Re: [RFC][PATCH v5 1/4] trace: Add trace any kernel object

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi Jeff,

Sorry for replying late!

On Sat, 13 Nov 2021 20:06:29 +0800
Jeff Xie <xiehuan09@gmail.com> wrote:

> Introduce a method based on function tracer to trace any object and get
> the value of the object dynamically. the object can be obtained from the
> dynamic event (kprobe_event/uprobe_event) or the static event(tracepoint).
> 
> Usage:
> When using the kprobe event, only need to set the objtrace(a new trigger),
> we can get the value of the object. The object is from the setting of the 
> kprobe event.
> 
> For example:
> For the function bio_add_page():
> 
> int bio_add_page(struct bio *bio, struct page *page,
> 	unsigned int len, unsigned int offset)
> 
> Firstly, we can set the base of the object, thus the first string "arg1"
> stands for the value of the first parameter of this function bio_add_gage(),
> 
> # echo 'p bio_add_page arg1=$arg1' >> ./kprobe_events
> 
> Secondly, we can get the value dynamically base the above object. 
> 
> find the offset of the bi_size in struct bio:
> $ gdb vmlinux
> (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
> $1 = (unsigned int *) 0x28
> 
> # echo 'objtrace:0x28(arg1):u32:1 if comm == "cat"' > ./events/kprobes/ \
> 	p_bio_add_page_0/trigger

You may need "objtrace:add:..." right? :-)

BTW, this value support is done in [2/4], you should focus on what this patch
does, not the entire series does. It seems what you need is a cover mail
for this series. The description like this must be done in the cover mail.
(For example, long trace output etc.)

> 
> The best way to use this is that we can set the entrance event and exit
> event, for example, the following example is to set the read_papes as
> the entrance event, and set the blk_account_io_start as the exit event.
> 
> # dd if=/dev/zero of=/test.txt bs=4k count=3
> # cd /sys/kernel/debug/tracing/
> # echo 0 > ./tracing_on
> # echo 'p read_pages' >> ./kprobe_events
> # echo 'p blk_account_io_start' >> ./kprobe_events
> # echo 'traceon if comm == "cat"' > ./events/kprobes/p_read_pages_0/trigger
> # echo 'traceoff if comm == "cat"' > ./events/kprobes/p_blk_account_io_start_0/trigger
> # echo 'p bio_add_page arg1=$arg1' >> ./kprobe_events
> # echo 'objtrace:0x28(arg1):u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
> 
> # du -sh /test.txt
> 12.0K   /test.txt
> 
> # cat  /test.txt > /dev/null
> # cat ./trace
> 
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 50/50   #P:1
> #
> #                                _-----=> irqs-off
> #                               / _----=> need-resched
> #                              | / _---=> hardirq/softirq
> #                              || / _--=> preempt-depth
> #                              ||| / _-=> migrate-disable
> #                              |||| /     delay
> #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
> #              | |         |   |||||     |         |
>              cat-95      [000] .....     1.412065: _raw_spin_unlock_irqrestore <-event_triggers_call object:0xffff888108af6328 value:0x0
>              cat-95      [000] .....     1.412066: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x0
>              cat-95      [000] .....     1.412066: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x0
>              cat-95      [000] .....     1.412066: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412066: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412066: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412067: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x1000
>              cat-95      [000] .....     1.412067: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x2000
>              cat-95      [000] .....     1.412067: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x2000
>              cat-95      [000] .....     1.412067: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x2000
>              cat-95      [000] .....     1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x2000
>              cat-95      [000] .....     1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x2000
>              cat-95      [000] .....     1.412068: submit_bio <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: submit_bio_noacct <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: __submit_bio <-submit_bio_noacct object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: blk_try_enter_queue <-__submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: submit_bio_checks <-__submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: __cond_resched <-submit_bio_checks object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: rcu_all_qs <-__cond_resched object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412068: should_fail_bio <-submit_bio_checks object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: create_task_io_context <-submit_bio_checks object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: kmem_cache_alloc_node <-create_task_io_context object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: should_failslab <-kmem_cache_alloc_node object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: _raw_spin_lock <-create_task_io_context object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: blk_mq_submit_bio <-__submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: __blk_queue_split <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: bvec_split_segs <-__blk_queue_split object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412069: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: __blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: dd_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: _raw_spin_lock <-dd_bio_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: blk_mq_sched_try_merge <-dd_bio_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: elv_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: elv_rqhash_find <-elv_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: dd_request_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: elv_rb_find <-dd_request_merge object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412070: __blk_mq_alloc_request <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: dd_limit_depth <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: blk_mq_get_tag <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: __blk_mq_get_tag <-blk_mq_get_tag object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: blk_mq_rq_ctx_init.isra.0 <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: ktime_get <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: dd_prepare_request <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: blk_account_io_start <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x3000
>              cat-95      [000] .....     1.412071: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x3000
> 
> 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         | 532 ++++++++++++++++++++++++++++
>  kernel/trace/trace_output.c         |  40 +++
>  8 files changed, 610 insertions(+)
>  create mode 100644 kernel/trace/trace_object.c
> 
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 3e475eeb5a99..84b5c12c7f44 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 6de5d4d63165..6d9e78a488aa 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -66,6 +66,7 @@ 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 b7c0f8e160fb..d2508f977fe6 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -49,6 +49,7 @@ enum trace_type {
>  	TRACE_TIMERLAT,
>  	TRACE_RAW_DATA,
>  	TRACE_FUNC_REPEATS,
> +	TRACE_OBJECT,
>  
>  	__TRACE_LAST_TYPE,
>  };
> @@ -460,6 +461,7 @@ 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)
>  
> @@ -1510,6 +1512,12 @@ 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..69465c2ffb7e
> --- /dev/null
> +++ b/kernel/trace/trace_object.c
> @@ -0,0 +1,532 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * trace any object
> + * 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 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 freelist;
> +};
> +
> +struct obj_pool {
> +	int maxactive;

