tracing/kprobe: Update symbol reference when loading module

Since the address of a module-local variable can only be
solved after the target module is loaded, the symbol
fetch-argument should be updated when loading target
module.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/r/20110627072703.6528.75042.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_kprobe.c

@@ -343,6 +343,14 @@ DEFINE_BASIC_FETCH_FUNCS(deref)
 DEFINE_FETCH_deref(string)
 DEFINE_FETCH_deref(string_size)
 
+static __kprobes void update_deref_fetch_param(struct deref_fetch_param *data)
+{
+	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
+		update_deref_fetch_param(data->orig.data);
+	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
+		update_symbol_cache(data->orig.data);
+}
+
 static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 {
 	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
@@ -376,6 +384,19 @@ DEFINE_BASIC_FETCH_FUNCS(bitfield)
 #define fetch_bitfield_string NULL
 #define fetch_bitfield_string_size NULL
 
+static __kprobes void
+update_bitfield_fetch_param(struct bitfield_fetch_param *data)
+{
+	/*
+	 * Don't check the bitfield itself, because this must be the
+	 * last fetch function.
+	 */
+	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
+		update_deref_fetch_param(data->orig.data);
+	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
+		update_symbol_cache(data->orig.data);
+}
+
 static __kprobes void
 free_bitfield_fetch_param(struct bitfield_fetch_param *data)
 {
@@ -389,6 +410,7 @@ free_bitfield_fetch_param(struct bitfield_fetch_param *data)
 		free_symbol_cache(data->orig.data);
 	kfree(data);
 }
+
 /* Default (unsigned long) fetch type */
 #define __DEFAULT_FETCH_TYPE(t) u##t
 #define _DEFAULT_FETCH_TYPE(t) __DEFAULT_FETCH_TYPE(t)
@@ -680,6 +702,16 @@ static struct trace_probe *alloc_trace_probe(const char *group,
 	return ERR_PTR(ret);
 }
 
+static void update_probe_arg(struct probe_arg *arg)
+{
+	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
+		update_bitfield_fetch_param(arg->fetch.data);
+	else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
+		update_deref_fetch_param(arg->fetch.data);
+	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
+		update_symbol_cache(arg->fetch.data);
+}
+
 static void free_probe_arg(struct probe_arg *arg)
 {
 	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
@@ -749,11 +781,14 @@ static void disable_trace_probe(struct trace_probe *tp, int flag)
 /* Internal register function - just handle k*probes and flags */
 static int __register_trace_probe(struct trace_probe *tp)
 {
-	int ret;
+	int i, ret;
 
 	if (trace_probe_is_registered(tp))
 		return -EINVAL;
 
+	for (i = 0; i < tp->nr_args; i++)
+		update_probe_arg(&tp->args[i]);
+
 	/* Set/clear disabled flag according to tp->flag */
 	if (trace_probe_is_enabled(tp))
 		tp->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;