perf probe: Show accessible local variables

Add -V (--vars) option for listing accessible local variables at given probe
point. This will help finding which local variables are available for event
arguments.

e.g.)
 # perf probe -V call_timer_fn:23
 Available variables at call_timer_fn:23
         @<run_timer_softirq+345>
                 function_type*  fn
                 int     preempt_count
                 long unsigned int       data
                 struct list_head        work_list
                 struct list_head*       head
                 struct timer_list*      timer
                 struct tvec_base*       base

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20101021101323.3542.40282.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

6 files changed, 480 insertions, 105 deletions

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 27d52dae5a43..72f5d9e21432 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -17,6 +17,8 @@ or
 'perf probe' --list
 or
 'perf probe' --line='FUNC[:RLN[+NUM|:RLN2]]|SRC:ALN[+NUM|:ALN2]'
+or
+'perf probe' --vars='PROBEPOINT'
 
 DESCRIPTION
 -----------
@@ -57,6 +59,11 @@ OPTIONS
         Show source code lines which can be probed. This needs an argument
         which specifies a range of the source code. (see LINE SYNTAX for detail)
 
+-V::
+--vars=::
+        Show available local variables at given probe point. The argument
+        syntax is same as PROBE SYNTAX, but NO ARGs.
+
 -f::
 --force::
         Forcibly add events with existing name.
diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 199d5e19554f..91bb6cf4e025 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -50,6 +50,8 @@ static struct {
         bool list_events;
         bool force_add;
         bool show_lines;
+        bool show_vars;
+        bool mod_events;
         int nevents;
         struct perf_probe_event events[MAX_PROBES];
         struct strlist *dellist;
@@ -57,7 +59,6 @@ static struct {
         int max_probe_points;
 } params;
 
-
 /* Parse an event definition. Note that any error must die. */
 static int parse_probe_event(const char *str)
 {
@@ -92,6 +93,7 @@ static int parse_probe_event_argv(int argc, const char **argv)
         len = 0;
         for (i = 0; i < argc; i++)
                 len += sprintf(&buf[len], "%s ", argv[i]);
+        params.mod_events = true;
         ret = parse_probe_event(buf);
         free(buf);
         return ret;
@@ -100,9 +102,10 @@ static int parse_probe_event_argv(int argc, const char **argv)
 static int opt_add_probe_event(const struct option *opt __used,
                               const char *str, int unset __used)
 {
-        if (str)
+        if (str) {
+                params.mod_events = true;
                 return parse_probe_event(str);
-        else
+        } else
                 return 0;
 }
 
@@ -110,6 +113,7 @@ static int opt_del_probe_event(const struct option *opt __used,
                                const char *str, int unset __used)
 {
         if (str) {
+                params.mod_events = true;
                 if (!params.dellist)
                         params.dellist = strlist__new(true, NULL);
                 strlist__add(params.dellist, str);
@@ -130,6 +134,25 @@ static int opt_show_lines(const struct option *opt __used,
 
         return ret;
 }
+
+static int opt_show_vars(const struct option *opt __used,
+                         const char *str, int unset __used)
+{
+        struct perf_probe_event *pev = &params.events[params.nevents];
+        int ret;
+
+        if (!str)
+                return 0;
+
+        ret = parse_probe_event(str);
+        if (!ret && pev->nargs != 0) {
+                pr_err("  Error: '--vars' doesn't accept arguments.\n");
+                return -EINVAL;
+        }
+        params.show_vars = true;
+
+        return ret;
+}
 #endif
 
 static const char * const probe_usage[] = {
@@ -139,6 +162,7 @@ static const char * const probe_usage[] = {
         "perf probe --list",
 #ifdef DWARF_SUPPORT
         "perf probe --line 'LINEDESC'",
+        "perf probe --vars 'PROBEPOINT'",
 #endif
         NULL
 };
@@ -180,6 +204,9 @@ static const struct option options[] = {
         OPT_CALLBACK('L', "line", NULL,
                      "FUNC[:RLN[+NUM|-RLN2]]|SRC:ALN[+NUM|-ALN2]",
                      "Show source code lines.", opt_show_lines),
+        OPT_CALLBACK('V', "vars", NULL,
+                     "FUNC[@SRC][+OFF|%return|:RL|;PT]|SRC:AL|SRC;PT",
+                     "Show accessible variables on PROBEDEF", opt_show_vars),
         OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name,
                    "file", "vmlinux pathname"),
         OPT_STRING('s', "source", &symbol_conf.source_prefix,
@@ -217,7 +244,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                 usage_with_options(probe_usage, options);
 
