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Date: Fri, 19 Nov 2021 23:01:18 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Jeff Xie <xiehuan09@...il.com>
Cc: rostedt@...dmis.org, mhiramat@...nel.org, mingo@...hat.com,
zanussi@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH v5 2/4] trace/objtrace: get the value of the object
Hi Jeff,
On Sat, 13 Nov 2021 20:06:30 +0800
Jeff Xie <xiehuan09@...il.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,
> Signed-off-by: Jeff Xie <xiehuan09@...il.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@...nel.org>
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