[DTrace-devel] [PATCH 4/5] dynvar: ensure there is always space for at least one dynvar if needed

[Kris Van Hees]

On Mon, May 01, 2023 at 10:34:36PM -0400, Eugene Loh via DTrace-devel wrote:
> Same comments as for aggsize patch (3/5).

See my reply to that email :)

> On 5/1/23 15:52, Kris Van Hees via DTrace-devel wrote:
> > When dynamic variables (or associative arrays) are used, raise the
> > dynvarsize option value if needed to ensure there is room for at least
> > one dynamic variable (or associative array element).
> > 
> > Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> > ---
> >   libdtrace/dt_bpf.c                            | 10 ++++--
> >   .../assocs/tst.dynvarsize-too-small.d         | 31 +++++++++++++++++++
> >   .../assocs/tst.dynvarsize-too-small.r         |  6 ++++
> >   3 files changed, 44 insertions(+), 3 deletions(-)
> >   create mode 100644 test/unittest/assocs/tst.dynvarsize-too-small.d
> >   create mode 100644 test/unittest/assocs/tst.dynvarsize-too-small.r
> > 
> > diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
> > index 0f33f245..e19833bd 100644
> > --- a/libdtrace/dt_bpf.c
> > +++ b/libdtrace/dt_bpf.c
> > @@ -846,9 +846,13 @@ gmap_create_dvars(dtrace_hdl_t *dtp)
> >   	if (dtp->dt_maxdvarsize == 0)
> >   		return 0;
> > -	nelems = dtp->dt_options[DTRACEOPT_DYNVARSIZE] / dtp->dt_maxdvarsize;
> > -	if (nelems == 0)
> > -		return 0;
> > +	nelems = dtp->dt_options[DTRACEOPT_DYNVARSIZE] /
> > +		 (dtp->dt_maxtuplesize + dtp->dt_maxdvarsize);
> > +	if (nelems == 0) {
> > +		dtp->dt_options[DTRACEOPT_DYNVARSIZE] =
> > +				dtp->dt_maxtuplesize + dtp->dt_maxdvarsize;
> > +		nelems = 1;
> > +	}
> >   	if (create_gmap(dtp, "dvars", BPF_MAP_TYPE_HASH, sizeof(uint64_t),
> >   			dtp->dt_maxdvarsize, nelems) == -1)
> > diff --git a/test/unittest/assocs/tst.dynvarsize-too-small.d b/test/unittest/assocs/tst.dynvarsize-too-small.d
> > new file mode 100644
> > index 00000000..27539194
> > --- /dev/null
> > +++ b/test/unittest/assocs/tst.dynvarsize-too-small.d
> > @@ -0,0 +1,31 @@
> > +/*
> > + * Oracle Linux DTrace.
> > + * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
> > + * Licensed under the Universal Permissive License v 1.0 as shown at
> > + * http://oss.oracle.com/licenses/upl.
> > + */
> > +
> > +/*
> > + * ASSERTION: If dynvarsize is too small to hold a single dynamic variable, the
> > + *	      size is increased automatically.
> > + *
> > + * SECTION: Aggregations/Aggregations
> > + */
> > +
> > +/*
> > + * Storing an int (4 byte integer) in an associative array indexed by an int
> > + * requires at least 20 bytes of dynamic variable storage.
> > + */
> > +#pragma D option quietresize=no
> > +#pragma D option dynvarsize=15
> > +
> > +BEGIN
> > +{
> > +	a[1] = 1;
> > +	exit(0);
> > +}
> > +
> > +ERROR
> > +{
> > +	exit(1);
> > +}
> > diff --git a/test/unittest/assocs/tst.dynvarsize-too-small.r b/test/unittest/assocs/tst.dynvarsize-too-small.r
> > new file mode 100644
> > index 00000000..b236110f
> > --- /dev/null
> > +++ b/test/unittest/assocs/tst.dynvarsize-too-small.r
> > @@ -0,0 +1,6 @@
> > +                   FUNCTION:NAME
> > +                          :BEGIN
> > +
> > +-- @@stderr --
> > +dtrace: script 'test/unittest/assocs/tst.dynvarsize-too-small.d' matched 2 probes
> > +dtrace: dynamic variable size raised to 20
> 
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