tracing/kprobes: Add argument name support

Add argument name assignment support and remove "alias" lines from format.
This allows user to assign unique name to each argument. For example,

$ echo p do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > kprobe_events

This assigns dfd, filename, flags, and mode to 1st - 4th arguments
respectively. Trace buffer shows those names too.

	<...>-1439  [000] 1200885.933147: do_sys_open+0x0/0xdf: dfd=ffffff9c filename=bfa898ac flags=8000 mode=0

This helps users to know what each value means.

Users can filter each events by these names too. Note that you can not
filter by argN anymore.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <20090910235337.22412.77383.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

2 files changed, 84 insertions, 90 deletions

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 8f882ebd1368..aaa6c1067c78 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -42,7 +42,8 @@ Synopsis of kprobe_events
   aN    : Fetch function argument. (N >= 0)(*)
   rv    : Fetch return value.(**)
   ra    : Fetch return address.(**)
-  +|-offs(FETCHARG) : fetch memory at FETCHARG +|- offs address.(***)
+  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
+  NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
 
   (*) aN may not correct on asmlinkaged functions and at the middle of
       function body.
@@ -62,12 +63,10 @@ enabled:
   You can enable/disable the probe by writing 1 or 0 on it.
 
 format:
-  This shows the format of this probe event. It also shows aliases of arguments
- which you specified to kprobe_events.
+  This shows the format of this probe event.
 
 filter:
-  You can write filtering rules of this event. And you can use both of aliase
- names and field names for describing filters.
+  You can write filtering rules of this event.
 
 id:
   This shows the id of this probe event.
@@ -85,10 +84,11 @@ Usage examples
 To add a probe as a new event, write a new definition to kprobe_events
 as below.
 
-  echo p:myprobe do_sys_open a0 a1 a2 a3 > /sys/kernel/debug/tracing/kprobe_events
+  echo p:myprobe do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > /sys/kernel/debug/tracing/kprobe_events
 
  This sets a kprobe on the top of do_sys_open() function with recording
-1st to 4th arguments as "myprobe" event.
+1st to 4th arguments as "myprobe" event. As this example shows, users can
+choose more familiar names for each arguments.
 
   echo r:myretprobe do_sys_open rv ra >> /sys/kernel/debug/tracing/kprobe_events
 
@@ -99,7 +99,7 @@ recording return value and return address as "myretprobe" event.
 
   cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format
 name: myprobe
-ID: 23
+ID: 75
 format:
         field:unsigned short common_type;       offset:0;       size:2;
         field:unsigned char common_flags;       offset:2;       size:1;
@@ -109,21 +109,15 @@ format:
 
         field: unsigned long ip;        offset:16;tsize:8;
         field: int nargs;       offset:24;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;
+        field: unsigned long dfd;       offset:32;tsize:8;
+        field: unsigned long filename;  offset:40;tsize:8;
+        field: unsigned long flags;     offset:48;tsize:8;
+        field: unsigned long mode;      offset:56;tsize:8;
 
-        alias: a0;      original: arg0;
-        alias: a1;      original: arg1;
-        alias: a2;      original: arg2;
-        alias: a3;      original: arg3;
+print fmt: "%lx: dfd=%lx filename=%lx flags=%lx mode=%lx", ip, REC->dfd, REC->filename, REC->flags, REC->mode
 
-print fmt: "%lx: 0x%lx 0x%lx 0x%lx 0x%lx", ip, arg0, arg1, arg2, arg3
 
-
- You can see that the event has 4 arguments and alias expressions
-corresponding to it.
+ You can see that the event has 4 arguments as in the expressions you specified.
 
   echo > /sys/kernel/debug/tracing/kprobe_events
 
@@ -135,12 +129,12 @@ corresponding to it.
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
-           <...>-1447  [001] 1038282.286875: do_sys_open+0x0/0xd6: 0x3 0x7fffd1ec4440 0x8000 0x0
-           <...>-1447  [001] 1038282.286878: sys_openat+0xc/0xe <- do_sys_open: 0xfffffffffffffffe 0xffffffff81367a3a
-           <...>-1447  [001] 1038282.286885: do_sys_open+0x0/0xd6: 0xffffff9c 0x40413c 0x8000 0x1b6
-           <...>-1447  [001] 1038282.286915: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
-           <...>-1447  [001] 1038282.286969: do_sys_open+0x0/0xd6: 0xffffff9c 0x4041c6 0x98800 0x10
-           <...>-1447  [001] 1038282.286976: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
+           <...>-1447  [001] 1038282.286875: do_sys_open+0x0/0xd6: dfd=3 filename=7fffd1ec4440 flags=8000 mode=0
+           <...>-1447  [001] 1038282.286878: sys_openat+0xc/0xe <- do_sys_open: rv=fffffffffffffffe ra=ffffffff81367a3a
+           <...>-1447  [001] 1038282.286885: do_sys_open+0x0/0xd6: dfd=ffffff9c filename=40413c flags=8000 mode=1b6
+           <...>-1447  [001] 1038282.286915: sys_open+0x1b/0x1d <- do_sys_open: rv=3 ra=ffffffff81367a3a
+           <...>-1447  [001] 1038282.286969: do_sys_open+0x0/0xd6: dfd=ffffff9c filename=4041c6 flags=98800 mode=10
+           <...>-1447  [001] 1038282.286976: sys_open+0x1b/0x1d <- do_sys_open: rv=3 ra=ffffffff81367a3a
 
