Re: powerpc new PLT and GOT

[Daniel Jacobowitz <drow at false dot org>]

On Wed, May 11, 2005 at 11:42:50PM +0930, Alan Modra wrote:
> The current PowerPC ABI requires PLT and GOT to be both writable and
> executable, which is a security concern.  It's worse than that actually,
> since the entire data segment ends up executable.
> 
> This patch implements binutils support for a new PLT and GOT on PowerPC,
> details of which are in the attached ABI proposal.  Note that the
> proposal is by no means final;  There's likely to be some change in
> .glink to do without the lwzu instructions, but I think it's solid
> enough to throw some code together.  Also, the ld support doesn't allow
> registers other than r30 as a GOT pointer.  We'll worry about that if
> and when gcc generates code using a different register.
> 
> From a user perspective, this ld change won't do anything until gcc
> starts generating code for the new PLT and GOT.  ie. ld will continue to
> link using the old PLT scheme.

I'm not oing to look at the code, but I have one comment on the ABI.
You've got a data section named .plt and a code section named .glink
(well, you note that the text stubs can be anywhere in the text
segment, but that's true on most architectures; I imagine that for now
they're all going in a single .glink section).

Everyone else seems to call the data section ".got.plt" and the text
section ".plt".  GDB even knows about this; it uses the name ".plt" to
help in skipping dynamic linker code.  Is there a reason why you can't
use the traditional names?

-- 
Daniel Jacobowitz
CodeSourcery, LLC