bt(5), btrace(8): execute END probe and print non-empty maps upon exit()

BPFTrace's exit() statement executes the END probe (if any) and prints
the contents of all non-empty maps before terminating the interpreter.

Implement this in btrace(8) with a halting check after each statement.
If a statement causes the program to halt, the condition bubbles up to
the top-level evaluation loop and causes rules_teardown() to run
immediately.

btrace(8) still performs a full rules_setup() if exit() is called
during the BEGIN probe, though the top-level evaluation loop is never
run.

One edge-like case: an exit() from the END probe is treated as an
early return; END is not executed multiple times.

Thread: https://marc.info/?l=openbsd-tech&m=169765169420751&w=2

ok mpi@

diff --git a/regress/usr.sbin/btrace/exit.bt b/regress/usr.sbin/btrace/exit.bt
index d7a9806..e3a9f72 100644 (file)
--- a/regress/usr.sbin/btrace/exit.bt
+++ b/regress/usr.sbin/btrace/exit.bt
@@ -6,5 +6,7 @@ BEGIN
 
 END
 {
+       printf("executed\n");
+       exit();
        printf("not executed\n");
 }

diff --git a/regress/usr.sbin/btrace/exit.ok b/regress/usr.sbin/btrace/exit.ok
index 9c13beb..68e4692 100644 (file)
--- a/regress/usr.sbin/btrace/exit.ok
+++ b/regress/usr.sbin/btrace/exit.ok
@@ -1 +1,2 @@
 exiting now...
+executed

diff --git a/regress/usr.sbin/btrace/mapoverwrite.ok b/regress/usr.sbin/btrace/mapoverwrite.ok
index e69de29..07f467c 100644 (file)
--- a/regress/usr.sbin/btrace/mapoverwrite.ok
+++ b/regress/usr.sbin/btrace/mapoverwrite.ok
@@ -0,0 +1,3 @@
+@map[3]: 33
+@map[1]: 22
+@map[0]: 11

diff --git a/usr.sbin/btrace/bt.5 b/usr.sbin/btrace/bt.5
index 76ae8e6..16d6bd8 100644 (file)
--- a/usr.sbin/btrace/bt.5
+++ b/usr.sbin/btrace/bt.5
@@ -1,4 +1,4 @@
-.\"    $OpenBSD: bt.5,v 1.16 2023/06/30 13:31:37 jsg Exp $
+.\"    $OpenBSD: bt.5,v 1.17 2023/10/22 19:30:35 cheloha Exp $
 .\"
 .\" Copyright (c) 2019 Martin Pieuchot <mpi@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: June 30 2023 $
+.Dd $Mdocdate: October 22 2023 $
 .Dt BT 5
 .Os
 .Sh NAME
@@ -127,6 +127,11 @@ from
 .Va @map .
 .It Fn exit
 Terminate execution with exit code 0.
+The
+.Ic END
+probe,
+if any,
+is executed and the contents of all non-empty maps are printed.
 .It Fn hist "value"
 Increment the bucket corresponding to
 .Va value

diff --git a/usr.sbin/btrace/btrace.c b/usr.sbin/btrace/btrace.c
index 847fa2f..78098d2 100644 (file)
--- a/usr.sbin/btrace/btrace.c
+++ b/usr.sbin/btrace/btrace.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: btrace.c,v 1.79 2023/10/12 15:16:44 cheloha Exp $ */
+/*     $OpenBSD: btrace.c,v 1.80 2023/10/22 19:30:35 cheloha Exp $ */
 
 /*
  * Copyright (c) 2019 - 2023 Martin Pieuchot <mpi@openbsd.org>
@@ -71,10 +71,10 @@ struct dtioc_probe_info     *dtpi_get_by_value(const char *, const char *,
  * Main loop and rule evaluation.
  */
 void                    rules_do(int);
-void                    rules_setup(int);
-void                    rules_apply(int, struct dt_evt *);
+int                     rules_setup(int);
+int                     rules_apply(int, struct dt_evt *);
 void                    rules_teardown(int);
-void                    rule_eval(struct bt_rule *, struct dt_evt *);
+int                     rule_eval(struct bt_rule *, struct dt_evt *);
 void                    rule_printmaps(struct bt_rule *);
 
 /*
@@ -84,7 +84,7 @@ uint64_t               builtin_nsecs(struct dt_evt *);
 const char             *builtin_kstack(struct dt_evt *);
 const char             *builtin_arg(struct dt_evt *, enum bt_argtype);
 struct bt_arg          *fn_str(struct bt_arg *, struct dt_evt *, char *);
-void                    stmt_eval(struct bt_stmt *, struct dt_evt *);
+int                     stmt_eval(struct bt_stmt *, struct dt_evt *);
 void                    stmt_bucketize(struct bt_stmt *, struct dt_evt *);
 void                    stmt_clear(struct bt_stmt *);
 void                    stmt_delete(struct bt_stmt *, struct dt_evt *);
@@ -405,6 +405,7 @@ void
 rules_do(int fd)
 {
        struct sigaction sa;
+       int halt = 0;
 
        memset(&sa, 0, sizeof(sa));
        sigemptyset(&sa.sa_mask);
@@ -415,9 +416,9 @@ rules_do(int fd)
        if (sigaction(SIGTERM, &sa, NULL))
                err(1, "sigaction");
 
-       rules_setup(fd);
+       halt = rules_setup(fd);
 
-       while (!quit_pending && g_nprobes > 0) {
+       while (!quit_pending && !halt && g_nprobes > 0) {
                static struct dt_evt devtbuf[64];
                ssize_t rlen;
                size_t i;
@@ -434,8 +435,11 @@ rules_do(int fd)
                if ((rlen % sizeof(struct dt_evt)) != 0)
                        err(1, "incorrect read");
 
-               for (i = 0; i < rlen / sizeof(struct dt_evt); i++)
-                       rules_apply(fd, &devtbuf[i]);
+               for (i = 0; i < rlen / sizeof(struct dt_evt); i++) {
+                       halt = rules_apply(fd, &devtbuf[i]);
+                       if (halt)
+                               break;
+               }
        }
 
        rules_teardown(fd);
@@ -484,7 +488,7 @@ rules_action_scan(struct bt_stmt *bs)
        return evtflags;
 }
 
-void
+int
 rules_setup(int fd)
 {
        struct dtioc_probe_info *dtpi;
@@ -493,7 +497,7 @@ rules_setup(int fd)
        struct bt_probe *bp;
        struct bt_stmt *bs;
        struct bt_arg *ba;
-       int dokstack = 0, on = 1;
+       int dokstack = 0, halt = 0, on = 1;
        uint64_t evtflags;
 
        TAILQ_FOREACH(r, &g_rules, br_next) {
@@ -553,7 +557,7 @@ rules_setup(int fd)
        clock_gettime(CLOCK_REALTIME, &bt_devt.dtev_tsp);
 
        if (rbegin)
-               rule_eval(rbegin, &bt_devt);
+               halt = rule_eval(rbegin, &bt_devt);
 
        /* Enable all probes */
        TAILQ_FOREACH(r, &g_rules, br_next) {
@@ -571,9 +575,14 @@ rules_setup(int fd)
                if (ioctl(fd, DTIOCRECORD, &on))
                        err(1, "DTIOCRECORD");
        }
+
+       return halt;
 }
 
-void
+/*
+ * Returns non-zero if the program should halt.
+ */
+int
 rules_apply(int fd, struct dt_evt *dtev)
 {
        struct bt_rule *r;
@@ -586,9 +595,11 @@ rules_apply(int fd, struct dt_evt *dtev)
                                continue;
 
                        dtai_cache(fd, &dt_dtpis[dtev->dtev_pbn - 1]);
-                       rule_eval(r, dtev);
+                       if (rule_eval(r, dtev))
+                               return 1;
                }
        }
+       return 0;
 }
 
 void
@@ -637,7 +648,10 @@ rules_teardown(int fd)
                rule_printmaps(r);
 }
 
-void
+/*
+ * Returns non-zero if the program should halt.
+ */
+int
 rule_eval(struct bt_rule *r, struct dt_evt *dtev)
 {
        struct bt_stmt *bs;
@@ -651,7 +665,7 @@ rule_eval(struct bt_rule *r, struct dt_evt *dtev)
        if (r->br_filter != NULL && r->br_filter->bf_condition != NULL) {
                if (stmt_test(r->br_filter->bf_condition, dtev) == false) {
                        bt_filtered++;
-                       return;
+                       return 0;
                }
        }
 
@@ -660,15 +674,19 @@ rule_eval(struct bt_rule *r, struct dt_evt *dtev)
                        struct bt_stmt *bbs = (struct bt_stmt *)bs->bs_var;
 
                        while (bbs != NULL) {
-                               stmt_eval(bbs, dtev);
+                               if (stmt_eval(bbs, dtev))
+                                       return 1;
                                bbs = SLIST_NEXT(bbs, bs_next);
                        }
 
                        continue;
                }
 
-               stmt_eval(bs, dtev);
+               if (stmt_eval(bs, dtev))
+                       return 1;
        }
+
+       return 0;
 }
 
 void
@@ -802,9 +820,14 @@ builtin_arg(struct dt_evt *dtev, enum bt_argtype dat)
        return buf;
 }
 
-void
+/*
+ * Returns non-zero if the program should halt.
+ */
+int
 stmt_eval(struct bt_stmt *bs, struct dt_evt *dtev)
 {
+       int halt = 0;
+
        switch (bs->bs_act) {
        case B_AC_BUCKETIZE:
                stmt_bucketize(bs, dtev);
@@ -816,7 +839,7 @@ stmt_eval(struct bt_stmt *bs, struct dt_evt *dtev)
                stmt_delete(bs, dtev);
                break;
        case B_AC_EXIT:
-               exit(0);
+               halt = 1;
                break;
        case B_AC_INSERT:
                stmt_insert(bs, dtev);
@@ -842,6 +865,7 @@ stmt_eval(struct bt_stmt *bs, struct dt_evt *dtev)
        default:
                xabort("no handler for action type %d", bs->bs_act);
        }
+       return halt;
 }
 
 /*