From nobody Fri Jun 12 17:17:03 2026 Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) (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 BBE623A783D; Wed, 13 May 2026 19:00:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.17 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778698822; cv=none; b=QfV79o/3DoOUFoVW9bvR96GK2Un3g9nLgDIJP6Fz1aZp8ILxcqO0rMPoWgpk/eHvaXBXAZnQcGWeOKzq79lYp/0Ku05T3Rcn2f+aSviPcndOqWmX78AdbLLSv7P9S4Qqe3Myo6J9MPtwizJf7SGJ7RNkdpUq5oJPJGtAo8ax/IM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778698822; c=relaxed/simple; bh=p9iJVpwidqE5mzaDvwm+CJT1EDavdcYjs9AHGsNwfh0=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=L1q+cxjWgQ9vgqRpy5AX/8BcPNR93cxdFAsx8D4FNa60uOTsl03ExmyUGALReGU2kkUSOP+U07VUrfMh5004wibCi1V8lh1MWU20eQZ/xXWzbntzRzSlAbXtgB01OD32v29Rh12RQrj4tFmY1AGRGRF1plc2h3u3iN9QTTdXXPo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf18.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id C5A311C030D; Wed, 13 May 2026 19:00:05 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf18.hostedemail.com (Postfix) with ESMTPA id C5D392E; Wed, 13 May 2026 19:00:03 +0000 (UTC) Date: Wed, 13 May 2026 15:00:07 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Peter Zijlstra , Ian Rogers Subject: [PATCH v2] tracing: Allow perf to read synthetic events Message-ID: <20260513150007.3b280e87@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspamout07 X-Rspamd-Queue-Id: C5D392E X-Stat-Signature: in9hqoyh6jabk3jfhtq9nopqueq3e1as X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18MCZlV3wFruJOpPUgUVntUzb69tTKUm5k= X-HE-Tag: 1778698803-813443 X-HE-Meta: U2FsdGVkX1+Bd2NGkSUpBjFdiYZKvDZLuFitjXwDzLjRxXgzHuczzo8nWA3CVFEzN6jvRCyS2AfOcNoTMjNWvw+T8TjVT8SYaqlxG5e5MfGqkjClvTA4iDbdgWFpRFaR9G4JdwnefSG0Hf+ozpT5oYYG26gYHC11llgt4Ld5l4+aQ9eMAg8o8LqMOuneSTV6D34QU7oD+ptO94G+XWKVscHF/kUaQEOqhLrWaPpxH8J98SW0U364X6NhyjnGlQqMvTSUTgoN9x0squvnnA10vdjR/dkMqeDxAgFvKIHhbnDRojnbBjlMl1N6lMavho9L0/wG7A6Qn9TWxENoJvbexJajOstJesp0eWzrY+46tY/fasCmum1BkDyC8FOrN2Ghh2OB2Uijsv5HOwk97tn2FQc6aosIthgLM5Y/OYGRpXVc7ekEz+P4ySlcnsA7s1ZwZ+3ebtih7PBV0lIdbJRaawJZUJNOiheZ8eirIQFyArE= Content-Type: text/plain; charset="utf-8" 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 --- 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_ev= ent *entry, return len; } =20 -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 =3D 0; - struct trace_event_file *trace_file =3D __data; - struct synth_trace_event *entry; - struct trace_event_buffer fbuffer; - struct trace_buffer *buffer; - struct synth_event *event; - int fields_size =3D 0; - - event =3D trace_file->event_call->data; - - if (trace_trigger_soft_disabled(trace_file)) - return; + int fields_size; =20 fields_size =3D event->n_u64 * sizeof(u64); =20 - for (i =3D 0; i < event->n_dynamic_fields; i++) { + for (int i =3D 0; i < event->n_dynamic_fields; i++) { unsigned int field_pos =3D event->dynamic_fields[i]->field_pos; char *str_val; + int val_idx; + int len; =20 val_idx =3D var_ref_idx[field_pos]; str_val =3D (char *)(long)var_ref_vals[val_idx]; @@ -535,18 +526,18 @@ static void trace_event_raw_event_synth(void *__data, =20 fields_size +=3D len; } + return fields_size; +} =20 - /* - * Avoid ring buffer recursion detection, as this event - * is being performed within another event. - */ - buffer =3D trace_file->tr->array_buffer.buffer; - guard(ring_buffer_nest)(buffer); - - entry =3D 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 =3D 0; + int i, n_u64; + int val_idx; + int len; =20 for (i =3D 0, n_u64 =3D 0; i < event->n_fields; i++) { val_idx =3D 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 =3D __data; + struct synth_trace_event *entry; + struct trace_event_buffer fbuffer; + struct trace_buffer *buffer; + struct synth_event *event; + int fields_size; + + event =3D trace_file->event_call->data; + + if (trace_trigger_soft_disabled(trace_file)) + return; + + fields_size =3D 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 =3D trace_file->tr->array_buffer.buffer; + guard(ring_buffer_nest)(buffer); + + entry =3D 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); =20 trace_event_buffer_commit(&fbuffer); } =20 +#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 =3D __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 =3D call->data; + + perf_head =3D this_cpu_ptr(call->perf_events); + + if (!perf_head || hlist_empty(perf_head)) + return; + + fields_size =3D get_field_size(event, var_ref_vals, var_ref_idx); + + size =3D ALIGN(sizeof(*entry) + fields_size, 8); + + entry =3D 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 *eve= nt) call->flags =3D TRACE_EVENT_FL_TRACEPOINT; call->class->reg =3D synth_event_reg; call->class->probe =3D trace_event_raw_event_synth; +#ifdef CONFIG_PERF_EVENTS + call->class->perf_probe =3D perf_event_raw_event_synth; +#endif call->data =3D event; call->tp =3D event->tp; =20 --=20 2.53.0