perf probe: Support tracing an entry of array

Add array-entry tracing support to perf probe. This enables to trace an entry
of array which is indexed by constant value, e.g. array[0].

For example:

  $ perf probe -a 'bio_split bi->bi_io_vec[0]'

Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100519195742.2885.5344.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 39 insertions, 17 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 914c67095d96..351baa9a3695 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -557,7 +557,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 /* Parse perf-probe event argument */
 static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 {
-        char *tmp;
+        char *tmp, *goodname;
         struct perf_probe_arg_field **fieldp;
 
         pr_debug("parsing arg: %s into ", str);
@@ -580,7 +580,7 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
                 pr_debug("type:%s ", arg->type);
         }
 
-        tmp = strpbrk(str, "-.");
+        tmp = strpbrk(str, "-.[");
         if (!is_c_varname(str) || !tmp) {
                 /* A variable, register, symbol or special value */
                 arg->var = strdup(str);
@@ -590,10 +590,11 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
                 return 0;
         }
 
-        /* Structure fields */
+        /* Structure fields or array element */
         arg->var = strndup(str, tmp - str);
         if (arg->var == NULL)
                 return -ENOMEM;
+        goodname = arg->var;
         pr_debug("%s, ", arg->var);
         fieldp = &arg->field;
 
@@ -601,22 +602,38 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
                 *fieldp = zalloc(sizeof(struct perf_probe_arg_field));
                 if (*fieldp == NULL)
                         return -ENOMEM;
-                if (*tmp == '.') {
-                        str = tmp + 1;
-                        (*fieldp)->ref = false;
-                } else if (tmp[1] == '>') {
-                        str = tmp + 2;
+                if (*tmp == '[') {      /* Array */
+                        str = tmp;
+                        (*fieldp)->index = strtol(str + 1, &tmp, 0);
                         (*fieldp)->ref = true;
-                } else {
-                        semantic_error("Argument parse error: %s\n", str);
-                        return -EINVAL;
+                        if (*tmp != ']' || tmp == str + 1) {
+                                semantic_error("Array index must be a"
+                                                " number.\n");
+                                return -EINVAL;
+                        }
+                        tmp++;
+                        if (*tmp == '\0')
+                                tmp = NULL;
+                } else {                /* Structure */
+                        if (*tmp == '.') {
+                                str = tmp + 1;
+                                (*fieldp)->ref = false;
+                        } else if (tmp[1] == '>') {
+                                str = tmp + 2;
+                                (*fieldp)->ref = true;
+                        } else {
+                                semantic_error("Argument parse error: %s\n",
+                                               str);
+                                return -EINVAL;
+                        }
+                        tmp = strpbrk(str, "-.[");
                 }
-
-                tmp = strpbrk(str, "-.");
                 if (tmp) {
                         (*fieldp)->name = strndup(str, tmp - str);
                         if ((*fieldp)->name == NULL)
                                 return -ENOMEM;
+                        if (*str != '[')
+                                goodname = (*fieldp)->name;
                         pr_debug("%s(%d), ", (*fieldp)->name, (*fieldp)->ref);
                         fieldp = &(*fieldp)->next;
                 }
@@ -624,11 +641,13 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
         (*fieldp)->name = strdup(str);
         if ((*fieldp)->name == NULL)
                 return -ENOMEM;
+        if (*str != '[')
+                goodname = (*fieldp)->name;
         pr_debug("%s(%d)\n", (*fieldp)->name, (*fieldp)->ref);
 
-        /* If no name is specified, set the last field name */
+        /* If no name is specified, set the last field name (not array index)*/
         if (!arg->name) {
-                arg->name = strdup((*fieldp)->name);
+                arg->name = strdup(goodname);
                 if (arg->name == NULL)
                         return -ENOMEM;
         }
@@ -776,8 +795,11 @@ int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
         len -= ret;
 
         while (field) {
-                ret = e_snprintf(tmp, len, "%s%s", field->ref ? "->" : ".",
-                                 field->name);
+                if (field->name[0] == '[')
+                        ret = e_snprintf(tmp, len, "%s", field->name);
+                else
+                        ret = e_snprintf(tmp, len, "%s%s",
+                                         field->ref ? "->" : ".", field->name);
                 if (ret <= 0)
                         goto error;
                 tmp += ret;