[DTrace-devel] [PATCH 1/5] Implement setopt()

[Nick Alcock]

On 7 Sep 2022, Kris Van Hees via DTrace-devel told this:

> The basic mechanics of the setopt() action are implemented in this
> patch.  Each dynamic runtime options that can be set using setopt()

s/options/option/

> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>  libdtrace/dt_cg.c      | 11 ++++++++++
>  libdtrace/dt_consume.c | 47 +++++++++++++++++++++++++++++++++---------
>  2 files changed, 48 insertions(+), 10 deletions(-)
>
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index cb51c474..ffab2443 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
>@@ -1751,6 +1751,17 @@ dt_cg_act_raise(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
>  static void
>  dt_cg_act_setopt(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
>  {
> +	dt_node_t	*opt = dnp->dn_args;
> +	dt_node_t	*val = opt->dn_list;
> +
> +	TRACE_REGSET("setopt(): Begin ");
> +	dt_cg_store_val(pcb, opt, DTRACEACT_LIBACT, NULL, DT_ACT_SETOPT);
> +
> +	/* If not value is given, we default to 0. */

s/not/no/

> +	if (val == NULL)
> +		val = dt_node_int(0);

So this defaults VAL to 0...

>@@ -2332,6 +2334,31 @@ dt_consume_one_probe(dtrace_hdl_t *dtp, FILE *fp, char *data, uint32_t size,
>  				ftruncate(fileno(fp), 0);
>  				fseeko(fp, 0, SEEK_SET);
>  
> +				continue;
> +			case DT_ACT_SETOPT: {
> +				caddr_t			opt = recdata;
> +				caddr_t			val;
> +				dtrace_recdesc_t	*vrec;
> +
> +				if (i == epd->dtdd_nrecs - 1)
> +					return dt_set_errno(dtp, EDT_BADSETOPT);
> +
> +				vrec = &epd->dtdd_recs[++i];
> +				if (vrec->dtrd_action != act &&
> +				    vrec->dtrd_arg != rec->dtrd_arg)
> +					return dt_set_errno(dtp, EDT_BADSETOPT);
> +
> +				if (vrec->dtrd_size > sizeof(uint64_t))
> +					val = data + vrec->dtrd_offset;
> +				else
> +					val = "1";

... and then this, uh, no I have absolutely no idea what this is doing.
I guess future patches will put larger things into the value than a
dt_node_int? (But then why nail a 1 in there rather than what the user
passed in when something integral-or-smaller is passed? Why 1 at all,
rather than the 0 up above? Doesn't this deserve a comment?)

-- 
NULL && (void)