Re: [rfc] Simplify ppc64_sysv_abi_adjust_breakpoint_address

[Luis Machado <luisgpm@linux.vnet.ibm.com>]

On Thu, 2008-10-09 at 19:51 +0200, Ulrich Weigand wrote:
> Luis Machado wrote:
> 
> > It seems we have a situation in which
> > "ppc64_sysv_abi_adjust_breakpoint_address" is still required, in a way.
> > 
> > Before removing this function, GDB was smart enough to know that the
> > entry point of a 64-bit PPC binary is, in reality, a function
> > descriptor, thus grabbing the correct breakpoint location from within
> > that address and setting it correctly.
> > 
> > After removing this function, GDB no longer knows that a specific
> > address is a function descriptor, and places a breakpoint at a data
> > section. The binary's code tries to fetch the correct address from the
> > function descriptor's address and ends up fetching the breakpoint
> > instruction, which makes no sense.
> > 
> > So, i see two ways:
> > 
> > 1 - Make GDB smart again, being able to determine if the address is of a
> > function descriptor or not, basically the way i was before this patch.
> > 
> > 2 - Assume the user knows what he's doing and that he knows where to
> > place a breakpoint when using the address of a function descriptor.
> 
> I'm not sure exactly what situation you're refering to ... is this
> about
>    break *0x.....
> where the address that was manually specified refers to a function
> descriptor instead of the function code?
> 
> In that case, I'd tend to consider this user error -- if you use
> hard-coded addresses, you should know what you're doing on the 
> platform.
> 
> If this is about something else, could you show a command line
> that does the wrong thing for you?
> 
> Bye,
> Ulrich
> 

This is exactly about placing breakpoint on numberic addresses like
"break *0x...". GDB used to do that correctly before that patch, but it
doesn't anymore. So, maybe it's OK to consider this is something the
user should be aware of...

Luis