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References: <20220204035644.734878-1-xiehuan09@gmail.com> <20220204035644.734878-2-xiehuan09@gmail.com>
In-Reply-To: <20220204035644.734878-2-xiehuan09@gmail.com>
From:   Jeff Xie <xiehuan09@gmail.com>
Date:   Wed, 27 Apr 2022 23:50:26 +0800
Message-ID: <CAEr6+ECsKNdbkqWH1qpLN=O0+jjZD4F788Oy6fSa1r5U7L-YSA@mail.gmail.com>
Subject: Re: [PATCH v9 1/4] trace: Add trace any kernel object
To:     Tom Zanussi <zanussi@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>, mingo@redhat.com,
        linux-kernel@vger.kernel.org
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Precedence: bulk

Hi Tom,

I have checked your patches:

https://lore.kernel.org/all/cover.1644010575.git.zanussi@kernel.org/

But I found that I can't use the generic function you implemented,
I don't know if I understand correctly, when you are free, hope you
can help to check it ;-) , thanks.

On Fri, Feb 4, 2022 at 11:57 AM Jeff Xie <xiehuan09@gmail.com> wrote:
>
> Introduce objtrace trigger to get the call flow by tracing any kernel
> object in the function parameter.
>
> The objtrace trigger makes a list of the target object address from
> the given event parameter, and records all kernel function calls
> which has the object address in its parameter.
>
> Syntax:
>         objtrace:add:obj[:count][if <filter>]
>
> Usage:
>         # echo 'p bio_add_page arg1=$arg1' > kprobe_events
>         # cd events/kprobes/p_bio_add_page_0
>         # echo 'objtrace:add:arg1:1 if comm == "cat"' > ./trigger
>         # cat /test.txt
>
> 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.c                |   3 +
>  kernel/trace/trace.h                |   8 +
>  kernel/trace/trace_entries.h        |  17 +
>  kernel/trace/trace_events_trigger.c |   1 +
>  kernel/trace/trace_object.c         | 515 ++++++++++++++++++++++++++++
>  kernel/trace/trace_output.c         |  40 +++
>  9 files changed, 596 insertions(+)
>  create mode 100644 kernel/trace/trace_object.c
>
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 70c069aef02c..3ccdbc1d25dd 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -685,6 +685,7 @@ 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 a5eb5e7fd624..c51b7eb1508d 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -250,6 +250,16 @@ 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.c b/kernel/trace/trace.c
> index a734d5ae34c8..b4513c2bbd52 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5605,6 +5605,9 @@ static const char readme_msg[] =
>         "\t            enable_hist:<system>:<event>\n"
>         "\t            disable_hist:<system>:<event>\n"
>  #endif
> +#ifdef CONFIG_TRACE_OBJECT
> +       "\t            objtrace:add:obj[:count][if <filter>]\n"
> +#endif
>  #ifdef CONFIG_STACKTRACE
>         "\t\t    stacktrace\n"
>  #endif
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 0f5e22238cd2..8b66515a36d5 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,
>  };
> @@ -472,6 +473,7 @@ 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)
>
> @@ -1537,6 +1539,12 @@ 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 d00fee705f9c..c3371a6902af 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -2025,6 +2025,7 @@ __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..540e387c613a
> --- /dev/null
> +++ b/kernel/trace/trace_object.c
> @@ -0,0 +1,515 @@
> +// 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"
> +
> +#define MAX_TRACED_OBJECT 5
> +#define OBJTRACE_CMD_LEN  10
> +static DEFINE_PER_CPU(unsigned int, trace_object_event_disable);
> +static DEFINE_RAW_SPINLOCK(trace_obj_lock);
> +static struct trace_event_file event_trace_file;
> +static const int max_args_num = 6;
> +static atomic_t trace_object_ref;
> +static atomic_t num_traced_obj;
> +static int exit_trace_object(void);
> +static int init_trace_object(void);
> +
> +static struct object_instance {
> +       void *obj;
> +} traced_obj[MAX_TRACED_OBJECT];
> +
> +/* objtrace private data */
> +struct objtrace_trigger_data {
> +       struct ftrace_event_field *field;
> +       char objtrace_cmd[OBJTRACE_CMD_LEN];
> +};
> +
> +static bool object_exist(void *obj)
> +{
> +       int i, max;
> +
> +       max = atomic_read(&num_traced_obj);
> +       smp_rmb();
> +       for (i = 0; i < max; i++) {
> +               if (traced_obj[i].obj == obj)
> +                       return true;
> +       }
> +       return false;
> +}
> +
> +static bool object_empty(void)
> +{
> +       return !atomic_read(&num_traced_obj);
> +}
> +
> +static void set_trace_object(void *obj)
> +{
> +       unsigned long flags;
> +
> +       if (in_nmi())
> +               return;
> +
> +       if (!obj)
> +               return;
> +
> +       if (object_exist(obj))
> +               return;
> +
> +       /* only this place has write operations */
> +       raw_spin_lock_irqsave(&trace_obj_lock, flags);
> +       if (atomic_read(&num_traced_obj) == MAX_TRACED_OBJECT) {
> +               trace_printk("object_pool is full, can't trace object:0x%px\n", obj);
> +               goto out;
> +       }
> +       traced_obj[atomic_read(&num_traced_obj)].obj = obj;
> +       /* make sure the num_traced_obj update always appears after traced_obj update */
> +       smp_wmb();
> +       atomic_inc(&num_traced_obj);
> +out:
> +       raw_spin_unlock_irqrestore(&trace_obj_lock, flags);
> +}
> +
> +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;
> +       unsigned int disabled;
> +       int n;
> +
> +       preempt_disable_notrace();
> +
> +       disabled = this_cpu_inc_return(trace_object_event_disable);
> +       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);
> +       /* The parameters of a function may match multiple objects */
> +       }
> +out:
> +       this_cpu_dec(trace_object_event_disable);
> +       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 objtrace_trigger_data *obj_data = data->private_data;
> +       struct ftrace_event_field *field;
> +       void *obj = NULL;
> +
> +       field = obj_data->field;
> +       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) {
> +               kfree(data->private_data);
> +               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, void *objtrace_data)
> +{
> +       long count = (long)data;
> +       struct objtrace_trigger_data *obj_data = objtrace_data;
> +
> +       seq_puts(m, name);
> +
> +       seq_printf(m, ":%s", obj_data->objtrace_cmd);
> +       seq_printf(m, ":%s", obj_data->field->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, data->private_data);
> +}
> +
> +static struct event_trigger_ops objecttrace_trigger_ops = {
> +       .trigger                = 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 = {
> +       .trigger                = 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_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;
> +}

