lib/test_fprobe: Add a test case for nr_maxactive

Add a test case for nr_maxactive. If the number of active
functions is more than nr_maxactive, it must be skipped.

Link: https://lkml.kernel.org/r/167526698856.433354.4430007340787176666.stgit@mhiramat.roam.corp.google.com

Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

lib/test_fprobe.c

@@ -17,8 +17,10 @@ static u32 rand1, entry_val, exit_val;
 /* Use indirect calls to avoid inlining the target functions */
 static u32 (*target)(u32 value);
 static u32 (*target2)(u32 value);
+static u32 (*target_nest)(u32 value, u32 (*nest)(u32));
 static unsigned long target_ip;
 static unsigned long target2_ip;
+static unsigned long target_nest_ip;
 
 static noinline u32 fprobe_selftest_target(u32 value)
 {
@@ -30,6 +32,11 @@ static noinline u32 fprobe_selftest_target2(u32 value)
 	return (value / div_factor) + 1;
 }
 
+static noinline u32 fprobe_selftest_nest_target(u32 value, u32 (*nest)(u32))
+{
+	return nest(value + 2);
+}
+
 static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip,
 				     struct pt_regs *regs, void *data)
 {
@@ -67,6 +74,19 @@ static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
 		KUNIT_EXPECT_NULL(current_test, data);
 }
 
+static notrace void nest_entry_handler(struct fprobe *fp, unsigned long ip,
+				     struct pt_regs *regs, void *data)
+{
+	KUNIT_EXPECT_FALSE(current_test, preemptible());
+}
+
+static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
+				    struct pt_regs *regs, void *data)
+{
+	KUNIT_EXPECT_FALSE(current_test, preemptible());
+	KUNIT_EXPECT_EQ(current_test, ip, target_nest_ip);
+}
+
 /* Test entry only (no rethook) */
 static void test_fprobe_entry(struct kunit *test)
 {
@@ -163,6 +183,25 @@ static void test_fprobe_data(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
 }
 
+/* Test nr_maxactive */
+static void test_fprobe_nest(struct kunit *test)
+{
+	static const char *syms[] = {"fprobe_selftest_target", "fprobe_selftest_nest_target"};
+	struct fprobe fp = {
+		.entry_handler = nest_entry_handler,
+		.exit_handler = nest_exit_handler,
+		.nr_maxactive = 1,
+	};
+
+	current_test = test;
+	KUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(&fp, syms, 2));
+
+	target_nest(rand1, target);
+	KUNIT_EXPECT_EQ(test, 1, fp.nmissed);
+
+	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
+}
+
 static unsigned long get_ftrace_location(void *func)
 {
 	unsigned long size, addr = (unsigned long)func;
@@ -178,8 +217,10 @@ static int fprobe_test_init(struct kunit *test)
 	rand1 = get_random_u32_above(div_factor);
 	target = fprobe_selftest_target;
 	target2 = fprobe_selftest_target2;
+	target_nest = fprobe_selftest_nest_target;
 	target_ip = get_ftrace_location(target);
 	target2_ip = get_ftrace_location(target2);
+	target_nest_ip = get_ftrace_location(target_nest);
 
 	return 0;
 }
@@ -189,6 +230,7 @@ static struct kunit_case fprobe_testcases[] = {
 	KUNIT_CASE(test_fprobe),
 	KUNIT_CASE(test_fprobe_syms),
 	KUNIT_CASE(test_fprobe_data),
+	KUNIT_CASE(test_fprobe_nest),
 	{}
 };