From nobody Mon Feb 9 01:51:11 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 E3C283358DE; Wed, 17 Dec 2025 16:37:47 +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=1765989471; cv=none; b=oezZmPoqUu8IQLzcYRip+IRQWT/Jb1fe65cODk4CIZbr3BKOl3GngNxuXNXEmrHJ9xNWfOhkvdzmhkZFOYeZlKRWgeq9bEAhjLPUb/7w0jgbyF9TEfawkXh5kaIA5CSOuGsPjz8ashiDpXkVm/G501Xep2rZszPyjPmHSbLMPls= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765989471; c=relaxed/simple; bh=NMZnqyZy1/Ec9VSOSCSL75tdHab4fNQnxN2xBOU2KAI=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=eWHnKerXQ5t8N5iFOJEc0OcEI6Q9VQ4tmfIFSX28lCMyvA9F9gxSZWH9/q3YG3bCvIiHUYewGFf2bJqjSR+c2iBz2k4AjsTF6LTnp4xRflWZNKaaecb3BiB6R0AXOvrMDGlnw0dcTr3aClv48vu9VNkt7x5PPtJfO1CAnNaADZM= 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 omf19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 4B7DD1370BA; Wed, 17 Dec 2025 16:37:46 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf19.hostedemail.com (Postfix) with ESMTPA id 4BF6A20027; Wed, 17 Dec 2025 16:37:44 +0000 (UTC) Date: Wed, 17 Dec 2025 11:39:20 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Ian Rogers , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Peter Zijlstra Subject: [PATCH] tracing: Allow perf to read synthetic events Message-ID: <20251217113920.50b56246@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-Queue-Id: 4BF6A20027 X-Stat-Signature: 8aetqh8zmqgmr67t39qiejgqn383c76g X-Rspamd-Server: rspamout05 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/Xc5N5Ma+hwUdjht/mv7MucOyTa2R+LTc= X-HE-Tag: 1765989464-234981 X-HE-Meta: U2FsdGVkX18BuGgTfFCpecoK8itU75LuieMvXk2C0KeeZ9dlQDZFEp7OskXe5CXAnd8oDG5gwrr95EjF3n5xqeFRXoEmsD4JKjD/vecGlhiTrx/hkJ1l1ugOXi9ENuv5Ibq4F5KOeh/EzVX+PGBtAsm1IGghflo07CP8rKdM9ECuQioKUnOwX3JcXp4YsCcscCm+UVil59iIXpjdvVqWgeBJheMMg6l52eqqvMOHvqa3dQM1Fy4XYVcO7uTxr6R8+1SdrF8XJODjpCK4aZUt8LUnYHv1cyjj0flPKInTKrwBktmLl3XwXO0faLuKryfiVxiSOt/V/Pmq5HFkihONctaBcKS33jmzfdLxz5EmdoMqSG7mvfLSIy1JZJh6d/cI7pFMoDH7ClvFmMlnTT1WkA== 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) --- 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 4554c458b78c..026e06f28958 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -493,28 +493,19 @@ static unsigned int trace_stack(struct synth_trace_ev= ent *entry, return len; } =20 -static notrace 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]; @@ -529,18 +520,18 @@ static notrace 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]; @@ -581,10 +572,83 @@ static notrace void trace_event_raw_event_synth(void = *__data, n_u64++; } } +} + +static notrace 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 notrace 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) { @@ -911,6 +975,9 @@ 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 2.51.0