         if (params.list_events) {
-                if (params.nevents != 0 || params.dellist) {
+                if (params.mod_events) {
                         pr_err("  Error: Don't use --list with --add/--del.\n");
                         usage_with_options(probe_usage, options);
                 }
@@ -225,6 +252,10 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                         pr_err("  Error: Don't use --list with --line.\n");
                         usage_with_options(probe_usage, options);
                 }
+                if (params.show_vars) {
+                        pr_err(" Error: Don't use --list with --vars.\n");
+                        usage_with_options(probe_usage, options);
+                }
                 ret = show_perf_probe_events();
                 if (ret < 0)
                         pr_err("  Error: Failed to show event list. (%d)\n",
@@ -234,9 +265,13 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
 
 #ifdef DWARF_SUPPORT
         if (params.show_lines) {
-                if (params.nevents != 0 || params.dellist) {
-                        pr_warning("  Error: Don't use --line with"
-                                   " --add/--del.\n");
+                if (params.mod_events) {
+                        pr_err("  Error: Don't use --line with"
+                               " --add/--del.\n");
+                        usage_with_options(probe_usage, options);
+                }
+                if (params.show_vars) {
+                        pr_err(" Error: Don't use --line with --vars.\n");
                         usage_with_options(probe_usage, options);
                 }
 
@@ -245,6 +280,18 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                         pr_err("  Error: Failed to show lines. (%d)\n", ret);
                 return ret;
         }
+        if (params.show_vars) {
+                if (params.mod_events) {
+                        pr_err("  Error: Don't use --vars with"
+                               " --add/--del.\n");
+                        usage_with_options(probe_usage, options);
+                }
+                ret = show_available_vars(params.events, params.nevents,
+                                          params.max_probe_points);
+                if (ret < 0)
+                        pr_err("  Error: Failed to show vars. (%d)\n", ret);
+                return ret;
+        }
 #endif
 
         if (params.dellist) {
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index fcc16e4349df..288ebe8279d2 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -378,6 +378,72 @@ end:
         return ret;
 }
 
+static int show_available_vars_at(int fd, struct perf_probe_event *pev,
+                                  int max_vls)
+{
+        char *buf;
+        int ret, i;
+        struct str_node *node;
+        struct variable_list *vls = NULL, *vl;
+
+        buf = synthesize_perf_probe_point(&pev->point);
+        if (!buf)
+                return -EINVAL;
+        pr_debug("Searching variables at %s\n", buf);
+
+        ret = find_available_vars_at(fd, pev, &vls, max_vls);
+        if (ret > 0) {
+                /* Some variables were found */
+                fprintf(stdout, "Available variables at %s\n", buf);
+                for (i = 0; i < ret; i++) {
+                        vl = &vls[i];
+                        /*
+                         * A probe point might be converted to
+                         * several trace points.
+                         */
+                        fprintf(stdout, "\t@<%s+%lu>\n", vl->point.symbol,
+                                vl->point.offset);
+                        free(vl->point.symbol);
+                        if (vl->vars) {
+                                strlist__for_each(node, vl->vars)
+                                        fprintf(stdout, "\t\t%s\n", node->s);
+                                strlist__delete(vl->vars);
+                        } else
+                                fprintf(stdout, "(No variables)\n");
+                }
+                free(vls);
+        } else
+                pr_err("Failed to find variables at %s (%d)\n", buf, ret);
+
+        free(buf);
+        return ret;
+}
+
+/* Show available variables on given probe point */
+int show_available_vars(struct perf_probe_event *pevs, int npevs,
+                        int max_vls)
+{
+        int i, fd, ret = 0;
+
+        ret = init_vmlinux();
+        if (ret < 0)
+                return ret;
+
+        fd = open_vmlinux();
+        if (fd < 0) {
+                pr_warning("Failed to open debuginfo file.\n");
+                return fd;
+        }
+
+        setup_pager();
+
+        for (i = 0; i < npevs && ret >= 0; i++)
+                ret = show_available_vars_at(fd, &pevs[i], max_vls);
+
+        close(fd);
+        return ret;
+}
+
 #else   /* !DWARF_SUPPORT */
 
 static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,
@@ -409,6 +475,12 @@ int show_line_range(struct line_range *lr __unused)
         return -ENOSYS;
 }
 
