From: Christian Ludwig <christian_ludwig@genua.de>
Subject: Re: btrace: Parse unset arguments to 0
To: Martin Pieuchot <mpi@openbsd.org>
Cc: "tech@openbsd.org" <tech@openbsd.org>
Date: Tue, 23 Jan 2024 11:11:31 +0100

Hi,

On Sun, Jan 21, 2024 at 07:38:45PM -0300 Martin Pieuchot wrote:
> On 12/01/24(Fri) 15:45, Christian Ludwig wrote:
> > Reading unset arguments from a static tracepoint crashes btrace.
> > Set them to "0" instead.
> 
> Thanks!  I would prefer if we could place the fix inside builtin_arg().
> The rational is that both `dt_dtpis' and `dt_args' are indexed by the
> probe number and are not independent.

Makes sense.

> Here's your fix adapted, ok?

Works like a charm. Thank you.

> Index: btrace.c
> ===================================================================
> RCS file: /cvs/src/usr.sbin/btrace/btrace.c,v
> diff -u -p -r1.81 btrace.c
> --- btrace.c	10 Nov 2023 18:56:21 -0000	1.81
> +++ btrace.c	21 Jan 2024 22:35:33 -0000
> @@ -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) {