On Fri, 2007-11-09 at 19:54 +0100, Ulrich Weigand wrote: > Hello, > > I've noticed that GDB hardware watchpoints do not work at all on Cell/B.E. > (when running without hypervisor); the kernel accepts the PTRACE_SET_DEBUGREG > call without error, but watchpoints never trigger. > > This turns out to be caused by a new hardware feature in the PowerPC 2.02 > architecture level: the DABRX register. This register controls in which > modes of operation (problem state, privileged state, hypervisor state) > the DABR register takes effect. (See Book III v 2.02 page 40.) > > The default setting of that register on Cell/B.E. (at least on IBM blades), > which the Linux kernel currently never modifies, is to ignore DABR in all > modes -- thus watchpoints do not work at all. > > The following hack sets the bit in the DABRX that enables the DABR for > problem state, whenever the DABR is set. With this patch on top of the > current Fedora 8 update kernel (kernel-2.6.23.1-48.fc8) watchpoints work > again -- all relevant test cases in the GDB test suite now pass. > > Obviously, the patch cannot be applied as-is; we need to make sure we are > on a machine that supports the DABRX feature. Arnd asked me to post this > anyway as a heads-up on that problem ...
Hrm, ok, something we missed, I'll have a look. The whole DABR / debug register handling need work anyway. Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