It seems that 'maxactive' is used only in the init_object_pool(), so
we may not need this.

> +	atomic_t nobject;
> +	struct freelist_head product_freelist;
> +	struct freelist_head customer_freelist;

Sorry, I might confuse you. You shouldn't use the freelist for active
list, which searches a specific entry in the list. The freelist is good
for pooling the unused object_instances but not good for search an entry.
So please use normal "list_head" for the list for active objects. And
in that case, we can use rcu_list operation on it. 

BTW, I rather like calling those "active_list" and "free_list", because
product/customer are unclear what it means.

> +};
> +static struct obj_pool *obj_pool;
> +
> +static bool object_exist(void *obj)
> +{
> +	struct freelist_node *node;
> +	struct object_instance *inst;
> +	bool ret = false;
> +
> +	node = obj_pool->customer_freelist.head;
> +
> +	while (node) {

Then, you can use list_for_each_entry_rcu() here.

> +		inst = container_of(node, struct object_instance, freelist);
> +		if (inst->object == obj) {
> +			ret = true;
> +			goto out;
> +		}
> +		node = node->next;
> +	}
> +out:
> +	return ret;
> +}
> +
> +static bool object_empty(void)
> +{
> +	bool ret;
> +
> +	ret = atomic_read(&obj_pool->nobject) == 0;
> +
> +	return ret;

Instead of use atomic_read(), you can check the list itself by

	return !list_empty_rcu(&obj_pool->active_list);

> +}
> +
> +
> +static void set_trace_object(void *obj)
> +{
> +	struct freelist_node *fn;
> +	struct object_instance *ins;
> +
> +	if (!obj)
> +		return;
> +
> +	if (object_exist(obj))
> +		goto out;

No need to use goto. Just return is OK.

> +
> +	fn = freelist_try_get(&obj_pool->product_freelist);
> +	if (!fn) {
> +		trace_printk("object_pool is full, can't trace object:0x%px\n", obj);
> +		return;
> +	}
> +
> +	ins = container_of(fn, struct object_instance, freelist);
> +	ins->object = obj;
> +
> +	freelist_add(&ins->freelist, &obj_pool->customer_freelist);
> +	atomic_inc(&obj_pool->nobject);

Here, you can use list_add_rcu().

> +
> +out:
> +	return;
> +}
> +
> +static inline void free_objects(struct freelist_node *node)

Usually, this kind of function will get the freelist_head, since
node can be a node in the middle of the list.

> +{
> +
> +	struct object_instance *inst;
> +
> +	while (node) {
> +		inst = container_of(node, struct object_instance, freelist);
> +		node = node->next;
> +		kfree(inst);
> +	}
> +}
> +
> +static inline void free_object_pool(void)
> +{
> +	free_objects(obj_pool->product_freelist.head);
> +	free_objects(obj_pool->customer_freelist.head);
> +	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;
> +	}
> +	obj_pool->maxactive = max_obj_pool;
> +	obj_pool->product_freelist.head = NULL;
> +	obj_pool->customer_freelist.head = NULL;

You don't need to these because you already allocated a zero-filled
object by kzalloc().

> +
> +	for (i = 0; i < obj_pool->maxactive; i++) {
> +		inst = kzalloc(sizeof(*inst), GFP_KERNEL);
> +		if (!inst) {
> +			free_object_pool();
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +		freelist_add(&inst->freelist, &obj_pool->product_freelist);
> +	}
> +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));

What is the purpose of this?
(BTW, if you use per_cpu variable, you don't need atomic ops, because there is
no racing with other cpus.)

> +
> +	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;

As I pointed in v3, please ensure the field->size == sizeof(void *).
(Note that memcpy() is available only if the both size is same.
For example, on the big endian architecture, copying 8bit 0x12 on 64bit
pointer will be 0x1200000000000000.)

Thank you,


> +
> +	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 c2ca40e8595b..76ca560af693 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -1552,6 +1552,45 @@ 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,
> @@ -1566,6 +1605,7 @@ static struct trace_event *events[] __initdata = {
>  	&trace_timerlat_event,
>  	&trace_raw_data_event,
>  	&trace_func_repeats_event,
> +	&trace_object_event,
>  	NULL
>  };
>  
> -- 
> 2.25.1
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>