[DTrace-devel] [PATCH] sdt and syscall probe descriptions broken when multiple probes

[Kris Van Hees]

Please disregard - wrong patch...

On Tue, Oct 20, 2020 at 09:03:14PM -0400, Kris Van Hees wrote:
> Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>
> 
> On Mon, Oct 19, 2020 at 01:07:51AM -0400, eugene.loh at oracle.com wrote:
> > From: Eugene Loh <eugene.loh at oracle.com>
> > 
> > The sdt and syscall providers are broken in that, when a probe
> > description corresponds to multiple probes, a BPF program is
> > attached to only one of the probes.  E.g., syscall:::entry will
> > attach a BPF program to only one probe, even though hundreds of
> > probes are indicated!  The problem is that the attach function
> > looks for an event_id, skipping the probe if there is no such ID,
> > but the ID exists for only the "representative probe."
> > 
> > Change the attach() function so that, if the event_id has not
> > yet been set, there is an attempt to set it.  This is how the
> > dtrace and fbt providers behave.
> > 
> > What is surprising is that, with this fix, there are no XPASS
> > tests.  That is, there had presumably been no XFAIL tests
> > ("expected fails") that had been failing due *only* to this
> > problem.  A quick survey of tests suggests that this is likely;
> > remarkably few tests rely on such functionality, and those that
> > do still fail due to other missing support (such as strings or
> > other providers).
> > 
> > Therefore, add a test to check the fix.
> > 
> > Orabug: 32036431
> > Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> > ---
> >  libdtrace/dt_prov_sdt.c            |  2 ++
> >  test/unittest/syscall/tst.entry.sh | 50 ++++++++++++++++++++++++++++++
> >  2 files changed, 52 insertions(+)
> >  create mode 100755 test/unittest/syscall/tst.entry.sh
> > 
> > diff --git a/libdtrace/dt_prov_sdt.c b/libdtrace/dt_prov_sdt.c
> > index 4b2ac31b..1414bdf3 100644
> > --- a/libdtrace/dt_prov_sdt.c
> > +++ b/libdtrace/dt_prov_sdt.c
> > @@ -71,6 +71,8 @@ int tp_attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
> >  {
> >  	tp_probe_t	*datap = prp->prv_data;
> >  
> > +	if (datap->event_id == -1)
> > +		prp->prov->impl->probe_info(dtp, prp, NULL, NULL);
> >  	if (datap->event_id == -1)
> >  		return 0;
> >  
> > diff --git a/test/unittest/syscall/tst.entry.sh b/test/unittest/syscall/tst.entry.sh
> > new file mode 100755
> > index 00000000..fc14f7cc
> > --- /dev/null
> > +++ b/test/unittest/syscall/tst.entry.sh
> > @@ -0,0 +1,50 @@
> > +#!/bin/bash
> > +#
> > +# Oracle Linux DTrace.
> > +# Copyright (c) 2020, 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.
> > +
> > +# Check that syscall:::entry picks up open*:entry.
> > +
> > +dtrace=$1
> > +
> > +DIRNAME="$tmpdir/entry.$$.$RANDOM"
> > +mkdir -p $DIRNAME
> > +cd $DIRNAME
> > +
> > +cat > main.c << EOF
> > +#include <unistd.h>
> > +#include <sys/stat.h>
> > +#include <fcntl.h>
> > +int main(int c, char **v) {
> > +    while (open("/dummy/path", O_RDWR) == -1) sleep(1);
> > +    return 0;
> > +}
> > +EOF
> > +
> > +gcc main.c
> > +if [ $? -ne 0 ]; then
> > +    echo ERROR: compilation failed
> > +    cat main.c
> > +    exit 1
> > +fi
> > +
> > +./a.out &
> > +pid=$!
> > +
> > +$dtrace $dt_flags -o tmp.log -n 'syscall:::entry /pid == '$pid'/ {}  tick-5s {exit(0)}'
> > +if [ $? -ne 0 ]; then
> > +    echo ERROR: dtrace failed
> > +    exit 1
> > +fi
> > +
> > +kill %1
> > +
> > +if [ `grep -c '^ *open.*:entry *$' tmp.log` -lt 4 ]; then
> > +    echo ERROR: insufficient probe firings
> > +    cat tmp.log
> > +    exit 1
> > +fi
> > +
> > +exit 0
> > -- 
> > 2.18.4
> > 
> > 
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> > DTrace-devel at oss.oracle.com
> > https://oss.oracle.com/mailman/listinfo/dtrace-devel
> 
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