[PATCH v4 13/17] rv: Add KUnit stub for current

[Gabriele Monaco <gmonaco@redhat.com>]

Some monitors do not only rely on tracepoint arguments but also on the
currently executing task.
This makes it more challenging to mock events in KUnit.

Define wrapper functions around current, the functionality is stubbed
only during KUnit, however the additional function call is necessary
whenever the KUnit tests are built in.

Reviewed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
---
 include/rv/da_monitor.h                       |  1 +
 include/rv/kunit.h                            | 13 +++++++++-
 include/rv/ltl_monitor.h                      |  1 +
 kernel/trace/rv/Kconfig                       |  3 +++
 .../trace/rv/monitors/pagefault/pagefault.c   |  2 +-
 kernel/trace/rv/monitors/sleep/sleep.c        | 24 +++++++++----------
 kernel/trace/rv/rv.c                          |  8 +++++++
 kernel/trace/rv/rv_monitors_test.c            |  9 +++++++
 8 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h
index 773564720ba1..9f7ba443d777 100644
--- a/include/rv/da_monitor.h
+++ b/include/rv/da_monitor.h
@@ -16,6 +16,7 @@
 
 #include <rv/automata.h>
 #include <linux/rv.h>
+#include <rv/kunit.h>
 #include <linux/stringify.h>
 #include <linux/bug.h>
 #include <linux/sched.h>
diff --git a/include/rv/kunit.h b/include/rv/kunit.h
index ff98b5137285..6d16a422a80c 100644
--- a/include/rv/kunit.h
+++ b/include/rv/kunit.h
@@ -2,7 +2,10 @@
 /*
  * Copyright (C) 2026-2029 Red Hat, Inc. Gabriele Monaco <gmonaco@redhat.com>
  *
- * Declaration of utilities to run KUnit tests.
+ * Declaration of wrappers to allow stubbing core functionality, like current,
+ * and other testing utilities.
+ * Necessary only when mocking may be needed. If the RV KUnit test is
+ * enabled, the wrappers incur an additional function call overhead.
  */
 
 #ifndef _RV_KUNIT_H
@@ -16,6 +19,7 @@
 
 int rv_set_testing(struct kunit_suite *suite);
 void rv_clear_testing(struct kunit_suite *suite);
+struct task_struct *rv_get_current(void);
 
 #define RV_KUNIT_MAX_MOCK_TASKS 8
 
@@ -23,6 +27,7 @@ struct rv_kunit_ctx {
 	int reactions, expected;
 	int mock_task_count;
 	struct task_struct *mock_tasks[RV_KUNIT_MAX_MOCK_TASKS];
+	struct task_struct *curr;
 };
 
 #define RV_KUNIT_EXPECT_REACTION(test, ctx)                             \
@@ -57,5 +62,11 @@ void prepare_test(struct kunit *test, const struct rv_kunit_mon *mon);
 void teardown_test(void *arg);
 struct task_struct *rv_kunit_alloc_mock_task(struct kunit *test);
 
+#define rv_mock_current(ctx, task) (ctx->curr = task)
+
+#else /* !CONFIG_RV_MONITORS_KUNIT_TEST */
+
+#define rv_get_current() current
+
 #endif /* CONFIG_RV_MONITORS_KUNIT_TEST */
 #endif /* _RV_KUNIT_H */
diff --git a/include/rv/ltl_monitor.h b/include/rv/ltl_monitor.h
index 56e83edcf0c4..d7dc01db4dd9 100644
--- a/include/rv/ltl_monitor.h
+++ b/include/rv/ltl_monitor.h
@@ -9,6 +9,7 @@
 #include <linux/stringify.h>
 #include <linux/seq_buf.h>
 #include <rv/instrumentation.h>
+#include <rv/kunit.h>
 #include <trace/events/task.h>
 #include <trace/events/sched.h>
 
diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig
index 34c1feb35a9b..7bae9723cdbf 100644
--- a/kernel/trace/rv/Kconfig
+++ b/kernel/trace/rv/Kconfig
@@ -121,4 +121,7 @@ config RV_MONITORS_KUNIT_TEST
 	  These tests verify that monitors correctly detect violations by
 	  triggering fake events and validating the expected reactions.
 
+	  Enabling this may slightly increase overhead of some monitors even
+	  when the KUnit test is not running.
+
 	  If unsure, say N.
diff --git a/kernel/trace/rv/monitors/pagefault/pagefault.c b/kernel/trace/rv/monitors/pagefault/pagefault.c
index 5e1a2a606783..e52500fd2de0 100644
--- a/kernel/trace/rv/monitors/pagefault/pagefault.c
+++ b/kernel/trace/rv/monitors/pagefault/pagefault.c
@@ -38,7 +38,7 @@ static void ltl_atoms_init(struct task_struct *task, struct ltl_monitor *mon, bo
 static void handle_page_fault(void *data, unsigned long address, struct pt_regs *regs,
 			      unsigned long error_code)
 {
-	ltl_atom_pulse(current, LTL_PAGEFAULT, true);
+	ltl_atom_pulse(rv_get_current(), LTL_PAGEFAULT, true);
 }
 
