[DTrace-devel] [PATCH 16/20] Build the global strtab once

[Kris Van Hees]

The global table of string constants was being re-created after every
compilation even though we only ever use it once, when we create the
BPF maps (right before loading BPF programs).

Instead, we now generate the global strtab during the BPF maps
creation.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_as.c  | 15 +++------------
 libdtrace/dt_bpf.c | 17 +++++++----------
 2 files changed, 10 insertions(+), 22 deletions(-)

diff --git a/libdtrace/dt_as.c b/libdtrace/dt_as.c
index 760f281c..d88fe65c 100644
--- a/libdtrace/dt_as.c
+++ b/libdtrace/dt_as.c
@@ -567,15 +567,9 @@ fail:
 	 * We keep the string table around (dtp->dt_csstab) because further
 	 * compilations may add more strings.  We will load a consolidated
 	 * compiled string table into a strtab BPF map so it can be used ny
-	 * all BPF programs we will be loading.  Since each DIFO will have a
-	 * string table that comprises the strings of all DIFOs before it along
-	 * with any new ones, we simply assign the latest (and most complete)
-	 * string table to dtp->dt_strtab (and the size as dtp->dt_strlen), so
-	 * that when we are ready to load and execute programs, we know we have
-	 * the latest and greatest string table to work with.
-	 *
-	 * Note that this means that we should *not* free dtp->dt_strtab later
-	 * because it will be free'd when the DIFO is destroyed.
+	 * all BPF programs we will be loading.  Therefore, each DIFO will have
+	 * a string table that comprises the strings of all DIFOs before it
+	 * along with any new ones.
 	 */
 	dp->dtdo_strlen = dt_strtab_size(dtp->dt_ccstab);
 	if (dp->dtdo_strlen > 0) {
@@ -586,9 +580,6 @@ fail:
 		dt_strtab_write(dtp->dt_ccstab,
 				(dt_strtab_write_f *)dt_strtab_copystr,
 				dp->dtdo_strtab);
-
-		dtp->dt_strtab = dp->dtdo_strtab;
-		dtp->dt_strlen = dp->dtdo_strlen;
 	} else
 		dp->dtdo_strtab = NULL;
 
diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 41bd8ecd..067bf0d5 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -256,16 +256,13 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
 	 * We may need to create a final copy of the string table because it is
 	 * possible entries were added after the last clause was compiled.
 	 */
-	if (dtp->dt_strlen < dt_strtab_size(dtp->dt_ccstab)) {
-		dtp->dt_strlen = dt_strtab_size(dtp->dt_ccstab);
-		dtp->dt_strtab = dt_zalloc(dtp, dtp->dt_strlen);
-		if (dtp->dt_strtab == NULL)
-			return dt_set_errno(dtp, EDT_NOMEM);
-
-		dt_strtab_write(dtp->dt_ccstab,
-				(dt_strtab_write_f *)dt_strtab_copystr,
-				dtp->dt_strtab);
-	}
+	dtp->dt_strlen = dt_strtab_size(dtp->dt_ccstab);
+	dtp->dt_strtab = dt_zalloc(dtp, dtp->dt_strlen);
+	if (dtp->dt_strtab == NULL)
+		return dt_set_errno(dtp, EDT_NOMEM);
+
+	dt_strtab_write(dtp->dt_ccstab, (dt_strtab_write_f *)dt_strtab_copystr,
+			dtp->dt_strtab);
 
 	st_mapfd = create_gmap(dtp, "strtab", BPF_MAP_TYPE_ARRAY,
 			       sizeof(uint32_t), dtp->dt_strlen, 1);
-- 
2.31.1