From patchwork Sun Jun 2 03:37:59 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13682668 X-Patchwork-Delegate: bpf@iogearbox.net 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 81DA42E622; Sun, 2 Jun 2024 03:37:26 +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=1717299446; cv=none; b=ZKofNEDGtOuUeZ48frhflLvEPUnetS5qN/B3gQ1wYCYj7MjB/Jb4j3p8cFeHepWViBhCqBO7rZixmjDU0SauFw320L/vz8ch100O6xR/pGDDGAhgvxPC0nB/Up3s/Fpl3d8NsCrMFFu0xIxZXB1jl7Hh0vd18MTb/xuxWAcBPS4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717299446; c=relaxed/simple; bh=RBw53ycHF+DElS6M+SUgA8ingNid6OrS+4Pj7y1fIh8=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=MobmohLu4vedNAjAZKsAFgQru6DtbKfxKprQS7fTJxiR7VHXrdOVNCOCQq/42co8CVhDVyPkzxab+OlG9wKkno0TAFoofMTUBWB67ogRQOfbJjZ2lO1+s5upr/KvZVE7chpnMlZVGFfPJf4rWO0fKVxpV+qw1b/AXGm57kZ5+iQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60C54C4AF49; Sun, 2 Jun 2024 03:37:26 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1sDc3F-000000094QR-2o5d; Sat, 01 Jun 2024 23:38:33 -0400 Message-ID: <20240602033833.525974288@goodmis.org> User-Agent: quilt/0.68 Date: Sat, 01 Jun 2024 23:37:59 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Alexei Starovoitov , Florent Revest , Martin KaFai Lau , bpf , Sven Schnelle , Alexei Starovoitov , Jiri Olsa , Arnaldo Carvalho de Melo , Daniel Borkmann , Alan Maguire , Peter Zijlstra , Thomas Gleixner , Guo Ren Subject: [PATCH v2 15/27] function_graph: Add "task variables" per task for fgraph_ops References: <20240602033744.563858532@goodmis.org> 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. Co-developed with Masami Hiramatsu: Link: https://lore.kernel.org/linux-trace-kernel/171509104383.162236.12239656156685718550.stgit@devnote2 Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- 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 e31ec8516de1..82cfc8e09cfd 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -1089,6 +1089,7 @@ 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 7fd9b03bd170..baa08249ffd5 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -54,6 +54,10 @@ * 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_OFFSET] + * | SHADOW_STACK_TASK_VARS(ret_stack)[15] | + * ... + * | SHADOW_STACK_TASK_VARS(ret_stack)[0] | * ret_stack[SHADOW_STACK_MAX_OFFSET] * ... * | | <- task->curr_ret_stack @@ -116,11 +120,19 @@ enum { #define SHADOW_STACK_SIZE (PAGE_SIZE) #define SHADOW_STACK_OFFSET (SHADOW_STACK_SIZE / sizeof(long)) /* Leave on a buffer at the end */ -#define SHADOW_STACK_MAX_OFFSET (SHADOW_STACK_OFFSET - (FGRAPH_FRAME_OFFSET + 1)) +#define SHADOW_STACK_MAX_OFFSET \ + (SHADOW_STACK_OFFSET - (FGRAPH_FRAME_OFFSET + 1 + FGRAPH_ARRAY_SIZE)) /* RET_STACK(): Return the frame from a given @offset from task @t */ #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_OFFSET - FGRAPH_ARRAY_SIZE])) + DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); int ftrace_graph_active; @@ -211,6 +223,44 @@ 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 @@ -766,6 +816,7 @@ 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: */ @@ -826,6 +877,7 @@ 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; @@ -959,6 +1011,24 @@ 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); } /* Always save the function, and reset at unregistering */