Re: [RFC][PATCH v5 2/4] trace/objtrace: get the value of the object

[Jeff Xie <xiehuan09@gmail.com>]

Hi Masami,

On Fri, Nov 19, 2021 at 10:01 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> Hi Jeff,
>
> On Sat, 13 Nov 2021 20:06:30 +0800
> Jeff Xie <xiehuan09@gmail.com> wrote:
>
> Please describe here what feature this patch adds.
> How to use, and new syntax, etc.
>
> BTW, the syntax for this value trace is a bit confusing.
>
> objtrace:add:OFFS(OBJ):TYPE[:COUNT]
>
> This trace "OBJ", but from the user point of view, this seems to trace
> "OFFS(OBJ)".
>
> I rather like make it optional and split from OBJ as below;
>
> objtrace:add:OBJ[,OFFS:TYPE][:COUNT]
>
> (Note that the part braced by [] is optional.)

Thank you for your suggestion, it does seem clearer, I will modify it like this.

> Thank you,
>
> > Signed-off-by: Jeff Xie <xiehuan09@gmail.com>
> > ---
> >  kernel/trace/trace_entries.h |   5 +-
> >  kernel/trace/trace_object.c  | 121 +++++++++++++++++++++++++++++------
> >  kernel/trace/trace_output.c  |   6 +-
> >  3 files changed, 107 insertions(+), 25 deletions(-)
> >
> > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > index bb120d9498a9..2407c45a568c 100644
> > --- a/kernel/trace/trace_entries.h
> > +++ b/kernel/trace/trace_entries.h
> > @@ -413,8 +413,9 @@ FTRACE_ENTRY(object, trace_object_entry,
> >               __field(        unsigned long,          ip              )
> >               __field(        unsigned long,          parent_ip       )
> >               __field(        unsigned long,          object          )
> > +             __field(        unsigned long,          value           )
> >       ),
> >
> > -     F_printk(" %ps <-- %ps object:%lx\n",
> > -              (void *)__entry->ip, (void *)__entry->parent_ip, __entry->object)
> > +     F_printk(" %ps <-- %ps object:%lx value:%lx\n", (void *)__entry->ip,
> > +            (void *)__entry->parent_ip, __entry->object, __entry->value)
> >  );
> > diff --git a/kernel/trace/trace_object.c b/kernel/trace/trace_object.c
> > index 69465c2ffb7e..14993f7d0e5a 100644
> > --- a/kernel/trace/trace_object.c
> > +++ b/kernel/trace/trace_object.c
> > @@ -11,14 +11,25 @@
> >
> >  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 objtrace_trigger_data {
> > +     struct ftrace_event_field *field;
> > +     long offset;
> > +     int type_size;
> > +};
> > +
> > +struct objtrace_fetch_type {
> > +     char *name;
> > +     int type_size;
> > +};
> > +
> >  struct object_instance {
> >       void *object;
> > +     int obj_type_size;
> >       struct freelist_node freelist;
> >  };
> >
> > @@ -59,8 +70,7 @@ static bool object_empty(void)
> >       return ret;
> >  }
> >
> > -
> > -static void set_trace_object(void *obj)
> > +static void set_trace_object(void *obj, int type_size)
> >  {
> >       struct freelist_node *fn;
> >       struct object_instance *ins;
> > @@ -79,6 +89,7 @@ static void set_trace_object(void *obj)
> >
> >       ins = container_of(fn, struct object_instance, freelist);
> >       ins->object = obj;
> > +     ins->obj_type_size = type_size;
> >
> >       freelist_add(&ins->freelist, &obj_pool->customer_freelist);
> >       atomic_inc(&obj_pool->nobject);
> > @@ -135,7 +146,7 @@ static int init_object_pool(void)
> >  }
> >
> >  static void submit_trace_object(unsigned long ip, unsigned long parent_ip,
> > -                              unsigned long object)
> > +                              unsigned long object, unsigned long value)
> >  {
> >
> >       struct trace_buffer *buffer;
> > @@ -152,6 +163,7 @@ static void submit_trace_object(unsigned long ip, unsigned long parent_ip,
> >       entry->ip                       = ip;
> >       entry->parent_ip                = parent_ip;
> >       entry->object                   = object;
> > +     entry->value                    = value;
> >
> >       event_trigger_unlock_commit(&event_trace_file, buffer, event,
> >               entry, pc);
> > @@ -161,10 +173,11 @@ 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;
> > +     struct freelist_node *node;
> > +     struct object_instance *inst;
> > +     unsigned long val = 0;
> >       long disabled;
> > -     int cpu, n;
> > +     int cpu;
> >
> >       preempt_disable_notrace();
> >
> > @@ -177,10 +190,14 @@ trace_object_events_call(unsigned long ip, unsigned long parent_ip,
> >       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);
> > +     node = obj_pool->customer_freelist.head;
> > +
> > +     while (node) {
> > +             inst = container_of(node, struct object_instance, freelist);
> > +             if (copy_from_kernel_nofault(&val, inst->object, inst->obj_type_size))
> > +                     goto out;
> > +             submit_trace_object(ip, parent_ip, (unsigned long)inst->object, val);
