On Wed, 2011-08-24 at 14:00 +1000, David Gibson wrote: > On Tue, Aug 23, 2011 at 02:57:56PM +0530, K.Prasad wrote: > > On Tue, Aug 23, 2011 at 03:09:31PM +1000, David Gibson wrote: > > > On Fri, Aug 19, 2011 at 01:23:38PM +0530, K.Prasad wrote: > > > > > > > > While PPC_PTRACE_SETHWDEBUG ptrace flag in PowerPC accepts > > > > PPC_BREAKPOINT_MODE_EXACT mode of breakpoint, the same is not intimated > > > > to the > > > > user-space debuggers (like GDB) who may want to use it. Hence we > > > > introduce a > > > > new PPC_DEBUG_FEATURE_DATA_BP_EXACT flag which will be populated on the > > > > "features" member of "struct ppc_debug_info" to advertise support for > > > > the > > > > same on Book3E PowerPC processors. > > > > > > I thought the idea was that the BP_EXACT mode was the default - if the > > > new interface was supported at all, then BP_EXACT was always > > > supported. So, why do you need a new flag? > > > > > > > Yes, BP_EXACT was always supported but not advertised through > > PPC_PTRACE_GETHWDBGINFO. We're now doing that. > > I can see that. But you haven't answered why.
BookS doesn't support BP_EXACT, that's why I suggested this flag. A BP_EXACT watchpoint triggers only when there's a memory access exactly at the given address. It doesn't trigger when there's (for example) a 4-byte write at an address immediately before which also changes the memory contents of the byte watched by the BP_EXACT watchpoint. a ranged watchpoint would trigger, so the semantics are different. As a general rule, GDB only sets ranged watchpoints and only uses BP_EXACT ones when the user sets a flag. I want GDB to fail when the user sets the flag on BookS since it can't provide the feature. -- []'s Thiago Jung Bauermann IBM Linux Technology Center _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
