Messages in this thread Patch in this message | | | Date | Wed, 19 Jan 2022 00:13:43 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v7 2/4] trace/objtrace: get the value of the object |
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Hi Jeff,
On Thu, 13 Jan 2022 09:38:33 +0800 Jeff Xie <xiehuan09@gmail.com> wrote:
> Using objtrace trigger to get the value of the object which from the kernel > function parameter. > > Syntax: > objtrace:add:obj[,offset][:type][:count][if <filter>] > > Usage: > # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events > # gdb vmlinux > (gdb) p &(((struct bio *)0)->bi_iter.bi_size) > $1 = (unsigned int *) 0x28 > # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ > p_bio_add_page_0/trigger > # cat /test.txt > > Signed-off-by: Jeff Xie <xiehuan09@gmail.com> > --- > kernel/trace/trace.c | 2 +- > kernel/trace/trace_entries.h | 5 +- > kernel/trace/trace_object.c | 190 +++++++++++++++++++++++++++++------ > kernel/trace/trace_output.c | 6 +- > 4 files changed, 169 insertions(+), 34 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 0b627963e343..d5332ece4c67 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -5591,7 +5591,7 @@ static const char readme_msg[] = > "\t disable_hist:<system>:<event>\n" > #endif > #ifdef CONFIG_TRACE_OBJECT > - "\t objtrace:add:obj[:count][if <filter>]\n" > + "\t objtrace:add:obj[,offset][:type][:count][if <filter>]\n" > #endif > #ifdef CONFIG_STACKTRACE > "\t\t stacktrace\n" > 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 4af1c117cbfa..774a9dff4d0a 100644 > --- a/kernel/trace/trace_object.c > +++ b/kernel/trace/trace_object.c > @@ -11,7 +11,6 @@ > #define MAX_TRACED_OBJECT 5 > 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); > @@ -19,8 +18,22 @@ static int init_trace_object(void); > > static struct object_instance { > void *obj; > + int obj_type_size; > } traced_obj[MAX_TRACED_OBJECT]; > > +/* objtrace private data */ > +struct objtrace_trigger_data { > + struct ftrace_event_field *field; > + int offset; > + int obj_type_size; > +}; > + > +/* get the type size for the special object */ > +struct objtrace_fetch_type { > + char *name; > + int type_size; > +}; > + > static bool object_exist(void *obj) > { > int i, max; > @@ -39,7 +52,7 @@ static bool object_empty(void) > return !atomic_read(&num_traced_obj); > } > > -static void set_trace_object(void *obj) > +static void set_trace_object(void *obj, int obj_type_size) > { > unsigned long flags; > > @@ -59,6 +72,7 @@ static void set_trace_object(void *obj) > goto out; > } > traced_obj[atomic_read(&num_traced_obj)].obj = obj; > + traced_obj[atomic_read(&num_traced_obj)].obj_type_size = obj_type_size; > /* make sure the num_traced_obj update always appears after traced_obj update */ > smp_wmb(); > atomic_inc(&num_traced_obj); > @@ -67,7 +81,7 @@ static void set_trace_object(void *obj) > } > > 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; > @@ -84,18 +98,66 @@ 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); > } > > +static inline long get_object_value(unsigned long *val, void *obj, int type_size) > +{ > + long ret = 0; > + > + switch (type_size) { > + case 1: { > + u8 tmp; > + > + ret = copy_from_kernel_nofault(&tmp, obj, sizeof(tmp)); > + if (ret) > + goto out; > + *val = tmp; > + break; > + } > + case 2: { > + u16 tmp; > + > + ret = copy_from_kernel_nofault(&tmp, obj, sizeof(tmp)); > + if (ret) > + goto out; > + *val = tmp; > + break; > + } > + case 4: { > + u32 tmp; > + > + ret = copy_from_kernel_nofault(&tmp, obj, sizeof(tmp)); > + if (ret) > + goto out; > + *val = tmp; > + break; > + } > + case 8: { > + u64 tmp; > + > + ret = copy_from_kernel_nofault(&tmp, obj, sizeof(tmp)); > + if (ret) > + goto out; > + *val = tmp; > + break; > + }
Can't you move the copy_from_kernel_nofault() outside of the switch-case? e.g.
char tmp[sizeof(u64)];
ret = copy_from_kernel_nofault(tmp, obj, sizeof(tmp)); if (ret) return ret;
switch (type_size) { case 1: *val = (unsigned long)*(u8 *)tmp; break; ... } return 0;
Thank you,
> + default: > + return -EINVAL; > + } > +out: > + return ret; > +} > + > 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; > - int bit, n; > + unsigned long val = 0; > + int bit, n, max; > > bit = ftrace_test_recursion_trylock(ip, parent_ip); > if (bit < 0) > @@ -104,11 +166,12 @@ 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);
This actually filtered the (function call) event which is related to the object.