+int show_available_vars(struct perf_probe_event *pevs __unused,
+                        int npevs __unused, int max_probe_points __unused)
+{
+        pr_warning("Debuginfo-analysis is not supported.\n");
+        return -ENOSYS;
+}
 #endif
 
 int parse_line_range_desc(const char *arg, struct line_range *lr)
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 5af39243a25b..727a7fe81a02 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -90,6 +90,12 @@ struct line_range {
         struct list_head        line_list;      /* Visible lines */
 };
 
+/* List of variables */
+struct variable_list {
+        struct probe_trace_point        point;  /* Actual probepoint */
+        struct strlist                  *vars;  /* Available variables */
+};
+
 /* Command string to events */
 extern int parse_perf_probe_command(const char *cmd,
                                     struct perf_probe_event *pev);
@@ -115,6 +121,8 @@ extern int add_perf_probe_events(struct perf_probe_event *pevs, int npevs,
 extern int del_perf_probe_events(struct strlist *dellist);
 extern int show_perf_probe_events(void);
 extern int show_line_range(struct line_range *lr);
+extern int show_available_vars(struct perf_probe_event *pevs, int npevs,
+                               int max_probe_points);
 
 
 /* Maximum index number of event-name postfix */
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index c6fe80ebb262..986027fa495f 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -172,8 +172,8 @@ static Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
                 return NULL;
 }
 
-/* Get type die, but skip qualifiers and typedef */
-static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+/* Get a type die, but skip qualifiers */
+static Dwarf_Die *__die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
 {
         int tag;
 
@@ -185,8 +185,17 @@ static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
         } while (tag == DW_TAG_const_type ||
                  tag == DW_TAG_restrict_type ||
                  tag == DW_TAG_volatile_type ||
-                 tag == DW_TAG_shared_type ||
-                 tag == DW_TAG_typedef);
+                 tag == DW_TAG_shared_type);
+
+        return vr_die;
+}
+
+/* Get a type die, but skip qualifiers and typedef */
+static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+{
+        do {
+                vr_die = __die_get_real_type(vr_die, die_mem);
+        } while (vr_die && dwarf_tag(vr_die) == DW_TAG_typedef);
 
         return vr_die;
 }
@@ -380,6 +389,60 @@ static Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
                               die_mem);
 }
 
+/* Get the name of given variable DIE */
+static int die_get_typename(Dwarf_Die *vr_die, char *buf, int len)
+{
+        Dwarf_Die type;
+        int tag, ret, ret2;
+        const char *tmp = "";
+
+        if (__die_get_real_type(vr_die, &type) == NULL)
+                return -ENOENT;
+
+        tag = dwarf_tag(&type);
+        if (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)
+                tmp = "*";
+        else if (tag == DW_TAG_subroutine_type) {
+                /* Function pointer */
+                ret = snprintf(buf, len, "(function_type)");
+                return (ret >= len) ? -E2BIG : ret;
+        } else {
+                if (!dwarf_diename(&type))
+                        return -ENOENT;
+                if (tag == DW_TAG_union_type)
+                        tmp = "union ";
+                else if (tag == DW_TAG_structure_type)
+                        tmp = "struct ";
+                /* Write a base name */
+                ret = snprintf(buf, len, "%s%s", tmp, dwarf_diename(&type));
+                return (ret >= len) ? -E2BIG : ret;
+        }
+        ret = die_get_typename(&type, buf, len);
+        if (ret > 0) {
+                ret2 = snprintf(buf + ret, len - ret, "%s", tmp);
+                ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
+        }
+        return ret;
+}
+
+/* Get the name and type of given variable DIE, stored as "type\tname" */
+static int die_get_varname(Dwarf_Die *vr_die, char *buf, int len)
+{
+        int ret, ret2;
+
+        ret = die_get_typename(vr_die, buf, len);
+        if (ret < 0) {
+                pr_debug("Failed to get type, make it unknown.\n");
+                ret = snprintf(buf, len, "(unknown_type)");
+        }
+        if (ret > 0) {
+                ret2 = snprintf(buf + ret, len - ret, "\t%s",
+                                dwarf_diename(vr_die));
+                ret = (ret2 >= len - ret) ? -E2BIG : ret2 + ret;
+        }
+        return ret;
+}
+
 /*
  * Probe finder related functions
  */
@@ -393,8 +456,13 @@ static struct probe_trace_arg_ref *alloc_trace_arg_ref(long offs)
         return ref;
 }
 
