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

From: Jeff Xie
Date: Fri Nov 26 2021 - 09:32:38 EST

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Hi Masami,

On Mon, Nov 22, 2021 at 1:15 AM Jeff Xie <xiehuan09@xxxxxxxxx> wrote:
>
> Hi Masami,
>
> On Fri, Nov 19, 2021 at 10:01 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> >
> > Hi Jeff,
> >
> > On Sat, 13 Nov 2021 20:06:30 +0800
> > Jeff Xie <xiehuan09@xxxxxxxxx> 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]

I have been thinking about this place for a long time, would it be
better if it like below?
objtrace:add:OBJ[,OFFS][:TYPE][:COUNT]

If the user does not specify the type, the default type will be u64.

> >
> > (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@xxxxxxxxx>
> > > ---
> > > 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@xxxxxxxxxx>
>
> Thanks,
> ---
> JeffXie

---
JeffXie

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