Finding module TOC address

[Benjamin Herrenschmidt]

On Thu, 2005-05-26 at 08:06 +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2005-05-25 at 21:42 +0300, Heikki Lindholm wrote:
> > Hello,
> > I need to use assembly jump to a function in a module. How do I find out 
> > the TOC that the function expects to find in r2? A quick peek at 
> > kernel/module.c didn't help much, maybe someone here could enlighten me.
> 
> You don't, there is no TOC on ppc32 ABI, at least the kernel version of
> it. r2 is reserved in the kernel and always contains "current".

Ooops ! As you stated privately, wrong list :)

So yes, ppc64 has a TOC :)

When you take the function pointer, what you should obtain is a
descriptor containing the actual pointer and the TOC (unless you are
calling the .xxx symbol, but that isn't very good to do).

So if you are doing a pointer-based jump, just load the TOC pointer
along with the function pointer from the descriptor. If you are doing a
direct jump (bl .blabla), I'm not 100% sure, you'll probably just load
the non-dot symbol address in a register to get the descriptor, and then
peek it for the toc value... Alan ? Is there some better way ?

Ben.