-/* Show a location */
-static int convert_variable_location(Dwarf_Die *vr_die, struct probe_finder *pf)
+/*
+ * Convert a location into trace_arg.
+ * If tvar == NULL, this just checks variable can be converted.
+ */
+static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
+                                     Dwarf_Op *fb_ops,
+                                     struct probe_trace_arg *tvar)
 {
         Dwarf_Attribute attr;
         Dwarf_Op *op;
@@ -403,7 +471,6 @@ static int convert_variable_location(Dwarf_Die *vr_die, struct probe_finder *pf)
         Dwarf_Word offs = 0;
         bool ref = false;
         const char *regs;
-        struct probe_trace_arg *tvar = pf->tvar;
         int ret;
 
         if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL)
@@ -411,16 +478,16 @@ static int convert_variable_location(Dwarf_Die *vr_die, struct probe_finder *pf)
 
         /* TODO: handle more than 1 exprs */
         if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL ||
-            dwarf_getlocation_addr(&attr, pf->addr, &op, &nops, 1) <= 0 ||
+            dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0 ||
             nops == 0) {
                 /* TODO: Support const_value */
-                pr_err("Failed to find the location of %s at this address.\n"
-                       " Perhaps, it has been optimized out.\n", pf->pvar->var);
                 return -ENOENT;
         }
 
         if (op->atom == DW_OP_addr) {
 static_var:
+                if (!tvar)
+                        return 0;
                 /* Static variables on memory (not stack), make @varname */
                 ret = strlen(dwarf_diename(vr_die));
                 tvar->value = zalloc(ret + 2);
@@ -435,14 +502,11 @@ static_var:
 
         /* If this is based on frame buffer, set the offset */
         if (op->atom == DW_OP_fbreg) {
-                if (pf->fb_ops == NULL) {
-                        pr_warning("The attribute of frame base is not "
-                                   "supported.\n");
+                if (fb_ops == NULL)
                         return -ENOTSUP;
-                }
                 ref = true;
                 offs = op->number;
-                op = &pf->fb_ops[0];
+                op = &fb_ops[0];
         }
 
         if (op->atom >= DW_OP_breg0 && op->atom <= DW_OP_breg31) {
@@ -458,13 +522,18 @@ static_var:
         } else if (op->atom == DW_OP_regx) {
                 regn = op->number;
         } else {
-                pr_warning("DW_OP %x is not supported.\n", op->atom);
+                pr_debug("DW_OP %x is not supported.\n", op->atom);
                 return -ENOTSUP;
         }
 
+        if (!tvar)
+                return 0;
+
         regs = get_arch_regstr(regn);
         if (!regs) {
-                pr_warning("Mapping for DWARF register number %u missing on this architecture.", regn);
+                /* This should be a bug in DWARF or this tool */
+                pr_warning("Mapping for DWARF register number %u "
+                           "missing on this architecture.", regn);
                 return -ERANGE;
         }
 
@@ -689,8 +758,14 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
         pr_debug("Converting variable %s into trace event.\n",
                  dwarf_diename(vr_die));
 
-        ret = convert_variable_location(vr_die, pf);
-        if (ret == 0 && pf->pvar->field) {
+        ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
+                                        pf->tvar);
+        if (ret == -ENOENT)
+                pr_err("Failed to find the location of %s at this address.\n"
+                       " Perhaps, it has been optimized out.\n", pf->pvar->var);
+        else if (ret == -ENOTSUP)
+                pr_err("Sorry, we don't support this variable location yet.\n");
+        else if (pf->pvar->field) {
                 ret = convert_variable_fields(vr_die, pf->pvar->var,
                                               pf->pvar->field, &pf->tvar->ref,
                                               &die_mem);
@@ -772,34 +847,12 @@ found:
         return ret;
 }
 
