On Mon, 25 Nov 2002, Ralf Baechle 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). -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
