On Wed, Dec 11, 2002 at 06:38:51PM +0100, Maciej W. Rozycki wrote: > On Wed, 11 Dec 2002, Daniel Jacobowitz wrote: > > > That way we expose more of the hardware to userland; and the thing > > that's most important to me is that GDB not have to know if it's on a > > MIPS32 or an R4650 when determining how watchpoints work. > > IWatch/DWatch are two particular watchpoints or distinguished by access > > type? I.E. what would GDB need to know to know which it is setting? > > The watchpoints would always be interfaced the same way, regardless of > the underlying implementation, of course. For the IWatch/DWatch, I'd > assign their numbers somehow (e.g. IWatch is watchpoint #0 and DWatch is > #1, following the sequence used for their CP0 register numbers). A user > such as GDB would have to determine the capabilities of all watchpoints as > I described and would discover that watchpoint #0 only accepts instruction > fetch events and watchpoint #1 only accepts data read/write ones. > > This way we can accept an arbitrary underlying implementation. This is what I don't like. Setting each individual watchpoint to determine their capabilities, when the kernel could just _report_ said capabilities. It's a difference in philosophy I suppose. I also have some concerns about making the probing indistinguishable from setting a watchpoint; if MIPS37 or MPIS256 has a substantially different watchpoint layout, we'll have to give it a whole new set of ptrace ops, which defeats the point of abstracting it. If we write up decent documentation for what a userspace implementation has to do to probe the current implementations, I guess I'm satisfied. -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer
