Return 0 when accessing an argument not defined in a probe.

Adapted from a fix from Christian Ludwig.

diff --git a/usr.sbin/btrace/btrace.c b/usr.sbin/btrace/btrace.c
index ac8b5d9..98c4af3 100644 (file)
--- a/usr.sbin/btrace/btrace.c
+++ b/usr.sbin/btrace/btrace.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: btrace.c,v 1.82 2024/01/23 22:04:15 mpi Exp $ */
+/*     $OpenBSD: btrace.c,v 1.83 2024/01/25 20:50:58 mpi Exp $ */
 
 /*
  * Copyright (c) 2019 - 2023 Martin Pieuchot <mpi@openbsd.org>
@@ -797,13 +797,18 @@ const char *
 builtin_arg(struct dt_evt *dtev, enum bt_argtype dat)
 {
        static char buf[sizeof("18446744073709551615")]; /* UINT64_MAX */
-       unsigned int argn;
+       struct dtioc_probe_info *dtpi;
        struct dtioc_arg_info *dtai;
        const char *argtype, *fmt;
+       unsigned int argn;
        long value;
 
-       dtai = dt_args[dtev->dtev_pbn - 1];
        argn = dat - B_AT_BI_ARG0;
+       dtpi = &dt_dtpis[dtev->dtev_pbn - 1];
+       if (dtpi == NULL || argn >= dtpi->dtpi_nargs)
+               return "0";
+
+       dtai = dt_args[dtev->dtev_pbn - 1];
        argtype = dtai[argn].dtai_argtype;
 
        if (strncmp(argtype, "int", DTNAMESIZE) == 0) {