From:   Jeff Xie <xiehuan09@gmail.com>
To:     rostedt@goodmis.org
Cc:     mhiramat@kernel.org, mingo@redhat.com, zanussi@kernel.org,
        linux-kernel@vger.kernel.org, Jeff Xie <xiehuan09@gmail.com>
Subject: [RFC][PATCH v6 1/5] trace: Add trace any kernel object
Date:   Tue, 30 Nov 2021 00:49:47 +0800
Message-Id: <20211129164951.220511-2-xiehuan09@gmail.com>
In-Reply-To: <20211129164951.220511-1-xiehuan09@gmail.com>
References: <20211129164951.220511-1-xiehuan09@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Introduce objtrace trigger to get the execution flow by tracing
any kernel object in the kernel parameter.

Signed-off-by: Jeff Xie <xiehuan09@gmail.com>
---
 include/linux/trace_events.h        |   1 +
 kernel/trace/Kconfig                |  10 +
 kernel/trace/Makefile               |   1 +
 kernel/trace/trace.h                |   8 +
 kernel/trace/trace_entries.h        |  17 +
 kernel/trace/trace_events_trigger.c |   1 +
 kernel/trace/trace_object.c         | 534 ++++++++++++++++++++++++++++
 kernel/trace/trace_output.c         |  40 +++
 8 files changed, 612 insertions(+)
 create mode 100644 kernel/trace/trace_object.c

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 2d167ac3452c..54baec78ce62 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -684,6 +684,7 @@ enum event_trigger_type {
 	ETT_EVENT_HIST		= (1 << 4),
 	ETT_HIST_ENABLE		= (1 << 5),
 	ETT_EVENT_EPROBE	= (1 << 6),
+	ETT_TRACE_OBJECT	= (1 << 7),
 };
 
 extern int filter_match_preds(struct event_filter *filter, void *rec);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 420ff4bc67fd..f69761cbfaaa 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -237,6 +237,16 @@ config FUNCTION_PROFILER
 
 	  If in doubt, say N.
 
+config TRACE_OBJECT
+	bool "Trace kernel object in function parameter"
+	depends on FUNCTION_TRACER
+	depends on HAVE_FUNCTION_ARG_ACCESS_API
+	select TRACING
+	default y
+	help
+	 You can trace the kernel object in the kernel function parameter.
+	 The kernel object is dynamically specified via event trigger.
+
 config STACK_TRACER
 	bool "Trace max stack"
 	depends on HAVE_FUNCTION_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index bedc5caceec7..b924b8e55922 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += trace_functions_graph.o
 obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
 obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += fgraph.o
+obj-$(CONFIG_TRACE_OBJECT) += trace_object.o
 ifeq ($(CONFIG_BLOCK),y)
 obj-$(CONFIG_EVENT_TRACING) += blktrace.o
 endif
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 38715aa6cfdf..46a1301ac47a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -54,6 +54,7 @@ enum trace_type {
 	TRACE_TIMERLAT,
 	TRACE_RAW_DATA,
 	TRACE_FUNC_REPEATS,
+	TRACE_OBJECT,
 
 	__TRACE_LAST_TYPE,
 };
@@ -469,6 +470,7 @@ extern void __ftrace_bad_type(void);
 			  TRACE_GRAPH_RET);		\
 		IF_ASSIGN(var, ent, struct func_repeats_entry,		\
 			  TRACE_FUNC_REPEATS);				\
+		IF_ASSIGN(var, ent, struct trace_object_entry, TRACE_OBJECT);\
 		__ftrace_bad_type();					\
 	} while (0)
 
@@ -1531,6 +1533,12 @@ static inline int register_trigger_hist_cmd(void) { return 0; }
 static inline int register_trigger_hist_enable_disable_cmds(void) { return 0; }
 #endif
 
+#ifdef CONFIG_TRACE_OBJECT
+extern int register_trigger_object_cmd(void);
+#else
+static inline int register_trigger_object_cmd(void) { return 0; }
+#endif
+
 extern int register_trigger_cmds(void);
 extern void clear_event_triggers(struct trace_array *tr);
 
