __pa for the same thing and it worked fine
> with previous kernel.
> But now, when I want to use kmalloc, I get addresses like 0xC9xxxxxx.
> The __pa gives me physical addresses 0x09xxxxxx which are out of my physical
> RAM.
> I tried old iopa function and got some real physical addresses and the
> module works.
> The virt_to_bus gives me too addresses like  0x09xxxxxx
> (ie substract kernel base address 0xC0000000 as usual).
> I don't understand why I get virtual addresses which seem to be out of my
> memory and why it runs.

Yeah, this looks strange, please, check that this address is really 
from kmalloc and not from vmalloc.

Also, check that PAGE_OFFSET is really 0xc000'0000.

> More, I have a global variable which is a little buffer. It is also mapped
> at a 0xC9xxxxxx address.

Is this global variable in the loaded module? If yes, this is normal, 
because modules are loaded into vmalloced space and you cannot use 
__pa for such addresses.


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