-/* Show a probe point to output buffer */
-static int convert_probe_point(Dwarf_Die *sp_die, struct probe_finder *pf)
+/* Convert subprogram DIE to trace point */
+static int convert_to_trace_point(Dwarf_Die *sp_die, Dwarf_Addr paddr,
+                                  bool retprobe, struct probe_trace_point *tp)
 {
-        struct probe_trace_event *tev;
         Dwarf_Addr eaddr;
-        Dwarf_Die die_mem;
         const char *name;
-        int ret, i;
-        Dwarf_Attribute fb_attr;
-        size_t nops;
-
-        if (pf->ntevs == pf->max_tevs) {
-                pr_warning("Too many( > %d) probe point found.\n",
-                           pf->max_tevs);
-                return -ERANGE;
-        }
-        tev = &pf->tevs[pf->ntevs++];
-
-        /* If no real subprogram, find a real one */
-        if (!sp_die || dwarf_tag(sp_die) != DW_TAG_subprogram) {
-                sp_die = die_find_real_subprogram(&pf->cu_die,
-                                                 pf->addr, &die_mem);
-                if (!sp_die) {
-                        pr_warning("Failed to find probe point in any "
-                                   "functions.\n");
-                        return -ENOENT;
-                }
-        }
 
         /* Copy the name of probe point */
         name = dwarf_diename(sp_die);
@@ -809,26 +862,45 @@ static int convert_probe_point(Dwarf_Die *sp_die, struct probe_finder *pf)
                                    dwarf_diename(sp_die));
                         return -ENOENT;
                 }
-                tev->point.symbol = strdup(name);
-                if (tev->point.symbol == NULL)
+                tp->symbol = strdup(name);
+                if (tp->symbol == NULL)
                         return -ENOMEM;
-                tev->point.offset = (unsigned long)(pf->addr - eaddr);
+                tp->offset = (unsigned long)(paddr - eaddr);
         } else
                 /* This function has no name. */
-                tev->point.offset = (unsigned long)pf->addr;
+                tp->offset = (unsigned long)paddr;
 
         /* Return probe must be on the head of a subprogram */
-        if (pf->pev->point.retprobe) {
-                if (tev->point.offset != 0) {
+        if (retprobe) {
+                if (eaddr != paddr) {
                         pr_warning("Return probe must be on the head of"
                                    " a real function\n");
                         return -EINVAL;
                 }
-                tev->point.retprobe = true;
+                tp->retprobe = true;
         }
 
-        pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
-                 tev->point.offset);
+        return 0;
+}
+
+/* Call probe_finder callback with real subprogram DIE */
+static int call_probe_finder(Dwarf_Die *sp_die, struct probe_finder *pf)
+{
+        Dwarf_Die die_mem;
+        Dwarf_Attribute fb_attr;
+        size_t nops;
+        int ret;
+
+        /* If no real subprogram, find a real one */
+        if (!sp_die || dwarf_tag(sp_die) != DW_TAG_subprogram) {
+                sp_die = die_find_real_subprogram(&pf->cu_die,
+                                                  pf->addr, &die_mem);
+                if (!sp_die) {
+                        pr_warning("Failed to find probe point in any "
+                                   "functions.\n");
+                        return -ENOENT;
+                }
+        }
 
         /* Get the frame base attribute/ops */
         dwarf_attr(sp_die, DW_AT_frame_base, &fb_attr);
@@ -848,22 +920,13 @@ static int convert_probe_point(Dwarf_Die *sp_die, struct probe_finder *pf)
 #endif
         }
 
-        /* Find each argument */
-        tev->nargs = pf->pev->nargs;
-        tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
-        if (tev->args == NULL)
-                return -ENOMEM;
-        for (i = 0; i < pf->pev->nargs; i++) {
-                pf->pvar = &pf->pev->args[i];
-                pf->tvar = &tev->args[i];
-                ret = find_variable(sp_die, pf);
-                if (ret != 0)
-                        return ret;
-        }
+        /* Call finder's callback handler */
+        ret = pf->callback(sp_die, pf);
 