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index cd41e863b51c..bb120d9498a9 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -401,3 +401,20 @@ FTRACE_ENTRY(timerlat, timerlat_entry,
 		 __entry->context,
 		 __entry->timer_latency)
 );
+
+/*
+ * trace object entry:
+ */
+FTRACE_ENTRY(object, trace_object_entry,
+
+	TRACE_OBJECT,
+
+	F_STRUCT(
+		__field(	unsigned long,		ip		)
+		__field(	unsigned long,		parent_ip	)
+		__field(	unsigned long,		object		)
+	),
+
+	F_printk(" %ps <-- %ps object:%lx\n",
+		 (void *)__entry->ip, (void *)__entry->parent_ip, __entry->object)
+);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 3d5c07239a2a..da2d871fa809 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1687,6 +1687,7 @@ __init int register_trigger_cmds(void)
 	register_trigger_enable_disable_cmds();
 	register_trigger_hist_enable_disable_cmds();
 	register_trigger_hist_cmd();
+	register_trigger_object_cmd();
 
 	return 0;
 }
diff --git a/kernel/trace/trace_object.c b/kernel/trace/trace_object.c
new file mode 100644
index 000000000000..83fccd587b63
--- /dev/null
+++ b/kernel/trace/trace_object.c
@@ -0,0 +1,534 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * trace the kernel object in the kernel function parameter
+ * Copyright (C) 2021 Jeff Xie <xiehuan09@gmail.com>
+ */
+
+#define pr_fmt(fmt) "trace_object: " fmt
+
+#include "trace_output.h"
+#include <linux/freelist.h>
+
+static DEFINE_PER_CPU(atomic_t, trace_object_event_disable);
+static DEFINE_RAW_SPINLOCK(object_spin_lock);
+static struct trace_event_file event_trace_file;
+static const int max_args_num = 6;
+static const int max_obj_pool = 10;
+static atomic_t trace_object_ref;
+static int exit_trace_object(void);
+static int init_trace_object(void);
+
+struct object_instance {
+	void *object;
+	struct freelist_node free_list;
+	struct list_head active_list;
+};
+
+struct obj_pool {
+	struct freelist_head free_list;
+	struct list_head active_list;
+};
+static struct obj_pool *obj_pool;
+
+static bool object_exist(void *obj)
+{
+	struct object_instance *inst;
+	bool ret = false;
+
+	list_for_each_entry_rcu(inst, &obj_pool->active_list, active_list) {
+		if (inst->object == obj) {
+			ret = true;
+			goto out;
+		}
+	}
+out:
+	return ret;
+}
+
+static bool object_empty(void)
+{
+	return list_empty(&obj_pool->active_list);
+}
+
+static void set_trace_object(void *obj)
+{
+	struct freelist_node *fn;
+	struct object_instance *ins;
+	unsigned long flags;
+
+	if (in_nmi())
+		return;
+
+	if (!obj)
+		return;
+
+	if (object_exist(obj))
+		return;
+
+	fn = freelist_try_get(&obj_pool->free_list);
+	if (!fn) {
+		trace_printk("object_pool is full, can't trace object:0x%px\n", obj);
+		return;
+	}
+
+	ins = container_of(fn, struct object_instance, free_list);
+	ins->object = obj;
+
+	raw_spin_lock_irqsave(&object_spin_lock, flags);
+	list_add_rcu(&ins->active_list, &obj_pool->active_list);
+	raw_spin_unlock_irqrestore(&object_spin_lock, flags);
+}
+
+static inline void free_free_list_objects(struct freelist_head *head)
+{
+
+	struct object_instance *inst;
+	struct freelist_node *node = head->head;
+
+	while (node) {
+		inst = container_of(node, struct object_instance, free_list);
+		node = node->next;
+		kfree(inst);
+	}
+}
+
+static inline void free_active_list_objects(struct list_head *head)
+{
+	struct object_instance *inst;
+
+	list_for_each_entry_rcu(inst, head, active_list)
+		kfree(inst);
+}
+
+static inline void free_object_pool(void)
+{
+	free_free_list_objects(&obj_pool->free_list);
+	free_active_list_objects(&obj_pool->active_list);
+	kfree(obj_pool);
+}
+
+
+static int init_object_pool(void)
+{
+	struct object_instance *inst;
+	int i, ret = 0;
+
+	obj_pool = kzalloc(sizeof(*obj_pool), GFP_KERNEL);
+	if (!obj_pool) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&obj_pool->active_list);
+
+	for (i = 0; i < max_obj_pool; i++) {
+		inst = kzalloc(sizeof(*inst), GFP_KERNEL);
+		if (!inst) {
+			free_object_pool();
+			ret = -ENOMEM;
+			goto out;
+		}
+		freelist_add(&inst->free_list, &obj_pool->free_list);
+	}
+out:
+	return ret;
+}
+
+static void submit_trace_object(unsigned long ip, unsigned long parent_ip,
+				 unsigned long object)
+{
+
+	struct trace_buffer *buffer;
+	struct ring_buffer_event *event;
+	struct trace_object_entry *entry;
+	int pc;
+
+	pc = preempt_count();
+	event = trace_event_buffer_lock_reserve(&buffer, &event_trace_file,
+			TRACE_OBJECT, sizeof(*entry), pc);
+	if (!event)
+		return;
+	entry   = ring_buffer_event_data(event);
