Re: [PATCH v3] Enable tracing of pseudo-registers on ARM

Antoine Tremblay
2016-02-23T19:34:09Z

Pedro Alves writes:

>> +
>> + return double_regnum;
>> +}
>> +
>> +/* Implementation of the ax_pseudo_register_collect gdbarch function. */
>> +
>> +static int
>> +arm_ax_pseudo_register_collect (struct gdbarch *gdbarch,
>> + struct agent_expr *ax, int reg)
>> +{
>> + int rawnum = arm_pseudo_register_to_register (gdbarch, reg);
>> +
>> + /* Error. */
>> + if (rawnum < 0)
>> + return 1;
>> +
>> + ax_reg_mask (ax, rawnum);
>
> Hmm, seems to me that gdb raw -> target raw mapping should be
> either here, or perhaps even in ax_reg / ax_reg_mask?
>

After more investigation, this can't be in ax_reg / ax_reg_mask for
pseudo registers as this function is solely reponsible to encode the
right number here.

> Consider the case of an expression requiring the collection of
> a _raw_ register, thus not even reaching here. Looking at
> ax-gdb.c/ax-general.c I don't see where is anything mapping gdb raw numbers
> to remote/tdesc numbers? So how does _that_ work? Are the register masks that gdb
> is computing actually wrong for the target, and things just happen
> to work because gdbserver ignores them and always collects all registers?

However yes it should be in ax_reg/ax_reg_mask for non-pseudo registers,
but this is not the objective of this patch, I suggest that such a
change be the subject of another patch maybe coupled with better
gdbserver handling of the R action.

I will send a v5 with the ax_pseudo_register_collect inside the
arm_ax_pseudo_register_collect/arm_ax_pseudo_register_push stack function.