From nobody Tue Feb 10 04:23:20 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96A36C4332F for ; Wed, 8 Nov 2023 14:27:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235696AbjKHO11 (ORCPT ); Wed, 8 Nov 2023 09:27:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235615AbjKHO1B (ORCPT ); Wed, 8 Nov 2023 09:27:01 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F60F1FE6 for ; Wed, 8 Nov 2023 06:26:59 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82C1EC433C8; Wed, 8 Nov 2023 14:26:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699453618; bh=g+niYb9NeHMllJMJ9gCEQ6bAowsEfv6df0ZgqQIH2uY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JgQnHPH3x0GHhljwQ2Si8wyhLTq1GotX78pAeAsJ8NMcjya5kHWVS2RZkGPJs6xCD OIHe9rpFpVaSfVj1vuUz71ZzW223I8orij0I2eCxhXeqMlPENxsR8T5+n1upKO3fdI XATsplRs4kwuO7BWShcK1wXmlzMmxRb892EYC8EUmEx9TDnKxlKze/44CU8CsgiAoS E/MQPCkBAN+m+FS2Ha6/37iKdBWvcWUN6BJ5iNHdbZ8dbRETXDn+Ssc2zIb+bnm+iV KvfdgL4zOL9RisPXXXZYkuCwLIbrzRky7SOX7e7X+RxKc4Hw5NWVgu55Z/CYibmsau r0ocptQuI4EDg== From: "Masami Hiramatsu (Google)" To: Alexei Starovoitov , Steven Rostedt , Florent Revest Cc: linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Sven Schnelle , Alexei Starovoitov , Jiri Olsa , Arnaldo Carvalho de Melo , Daniel Borkmann , Alan Maguire , Mark Rutland , Peter Zijlstra , Thomas Gleixner , Guo Ren Subject: [RFC PATCH v2 13/31] function_graph: Add "task variables" per task for fgraph_ops Date: Wed, 8 Nov 2023 23:26:53 +0900 Message-Id: <169945361301.55307.14643353930499117634.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169945345785.55307.5003201137843449313.stgit@devnote2> References: <169945345785.55307.5003201137843449313.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt (VMware) Add a "task variables" array on the tasks shadow ret_stack that is the size of longs for each possible registered fgraph_ops. That's a total of 16, taking up 8 * 16 =3D 128 bytes (out of a page size 4k). This will allow for fgraph_ops to do specific features on a per task basis having a way to maintain state for each task. Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Masami Hiramatsu (Google) --- Changes in v2: - Make description lines shorter than 76 chars. --- include/linux/ftrace.h | 2 + kernel/trace/fgraph.c | 73 ++++++++++++++++++++++++++++++++++++++++++++= +++- 2 files changed, 74 insertions(+), 1 deletion(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index d30eb8a97a50..3f9f1f48e8fd 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -1071,6 +1071,7 @@ struct fgraph_ops { trace_func_graph_ret_t retfunc; struct ftrace_ops ops; /* for the hash lists */ void *private; + int idx; }; =20 /* @@ -1109,6 +1110,7 @@ ftrace_graph_get_ret_stack(struct task_struct *task, = int idx); =20 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret, unsigned long *retp); +unsigned long *fgraph_get_task_var(struct fgraph_ops *gops); =20 /* * Sometimes we don't want to trace a function with the function diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 97cf320d20a8..79bdd3c775dd 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -92,10 +92,18 @@ enum { #define SHADOW_STACK_SIZE (PAGE_SIZE) #define SHADOW_STACK_INDEX (SHADOW_STACK_SIZE / sizeof(long)) /* Leave on a buffer at the end */ -#define SHADOW_STACK_MAX_INDEX (SHADOW_STACK_INDEX - (FGRAPH_RET_INDEX + 1= )) +#define SHADOW_STACK_MAX_INDEX \ + (SHADOW_STACK_INDEX - (FGRAPH_RET_INDEX + 1 + FGRAPH_ARRAY_SIZE)) =20 #define RET_STACK(t, index) ((struct