On Tue, 23 Feb 2021 at 18:24, Daniel Thompson <daniel.thomp...@linaro.org> wrote: > > On Tue, Feb 23, 2021 at 02:33:50PM +0530, Sumit Garg wrote: > > Thanks Doug for your comments. > > > > On Tue, 23 Feb 2021 at 05:28, Doug Anderson <diand...@chromium.org> wrote: > > > > To be clear there is still a very small window between call to > > > > free_initmem() and system_state = SYSTEM_RUNNING which can lead to > > > > removal of freed .init.text section breakpoints but I think we can live > > > > with that. > > > > > > I know kdb / kgdb tries to keep out of the way of the rest of the > > > system and so there's a bias to just try to infer the state of the > > > rest of the system, but this feels like a halfway solution when really > > > a cleaner solution really wouldn't intrude much on the main kernel. > > > It seems like it's at least worth asking if we can just add a call > > > like kgdb_drop_init_breakpoints() into main.c. Then we don't have to > > > try to guess the state... > > Just for the record, +1. This would be a better approach. > > > > Sounds reasonable, will post RFC for this. I think we should call such > > function as kgdb_free_init_mem() in similar way as: > > - kprobe_free_init_mem() > > - ftrace_free_init_mem() > > As is matching the names... > > > > @@ -378,8 +382,13 @@ int dbg_deactivate_sw_breakpoints(void) > > int i; > > > > for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { > > - if (kgdb_break[i].state != BP_ACTIVE) > > + if (kgdb_break[i].state < BP_ACTIVE_INIT) > > + continue; > > + if (system_state >= SYSTEM_RUNNING && > > + kgdb_break[i].state == BP_ACTIVE_INIT) { > > + kgdb_break[i].state = BP_UNDEFINED; > > continue; > > + } > > error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); > > if (error) { > > pr_info("BP remove failed: %lx\n", > > > > > > > > > + kgdb_break[i].state = BP_ACTIVE; > > > > + else > > > > + kgdb_break[i].state = BP_ACTIVE_INIT; > > > > > > I don't really see what the "BP_ACTIVE_INIT" state gets you. Why not > > > just leave it as "BP_ACTIVE" and put all the logic fully in > > > dbg_deactivate_sw_breakpoints()? > > > > Please see my response above. > > > > [which was] > > > "BP_ACTIVE_INIT" state is added specifically to handle this scenario > > > as to keep track of breakpoints that actually belong to the .init.text > > > section. And we should be able to again set breakpoints after free > > > since below change in this patch would mark them as "BP_UNDEFINED": > > This answer does not say whether the BP_ACTIVE_INIT state needs to be > per-breakpoint state or whether we can infer it from the global state. > > Changing the state of breakpoints in .init is a one-shot activity > whether it is triggered explicitly (e.g. kgdb_free_init_mem) or implicitly > (run the first time dbg_deactivate_sw_breakpoints is called with the system > state >= running). > > As Doug has suggested it is quite possible to unify all the logic to > handle .init within a single function by running that function when the > state changes globally. >
Ah, I see. Thanks for further clarification. Will get rid of BP_ACTIVE_INIT state. -Sumit > > Daniel.