perf probe: Support "$vars" meta argument syntax for local variables

Support "$vars" meta argument syntax for tracing all local variables at
probe point.

Now you can trace all available local variables (including function
parameters) at the probe point by passing $vars.

 # perf probe --add foo $vars

This automatically finds all local variables at foo() and adds it as
probe arguments.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20131011071023.15557.51770.stgit@udc4-manage.rcp.hitachi.co.jp
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 779b2da..9c6989c 100644 (file)
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -47,7 +47,6 @@
 #include "session.h"
 
 #define MAX_CMDLEN 256
-#define MAX_PROBE_ARGS 128
 #define PERFPROBE_GROUP "probe"
 
 bool probe_event_dry_run;      /* Dry run flag */

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index c09e0a9..5a46be9 100644 (file)
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1136,12 +1136,78 @@ found:
        return ret;
 }
 
+struct local_vars_finder {
+       struct probe_finder *pf;
+       struct perf_probe_arg *args;
+       int max_args;
+       int nargs;
+       int ret;
+};
+
+/* Collect available variables in this scope */
+static int copy_variables_cb(Dwarf_Die *die_mem, void *data)
+{
+       struct local_vars_finder *vf = data;
+       int tag;
+
+       tag = dwarf_tag(die_mem);
+       if (tag == DW_TAG_formal_parameter ||
+           tag == DW_TAG_variable) {
+               if (convert_variable_location(die_mem, vf->pf->addr,
+                                             vf->pf->fb_ops, NULL) == 0) {
+                       vf->args[vf->nargs].var = (char *)dwarf_diename(die_mem);
+                       if (vf->args[vf->nargs].var == NULL) {
+                               vf->ret = -ENOMEM;
+                               return DIE_FIND_CB_END;
+                       }
+                       pr_debug(" %s", vf->args[vf->nargs].var);
+                       vf->nargs++;
+               }
+       }
+
+       if (dwarf_haspc(die_mem, vf->pf->addr))
+               return DIE_FIND_CB_CONTINUE;
+       else
+               return DIE_FIND_CB_SIBLING;
+}
+
+static int expand_probe_args(Dwarf_Die *sc_die, struct probe_finder *pf,
+                            struct perf_probe_arg *args)
+{
+       Dwarf_Die die_mem;
+       int i;
+       int n = 0;
+       struct local_vars_finder vf = {.pf = pf, .args = args,
+                               .max_args = MAX_PROBE_ARGS, .ret = 0};
+
+       for (i = 0; i < pf->pev->nargs; i++) {
+               /* var never be NULL */
+               if (strcmp(pf->pev->args[i].var, "$vars") == 0) {
+                       pr_debug("Expanding $vars into:");
+                       vf.nargs = n;
+                       /* Special local variables */
+                       die_find_child(sc_die, copy_variables_cb, (void *)&vf,
+                                      &die_mem);
+                       pr_debug(" (%d)\n", vf.nargs - n);
+                       if (vf.ret < 0)
+                               return vf.ret;
+                       n = vf.nargs;
+               } else {
+                       /* Copy normal argument */
+                       args[n] = pf->pev->args[i];
+                       n++;
+               }
+       }
+       return n;
+}
+
 /* Add a found probe point into trace event list */
 static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
 {
        struct trace_event_finder *tf =
                        container_of(pf, struct trace_event_finder, pf);
        struct probe_trace_event *tev;
+       struct perf_probe_arg *args;
        int ret, i;
 
        /* Check number of tevs */
@@ -1161,21 +1227,35 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
        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)
+       /* Expand special probe argument if exist */
+       args = zalloc(sizeof(struct perf_probe_arg) * MAX_PROBE_ARGS);
+       if (args == NULL)
                return -ENOMEM;
-       for (i = 0; i < pf->pev->nargs; i++) {
-               pf->pvar = &pf->pev->args[i];
+
+       ret = expand_probe_args(sc_die, pf, args);
+       if (ret < 0)
+               goto end;
+
+       tev->nargs = ret;
+       tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
+       if (tev->args == NULL) {
+               ret = -ENOMEM;
+               goto end;
+       }
+
+       /* Find each argument */
+       for (i = 0; i < tev->nargs; i++) {
+               pf->pvar = &args[i];
                pf->tvar = &tev->args[i];
                /* Variable should be found from scope DIE */
                ret = find_variable(sc_die, pf);
                if (ret != 0)
-                       return ret;
+                       break;
        }
 
-       return 0;
+end:
+       free(args);
+       return ret;
 }
 
 /* Find probe_trace_events specified by perf_probe_event from debuginfo */

diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 3f0c29d..d6dab0e 100644 (file)
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -7,6 +7,7 @@
 
 #define MAX_PROBE_BUFFER       1024
 #define MAX_PROBES              128
+#define MAX_PROBE_ARGS          128
 
 static inline int is_c_varname(const char *name)
 {