> - /* The parameters of a function may match multiple objects */ > + max = atomic_read(&num_traced_obj); > + smp_rmb(); > + for (n = 0; n < max; n++) { > + if (get_object_value(&val, traced_obj[n].obj, traced_obj[n].obj_type_size)) > + goto out; > + submit_trace_object(ip, parent_ip, (unsigned long)traced_obj[n].obj, val);
But you lost the filter here. This is because you saves the "object + offset" address below;
> } > out: > ftrace_test_recursion_unlock(bit); > @@ -124,12 +187,15 @@ 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)); > + /* get the final object */ > + obj = val + obj_data->offset;
Here, you saved the object address including offset. This means you can not filter the actual function related to the object.
Please recover the filter.
> + set_trace_object(obj, obj_data->obj_type_size);
You can save the offset with type-size and object address itself.
Thank you,
> } > > static void > @@ -140,8 +206,10 @@ trace_object_trigger_free(struct event_trigger_ops *ops, > return; > > data->ref--; > - if (!data->ref) > + if (!data->ref) { > + kfree(data->private_data); > trigger_data_free(data); > + } > } > > static void > @@ -276,6 +344,22 @@ 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, > @@ -283,19 +367,22 @@ 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; > - char *trigger = NULL; > - char *arg; > - char *number; > - int ret; > + char *type, *tr, *obj, *tmp, *trigger = NULL; > + char *number, *objtrace_cmd; > + int ret, i, def_type_size, obj_type_size = 0; > + long offset = 0; > > ret = -EINVAL; > if (!param) > goto out; > > - /* separate the trigger from the filter (c:a:n [if filter]) */ > + /* > + * separate the trigger from the filter: > + * objtrace:add:OBJ[,OFFS][:TYPE][:COUNT] [if filter] > + */ > trigger = strsep(¶m, " \t"); > if (!trigger) > goto out; > @@ -309,33 +396,79 @@ event_object_trigger_callback(struct event_command *cmd_ops, > if (!objtrace_cmd || strcmp(objtrace_cmd, "add")) > goto out; > > - arg = strsep(&trigger, ":"); > - if (!arg) > + obj = strsep(&trigger, ":"); > + if (!obj) > goto out; > + > + tr = strchr(obj, ','); > + if (!tr) > + offset = 0; > + else { > + *tr++ = '\0'; > + ret = kstrtol(tr, 0, &offset); > + if (ret) > + goto out; > + } > + > + ret = -EINVAL; > call = file->event_call; > - field = trace_find_event_field(call, arg); > + field = trace_find_event_field(call, obj); > if (!field) > goto out; > > if (field->size != sizeof(void *)) > goto out; > + def_type_size = sizeof(void *); > + if (!trigger) { > + obj_type_size = def_type_size; > + goto skip_get_type; > + } > > + tmp = trigger; > + type = strsep(&trigger, ":"); > + if (!type) > + obj_type_size = def_type_size; > + else if (isdigit(type[0])) { > + obj_type_size = def_type_size; > + trigger = tmp; > + } else { > + for (i = 0; objtrace_fetch_types[i].name; i++) { > + if (strcmp(objtrace_fetch_types[i].name, type) == 0) { > + obj_type_size = objtrace_fetch_types[i].type_size; > + break; > + } > + } > + } > + if (!obj_type_size) > + goto out; > +skip_get_type: > 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->obj_type_size = obj_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; > @@ -390,6 +523,7 @@ 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 d747aed27104..12a971927d8c 100644 > --- a/kernel/trace/trace_output.c > +++ b/kernel/trace/trace_output.c > @@ -1553,6 +1553,7 @@ 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); > @@ -1565,9 +1566,8 @@ 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>
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