+	entry->ip                       = ip;
+	entry->parent_ip                = parent_ip;
+	entry->object			= object;
+
+	event_trigger_unlock_commit(&event_trace_file, buffer, event,
+		entry, pc);
+}
+
+static void
+trace_object_events_call(unsigned long ip, unsigned long parent_ip,
+		struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	struct pt_regs *pt_regs = ftrace_get_regs(fregs);
+	unsigned long obj;
+	long disabled;
+	int cpu, n;
+
+	preempt_disable_notrace();
+
+	cpu = raw_smp_processor_id();
+	disabled = atomic_inc_return(&per_cpu(trace_object_event_disable, cpu));
+
+	if (disabled != 1)
+		goto out;
+
+	if (object_empty())
+		goto out;
+
+	for (n = 0; n < max_args_num; n++) {
+		obj = regs_get_kernel_argument(pt_regs, n);
+		if (object_exist((void *)obj))
+			submit_trace_object(ip, parent_ip, obj);
+	}
+
+out:
+	atomic_dec(&per_cpu(trace_object_event_disable, cpu));
+	preempt_enable_notrace();
+}
+
+static struct ftrace_ops trace_ops = {
+	.func  = trace_object_events_call,
+	.flags = FTRACE_OPS_FL_SAVE_REGS,
+};
+
+static void
+trace_object_trigger(struct event_trigger_data *data,
+		   struct trace_buffer *buffer,  void *rec,
+		   struct ring_buffer_event *event)
+{
+
+	struct ftrace_event_field *field = data->private_data;
+	void *obj = NULL;
+
+	memcpy(&obj, rec + field->offset, sizeof(obj));
+	set_trace_object(obj);
+}
+
+static void
+trace_object_trigger_free(struct event_trigger_ops *ops,
+		   struct event_trigger_data *data)
+{
+	if (WARN_ON_ONCE(data->ref <= 0))
+		return;
+
+	data->ref--;
+	if (!data->ref)
+		trigger_data_free(data);
+}
+
+static void
+trace_object_count_trigger(struct event_trigger_data *data,
+			 struct trace_buffer *buffer, void *rec,
+			 struct ring_buffer_event *event)
+{
+	if (!data->count)
+		return;
+
+	if (data->count != -1)
+		(data->count)--;
+
+	trace_object_trigger(data, buffer, rec, event);
+}
+
+static int event_object_trigger_init(struct event_trigger_ops *ops,
+		       struct event_trigger_data *data)
+{
+	data->ref++;
+	return 0;
+}
+
+static int
+event_trigger_print(const char *name, struct seq_file *m,
+		    void *data, char *filter_str)
+{
+	long count = (long)data;
+
+	seq_puts(m, name);
+
+	if (count == -1)
+		seq_puts(m, ":unlimited");
+	else
+		seq_printf(m, ":count=%ld", count);
+
+	if (filter_str)
+		seq_printf(m, " if %s\n", filter_str);
+	else
+		seq_putc(m, '\n');
+
+	return 0;
+}
+
+static int
+trace_object_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+			 struct event_trigger_data *data)
+{
+	return event_trigger_print("objtrace", m, (void *)data->count,
+				   data->filter_str);
+}
+
+static struct event_trigger_ops objecttrace_trigger_ops = {
+	.func			= trace_object_trigger,
+	.print			= trace_object_trigger_print,
+	.init			= event_object_trigger_init,
+	.free			= trace_object_trigger_free,
+};
+
+static struct event_trigger_ops objecttrace_count_trigger_ops = {
+	.func			= trace_object_count_trigger,
+	.print			= trace_object_trigger_print,
+	.init			= event_object_trigger_init,
+	.free			= trace_object_trigger_free,
+};
+
+static struct event_trigger_ops *
+objecttrace_get_trigger_ops(char *cmd, char *param)
+{
+	return param ? &objecttrace_count_trigger_ops : &objecttrace_trigger_ops;
+}
+
+static int register_object_trigger(char *glob, struct event_trigger_ops *ops,
+			    struct event_trigger_data *data,
+			    struct trace_event_file *file)
+{
+	struct event_trigger_data *test;
+	int ret = 0;
+
+	lockdep_assert_held(&event_mutex);
+
+	list_for_each_entry(test, &file->triggers, list) {
+		if (test->cmd_ops->trigger_type == data->cmd_ops->trigger_type) {
+			ret = -EEXIST;
+			goto out;
+		}
+	}
+
+	if (data->ops->init) {
+		ret = data->ops->init(data->ops, data);
+		if (ret < 0)
+			goto out;
+	}
+
+	list_add_rcu(&data->list, &file->triggers);
+	ret++;
+
+	update_cond_flag(file);
+	if (trace_event_trigger_enable_disable(file, 1) < 0) {
+		list_del_rcu(&data->list);
+		update_cond_flag(file);
+		ret--;
+	}
+	init_trace_object();
+out:
+	return ret;
+}
+
+static void unregister_object_trigger(char *glob, struct event_trigger_ops *ops,
+			       struct event_trigger_data *test,
+			       struct trace_event_file *file)
+{
+	struct event_trigger_data *data;
+	bool unregistered = false;
+
+	lockdep_assert_held(&event_mutex);
+
+	list_for_each_entry(data, &file->triggers, list) {
+		if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) {
+			unregistered = true;
+			list_del_rcu(&data->list);
+			trace_event_trigger_enable_disable(file, 0);
+			update_cond_flag(file);
