[DTrace-devel] [PATCH v2 1/7] libdtrace: Support multiple DTrace handles per process

[Alan Maguire]

For use cases like PCP we require multiple DTrace handles
in a process; to fix this ensure we tie global map creation
to the handle and also allow BEGIN and END probes to already
exist.  Later work can capitalize on efficiences like sharing
kernel type info, but for now this is enough to make multiple
instances work.

Signed-off-by: Alan Maguire <alan.maguire at oracle.com>
---
 libdtrace/dt_bpf.c         | 6 ++----
 libdtrace/dt_impl.h        | 1 +
 libdtrace/dt_prov_dtrace.c | 6 +++++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 146a66e3..be8a4229 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -25,8 +25,6 @@
 #include <dt_btf.h>
 #include <port.h>
 
-static boolean_t	dt_gmap_done = 0;
-
 #define BPF_CG_LICENSE	"GPL";
 
 int
@@ -1076,11 +1074,11 @@ int
 dt_bpf_gmap_create(dtrace_hdl_t *dtp)
 {
 	/* If we already created the global maps, return success. */
-	if (dt_gmap_done)
+	if (dtp->dt_gmap_done)
 		return 0;
 
 	/* Mark global maps creation as completed. */
-	dt_gmap_done = 1;
+	dtp->dt_gmap_done = 1;
 
 #define CREATE_MAP(name) \
 	if (gmap_create_##name(dtp) == -1) \
diff --git a/libdtrace/dt_impl.h b/libdtrace/dt_impl.h
index 5282efbd..7db2ba93 100644
--- a/libdtrace/dt_impl.h
+++ b/libdtrace/dt_impl.h
@@ -433,6 +433,7 @@ struct dtrace_hdl {
 	dt_list_t dt_lib_dep_sorted;	/* dependency sorted library list */
 	dt_global_pcap_t dt_pcap; /* global tshark/pcap state */
 	char *dt_freopen_filename; /* filename for freopen() action */
+	boolean_t dt_gmap_done;	/* global map created */
 };
 
 /*
diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
index 4b788507..8118ab23 100644
--- a/libdtrace/dt_prov_dtrace.c
+++ b/libdtrace/dt_prov_dtrace.c
@@ -243,7 +243,11 @@ static int attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
 			close(fd);
 		}
 		free(spec);
-		if (rc == -1)
+		/*
+		 * Multiple handles in a process mean we may have BEGIN/END
+		 * uprobe events already.
+		 * */
+		if (rc == -1 && errno != EEXIST)
 			return -ENOENT;
 
 		/* open format file */
-- 
2.43.5