From patchwork Mon Dec 18 13:14:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13496938 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 D25D71D13E; Mon, 18 Dec 2023 13:14:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y2Af6x2n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BF6AC433C7; Mon, 18 Dec 2023 13:14:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702905256; bh=6cRbrv/l5bMX1auuYxXapw7O2xxXDa2GVYJzQXpe6qc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y2Af6x2nRsveW1/3yVS01WKcCwiXsa3EnEJLBKkFdJRY7ZTDQ6s3I3uXTHJxnKMbn N1eTU5YwE9e5k2kCbxK+Q67U+aBCOQdOLRzjnSBFZEQUsY/Fv1Rkjss1MqB32vMdCH F2/sKYh7bX7udxuxvmZkXlLRs+O8kVXh6rqPauiP8RTT5zjtrX1b8dGT9bNfG5c/Eq dJeqX9E9DqlV2mpkVsJPYu5eUrKGj9V/2/csJJDnyjajjrEG6tuUmT0fd2jIqXwzOZ inzDvGrVsbXj8p0P5SC/cZ3pVJslppcTb5w6OA7e8PaZkr9twYRTOZkCS75Ku/dHpQ eApnoGl+ztiQw== 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 v5 13/34] function_graph: Add "task variables" per task for fgraph_ops Date: Mon, 18 Dec 2023 22:14:10 +0900 Message-Id: <170290524998.220107.4609430123514665288.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <170290509018.220107.1347127510564358608.stgit@devnote2> References: <170290509018.220107.1347127510564358608.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 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 | 70 +++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 70 insertions(+), 1 deletion(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index c431a33fe789..09ca4bba63f2 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 idx); 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 aa5e4ec9fbb2..6e52c4989ef3 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)) #define RET_STACK(t, index) ((struct ftrace_ret_stack *)(&(t)->ret_stack[index])) +/* + * 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; @@ -182,6 +190,44 @@ 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 index into @t->ret_stack to find the ret_stack entry * @index: Where to place the index into @t->ret_stack of that entry @@ -788,6 +834,7 @@ 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: */ @@ -848,6 +895,7 @@ 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; @@ -946,6 +994,24 @@ 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; @@ -995,6 +1061,8 @@ 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);