[PATCH] HACK: ftrace stress test

[Mark Rutland]

Try to check that ops->func() is called with the correct ops.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
---
 lib/Makefile  |   3 +
 lib/fstress.c | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 161 insertions(+)
 create mode 100644 lib/fstress.c

diff --git a/lib/Makefile b/lib/Makefile
index 6b09731d8e619..678a916d4f0a0 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -36,6 +36,9 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 nmi_backtrace.o win_minmax.o memcat_p.o \
 	 buildid.o objpool.o
 
+obj-y += fstress.o
+CFLAGS_fstress.o += $(CC_FLAGS_FTRACE)
+
 lib-$(CONFIG_PRINTK) += dump_stack.o
 lib-$(CONFIG_SMP) += cpumask.o
 
diff --git a/lib/fstress.c b/lib/fstress.c
new file mode 100644
index 0000000000000..1ec2303f67f6f
--- /dev/null
+++ b/lib/fstress.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt)	"fstress: " fmt
+
+#include <linux/bug.h>
+#include <linux/errno.h>
+#include <linux/ftrace.h>
+#include <linux/init.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+
+#define DEFINE_OPS(x)							\
+	static void trace_func_##x(unsigned long ip,			\
+				   unsigned long parent_ip,		\
+				   struct ftrace_ops *op,		\
+				   struct ftrace_regs *fregs);		\
+									\
+	struct ftrace_ops ops_##x =  {					\
+		.func = trace_func_##x,					\
+	};								\
+									\
+	static void trace_func_##x(unsigned long ip,			\
+				   unsigned long parent_ip,		\
+				   struct ftrace_ops *op,		\
+				   struct ftrace_regs *fregs)		\
+	{								\
+		struct ftrace_ops *expected = &ops_##x;			\
+		if (op == expected)					\
+			return;						\
+		panic("%s(%pS, %pS, %pS, %pS) expected ops %pS\n",	\
+		      __func__, (void *)ip, (void *)parent_ip,		\
+		      op, fregs, expected);				\
+	}
+
+DEFINE_OPS(a);
+DEFINE_OPS(b);
+DEFINE_OPS(c);
+DEFINE_OPS(d);
+
+static struct ftrace_ops *fstress_ops[] = {
+	&ops_a,
+	&ops_b,
+	&ops_c,
+	&ops_d,
+};
+
+static noinline void tracee(void)
+{
+	/*
+	 * Do nothing, but prevent compiler from eliding calls to this
+	 * function.
+	 */
+	barrier();
+}
+
+static noinline int fstress_tracee_thread(void *unused)
+{
+	while (!kthread_should_stop()) {
+		for (int i = 0; i < 100; i++)
+			tracee();
+		cond_resched();
+	}
+
+	return 0;
+}
+
+static int fstress_manager_thread(void *unused)
+{
+	while (!kthread_should_stop()) {
+		int nr_ops = ARRAY_SIZE(fstress_ops);
+
+		for (int i = 0; i <= nr_ops; i++) {
+			if (i < nr_ops)
+				WARN_ON_ONCE(register_ftrace_function(fstress_ops[i]));
+			if (i > 0)
+				WARN_ON_ONCE(unregister_ftrace_function(fstress_ops[i - 1]));
+
+			/*
+			 * TODO: introduce some delay here, so that we spent
+			 * more time with a single tracer enabled (rather than
+			 * the list func).
+			 */
+		}
+
+		cond_resched();
+	}
+
+	return 0;
+}
+
+#define NR_TRACEE_THREADS	25
+
+struct task_struct *tracee_threads[NR_TRACEE_THREADS];
+struct task_struct *manager_thread;
+
+static __init int fstress_init(void)
+{
+	int ret;
+
+	pr_info("Initializing ops\n");
+	for (int i = 0; i < ARRAY_SIZE(fstress_ops); i++) {
+		ret = ftrace_set_filter_ip(fstress_ops[i], (unsigned long)tracee, 0, 0);
+		ret = 0;
+		if (ret) {
+			pr_err("Cannot set filter: %d\n", ret);
+			goto out_free_filters;
+		}
+	}
+
+	pr_info("Creating tracee threads\n");
+	for (int i = 0; i < NR_TRACEE_THREADS; i++) {
+		tracee_threads[i] = kthread_create(fstress_tracee_thread, NULL, "fstress_%d", i);
+		if (!tracee_threads[i]) {
+			pr_err("Cannot create tracee thread %d\n", i);
+			goto out_free_tracees;
+		}
+	}
+
+	pr_info("Creating manager thread\n");
+	manager_thread = kthread_create(fstress_manager_thread, NULL, "fstress_manager");
+	if (!manager_thread) {
+		pr_err("Cannot create manager thread\n");
+		goto out_free_tracees;
+	}
+
+	pr_info("Starting threads\n");
+	for (int i = 0; i < NR_TRACEE_THREADS; i++)
+		wake_up_process(tracee_threads[i]);
+	wake_up_process(manager_thread);
+
+	return 0;
+
+out_free_tracees:
+	for (int i = 0; i < NR_TRACEE_THREADS; i++) {
+		if (tracee_threads[i])
+			kthread_stop(tracee_threads[i]);
+	}
+out_free_filters:
+	for (int i = 0; i < ARRAY_SIZE(fstress_ops); i++)
+		ftrace_free_filter(fstress_ops[i]);
+
+	return -EAGAIN;
+}
+
+static __exit void fstress_exit(void)
+{
+	kthread_stop(manager_thread);
+
+	for (int i = 0; i < NR_TRACEE_THREADS; i++)
+		kthread_stop(tracee_threads[i]);
+
+	for (int i = 0; i < ARRAY_SIZE(fstress_ops); i++)
+		ftrace_free_filter(fstress_ops[i]);
+}
+
+module_init(fstress_init);
+module_exit(fstress_exit);
+MODULE_LICENSE("GPL");
-- 
2.30.2