perf probe: Add data structure member access support

Support accessing members in the data structures. With this,
perf-probe accepts data-structure members(IOW, it now accepts
dot '.' and arrow '->' operators) as probe arguemnts.

e.g.

 ./perf probe --add 'schedule:44 rq->curr'

 ./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry'

Note that '>' can be interpreted as redirection in command-line.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100316220626.32050.57552.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 86 insertions, 4 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 4e3c1aea7892..64dea6c3d58a 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -262,6 +262,49 @@ static void parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
                  pp->lazy_line);
 }
 
+/* Parse perf-probe event argument */
+static void parse_perf_probe_arg(const char *str, struct perf_probe_arg *arg)
+{
+        const char *tmp;
+        struct perf_probe_arg_field **fieldp;
+
+        pr_debug("parsing arg: %s into ", str);
+
+        tmp = strpbrk(str, "-.");
+        if (!is_c_varname(str) || !tmp) {
+                /* A variable, register, symbol or special value */
+                arg->name = xstrdup(str);
+                pr_debug("%s\n", arg->name);
+                return;
+        }
+
+        /* Structure fields */
+        arg->name = xstrndup(str, tmp - str);
+        pr_debug("%s, ", arg->name);
+        fieldp = &arg->field;
+
+        do {
+                *fieldp = xzalloc(sizeof(struct perf_probe_arg_field));
+                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", str);
+
+                tmp = strpbrk(str, "-.");
+                if (tmp) {
+                        (*fieldp)->name = xstrndup(str, tmp - str);
+                        pr_debug("%s(%d), ", (*fieldp)->name, (*fieldp)->ref);
+                        fieldp = &(*fieldp)->next;
+                }
+        } while (tmp);
+        (*fieldp)->name = xstrdup(str);
+        pr_debug("%s(%d)\n", (*fieldp)->name, (*fieldp)->ref);
+}
+
 /* Parse perf-probe event command */
 void parse_perf_probe_command(const char *cmd, struct perf_probe_event *pev)
 {
@@ -281,7 +324,7 @@ void parse_perf_probe_command(const char *cmd, struct perf_probe_event *pev)
         pev->nargs = argc - 1;
         pev->args = xzalloc(sizeof(struct perf_probe_arg) * pev->nargs);
         for (i = 0; i < pev->nargs; i++) {
-                pev->args[i].name = xstrdup(argv[i + 1]);
+                parse_perf_probe_arg(argv[i + 1], &pev->args[i]);
                 if (is_c_varname(pev->args[i].name) && pev->point.retprobe)
                         semantic_error("You can't specify local variable for"
                                        " kretprobe");
@@ -353,6 +396,33 @@ void parse_kprobe_trace_command(const char *cmd, struct kprobe_trace_event *tev)
         argv_free(argv);
 }
 
+/* Compose only probe arg */
+int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
+{
+        struct perf_probe_arg_field *field = pa->field;
+        int ret;
+        char *tmp = buf;
+
+        ret = e_snprintf(tmp, len, "%s", pa->name);
+        if (ret <= 0)
+                goto error;
+        tmp += ret;
+        len -= ret;
+
+        while (field) {
+                ret = e_snprintf(tmp, len, "%s%s", field->ref ? "->" : ".",
+                                 field->name);
+                if (ret <= 0)
+                        goto error;
+                tmp += ret;
+                len -= ret;
+                field = field->next;
+        }
+        return tmp - buf;
+error:
+        die("Failed to synthesize perf probe argument: %s", strerror(-ret));
+}
+
 /* Compose only probe point (not argument) */
 static char *synthesize_perf_probe_point(struct perf_probe_point *pp)
 {
@@ -563,6 +633,7 @@ void convert_to_perf_probe_event(struct kprobe_trace_event *tev,
 void clear_perf_probe_event(struct perf_probe_event *pev)
 {
         struct perf_probe_point *pp = &pev->point;
+        struct perf_probe_arg_field *field, *next;
         int i;
 
         if (pev->event)
@@ -575,9 +646,18 @@ void clear_perf_probe_event(struct perf_probe_event *pev)
                 free(pp->function);
         if (pp->lazy_line)
                 free(pp->lazy_line);
-        for (i = 0; i < pev->nargs; i++)
+        for (i = 0; i < pev->nargs; i++) {
                 if (pev->args[i].name)
                         free(pev->args[i].name);
+                field = pev->args[i].field;
+                while (field) {
+                        next = field->next;
+                        if (field->name)
+                                free(field->name);
+                        free(field);
+                        field = next;
+                }
+        }
         if (pev->args)
                 free(pev->args);
         memset(pev, 0, sizeof(*pev));
@@ -682,8 +762,10 @@ static void show_perf_probe_event(struct perf_probe_event *pev)
 
         if (pev->nargs > 0) {
                 printf(" with");
-                for (i = 0; i < pev->nargs; i++)
-                        printf(" %s", pev->args[i].name);
+                for (i = 0; i < pev->nargs; i++) {
+                        synthesize_perf_probe_arg(&pev->args[i], buf, 128);
+                        printf(" %s", buf);
+                }
         }
         printf(")\n");
         free(place);