+			break;
+		}
+	}
+
+	if (unregistered && data->ops->free) {
+		data->ops->free(data->ops, data);
+		exit_trace_object();
+	}
+}
+
+static int
+event_object_trigger_callback(struct event_command *cmd_ops,
+		       struct trace_event_file *file,
+		       char *glob, char *cmd, char *param)
+{
+	struct event_trigger_data *trigger_data;
+	struct event_trigger_ops *trigger_ops;
+	struct trace_event_call *call;
+	struct ftrace_event_field *field;
+	char *objtrace_cmd;
+	char *trigger = NULL;
+	char *arg;
+	char *number;
+	int ret;
+
+	ret = -EINVAL;
+	if (!param)
+		goto out;
+
+	/* separate the trigger from the filter (c:a:n [if filter]) */
+	trigger = strsep(&param, " \t");
+	if (!trigger)
+		goto out;
+	if (param) {
+		param = skip_spaces(param);
+		if (!*param)
+			param = NULL;
+	}
+
+	objtrace_cmd = strsep(&trigger, ":");
+	if (!objtrace_cmd || strcmp(objtrace_cmd, "add"))
+		goto out;
+
+	arg = strsep(&trigger, ":");
+	if (!arg)
+		goto out;
+	call = file->event_call;
+	field = trace_find_event_field(call, arg);
+	if (!field)
+		goto out;
+
+	if (field->size != sizeof(void *))
+		goto out;
+
+	trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
+
+	ret = -ENOMEM;
+	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
+	if (!trigger_data)
+		goto out;
+
+	trigger_data->count = -1;
+	trigger_data->ops = trigger_ops;
+	trigger_data->cmd_ops = cmd_ops;
+	trigger_data->private_data = field;
+	INIT_LIST_HEAD(&trigger_data->list);
+	INIT_LIST_HEAD(&trigger_data->named_list);
+
+	if (glob[0] == '!') {
+		cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
+		kfree(trigger_data);
+		ret = 0;
+		goto out;
+	}
+
+	if (trigger) {
+		number = strsep(&trigger, ":");
+
+		ret = -EINVAL;
+		if (!strlen(number))
+			goto out_free;
+
+		/*
+		 * We use the callback data field (which is a pointer)
+		 * as our counter.
+		 */
+		ret = kstrtoul(number, 0, &trigger_data->count);
+		if (ret)
+			goto out_free;
+	}
+
+	if (!param) /* if param is non-empty, it's supposed to be a filter */
+		goto out_reg;
+
+	if (!cmd_ops->set_filter)
+		goto out_reg;
+
+	ret = cmd_ops->set_filter(param, trigger_data, file);
+	if (ret < 0)
+		goto out_free;
+
+ out_reg:
+	/* Up the trigger_data count to make sure reg doesn't free it on failure */
+	event_object_trigger_init(trigger_ops, trigger_data);
+	ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
+	/*
+	 * The above returns on success the # of functions enabled,
+	 * but if it didn't find any functions it returns zero.
+	 * Consider no functions a failure too.
+	 */
+	if (!ret) {
+		cmd_ops->unreg(glob, trigger_ops, trigger_data, file);
+		ret = -ENOENT;
+	} else if (ret > 0)
+		ret = 0;
+
+	/* Down the counter of trigger_data or free it if not used anymore */
+	trace_object_trigger_free(trigger_ops, trigger_data);
+ out:
+	return ret;
+
+ out_free:
+	if (cmd_ops->set_filter)
+		cmd_ops->set_filter(NULL, trigger_data, NULL);
+	kfree(trigger_data);
+	goto out;
+}
+
+static struct event_command trigger_object_cmd = {
+	.name			= "objtrace",
+	.trigger_type		= ETT_TRACE_OBJECT,
+	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.func			= event_object_trigger_callback,
+	.reg			= register_object_trigger,
+	.unreg			= unregister_object_trigger,
+	.get_trigger_ops	= objecttrace_get_trigger_ops,
+	.set_filter		= set_trigger_filter,
+};
+
+__init int register_trigger_object_cmd(void)
+{
+	int ret;
+
+	ret = register_event_command(&trigger_object_cmd);
+	WARN_ON(ret < 0);
+
+	return ret;
+}
+
+static int init_trace_object(void)
+{
+	int ret;
+
+	if (atomic_inc_return(&trace_object_ref) != 1) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = init_object_pool();
+	if (ret)
+		goto out;
+
+	event_trace_file.tr = top_trace_array();
+	if (WARN_ON(!event_trace_file.tr)) {
+		ret = -1;
+		goto out;
+	}
+	ret = register_ftrace_function(&trace_ops);
+out:
+	return ret;
+}
+
+static int exit_trace_object(void)
+{
+	int ret;
+
+	if (WARN_ON_ONCE(atomic_read(&trace_object_ref) <= 0))
+		goto out;
+
+	if (atomic_dec_return(&trace_object_ref) != 0) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = unregister_ftrace_function(&trace_ops);
+	if (ret) {
+		pr_err("can't unregister ftrace for trace object\n");
+		goto out;
+	}
+	free_object_pool();
+out:
+	return ret;
+}
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 3547e7176ff7..d747aed27104 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1543,6 +1543,45 @@ static struct trace_event trace_func_repeats_event = {
 	.funcs		= &trace_func_repeats_funcs,
 };
 