Can't replace the register_object_trigger() with register_trigger(),
as there will be no place to invoke the init_trace_object(), maybe It
will be better to add a callback in struct event_command,
for example, cmd_ops->init()

> +static void unregister_object_trigger(char *glob,
> +                              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) {
> +               if (data->ops->free)
> +                       data->ops->free(data->ops, data);
> +               exit_trace_object();
> +       }
> +}
> +

Can't replace the unregister_object_trigger() with unregister_trigger(),
as there will be no place to invoke the exit_trace_object().Maybe need
to add a callback, for example cmd_ops->free().

> +static bool field_exist(struct trace_event_file *file,
> +                       struct event_command *cmd_ops,
> +                       const char *field_name)
> +{
> +       struct event_trigger_data *data;
> +       struct objtrace_trigger_data *obj_data;
> +
> +       lockdep_assert_held(&event_mutex);
> +
> +       list_for_each_entry(data, &file->triggers, list) {
> +               if (data->cmd_ops->trigger_type == cmd_ops->trigger_type) {
> +                       obj_data = data->private_data;
> +                       if (!strcmp(obj_data->field->name, field_name))
> +                               return true;
> +               }
> +       }
> +
> +       return false;
> +}
> +
> +static int
> +event_object_trigger_parse(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 objtrace_trigger_data *obj_data;
> +       struct trace_event_call *call;
> +       struct ftrace_event_field *field;
> +       char *objtrace_cmd;
> +       char *trigger = NULL;
> +       char *arg;
> +       char *number;
> +       int ret;
> +       bool remove = false;
> +
> +       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;
> +
> +       if (glob[0] == '!')
> +               remove = true;
> +
> +       if (remove && !field_exist(file, cmd_ops, field->name))
> +       goto out;
> +       trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
> +       ret = -ENOMEM;
> +       obj_data = kzalloc(sizeof(*obj_data), GFP_KERNEL);
> +       if (!obj_data)
> +               goto out;
> +       obj_data->field = field;
> +       snprintf(obj_data->objtrace_cmd, OBJTRACE_CMD_LEN, objtrace_cmd);
> +
> +       trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
> +       if (!trigger_data) {
> +               kfree(obj_data);
> +               goto out;
> +       }
> +
> +       trigger_data->count = -1;
> +       trigger_data->ops = trigger_ops;
> +       trigger_data->cmd_ops = cmd_ops;
> +       trigger_data->private_data = obj_data;
> +       INIT_LIST_HEAD(&trigger_data->list);
> +       INIT_LIST_HEAD(&trigger_data->named_list);
> +
> +       if (remove) {
> +               cmd_ops->unreg(glob+1, trigger_data, file);
> +               kfree(obj_data);
> +               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_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_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(obj_data);
> +       kfree(trigger_data);
> +       goto out;
> +}

Can't replace the event_object_trigger_parse() with event_trigger_parse().
Because the event_object_trigger_parse() needs to parse more fields,
for example need to parse objtrace_cmd("add" etc.,)
and need to use other special private_data. Maybe It will have to use
the event_object_trigger_parse().

> +static struct event_command trigger_object_cmd = {
> +       .name                   = "objtrace",
> +       .trigger_type           = ETT_TRACE_OBJECT,
> +       .flags                  = EVENT_CMD_FL_NEEDS_REC,
> +       .parse                  = event_object_trigger_parse,
> +       .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;
> +       }
> +
> +       event_trace_file.tr = top_trace_array();
> +       if (WARN_ON(!event_trace_file.tr)) {
> +               ret = -1;
> +               atomic_dec(&trace_object_ref);
> +               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)) {
> +               ret = -1;
> +               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;
> +       }
> +       atomic_set(&num_traced_obj, 0);
> +out:
> +       return ret;
> +}
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index 8aa493d25c73..265428154638 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -1547,6 +1547,45 @@ 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,
> @@ -1561,6 +1600,7 @@ static struct trace_event *events[] __initdata = {
>         &trace_timerlat_event,
>         &trace_raw_data_event,
>         &trace_func_repeats_event,
> +       &trace_object_event,
>         NULL
>  };
>
> --
> 2.25.1
>

Thanks,
JeffXie