         /* *pf->fb_ops will be cached in libdw. Don't free it. */
         pf->fb_ops = NULL;
-        return 0;
+
+        return ret;
 }
 
 /* Find probe point from its line number */
@@ -899,7 +962,7 @@ static int find_probe_point_by_line(struct probe_finder *pf)
                          (int)i, lineno, (uintmax_t)addr);
                 pf->addr = addr;
 
-                ret = convert_probe_point(NULL, pf);
+                ret = call_probe_finder(NULL, pf);
                 /* Continuing, because target line might be inlined. */
         }
         return ret;
@@ -1012,7 +1075,7 @@ static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
                          (int)i, lineno, (unsigned long long)addr);
                 pf->addr = addr;
 
-                ret = convert_probe_point(sp_die, pf);
+                ret = call_probe_finder(sp_die, pf);
                 /* Continuing, because target line might be inlined. */
         }
         /* TODO: deallocate lines, but how? */
@@ -1047,7 +1110,7 @@ static int probe_point_inline_cb(Dwarf_Die *in_die, void *data)
                 pr_debug("found inline addr: 0x%jx\n",
                          (uintmax_t)pf->addr);
 
-                param->retval = convert_probe_point(in_die, pf);
+                param->retval = call_probe_finder(in_die, pf);
                 if (param->retval < 0)
                         return DWARF_CB_ABORT;
         }
@@ -1085,7 +1148,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
                         }
                         pf->addr += pp->offset;
                         /* TODO: Check the address in this function */
-                        param->retval = convert_probe_point(sp_die, pf);
+                        param->retval = call_probe_finder(sp_die, pf);
                 }
         } else {
                 struct dwarf_callback_param _param = {.data = (void *)pf,
@@ -1107,70 +1170,229 @@ static int find_probe_point_by_func(struct probe_finder *pf)
         return _param.retval;
 }
 
-/* Find probe_trace_events specified by perf_probe_event from debuginfo */
-int find_probe_trace_events(int fd, struct perf_probe_event *pev,
-                             struct probe_trace_event **tevs, int max_tevs)
+/* Find probe points from debuginfo */
+static int find_probes(int fd, struct probe_finder *pf)
 {
-        struct probe_finder pf = {.pev = pev, .max_tevs = max_tevs};
-        struct perf_probe_point *pp = &pev->point;
+        struct perf_probe_point *pp = &pf->pev->point;
         Dwarf_Off off, noff;
         size_t cuhl;
         Dwarf_Die *diep;
         Dwarf *dbg;
         int ret = 0;
 
-        pf.tevs = zalloc(sizeof(struct probe_trace_event) * max_tevs);
-        if (pf.tevs == NULL)
-                return -ENOMEM;
-        *tevs = pf.tevs;
-        pf.ntevs = 0;
-
         dbg = dwarf_begin(fd, DWARF_C_READ);
         if (!dbg) {
                 pr_warning("No dwarf info found in the vmlinux - "
                         "please rebuild with CONFIG_DEBUG_INFO=y.\n");
-                free(pf.tevs);
-                *tevs = NULL;
                 return -EBADF;
         }
 
 #if _ELFUTILS_PREREQ(0, 142)
         /* Get the call frame information from this dwarf */
-        pf.cfi = dwarf_getcfi(dbg);
+        pf->cfi = dwarf_getcfi(dbg);
 #endif
 
         off = 0;
-        line_list__init(&pf.lcache);
+        line_list__init(&pf->lcache);
         /* Loop on CUs (Compilation Unit) */
         while (!dwarf_nextcu(dbg, off, &noff, &cuhl, NULL, NULL, NULL) &&
                ret >= 0) {
                 /* Get the DIE(Debugging Information Entry) of this CU */
-                diep = dwarf_offdie(dbg, off + cuhl, &pf.cu_die);
+                diep = dwarf_offdie(dbg, off + cuhl, &pf->cu_die);
                 if (!diep)
                         continue;
 
