Re: [PATCH v5] tracing/eprobes: Allow use of BTF names to dereference pointers

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 19 May 2026 13:01:44 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> @@ -636,11 +694,12 @@ static int parse_btf_arg(char *varname,
>  	struct fetch_insn *code = *pcode;
>  	const struct btf_param *params;
>  	const struct btf_type *type;
> +	struct btf *btf = ctx_btf(ctx);
>  	char *field = NULL;
>  	int i, is_ptr, ret;
>  	u32 tid;
>  
> -	if (WARN_ON_ONCE(!ctx->funcname))
> +	if (WARN_ON_ONCE(!ctx->funcname && !(ctx->flags & TPARG_FL_TYPECAST)))
>  		return -EINVAL;
>  
>  	is_ptr = split_next_field(varname, &field, ctx);
> @@ -653,6 +712,14 @@ static int parse_btf_arg(char *varname,
>  		return -EOPNOTSUPP;
>  	}
>  
> +	if (ctx->flags & TPARG_FL_TEVENT) {
> +		int ret;
> +
> +		ret = parse_trace_event(varname, code, ctx);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
>  	if (ctx->flags & TPARG_FL_RETURN && !strcmp(varname, "$retval")) {
>  		code->op = FETCH_OP_RETVAL;
>  		/* Check whether the function return type is not void */
> @@ -672,7 +739,7 @@ static int parse_btf_arg(char *varname,
>  		return 0;
>  	}
>  
> -	if (!ctx->btf) {
> +	if (!btf) {
>  		ret = query_btf_context(ctx);

Oops, need a:

		btf = ctx->btf;

here!

-- Steve

>  		if (ret < 0 || ctx->nr_params == 0) {
>  			trace_probe_log_err(ctx->offset, NO_BTF_ENTRY);