From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 313972D836D; Thu, 14 May 2026 18:28:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778783331; cv=none; b=sV2NYN12r3pGrEcSjCJ3XiNtfH0FSoCtQOMGH6mDo+l3E65vqDBfzq+qMqWbraoeWdmEs5msH2Drp4b/G97/cMG91Wwqp7nXKc15sq1qapc2AISEpGIm2SiB4uIBX/hj/uZg7d1aujgHGeexTMZK6TfiSOc/z9gEPJ+66+pdTbw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778783331; c=relaxed/simple; bh=A0xbDquRvnyW2D8cpPeGpARcAjX2yjAc8rCfXyXZ+m0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tbVdjR8UKinhf1fZXhQYA6oY+hKNiwY+BkFnHs/k/g9ZiJkUWvp9W6cvZGH5ewhOg2QAtv4GxeojpCO89FuQ2cvganm6+r+3nX/wvx9K8uH8MbR/9/5rXvbyDsm2nAPj1uEz19meq11F0w1CW8QY8PrQrj1WhtNw79jIWR6zaXs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cdpXsltz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cdpXsltz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C1E22C2BCB3; Thu, 14 May 2026 18:28:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778783331; bh=A0xbDquRvnyW2D8cpPeGpARcAjX2yjAc8rCfXyXZ+m0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cdpXsltzlfr6ukk9YEDrM7fqZ7N58jmotCJRI9ZG/OYZmpJM9ZoG/RdUKOQOcvZ7w rCdQ+M8C0BP1nGiZPEci0Ln0IMzCdSm2YXqnxezLpER4UueG4c0No2UYx3itVpkw0P 8vkUzdnX4u+KW833UBQmpIe5p2xDRl8B/4+RfCkFx76qGT3nldjx+t8L4u0RgsISsg nH/3JqrhQR5jQxO+NcQRZVTj4FQBAc18qTQwNpdunTed2e3dFhOV4MNI/VQok0x3gi MXe2ju0FYxiwZp0AnPSA06y4aJoc+WoJLGFCTdpq6IPcghVove8XLw7swRcYnOZKC/ xFkK1bXSAdaqQ== Date: Thu, 14 May 2026 11:28:46 -0700 From: Namhyung Kim To: Steven Rostedt Cc: LKML , Linux Trace Kernel , Masami Hiramatsu , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Jiri Olsa , Peter Zijlstra , Ian Rogers Subject: Re: [PATCH v2] tracing: Allow perf to read synthetic events Message-ID: References: <20260513150007.3b280e87@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260513150007.3b280e87@gandalf.local.home> On Wed, May 13, 2026 at 03:00:07PM -0400, Steven Rostedt wrote: > From: Steven Rostedt > > Currently, perf can not enable synthetic events. When it does, it either > causes a warning in the kernel or errors with "no such device". > > Add the necessary code to allow perf to also attach to synthetic events. > > Reported-by: Ian Rogers > Signed-off-by: Steven Rostedt (Google) Acked-by: Namhyung Kim Thanks, Namhyung > --- > Changes since v1: https://patch.msgid.link/20251217113920.50b56246@gandalf.local.home > > - Forward ported to v7.1-rc2 > > kernel/trace/trace_events_synth.c | 121 +++++++++++++++++++++++------- > 1 file changed, 94 insertions(+), 27 deletions(-) > > diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c > index 39ac4eba0702..e6871230bde9 100644 > --- a/kernel/trace/trace_events_synth.c > +++ b/kernel/trace/trace_events_synth.c > @@ -499,28 +499,19 @@ static unsigned int trace_stack(struct synth_trace_event *entry, > return len; > } > > -static void trace_event_raw_event_synth(void *__data, > - u64 *var_ref_vals, > - unsigned int *var_ref_idx) > +static __always_inline int get_field_size(struct synth_event *event, > + u64 *var_ref_vals, > + unsigned int *var_ref_idx) > { > - unsigned int i, n_u64, val_idx, len, data_size = 0; > - struct trace_event_file *trace_file = __data; > - struct synth_trace_event *entry; > - struct trace_event_buffer fbuffer; > - struct trace_buffer *buffer; > - struct synth_event *event; > - int fields_size = 0; > - > - event = trace_file->event_call->data; > - > - if (trace_trigger_soft_disabled(trace_file)) > - return; > + int fields_size; > > fields_size = event->n_u64 * sizeof(u64); > > - for (i = 0; i < event->n_dynamic_fields; i++) { > + for (int i = 0; i < event->n_dynamic_fields; i++) { > unsigned int field_pos = event->dynamic_fields[i]->field_pos; > char *str_val; > + int val_idx; > + int len; > > val_idx = var_ref_idx[field_pos]; > str_val = (char *)(long)var_ref_vals[val_idx]; > @@ -535,18 +526,18 @@ static void trace_event_raw_event_synth(void *__data, > > fields_size += len; > } > + return fields_size; > +} > > - /* > - * Avoid ring buffer recursion detection, as this event > - * is being performed within another event. > - */ > - buffer = trace_file->tr->array_buffer.buffer; > - guard(ring_buffer_nest)(buffer); > - > - entry = trace_event_buffer_reserve(&fbuffer, trace_file, > - sizeof(*entry) + fields_size); > - if (!entry) > - return; > +static __always_inline void write_synth_entry(struct synth_event *event, > + struct synth_trace_event *entry, > + u64 *var_ref_vals, > + unsigned int *var_ref_idx) > +{ > + int data_size = 0; > + int i, n_u64; > + int val_idx; > + int len; > > for (i = 0, n_u64 = 0; i < event->n_fields; i++) { > val_idx = var_ref_idx[i]; > @@ -587,10 +578,83 @@ static void trace_event_raw_event_synth(void *__data, > n_u64++; > } > } > +} > + > +static void trace_event_raw_event_synth(void *__data, > + u64 *var_ref_vals, > + unsigned int *var_ref_idx) > +{ > + struct trace_event_file *trace_file = __data; > + struct synth_trace_event *entry; > + struct trace_event_buffer fbuffer; > + struct trace_buffer *buffer; > + struct synth_event *event; > + int fields_size; > + > + event = trace_file->event_call->data; > + > + if (trace_trigger_soft_disabled(trace_file)) > + return; > + > + fields_size = get_field_size(event, var_ref_vals, var_ref_idx); > + > + /* > + * Avoid ring buffer recursion detection, as this event > + * is being performed within another event. > + */ > + buffer = trace_file->tr->array_buffer.buffer; > + guard(ring_buffer_nest)(buffer); > + > + entry = trace_event_buffer_reserve(&fbuffer, trace_file, > + sizeof(*entry) + fields_size); > + if (!entry) > + return; > + > + write_synth_entry(event, entry, var_ref_vals, var_ref_idx); > > trace_event_buffer_commit(&fbuffer); > } > > +#ifdef CONFIG_PERF_EVENTS > +static void perf_event_raw_event_synth(void *__data, > + u64 *var_ref_vals, > + unsigned int *var_ref_idx) > +{ > + struct trace_event_call *call = __data; > + struct synth_trace_event *entry; > + struct hlist_head *perf_head; > + struct synth_event *event; > + struct pt_regs *regs; > + int fields_size; > + size_t size; > + int context; > + > + event = call->data; > + > + perf_head = this_cpu_ptr(call->perf_events); > + > + if (!perf_head || hlist_empty(perf_head)) > + return; > + > + fields_size = get_field_size(event, var_ref_vals, var_ref_idx); > + > + size = ALIGN(sizeof(*entry) + fields_size, 8); > + > + entry = perf_trace_buf_alloc(size, ®s, &context); > + > + if (unlikely(!entry)) > + return; > + > + write_synth_entry(event, entry, var_ref_vals, var_ref_idx); > + > + perf_fetch_caller_regs(regs); > + > + perf_trace_buf_submit(entry, size, context, > + call->event.type, 1, regs, > + perf_head, NULL); > +} > +#endif > + > static void free_synth_event_print_fmt(struct trace_event_call *call) > { > if (call) { > @@ -917,6 +981,9 @@ static int register_synth_event(struct synth_event *event) > call->flags = TRACE_EVENT_FL_TRACEPOINT; > call->class->reg = synth_event_reg; > call->class->probe = trace_event_raw_event_synth; > +#ifdef CONFIG_PERF_EVENTS > + call->class->perf_probe = perf_event_raw_event_synth; > +#endif > call->data = event; > call->tp = event->tp; > > -- > 2.53.0 >