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Date: Fri, 29 May 2026 13:25:08 +0900
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Linux trace kernel
 <linux-trace-kernel@vger.kernel.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Mark Rutland <mark.rutland@arm.com>, Peter Zijlstra <peterz@infradead.org>,
 Namhyung Kim <namhyung@kernel.org>, Takaya Saeki <takayas@google.com>,
 Douglas Raillard <douglas.raillard@arm.com>, Tom Zanussi
 <zanussi@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Thomas
 Gleixner <tglx@linutronix.de>, Ian Rogers <irogers@google.com>, Jiri Olsa
 <olsajiri@gmail.com>
Subject: Re: [PATCH v6] tracing/eprobes: Allow use of BTF names to
 dereference pointers
Message-Id: <20260529132508.2e98cab925fdb1fa7be21a9b@kernel.org>
In-Reply-To: <20260521225033.56458336@fedora>
References: <20260521225033.56458336@fedora>
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On Thu, 21 May 2026 22:50:33 -0400
Steven Rostedt <rostedt@kernel.org> wrote:

> +	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_TYPECAST) {
> +			type = ctx->last_struct;
> +			goto found_type;
> +		}
> +		return 0;

Here is a bit complicated but a buggy case.

parse_btf_arg() is not used for eprobe arguments because those
requires '$' prefix. However, only if it has a typecast, this
parse_btf_arg() is called for eprobes.

Thus, we should report a kernel bug if !ctx->flags & TPARG_FL_TYPECAST
here. Something like this:

		if (WARN_ONCE(!(ctx->flags & TPARG_FL_TYPECAST)))
			return -EINVAL;
		type = ctx->last_struct;
		goto found_type;

Thanks,
-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>