Re: [PATCH -tip v8 7/7] tracing: add kprobe-based event tracer

Masami Hiramatsu
2009-05-30T13:15:45Z

Steven Rostedt wrote:
>
>
> On Thu, 28 May 2009, Masami Hiramatsu wrote:
>
>> +#undef SHOW_FIELD
>> +#define SHOW_FIELD(type, item, name) \
>> + do { \
>> + ret = trace_seq_printf(s, "\tfield: " #type " %s;\t" \
>> + "offset:%u;tsize:%u;\n", name, \
>> + (unsigned)offsetof(typeof(field), item),\
>> + (unsigned)sizeof(type)); \
>> + if (!ret) \
>> + return 0; \
>> + } while (0)
>> +
>> +static int __probe_event_show_format(struct ftrace_event_call *event_call,
>> + struct trace_seq *s, const char *fmt,
>> + const char *arg)
>> +{
>> + struct kprobe_trace_entry field __attribute__((unused));
>
> You use kprobe_trace_entry for both kprobe and kretprobe.

Ah, right. I'll fix that.

Thank you for reviewing!

>
>> + int ret, i;
>> + char buf[MAX_ARGSTR_LEN + 1];
>> + struct trace_probe *tp = container_of(event_call,
>> + struct trace_probe, call);
>> +
>> + /* Show fields */
>> + for (i = 0; i < tp->nr_args; i++) {
>> + sprintf(buf, "arg%d", i);
>> + SHOW_FIELD(unsigned long, args[i], buf);
>> + }
>> + trace_seq_puts(s, "\n");
>> +
>> + /* Show aliases */
>> + for (i = 0; i < tp->nr_args; i++) {
>> + if (trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]))
>> + return 0;
>> + if (!trace_seq_printf(s, "\talias: %s;\toriginal: arg%d;\n",
>> + buf, i))
>> + return 0;
>> + }
>> + /* Show format */
>> + if (!trace_seq_printf(s, "\nprint fmt: \"%s", fmt))
>> + return 0;
>> +
>> + for (i = 0; i < tp->nr_args; i++)
>> + if (!trace_seq_puts(s, " 0x%lx"))
>> + return 0;
>> +
>> + if (!trace_seq_printf(s, "\", %s", arg))
>> + return 0;
>> +
>> + for (i = 0; i < tp->nr_args; i++)
>> + if (!trace_seq_printf(s, ", arg%d", i))
>> + return 0;
>> +
>> + return trace_seq_puts(s, "\n");
>> +}
>> +
>> +static int kprobe_event_show_format(struct ftrace_event_call *call,
>> + struct trace_seq *s)
>> +{
>> + struct kprobe_trace_entry field __attribute__((unused));
>> + int ret;
>> +
>> + SHOW_FIELD(unsigned long, ip, "ip");
>> + SHOW_FIELD(int, nargs, "nargs");
>> +
>> + return __probe_event_show_format(call, s, "%lx:", "ip");
>> +}
>> +
>> +static int kretprobe_event_show_format(struct ftrace_event_call *call,
>> + struct trace_seq *s)
>> +{
>> + struct kretprobe_trace_entry field __attribute__((unused));
>> + int ret;
>> +
>> + SHOW_FIELD(unsigned long, func, "func");
>> + SHOW_FIELD(unsigned long, ret_ip, "ret_ip");
>> + SHOW_FIELD(int, nargs, "nargs");
>> +
>> + return __probe_event_show_format(call, s, "%lx <- %lx:",
>> + "func, ret_ip");
>> +}
>
> Thus we end up with:
>
> format:
> field:unsigned short common_type; offset:0; size:2;
> field:unsigned char common_flags; offset:2; size:1;
> field:unsigned char common_preempt_count; offset:3;
> size:1;
> field:int common_pid; offset:4; size:4;
> field:int common_tgid; offset:8; size:4;
>
> field: unsigned long func; offset:16;tsize:8;
> field: unsigned long ret_ip; offset:24;tsize:8;
> field: int nargs; offset:32;tsize:4;
> field: unsigned long arg0; offset:32;tsize:8;
> field: unsigned long arg1; offset:40;tsize:8;
> field: unsigned long arg2; offset:48;tsize:8;
> field: unsigned long arg3; offset:56;tsize:8;
>
> Notice that nargs and arg0 are both at offest 32.
>
> -- Steve
>

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.