                 /* Check if target file is included. */
                 if (pp->file)
-                        pf.fname = cu_find_realpath(&pf.cu_die, pp->file);
+                        pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
                 else
-                        pf.fname = NULL;
+                        pf->fname = NULL;
 
-                if (!pp->file || pf.fname) {
+                if (!pp->file || pf->fname) {
                         if (pp->function)
-                                ret = find_probe_point_by_func(&pf);
+                                ret = find_probe_point_by_func(pf);
                         else if (pp->lazy_line)
-                                ret = find_probe_point_lazy(NULL, &pf);
+                                ret = find_probe_point_lazy(NULL, pf);
                         else {
-                                pf.lno = pp->line;
-                                ret = find_probe_point_by_line(&pf);
+                                pf->lno = pp->line;
+                                ret = find_probe_point_by_line(pf);
                         }
                 }
                 off = noff;
         }
-        line_list__free(&pf.lcache);
+        line_list__free(&pf->lcache);
         dwarf_end(dbg);
 
-        return (ret < 0) ? ret : pf.ntevs;
+        return ret;
+}
+
+/* Add a found probe point into trace event list */
+static int add_probe_trace_event(Dwarf_Die *sp_die, struct probe_finder *pf)
+{
+        struct trace_event_finder *tf =
+                        container_of(pf, struct trace_event_finder, pf);
+        struct probe_trace_event *tev;
+        int ret, i;
+
+        /* Check number of tevs */
+        if (tf->ntevs == tf->max_tevs) {
+                pr_warning("Too many( > %d) probe point found.\n",
+                           tf->max_tevs);
+                return -ERANGE;
+        }
+        tev = &tf->tevs[tf->ntevs++];
+
+        ret = convert_to_trace_point(sp_die, pf->addr, pf->pev->point.retprobe,
+                                     &tev->point);
+        if (ret < 0)
+                return ret;
+
+        pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
+                 tev->point.offset);
+
+        /* Find each argument */
+        tev->nargs = pf->pev->nargs;
+        tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
+        if (tev->args == NULL)
+                return -ENOMEM;
+        for (i = 0; i < pf->pev->nargs; i++) {
+                pf->pvar = &pf->pev->args[i];
+                pf->tvar = &tev->args[i];
+                ret = find_variable(sp_die, pf);
+                if (ret != 0)
+                        return ret;
+        }
+
+        return 0;
+}
+
+/* Find probe_trace_events specified by perf_probe_event from debuginfo */
+int find_probe_trace_events(int fd, struct perf_probe_event *pev,
+                            struct probe_trace_event **tevs, int max_tevs)
+{
+        struct trace_event_finder tf = {
+                        .pf = {.pev = pev, .callback = add_probe_trace_event},
+                        .max_tevs = max_tevs};
+        int ret;
+
+        /* Allocate result tevs array */
+        *tevs = zalloc(sizeof(struct probe_trace_event) * max_tevs);
+        if (*tevs == NULL)
+                return -ENOMEM;
+
+        tf.tevs = *tevs;
+        tf.ntevs = 0;
+
+        ret = find_probes(fd, &tf.pf);
+        if (ret < 0) {
+                free(*tevs);
+                *tevs = NULL;
+                return ret;
+        }
+
+        return (ret < 0) ? ret : tf.ntevs;
+}
+
+#define MAX_VAR_LEN 64
+
+/* Collect available variables in this scope */
+static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
+{
+        struct available_var_finder *af = data;
+        struct variable_list *vl;
+        char buf[MAX_VAR_LEN];
+        int tag, ret;
+
+        vl = &af->vls[af->nvls - 1];
+
+        tag = dwarf_tag(die_mem);
+        if (tag == DW_TAG_formal_parameter ||
+            tag == DW_TAG_variable) {
+                ret = convert_variable_location(die_mem, af->pf.addr,
+                                                af->pf.fb_ops, NULL);
+                if (ret == 0) {
+                        ret = die_get_varname(die_mem, buf, MAX_VAR_LEN);
+                        if (ret > 0)
+                                strlist__add(vl->vars, buf);
+                }
+        }
+
+        if (dwarf_haspc(die_mem, af->pf.addr))
+                return DIE_FIND_CB_CONTINUE;
+        else
+                return DIE_FIND_CB_SIBLING;
+}
+
+/* Add a found vars into available variables list */
+static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf)
+{
+        struct available_var_finder *af =
+                        container_of(pf, struct available_var_finder, pf);
+        struct variable_list *vl;
+        Dwarf_Die die_mem;
+        int ret;
+
+        /* Check number of tevs */
+        if (af->nvls == af->max_vls) {
+                pr_warning("Too many( > %d) probe point found.\n", af->max_vls);
+                return -ERANGE;
+        }
+        vl = &af->vls[af->nvls++];
+
+        ret = convert_to_trace_point(sp_die, pf->addr, pf->pev->point.retprobe,
+                                     &vl->point);
+        if (ret < 0)
+                return ret;
+
+        pr_debug("Probe point found: %s+%lu\n", vl->point.symbol,
+                 vl->point.offset);
+
+        /* Find local variables */
+        vl->vars = strlist__new(true, NULL);
+        if (vl->vars == NULL)
+                return -ENOMEM;
+        die_find_child(sp_die, collect_variables_cb, (void *)af, &die_mem);
+
+        if (strlist__empty(vl->vars)) {
+                strlist__delete(vl->vars);
+                vl->vars = NULL;
+        }
+
+        return ret;
+}
+
+/* Find available variables at given probe point */
+int find_available_vars_at(int fd, struct perf_probe_event *pev,
+                           struct variable_list **vls, int max_vls)
+{
+        struct available_var_finder af = {
+                        .pf = {.pev = pev, .callback = add_available_vars},
+                        .max_vls = max_vls};
+        int ret;
+
+        /* Allocate result vls array */
+        *vls = zalloc(sizeof(struct variable_list) * max_vls);
+        if (*vls == NULL)
+                return -ENOMEM;
+
+        af.vls = *vls;
+        af.nvls = 0;
+
+        ret = find_probes(fd, &af.pf);
+        if (ret < 0) {
+                /* Free vlist for error */
+                while (af.nvls--) {
+                        if (af.vls[af.nvls].point.symbol)
+                                free(af.vls[af.nvls].point.symbol);
+                        if (af.vls[af.nvls].vars)
+                                strlist__delete(af.vls[af.nvls].vars);
+                }
+                free(af.vls);
+                *vls = NULL;
+                return ret;
+        }
+
+        return (ret < 0) ? ret : af.nvls;
 }
 
