Re: PATCH: target/19520: protected function pointer doesn't work right

[Daniel Jacobowitz <drow at false dot org>]

On Thu, Jan 20, 2005 at 03:59:19PM -0800, H. J. Lu wrote:
> On Thu, Jan 20, 2005 at 05:59:07PM -0500, Daniel Jacobowitz wrote:
> > On Thu, Jan 20, 2005 at 02:56:47PM -0800, H. J. Lu wrote:
> > > The issue is the function address of a protected function isn't
> > > necessarily the same as the address of the function body nor has to
> > > be in the same DSO where the function is defined. In that case, the
> > > only optimization we can do is to skip PLT when branch. This
> > > patch marks if a symbol is protected and also treats a protected
> > > function as normal. But it will skip PLT when generating the branch
> > > instruction.
> > 
> > Is there clear documentation of these very odd semantics somewhere? 
> 
> It has been that way with PLT from day 1. Basically, PLT is usually
> used to redirect the function call. Linker will resolve undefined
> function address to the PLT entry. To make sure function address
> comprison works correctly, everyone has to agree on a unique function
> address, which is the PLT entry if it will ever be used. The protected
> function makes it tricky.

That doesn't answer my question :-)

> > How about test cases?
> > 
> 
> Is there a place I can add it? I need to build a shared library,
> link a main against it and run the main.

Binutils has a number of C tests like these already.  They don't run
when cross, but they're better than nothing.

-- 
Daniel Jacobowitz