[DTrace-devel] [PATCH v2] Add dt_bpf_map_lookup() function to retrieve values from BPF maps

[Kris Van Hees]

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_bpf.c | 47 ++++++++++++++++++++++++++++++----------------
 libdtrace/dt_bpf.h |  1 +
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index d6d05dc8..853e3521 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -51,6 +51,37 @@ dt_bpf_error(dtrace_hdl_t *dtp, const char *fmt, ...)
 	return dt_set_errno(dtp, EDT_BPF);
 }
 
+/*
+ * Load the value for the given key in the map referenced by the given fd.
+ */
+int dt_bpf_map_lookup(int fd, const void *key, void *val)
+{
+	union bpf_attr attr;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.map_fd = fd;
+	attr.key = (uint64_t)(unsigned long)key;
+	attr.value = (uint64_t)(unsigned long)val;
+
+	return bpf(BPF_MAP_LOOKUP_ELEM, &attr);
+}
+
+/*
+ * Store the (key, value) pair in the map referenced by the given fd.
+ */
+int dt_bpf_map_update(int fd, const void *key, const void *val)
+{
+	union bpf_attr attr;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.map_fd = fd;
+	attr.key = (uint64_t)(unsigned long)key;
+	attr.value = (uint64_t)(unsigned long)val;
+	attr.flags = 0;
+
+	return bpf(BPF_MAP_UPDATE_ELEM, &attr);
+}
+
 static int
 create_gmap(dtrace_hdl_t *dtp, const char *name, enum bpf_map_type type,
 	    int ksz, int vsz, int size)
@@ -185,22 +216,6 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
 	return 0;
 }
 
-/*
- * Store the (key, value) pair in the map referenced by the given fd.
- */
-int dt_bpf_map_update(int fd, const void *key, const void *val)
-{
-	union bpf_attr attr;
-
-	memset(&attr, 0, sizeof(attr));
-	attr.map_fd = fd;
-	attr.key = (uint64_t)(unsigned long)key;
-	attr.value = (uint64_t)(unsigned long)val;
-	attr.flags = 0;
-
-	return bpf(BPF_MAP_UPDATE_ELEM, &attr);
-}
-
 /*
  * Perform relocation processing on a program.
  */
diff --git a/libdtrace/dt_bpf.h b/libdtrace/dt_bpf.h
index c4a4a99c..e87d4653 100644
--- a/libdtrace/dt_bpf.h
+++ b/libdtrace/dt_bpf.h
@@ -23,6 +23,7 @@ extern int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu,
 extern int bpf(enum bpf_cmd cmd, union bpf_attr *attr);
 
 extern int dt_bpf_gmap_create(dtrace_hdl_t *);
+extern int dt_bpf_map_lookup(int fd, const void *key, void *val);
 extern int dt_bpf_map_update(int fd, const void *key, const void *val);
 extern int dt_bpf_load_progs(dtrace_hdl_t *, uint_t);
 
-- 
2.28.0