On Mon, Nov 25, 2002 at 12:55:11PM +0100, Maciej W. Rozycki wrote: > > The whole watch stuff in the the kernel is pretty much an ad-hoc API > > which I did create to debug a stack overflow. I'm sure if you're > > going to use it you'll find problems. For userspace for example you'd > > have to switch the watch register when switching the MMU context so > > each process gets it's own virtual watch register. Beyond that there > > are at least two different formats of watch registers implemented in > > actual silicon, the original R4000-style and the MIPS32/MIPS64 style > > watch registers and the kernel's watch code only know the R4000 style > > one. So check your CPU's manual ... > > I think the best use of the watch exception would be making it available > to userland via PTRACE_PEEKUSR and PTRACE_POKEUSR for hardware watchpoint > support (e.g. for gdb). Hardware support is absolutely necessary for > watching read accesses and much beneficial for write ones (otherwise gdb > single-steps code which sucks performace-wise). Agreed. And because such an extension would be fully backward compatible introduction is no problem. So time to come up with a reasonable API. MIPS32 / MIPS64 extend the R4000's watch capabilities significantly, something we don't want to ignore. Ralf
