Matheus Branco Borella <dark.ryu....@gmail.com> writes:
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1725 > > This fix is implemented by having the vCont handler set the value of > `gdbserver_state.c_cpu` if any threads are to be resumed. The specific CPU > is picked arbitrarily from the ones to be resumed, but it should be okay, as > all > GDB cares about is that it is a resumed thread. > > Keep in mind that because this patch overwrites `c_cpu`, it breaks cases where > $vCont is used together with $Hc, so there might be more work to be > done here. That doesn't sound good. Is that a possible case or an invalid one because we shouldn't see gdbs using both? > It might also be the case that it breaking this, specifically, isn't of > consequence, seeing as single stepping with $vCont already overwrites `c_cpu` > anyway, so you could say the implementation already behaves oddly as far as > mixing $vCont and $Hc is concerned. It would be nice to have some unit tests for this behaviour to defend it. See the various tests in tests/tcg that call $(GDB_SCRIPT) for examples. BTW you are missing a Signed-off-by: tag which we will need to take a patch submission. See: https://qemu.readthedocs.io/en/latest/devel/submitting-a-patch.html > --- > gdbstub/gdbstub.c | 31 ++++++++++++++++++++++++++++++- > 1 file changed, 30 insertions(+), 1 deletion(-) > > diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c > index be18568d0a..4f7ac5ddfe 100644 > --- a/gdbstub/gdbstub.c > +++ b/gdbstub/gdbstub.c > @@ -595,6 +595,15 @@ static int gdb_handle_vcont(const char *p) > * or incorrect parameters passed. > */ > res = 0; > + > + /* > + * target_count and last_target keep track of how many CPUs we are going > to > + * step or resume, and a pointer to the state structure of one of them, > + * respectivelly > + */ > + int target_count = 0; > + CPUState *last_target = NULL; > + > while (*p) { > if (*p++ != ';') { > res = -ENOTSUP; > @@ -639,8 +648,10 @@ static int gdb_handle_vcont(const char *p) > while (cpu) { > if (newstates[cpu->cpu_index] == 1) { > newstates[cpu->cpu_index] = cur_action; > - } > > + target_count++; > + last_target = cpu; > + } > cpu = gdb_next_attached_cpu(cpu); > } > break; > @@ -657,6 +668,9 @@ static int gdb_handle_vcont(const char *p) > while (cpu) { > if (newstates[cpu->cpu_index] == 1) { > newstates[cpu->cpu_index] = cur_action; > + > + target_count++; > + last_target = cpu; > } > > cpu = gdb_next_cpu_in_process(cpu); > @@ -675,10 +689,25 @@ static int gdb_handle_vcont(const char *p) > /* only use if no previous match occourred */ > if (newstates[cpu->cpu_index] == 1) { > newstates[cpu->cpu_index] = cur_action; > + > + target_count++; > + last_target = cpu; > } > break; > } > } > + > + /* > + * if we're about to resume a specific set of CPUs/threads, make it so > that > + * in case execution gets interrupted, we can send GDB a stop reply with > a > + * correct value. it doesn't really matter which CPU we tell GDB the > signal > + * happened in (VM pauses stop all of them anyway), so long as it is one > of > + * the ones we resumed/single stepped here. > + */ > + if (target_count > 0) { > + gdbserver_state.c_cpu = last_target; > + } > + > gdbserver_state.signal = signal; > gdb_continue_partial(newstates); Looks reasonable at first glance but I would like some tests. -- Alex Bennée Virtualisation Tech Lead @ Linaro
