[DTrace-devel] [PATCH v3 02/19] Add a dt_provider_discover() function

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

It is possible for new providers and probes to appear after dtrace_go().
Add a function that can be called for such discovery, on a per-provider
basis.  Each provider that supports such discovery needs to provide:

*)  a function discover() that performs discovery on behalf of the provider

*)  a function add_probe() that adds a particular (discovered) probe

To support looping over providers, move dt_providers[] from
dt_open.c to dt_provider.c and extern it in dt_provider.h.

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_bpf.c      |  6 +++++
 libdtrace/dt_open.c     | 22 +---------------
 libdtrace/dt_provider.c | 57 +++++++++++++++++++++++++++++++++++++++++
 libdtrace/dt_provider.h |  6 +++++
 libdtrace/dt_work.c     |  3 +++
 5 files changed, 73 insertions(+), 21 deletions(-)

diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index ad11d178e..7a36b6187 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -1275,6 +1275,12 @@ dt_bpf_load_progs(dtrace_hdl_t *dtp, uint_t cflags)
 		int		fd;
 		int		rc = -1;
 
+		if (prp->prov->impl->prog_type == BPF_PROG_TYPE_UNSPEC) {
+			if (prp->prov->impl->add_probe)
+				prp->prov->impl->add_probe(dtp, prp);
+			continue;
+		}
+
 		dp = prp->difo;
 		if (dp == NULL)
 			continue;
diff --git a/libdtrace/dt_open.c b/libdtrace/dt_open.c
index 848141ddc..1f586fc4f 100644
--- a/libdtrace/dt_open.c
+++ b/libdtrace/dt_open.c
@@ -61,26 +61,6 @@ const dt_version_t _dtrace_versions[] = {
 	0
 };
 
-/*
- * List of provider modules that register providers and probes.  A single
- * provider module may create multiple providers.
- */
-static const dt_provimpl_t *dt_providers[] = {
-	&dt_dtrace,		/* list dt_dtrace first */
-	&dt_cpc,
-	&dt_fbt_fprobe,
-	&dt_io,
-	&dt_ip,
-	&dt_lockstat,
-	&dt_proc,
-	&dt_profile,
-	&dt_rawtp,
-	&dt_sched,
-	&dt_sdt,
-	&dt_syscall,
-	&dt_uprobe,
-};
-
 /*
  * Table of global identifiers.  This is used to populate the global identifier
  * hash when a new dtrace client open occurs.  For more info see dt_ident.h.
@@ -1210,7 +1190,7 @@ dtrace_init(dtrace_hdl_t *dtp)
 	 * known providers.
 	 */
 	dt_probe_init(dtp);
-	for (i = 0; i < ARRAY_SIZE(dt_providers); i++) {
+	for (i = 0; dt_providers[i]; i++) {
 		int	n;
 
 		n = dt_providers[i]->populate(dtp);
diff --git a/libdtrace/dt_provider.c b/libdtrace/dt_provider.c
index 8cfef0ba2..5f9766183 100644
--- a/libdtrace/dt_provider.c
+++ b/libdtrace/dt_provider.c
@@ -18,10 +18,32 @@
 #include <port.h>
 
 #include <dt_provider.h>
+#include <dt_probe.h>
 #include <dt_module.h>
 #include <dt_string.h>
 #include <dt_list.h>
 
+/*
+ * List of provider modules that register providers and probes.  A single
+ * provider module may create multiple providers.
+ */
+const dt_provimpl_t *dt_providers[] = {
+	&dt_dtrace,		/* list dt_dtrace first */
+	&dt_cpc,
+	&dt_fbt_fprobe,
+	&dt_io,
+	&dt_ip,
+	&dt_lockstat,
+	&dt_proc,
+	&dt_profile,
+	&dt_rawtp,
+	&dt_sched,
+	&dt_sdt,
+	&dt_syscall,
+	&dt_uprobe,
+	NULL
+};
+
 static uint32_t
 dt_provider_hval(const dt_provider_t *pvp)
 {
@@ -149,3 +171,38 @@ dt_provider_xref(dtrace_hdl_t *dtp, dt_provider_t *pvp, id_t id)
 	BT_SET(pvp->pv_xrefs, id);
 	return 0;
 }
+
+int
+dt_provider_discover(dtrace_hdl_t *dtp)
+{
+	int i, prid = dtp->dt_probe_id;
+
+	/* Discover new probes. */
+	for (i = 0; dt_providers[i]; i++) {
+		int n;
+
+		if (dt_providers[i]->discover == NULL)
+			continue;
+
+		n = dt_providers[i]->discover(dtp);
+		if (n < 0)
+			return -1;        /* errno is already set */
+	}
+
+	/* Add them. */
+	for ( ; prid < dtp->dt_probe_id; prid++) {
+		dt_probe_t	*prp = dtp->dt_probes[prid];
+		int		rc;
+
+		dt_probe_enable(dtp, prp);
+
+		if (prp->prov->impl->add_probe == NULL)
+			continue;
+
+		rc = prp->prov->impl->add_probe(dtp, prp);
+		if (rc < 0)
+			return rc;
+	}
+
+	return 0;
+}
diff --git a/libdtrace/dt_provider.h b/libdtrace/dt_provider.h
index 17b1844cb..384d4fd33 100644
--- a/libdtrace/dt_provider.h
+++ b/libdtrace/dt_provider.h
@@ -62,6 +62,9 @@ typedef struct dt_provimpl {
 	int (*probe_info)(dtrace_hdl_t *dtp,	/* get probe info */
 			  const struct dt_probe *prp,
 			  int *argcp, dt_argdesc_t **argvp);
+	int (*discover)(dtrace_hdl_t *dtp);	/* discover new probes */
+	int (*add_probe)(dtrace_hdl_t *dtp,	/* add a new probe */
+			 struct dt_probe *prp);
 	void (*detach)(dtrace_hdl_t *dtp,	/* probe cleanup */
 		       const struct dt_probe *prb);
 	void (*probe_destroy)(dtrace_hdl_t *dtp, /* free probe data */
@@ -86,6 +89,8 @@ extern dt_provimpl_t dt_sdt;
 extern dt_provimpl_t dt_syscall;
 extern dt_provimpl_t dt_uprobe;
 
+extern const dt_provimpl_t *dt_providers[];
+
 typedef struct dt_provider {
 	dt_list_t pv_list;		/* list forward/back pointers */
 	struct dt_hentry he;		/* htab links */
@@ -110,6 +115,7 @@ extern dt_provider_t *dt_provider_create(dtrace_hdl_t *, const char *,
 					 const dt_provimpl_t *,
 					 const dtrace_pattr_t *, void *);
 extern int dt_provider_xref(dtrace_hdl_t *, dt_provider_t *, id_t);
+extern int dt_provider_discover(dtrace_hdl_t *dtp);
 
 #ifdef	__cplusplus
 }
diff --git a/libdtrace/dt_work.c b/libdtrace/dt_work.c
index 11335345a..5318cdb7e 100644
--- a/libdtrace/dt_work.c
+++ b/libdtrace/dt_work.c
@@ -362,6 +362,9 @@ dtrace_work(dtrace_hdl_t *dtp, FILE *fp, dtrace_consume_probe_f *pfunc,
 	dtrace_workstatus_t	rval;
 	int			gen;
 
+	if (dt_provider_discover(dtp) < 0)
+		return DTRACE_WORKSTATUS_ERROR;
+
 	switch (dtrace_status(dtp)) {
 	case DTRACE_STATUS_EXITED:
 	case DTRACE_STATUS_STOPPED:
-- 
2.43.5