 
  Each line shows when the kernel hits a probe, and <- SYMBOL means kernel
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 730e992d28da..44dad1aa95d3 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -176,9 +176,14 @@ static __kprobes void free_indirect_fetch_data(struct indirect_fetch_data *data)
 }
 
 /**
- * kprobe_trace_core
+ * Kprobe tracer core functions
  */
 
+struct probe_arg {
+        struct fetch_func       fetch;
+        const char              *name;
+};
+
 struct trace_probe {
         struct list_head        list;
         struct kretprobe        rp;     /* Use rp.kp for kprobe use */
@@ -187,12 +192,12 @@ struct trace_probe {
         struct ftrace_event_call        call;
         struct trace_event              event;
         unsigned int            nr_args;
-        struct fetch_func       args[];
+        struct probe_arg        args[];
 };
 
 #define SIZEOF_TRACE_PROBE(n)                   \
         (offsetof(struct trace_probe, args) +   \
-        (sizeof(struct fetch_func) * (n)))
+        (sizeof(struct probe_arg) * (n)))
 
 static int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs);
 static int kretprobe_trace_func(struct kretprobe_instance *ri,
@@ -301,15 +306,21 @@ error:
         return ERR_PTR(-ENOMEM);
 }
 
+static void free_probe_arg(struct probe_arg *arg)
+{
+        if (arg->fetch.func == fetch_symbol)
+                free_symbol_cache(arg->fetch.data);
+        else if (arg->fetch.func == fetch_indirect)
+                free_indirect_fetch_data(arg->fetch.data);
+        kfree(arg->name);
+}
+
 static void free_trace_probe(struct trace_probe *tp)
 {
         int i;
 
         for (i = 0; i < tp->nr_args; i++)
-                if (tp->args[i].func == fetch_symbol)
-                        free_symbol_cache(tp->args[i].data);
-                else if (tp->args[i].func == fetch_indirect)
-                        free_indirect_fetch_data(tp->args[i].data);
+                free_probe_arg(&tp->args[i]);
 
         kfree(tp->call.name);
         kfree(tp->symbol);
@@ -532,11 +543,13 @@ static int create_trace_probe(int argc, char **argv)
          *  %REG        : fetch register REG
          * Indirect memory fetch:
          *  +|-offs(ARG) : fetch memory at ARG +|- offs address.
+         * Alias name of args:
+         *  NAME=FETCHARG : set NAME as alias of FETCHARG.
          */
         struct trace_probe *tp;
         int i, ret = 0;
         int is_return = 0;
-        char *symbol = NULL, *event = NULL;
+        char *symbol = NULL, *event = NULL, *arg = NULL;
         unsigned long offset = 0;
         void *addr = NULL;
         char buf[MAX_EVENT_NAME_LEN];
@@ -596,12 +609,21 @@ static int create_trace_probe(int argc, char **argv)
         /* parse arguments */
         ret = 0;
         for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
-                if (strlen(argv[i]) > MAX_ARGSTR_LEN) {
-                        pr_info("Argument%d(%s) is too long.\n", i, argv[i]);
+                /* Parse argument name */
+                arg = strchr(argv[i], '=');
+                if (arg)
+                        *arg++ = '\0';
+                else
+                        arg = argv[i];
+                tp->args[i].name = kstrdup(argv[i], GFP_KERNEL);
+
+                /* Parse fetch argument */
+                if (strlen(arg) > MAX_ARGSTR_LEN) {
+                        pr_info("Argument%d(%s) is too long.\n", i, arg);
                         ret = -ENOSPC;
                         goto error;
                 }
-                ret = parse_probe_arg(argv[i], &tp->args[i], is_return);
+                ret = parse_probe_arg(arg, &tp->args[i].fetch, is_return);
                 if (ret)
                         goto error;
         }
@@ -664,12 +686,12 @@ static int probes_seq_show(struct seq_file *m, void *v)
                 seq_printf(m, " 0x%p", tp->rp.kp.addr);
 
