perf probe: Support basic type casting

Add basic type casting for arguments to perf probe. This allows
users to specify the actual type of arguments. Of course, if
user sets invalid types, kprobe-tracer rejects that.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100412171722.3790.50372.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-probe.txt

@@ -85,9 +85,10 @@ PROBE ARGUMENT
 --------------
 Each probe argument follows below syntax.
 
- [NAME=]LOCALVAR|$retval|%REG|@SYMBOL
+ [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
 
 'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
+'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo.
 
 LINE SYNTAX
 -----------

tools/perf/util/probe-event.c

@@ -435,7 +435,7 @@ static void parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 }
 
 /* Parse perf-probe event argument */
-static void parse_perf_probe_arg(const char *str, struct perf_probe_arg *arg)
+static void parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 {
 	char *tmp;
 	struct perf_probe_arg_field **fieldp;
@@ -445,9 +445,17 @@ static void parse_perf_probe_arg(const char *str, struct perf_probe_arg *arg)
 	tmp = strchr(str, '=');
 	if (tmp) {
 		arg->name = xstrndup(str, tmp - str);
+		pr_debug("name:%s ", arg->name);
 		str = tmp + 1;
 	}
 
+	tmp = strchr(str, ':');
+	if (tmp) {	/* Type setting */
+		*tmp = '\0';
+		arg->type = xstrdup(tmp + 1);
+		pr_debug("type:%s ", arg->type);
+	}
+
 	tmp = strpbrk(str, "-.");
 	if (!is_c_varname(str) || !tmp) {
 		/* A variable, register, symbol or special value */
@@ -603,6 +611,15 @@ int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
 		len -= ret;
 		field = field->next;
 	}
+
+	if (pa->type) {
+		ret = e_snprintf(tmp, len, ":%s", pa->type);
+		if (ret <= 0)
+			goto error;
+		tmp += ret;
+		len -= ret;
+	}
+
 	return tmp - buf;
 error:
 	die("Failed to synthesize perf probe argument: %s", strerror(-ret));
@@ -825,6 +842,8 @@ void clear_perf_probe_event(struct perf_probe_event *pev)
 			free(pev->args[i].name);
 		if (pev->args[i].var)
 			free(pev->args[i].var);
+		if (pev->args[i].type)
+			free(pev->args[i].type);
 		field = pev->args[i].field;
 		while (field) {
 			next = field->next;
@@ -1145,6 +1164,8 @@ static int convert_to_kprobe_trace_events(struct perf_probe_event *pev,
 			if (pev->args[i].name)
 				tev->args[i].name = xstrdup(pev->args[i].name);
 			tev->args[i].value = xstrdup(pev->args[i].var);
+			if (pev->args[i].type)
+				tev->args[i].type = xstrdup(pev->args[i].type);
 		}
 	}
 

tools/perf/util/probe-event.h

@@ -57,6 +57,7 @@ struct perf_probe_arg_field {
 struct perf_probe_arg {
 	char				*name;	/* Argument name */
 	char				*var;	/* Variable name */
+	char				*type;	/* Type name */
 	struct perf_probe_arg_field	*field;	/* Structure fields */
 };
 

tools/perf/util/probe-finder.c

@@ -547,7 +547,10 @@ static void convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 					&die_mem);
 		vr_die = &die_mem;
 	}
-	convert_variable_type(vr_die, pf->tvar);
+	if (pf->pvar->type)
+		pf->tvar->type = xstrdup(pf->pvar->type);
+	else
+		convert_variable_type(vr_die, pf->tvar);
 	/* *expr will be cached in libdw. Don't free it. */
 	return ;
 error:
@@ -560,13 +563,16 @@ error:
 static void find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
 {
 	Dwarf_Die vr_die;
-	char buf[32];
+	char buf[32], *ptr;
 
 	/* TODO: Support arrays */
 	if (pf->pvar->name)
 		pf->tvar->name = xstrdup(pf->pvar->name);
 	else {
 		synthesize_perf_probe_arg(pf->pvar, buf, 32);
+		ptr = strchr(buf, ':');	/* Change type separator to _ */
+		if (ptr)
+			*ptr = '_';
 		pf->tvar->name = xstrdup(buf);
 	}