 /* Reverse search */
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 4507d519f183..baffd25f39c9 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -25,17 +25,22 @@ extern int find_probe_trace_events(int fd, struct perf_probe_event *pev,
 extern int find_perf_probe_point(int fd, unsigned long addr,
                                  struct perf_probe_point *ppt);
 
+/* Find a line range */
 extern int find_line_range(int fd, struct line_range *lr);
 
+/* Find available variables */
+extern int find_available_vars_at(int fd, struct perf_probe_event *pev,
+                                  struct variable_list **vls, int max_points);
+
 #include <dwarf.h>
 #include <libdw.h>
 #include <version.h>
 
 struct probe_finder {
         struct perf_probe_event *pev;           /* Target probe event */
-        struct probe_trace_event *tevs;         /* Result trace events */
-        int                     ntevs;          /* Number of trace events */
-        int                     max_tevs;       /* Max number of trace events */
+
+        /* Callback when a probe point is found */
+        int (*callback)(Dwarf_Die *sp_die, struct probe_finder *pf);
 
         /* For function searching */
         int                     lno;            /* Line number */
@@ -53,6 +58,20 @@ struct probe_finder {
         struct probe_trace_arg  *tvar;          /* Current result variable */
 };
 
+struct trace_event_finder {
+        struct probe_finder     pf;
+        struct probe_trace_event *tevs;         /* Found trace events */
+        int                     ntevs;          /* Number of trace events */
+        int                     max_tevs;       /* Max number of trace events */
+};
+
+struct available_var_finder {
+        struct probe_finder     pf;
+        struct variable_list    *vls;           /* Found variable lists */
+        int                     nvls;           /* Number of variable lists */
+        int                     max_vls;        /* Max no. of variable lists */
+};
+
 struct line_finder {
         struct line_range       *lr;            /* Target line range */