> > +             node = node->next;
> >       }
> >
> >  out:
> > @@ -198,12 +215,14 @@ 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, *val = NULL;
> >
> > -     struct ftrace_event_field *field = data->private_data;
> > -     void *obj = NULL;
> > -
> > -     memcpy(&obj, rec + field->offset, sizeof(obj));
> > -     set_trace_object(obj);
> > +     field = obj_data->field;
> > +     memcpy(&val, rec + field->offset, sizeof(val));
> > +     obj = val + obj_data->offset;
> > +     set_trace_object(obj, obj_data->type_size);
> >  }
> >
> >  static void
> > @@ -350,6 +369,22 @@ static void unregister_object_trigger(char *glob, struct event_trigger_ops *ops,
> >       }
> >  }
> >
> > +static const struct objtrace_fetch_type objtrace_fetch_types[] = {
> > +     {"u8", 1},
> > +     {"s8", 1},
> > +     {"x8", 1},
> > +     {"u16", 2},
> > +     {"s16", 2},
> > +     {"x16", 2},
> > +     {"u32", 4},
> > +     {"s32", 4},
> > +     {"x32", 4},
> > +     {"u64", 8},
> > +     {"s64", 8},
> > +     {"x64", 8},
> > +     {}
> > +};
> > +
> >  static int
> >  event_object_trigger_callback(struct event_command *cmd_ops,
> >                      struct trace_event_file *file,
> > @@ -357,13 +392,15 @@ event_object_trigger_callback(struct event_command *cmd_ops,
> >  {
> >       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;
> > +     long offset = 0;
> >       char *trigger = NULL;
> > -     char *arg;
> > +     char *arg, *type, *tr, *tr_end;
> >       char *number;
> > -     int ret;
> > +     int ret, i, type_size = 0;
> >
> >       ret = -EINVAL;
> >       if (!param)
> > @@ -386,6 +423,38 @@ event_object_trigger_callback(struct event_command *cmd_ops,
> >       arg = strsep(&trigger, ":");
> >       if (!arg)
> >               goto out;
> > +
> > +     tr = strchr(arg, '(');
> > +     /* now force to get the value of the val. */
> > +     if (!tr)
> > +             goto out;
> > +     tr_end = strchr(tr, ')');
> > +     if (!tr_end)
> > +             goto out;
> > +     *tr++ = '\0';
> > +     *tr_end = '\0';
> > +     ret = kstrtol(arg, 0, &offset);
> > +     if (ret)
> > +             goto out;
> > +     arg = tr;
> > +     ret = -EINVAL;
> > +     if (!trigger)
> > +             goto out;
> > +
> > +     type = strsep(&trigger, ":");
> > +     if (!type)
> > +             goto out;
> > +     for (i = 0; objtrace_fetch_types[i].name; i++) {
> > +             if (strcmp(objtrace_fetch_types[i].name, type) == 0) {
> > +                     type_size = objtrace_fetch_types[i].type_size;
> > +                     break;
> > +             }
> > +     }
> > +
> > +     if (type_size == 0)
> > +             goto out;
> > +
> > +
> >       call = file->event_call;
> >       field = trace_find_event_field(call, arg);
> >       if (!field)
> > @@ -394,19 +463,30 @@ event_object_trigger_callback(struct event_command *cmd_ops,
> >       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;
> > +     obj_data->offset = offset;
> > +     obj_data->type_size = type_size;
> > +
> >       trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
> > -     if (!trigger_data)
> > +     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 = field;
> > +     trigger_data->private_data = obj_data;
> >       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(obj_data);
> >               kfree(trigger_data);
> >               ret = 0;
> >               goto out;
> > @@ -461,6 +541,7 @@ event_object_trigger_callback(struct event_command *cmd_ops,
> >   out_free:
> >       if (cmd_ops->set_filter)
> >               cmd_ops->set_filter(NULL, trigger_data, NULL);
> > +     kfree(obj_data);
> >       kfree(trigger_data);
> >       goto out;
> >  }
> > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> > index 76ca560af693..c8c427c23127 100644
> > --- a/kernel/trace/trace_output.c
> > +++ b/kernel/trace/trace_output.c
> > @@ -1562,6 +1562,7 @@ static enum print_line_t trace_object_print(struct trace_iterator *iter, int fla
> >       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_printf(s, " value:0x%lx", field->value);
> >       trace_seq_putc(s, '\n');
> >
> >       return trace_handle_return(s);
> > @@ -1574,9 +1575,8 @@ static enum print_line_t trace_object_raw(struct trace_iterator *iter, int flags
> >
> >       trace_assign_type(field, iter->ent);
> >
> > -     trace_seq_printf(&iter->seq, "%lx %lx\n",
> > -                      field->ip,
> > -                      field->parent_ip);
> > +     trace_seq_printf(&iter->seq, "%lx %lx %lx %lx\n", field->ip,
> > +                     field->parent_ip, field->object, field->value);
> >
> >       return trace_handle_return(&iter->seq);
> >  }
> > --
> > 2.25.1
> >
>
>
> --
> Masami Hiramatsu <mhiramat@kernel.org>

Thanks,
---
JeffXie