         for (i = 0; i < tp->nr_args; i++) {
-                ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
+                ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i].fetch);
                 if (ret < 0) {
                         pr_warning("Argument%d decoding error(%d).\n", i, ret);
                         return ret;
                 }
-                seq_printf(m, " %s", buf);
+                seq_printf(m, " %s=%s", tp->args[i].name, buf);
         }
         seq_printf(m, "\n");
         return 0;
@@ -824,7 +846,7 @@ static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
         entry->nargs = tp->nr_args;
         entry->ip = (unsigned long)kp->addr;
         for (i = 0; i < tp->nr_args; i++)
-                entry->args[i] = call_fetch(&tp->args[i], regs);
+                entry->args[i] = call_fetch(&tp->args[i].fetch, regs);
 
         if (!filter_current_check_discard(buffer, call, entry, event))
                 trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -858,7 +880,7 @@ static __kprobes int kretprobe_trace_func(struct kretprobe_instance *ri,
         entry->func = (unsigned long)tp->rp.kp.addr;
         entry->ret_ip = (unsigned long)ri->ret_addr;
         for (i = 0; i < tp->nr_args; i++)
-                entry->args[i] = call_fetch(&tp->args[i], regs);
+                entry->args[i] = call_fetch(&tp->args[i].fetch, regs);
 
         if (!filter_current_check_discard(buffer, call, entry, event))
                 trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -872,9 +894,13 @@ print_kprobe_event(struct trace_iterator *iter, int flags)
 {
         struct kprobe_trace_entry *field;
         struct trace_seq *s = &iter->seq;
+        struct trace_event *event;
+        struct trace_probe *tp;
         int i;
 
         field = (struct kprobe_trace_entry *)iter->ent;
+        event = ftrace_find_event(field->ent.type);
+        tp = container_of(event, struct trace_probe, event);
 
         if (!seq_print_ip_sym(s, field->ip, flags | TRACE_ITER_SYM_OFFSET))
                 goto partial;
@@ -883,7 +909,8 @@ print_kprobe_event(struct trace_iterator *iter, int flags)
                 goto partial;
 
         for (i = 0; i < field->nargs; i++)
-                if (!trace_seq_printf(s, " 0x%lx", field->args[i]))
+                if (!trace_seq_printf(s, " %s=%lx",
+                                      tp->args[i].name, field->args[i]))
                         goto partial;
 
         if (!trace_seq_puts(s, "\n"))
@@ -899,9 +926,13 @@ print_kretprobe_event(struct trace_iterator *iter, int flags)
 {
         struct kretprobe_trace_entry *field;
         struct trace_seq *s = &iter->seq;
+        struct trace_event *event;
+        struct trace_probe *tp;
         int i;
 
         field = (struct kretprobe_trace_entry *)iter->ent;
+        event = ftrace_find_event(field->ent.type);
+        tp = container_of(event, struct trace_probe, event);
 
         if (!seq_print_ip_sym(s, field->ret_ip, flags | TRACE_ITER_SYM_OFFSET))
                 goto partial;
@@ -916,7 +947,8 @@ print_kretprobe_event(struct trace_iterator *iter, int flags)
                 goto partial;
 
         for (i = 0; i < field->nargs; i++)
-                if (!trace_seq_printf(s, " 0x%lx", field->args[i]))
+                if (!trace_seq_printf(s, " %s=%lx",
+                                      tp->args[i].name, field->args[i]))
                         goto partial;
 
         if (!trace_seq_puts(s, "\n"))
@@ -972,7 +1004,6 @@ static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
 {
         int ret, i;
         struct kprobe_trace_entry field;
-        char buf[MAX_ARGSTR_LEN + 1];
         struct trace_probe *tp = (struct trace_probe *)event_call->data;
 
         ret = trace_define_common_fields(event_call);
@@ -981,16 +1012,9 @@ static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
 
         DEFINE_FIELD(unsigned long, ip, "ip", 0);
         DEFINE_FIELD(int, nargs, "nargs", 1);
-        for (i = 0; i < tp->nr_args; i++) {
-                /* Set argN as a field */
-                sprintf(buf, "arg%d", i);
-                DEFINE_FIELD(unsigned long, args[i], buf, 0);
-                /* Set argument string as an alias field */
-                ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
-                if (ret < 0)
-                        return ret;
-                DEFINE_FIELD(unsigned long, args[i], buf, 0);
-        }
+        /* Set argument names as fields */
+        for (i = 0; i < tp->nr_args; i++)
+                DEFINE_FIELD(unsigned long, args[i], tp->args[i].name, 0);
         return 0;
 }
 