ftrace_ret_stack *)(&(t)->ret_stack[i= ndex])) =20 +/* + * Each fgraph_ops has a reservered unsigned long at the end (top) of the + * ret_stack to store task specific state. + */ +#define SHADOW_STACK_TASK_VARS(ret_stack) \ + ((unsigned long *)(&(ret_stack)[SHADOW_STACK_INDEX - FGRAPH_ARRAY_SIZE])) + DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); int ftrace_graph_active; =20 @@ -131,6 +139,44 @@ static void return_run(struct ftrace_graph_ret *trace,= struct fgraph_ops *ops) { } =20 +static void ret_stack_set_task_var(struct task_struct *t, int idx, long va= l) +{ + unsigned long *gvals =3D SHADOW_STACK_TASK_VARS(t->ret_stack); + + gvals[idx] =3D val; +} + +static unsigned long * +ret_stack_get_task_var(struct task_struct *t, int idx) +{ + unsigned long *gvals =3D SHADOW_STACK_TASK_VARS(t->ret_stack); + + return &gvals[idx]; +} + +static void ret_stack_init_task_vars(unsigned long *ret_stack) +{ + unsigned long *gvals =3D SHADOW_STACK_TASK_VARS(ret_stack); + + memset(gvals, 0, sizeof(*gvals) * FGRAPH_ARRAY_SIZE); +} + +/** + * fgraph_get_task_var - retrieve a task specific state variable + * @gops: The ftrace_ops that owns the task specific variable + * + * Every registered fgraph_ops has a task state variable + * reserved on the task's ret_stack. This function returns the + * address to that variable. + * + * Returns the address to the fgraph_ops @gops tasks specific + * unsigned long variable. + */ +unsigned long *fgraph_get_task_var(struct fgraph_ops *gops) +{ + return ret_stack_get_task_var(current, gops->idx); +} + /* * @offset: The index into @t->ret_stack to find the ret_stack entry * @index: Where to place the index into @t->ret_stack of that entry @@ -708,6 +754,7 @@ static int alloc_retstack_tasklist(unsigned long **ret_= stack_list) =20 if (t->ret_stack =3D=3D NULL) { atomic_set(&t->trace_overrun, 0); + ret_stack_init_task_vars(ret_stack_list[start]); t->curr_ret_stack =3D 0; t->curr_ret_depth =3D -1; /* Make sure the tasks see the 0 first: */ @@ -768,6 +815,7 @@ static void graph_init_task(struct task_struct *t, unsigned long *ret_stack) { atomic_set(&t->trace_overrun, 0); + ret_stack_init_task_vars(ret_stack); t->ftrace_timestamp =3D 0; t->curr_ret_stack =3D 0; t->curr_ret_depth =3D -1; @@ -866,6 +914,24 @@ static int start_graph_tracing(void) return ret; } =20 +static void init_task_vars(int idx) +{ + struct task_struct *g, *t; + int cpu; + + for_each_online_cpu(cpu) { + if (idle_task(cpu)->ret_stack) + ret_stack_set_task_var(idle_task(cpu), idx, 0); + } + + read_lock(&tasklist_lock); + for_each_process_thread(g, t) { + if (t->ret_stack) + ret_stack_set_task_var(t, idx, 0); + } + read_unlock(&tasklist_lock); +} + int register_ftrace_graph(struct fgraph_ops *gops) { int command =3D 0; @@ -901,6 +967,7 @@ int register_ftrace_graph(struct fgraph_ops *gops) fgraph_array[i] =3D gops; if (i + 1 > fgraph_array_cnt) fgraph_array_cnt =3D i + 1; + gops->idx =3D i; =20 ftrace_graph_active++; =20 @@ -918,6 +985,8 @@ int register_ftrace_graph(struct fgraph_ops *gops) ftrace_graph_return =3D return_run; ftrace_graph_entry =3D entry_run; command =3D FTRACE_START_FUNC_RET; + } else { + init_task_vars(gops->idx); } =20 ret =3D ftrace_startup(&gops->ops, command); @@ -942,6 +1011,8 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) if (i >=3D fgraph_array_cnt) goto out; =20 + WARN_ON_ONCE(gops->idx !=3D i); + fgraph_array[i] =3D &fgraph_stub; if (i + 1 =3D=3D fgraph_array_cnt) { for (; i >=3D 0; i--)