From patchwork Tue May 7 14:10:43 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13657129 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 3E4BB15FA88; Tue, 7 May 2024 14:10:49 +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=1715091050; cv=none; b=uujsEKNwdzrXbkxXDUeNPWINMdO8ZK+xGVjlL5TisubJLASFNVKeqTrybLBizp6dU++Z1PHZtKJIXGwcjN6Tq3+EtZbDRAMOFUKPpcoOUThJGA2Q4AqTs/Q2Jz7eWvHrsEvNbzfFJR0JOw72xskyKIqF1v4nMb+T2SJ0PKLt3oY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715091050; c=relaxed/simple; bh=qWvu9ZFCjlBOu1i63Fm0oy0TG0/H41kpL9VGm49UIW4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=U3flft7/gbMrXPt4jTuZaWXmpFnJMAeTc+YmxP2Chv4FCYipSV/9uA2mrM38oZSNAAUdmXSn8rexH/BT4lR/ZBdZEDuG0qPrl0EtLxuAfoolym5R7J6Kr3fT3RTly83RQWvmdlBZm42PtDh/sF0L3MOclaDlgvKJlpzPo3Nhneo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=a8yABE/E; 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="a8yABE/E" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 347ADC2BBFC; Tue, 7 May 2024 14:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715091049; bh=qWvu9ZFCjlBOu1i63Fm0oy0TG0/H41kpL9VGm49UIW4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a8yABE/ERlCeBj4KAGDbgpNSOoOviKqSn+sgt2TcKsgWcHPCBskzoOE6aDTUgI/nW fpOI2dmq1V7u0oxdz+CuWG/I/AnsIGfgKdvyNciSPol/FaW3EYEZ5ujANc8HO3bDzC OY3bnDGuSW2hLp0jpqEw7jMu1xl1h2nTr2hlp5Do8PuY0IlJjs0VmCAiDZBj+KghOO AvKBhKhyqRiH1cIKlJWVI6GLEyGPVI6nHWEwCb4xpAxfxjpx8UGcHhvRa36q4BKLE+ 6D+oQJ/r1ZSGgc4qKk7lRnABPx5fHlTRdPbuHVdNJ6BVrcJteLUBLhdP3T9JxXMRCg 6NgfKRf3xQX5Q== 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: [PATCH v10 14/36] function_graph: Add "task variables" per task for fgraph_ops Date: Tue, 7 May 2024 23:10:43 +0900 Message-Id: <171509104383.162236.12239656156685718550.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <171509088006.162236.7227326999861366050.stgit@devnote2> References: <171509088006.162236.7227326999861366050.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 = 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 v10: - Explain where the task vars is placed in shadow stack. Changes in v3: - Move fgraph_ops::idx to previous patch in the series. Changes in v2: - Make description lines shorter than 76 chars. --- include/linux/ftrace.h | 1 + kernel/trace/fgraph.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 74 insertions(+), 1 deletion(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index b11af9d88438..97f7d1cf4f8f 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -1116,6 +1116,7 @@ ftrace_graph_get_ret_stack(struct task_struct *task, int skip); 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); /* * 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 c00a299decb1..3498e8fd8e53 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -46,6 +46,10 @@ * on the return of the function being traced, this is what will be on the * task's shadow ret_stack: (the stack grows upward) * + * ret_stack[SHADOW_STACK_IN_WORD] + * | SHADOW_STACK_TASK_VARS(ret_stack)[15] | + * ... + * | SHADOW_STACK_TASK_VARS(ret_stack)[0] | * ret_stack[SHADOW_STACK_MAX_OFFSET] * ... * | | <- task->curr_ret_stack @@ -90,10 +94,18 @@ enum { #define SHADOW_STACK_SIZE (PAGE_SIZE) #define SHADOW_STACK_IN_WORD (SHADOW_STACK_SIZE / sizeof(long)) /* Leave on a buffer at the end */ -#define SHADOW_STACK_MAX_OFFSET (SHADOW_STACK_IN_WORD - (FGRAPH_FRAME_OFFSET + 1)) +#define SHADOW_STACK_MAX_OFFSET \ + (SHADOW_STACK_IN_WORD - (FGRAPH_FRAME_OFFSET + 1 + FGRAPH_ARRAY_SIZE)) #define RET_STACK(t, offset) ((struct ftrace_ret_stack *)(&(t)->ret_stack[offset])) +/* + * 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_IN_WORD - FGRAPH_ARRAY_SIZE])) + DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); int ftrace_graph_active; @@ -184,6 +196,44 @@ static void return_run(struct ftrace_graph_ret *trace, struct fgraph_ops *ops) { } +static void ret_stack_set_task_var(struct task_struct *t, int idx, long val) +{ + unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); + + gvals[idx] = val; +} + +static unsigned long * +ret_stack_get_task_var(struct task_struct *t, int idx) +{ + unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); + + return &gvals[idx]; +} + +static void ret_stack_init_task_vars(unsigned long *ret_stack) +{ + unsigned long *gvals = 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 offset into @t->ret_stack to find the ret_stack entry * @frame_offset: Where to place the offset into @t->ret_stack of that entry @@ -793,6 +843,7 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list) if (t->ret_stack == NULL) { atomic_set(&t->trace_overrun, 0); + ret_stack_init_task_vars(ret_stack_list[start]); t->curr_ret_stack = 0; t->curr_ret_depth = -1; /* Make sure the tasks see the 0 first: */ @@ -853,6 +904,7 @@ 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 = 0; t->curr_ret_stack = 0; t->curr_ret_depth = -1; @@ -951,6 +1003,24 @@ static int start_graph_tracing(void) return ret; } +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 = 0; @@ -997,6 +1067,8 @@ int register_ftrace_graph(struct fgraph_ops *gops) ftrace_graph_return = return_run; ftrace_graph_entry = entry_run; command = FTRACE_START_FUNC_RET; + } else { + init_task_vars(gops->idx); } ret = ftrace_startup(&gops->ops, command);