@@ -998,7 +1022,6 @@ static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
 {
         int ret, i;
         struct kretprobe_trace_entry field;
-        char buf[MAX_ARGSTR_LEN + 1];
         struct trace_probe *tp = (struct trace_probe *)event_call->data;
 
         ret = trace_define_common_fields(event_call);
@@ -1008,16 +1031,9 @@ static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
         DEFINE_FIELD(unsigned long, func, "func", 0);
         DEFINE_FIELD(unsigned long, ret_ip, "ret_ip", 0);
         DEFINE_FIELD(int, nargs, "nargs", 1);
-        for (i = 0; i < tp->nr_args; i++) {
-                /* Set argN as a field */
-                sprintf(buf, "arg%d", i);
-                DEFINE_FIELD(unsigned long, args[i], buf, 0);
-                /* Set argument string as an alias field */
-                ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
-                if (ret < 0)
-                        return ret;
-                DEFINE_FIELD(unsigned long, args[i], buf, 0);
-        }
+        /* Set argument names as fields */
+        for (i = 0; i < tp->nr_args; i++)
+                DEFINE_FIELD(unsigned long, args[i], tp->args[i].name, 0);
         return 0;
 }
 
@@ -1025,31 +1041,21 @@ static int __probe_event_show_format(struct trace_seq *s,
                                      struct trace_probe *tp, const char *fmt,
                                      const char *arg)
 {
-        int i, ret;
-        char buf[MAX_ARGSTR_LEN + 1];
+        int i;
 
-        /* Show aliases */
-        for (i = 0; i < tp->nr_args; i++) {
-                ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
-                if (ret < 0)
-                        return ret;
-                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"))
+                if (!trace_seq_printf(s, " %s=%%lx", tp->args[i].name))
                         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))
+                if (!trace_seq_printf(s, ", REC->%s", tp->args[i].name))
                         return 0;
 
         return trace_seq_puts(s, "\n");
@@ -1071,17 +1077,14 @@ static int kprobe_event_show_format(struct ftrace_event_call *call,
 {
         struct kprobe_trace_entry field __attribute__((unused));
         int ret, i;
-        char buf[8];
         struct trace_probe *tp = (struct trace_probe *)call->data;
 
         SHOW_FIELD(unsigned long, ip, "ip");
         SHOW_FIELD(int, nargs, "nargs");
 
         /* Show fields */
-        for (i = 0; i < tp->nr_args; i++) {
-                sprintf(buf, "arg%d", i);
-                SHOW_FIELD(unsigned long, args[i], buf);
-        }
+        for (i = 0; i < tp->nr_args; i++)
+                SHOW_FIELD(unsigned long, args[i], tp->args[i].name);
         trace_seq_puts(s, "\n");
 
         return __probe_event_show_format(s, tp, "%lx:", "ip");
@@ -1092,7 +1095,6 @@ static int kretprobe_event_show_format(struct ftrace_event_call *call,
 {
         struct kretprobe_trace_entry field __attribute__((unused));
         int ret, i;
-        char buf[8];
         struct trace_probe *tp = (struct trace_probe *)call->data;
 
         SHOW_FIELD(unsigned long, func, "func");
@@ -1100,10 +1102,8 @@ static int kretprobe_event_show_format(struct ftrace_event_call *call,
         SHOW_FIELD(int, nargs, "nargs");
 
         /* Show fields */
-        for (i = 0; i < tp->nr_args; i++) {
-                sprintf(buf, "arg%d", i);
-                SHOW_FIELD(unsigned long, args[i], buf);
-        }
+        for (i = 0; i < tp->nr_args; i++)
+                SHOW_FIELD(unsigned long, args[i], tp->args[i].name);
         trace_seq_puts(s, "\n");
 
         return __probe_event_show_format(s, tp, "%lx <- %lx:",
@@ -1140,7 +1140,7 @@ static __kprobes int kprobe_profile_func(struct kprobe *kp,
                 entry->nargs = tp->nr_args;
                 entry->ip = (unsigned long)kp->addr;
                 for (i = 0; i < tp->nr_args; i++)
-                        entry->args[i] = call_fetch(&tp->args[i], regs);
+                        entry->args[i] = call_fetch(&tp->args[i].fetch, regs);
                 perf_tpcounter_event(call->id, entry->ip, 1, entry, size);
         } while (0);
         return 0;
@@ -1175,7 +1175,7 @@ static __kprobes int kretprobe_profile_func(struct kretprobe_instance *ri,
                 entry->func = (unsigned long)tp->rp.kp.addr;
                 entry->ret_ip = (unsigned long)ri->ret_addr;
                 for (i = 0; i < tp->nr_args; i++)
-                        entry->args[i] = call_fetch(&tp->args[i], regs);
+                        entry->args[i] = call_fetch(&tp->args[i].fetch, regs);
                 perf_tpcounter_event(call->id, entry->ret_ip, 1, entry, size);
         } while (0);
         return 0;