+/* TRACE_OBJECT */
+static enum print_line_t trace_object_print(struct trace_iterator *iter, int flags,
+					struct trace_event *event)
+{
+	struct trace_object_entry *field;
+	struct trace_seq *s = &iter->seq;
+
+	trace_assign_type(field, iter->ent);
+	print_fn_trace(s, field->ip, field->parent_ip, flags);
+	trace_seq_printf(s, " object:0x%lx", field->object);
+	trace_seq_putc(s, '\n');
+
+	return trace_handle_return(s);
+}
+
+static enum print_line_t trace_object_raw(struct trace_iterator *iter, int flags,
+				      struct trace_event *event)
+{
+	struct trace_object_entry *field;
+
+	trace_assign_type(field, iter->ent);
+
+	trace_seq_printf(&iter->seq, "%lx %lx\n",
+			 field->ip,
+			 field->parent_ip);
+
+	return trace_handle_return(&iter->seq);
+}
+
+static struct trace_event_functions trace_object_funcs = {
+	.trace		= trace_object_print,
+	.raw		= trace_object_raw,
+};
+
+static struct trace_event trace_object_event = {
+	.type		= TRACE_OBJECT,
+	.funcs		= &trace_object_funcs,
+};
+
 static struct trace_event *events[] __initdata = {
 	&trace_fn_event,
 	&trace_ctx_event,
@@ -1557,6 +1596,7 @@ static struct trace_event *events[] __initdata = {
 	&trace_timerlat_event,
 	&trace_raw_data_event,
 	&trace_func_repeats_event,
+	&trace_object_event,
 	NULL
 };
 
-- 
2.25.1