 static int enable_pagefault(void)
diff --git a/kernel/trace/rv/monitors/sleep/sleep.c b/kernel/trace/rv/monitors/sleep/sleep.c
index 12328ce663f5..71d2005ce520 100644
--- a/kernel/trace/rv/monitors/sleep/sleep.c
+++ b/kernel/trace/rv/monitors/sleep/sleep.c
@@ -102,7 +102,7 @@ static void handle_sched_waking(void *data, struct task_struct *task)
 	if (this_cpu_read(hardirq_context)) {
 		ltl_atom_pulse(task, LTL_WOKEN_BY_HARDIRQ, true);
 	} else if (in_task()) {
-		if (current->prio <= task->prio)
+		if (rv_get_current()->prio <= task->prio)
 			ltl_atom_pulse(task, LTL_WOKEN_BY_EQUAL_OR_HIGHER_PRIO, true);
 	} else if (in_nmi()) {
 		ltl_atom_pulse(task, LTL_WOKEN_BY_NMI, true);
@@ -112,12 +112,12 @@ static void handle_sched_waking(void *data, struct task_struct *task)
 static void handle_contention_begin(void *data, void *lock, unsigned int flags)
 {
 	if (flags & LCB_F_RT)
-		ltl_atom_update(current, LTL_BLOCK_ON_RT_MUTEX, true);
+		ltl_atom_update(rv_get_current(), LTL_BLOCK_ON_RT_MUTEX, true);
 }
 
 static void handle_contention_end(void *data, void *lock, int ret)
 {
-	ltl_atom_update(current, LTL_BLOCK_ON_RT_MUTEX, false);
+	ltl_atom_update(rv_get_current(), LTL_BLOCK_ON_RT_MUTEX, false);
 }
 
 static void handle_sys_enter(void *data, struct pt_regs *regs, long id)
@@ -126,7 +126,7 @@ static void handle_sys_enter(void *data, struct pt_regs *regs, long id)
 	unsigned long args[6];
 	int op, cmd;
 
-	mon = ltl_get_monitor(current);
+	mon = ltl_get_monitor(rv_get_current());
 
 	switch (id) {
 #ifdef __NR_clock_nanosleep
@@ -135,11 +135,11 @@ static void handle_sys_enter(void *data, struct pt_regs *regs, long id)
 #ifdef __NR_clock_nanosleep_time64
 	case __NR_clock_nanosleep_time64:
 #endif
-		syscall_get_arguments(current, regs, args);
+		syscall_get_arguments(rv_get_current(), regs, args);
 		ltl_atom_set(mon, LTL_NANOSLEEP_CLOCK_MONOTONIC, args[0] == CLOCK_MONOTONIC);
 		ltl_atom_set(mon, LTL_NANOSLEEP_CLOCK_TAI, args[0] == CLOCK_TAI);
 		ltl_atom_set(mon, LTL_NANOSLEEP_TIMER_ABSTIME, args[1] == TIMER_ABSTIME);
-		ltl_atom_update(current, LTL_CLOCK_NANOSLEEP, true);
+		ltl_atom_update(rv_get_current(), LTL_CLOCK_NANOSLEEP, true);
 		break;
 
 #ifdef __NR_futex
@@ -148,25 +148,25 @@ static void handle_sys_enter(void *data, struct pt_regs *regs, long id)
 #ifdef __NR_futex_time64
 	case __NR_futex_time64:
 #endif
-		syscall_get_arguments(current, regs, args);
+		syscall_get_arguments(rv_get_current(), regs, args);
 		op = args[1];
 		cmd = op & FUTEX_CMD_MASK;
 
 		switch (cmd) {
 		case FUTEX_LOCK_PI:
 		case FUTEX_LOCK_PI2:
-			ltl_atom_update(current, LTL_FUTEX_LOCK_PI, true);
+			ltl_atom_update(rv_get_current(), LTL_FUTEX_LOCK_PI, true);
 			break;
 		case FUTEX_WAIT:
 		case FUTEX_WAIT_BITSET:
 		case FUTEX_WAIT_REQUEUE_PI:
-			ltl_atom_update(current, LTL_FUTEX_WAIT, true);
+			ltl_atom_update(rv_get_current(), LTL_FUTEX_WAIT, true);
 			break;
 		}
 		break;
 #ifdef __NR_epoll_wait
 	case __NR_epoll_wait:
-		ltl_atom_update(current, LTL_EPOLL_WAIT, true);
+		ltl_atom_update(rv_get_current(), LTL_EPOLL_WAIT, true);
 		break;
 #endif
 	}
@@ -174,7 +174,7 @@ static void handle_sys_enter(void *data, struct pt_regs *regs, long id)
 
 static void handle_sys_exit(void *data, struct pt_regs *regs, long ret)
 {
-	struct ltl_monitor *mon = ltl_get_monitor(current);
+	struct ltl_monitor *mon = ltl_get_monitor(rv_get_current());
 
 	ltl_atom_set(mon, LTL_FUTEX_LOCK_PI, false);
 	ltl_atom_set(mon, LTL_FUTEX_WAIT, false);
@@ -182,7 +182,7 @@ static void handle_sys_exit(void *data, struct pt_regs *regs, long ret)
 	ltl_atom_set(mon, LTL_NANOSLEEP_CLOCK_TAI, false);
 	ltl_atom_set(mon, LTL_NANOSLEEP_TIMER_ABSTIME, false);
 	ltl_atom_set(mon, LTL_EPOLL_WAIT, false);
-	ltl_atom_update(current, LTL_CLOCK_NANOSLEEP, false);
+	ltl_atom_update(rv_get_current(), LTL_CLOCK_NANOSLEEP, false);
 }
 
 static void handle_kthread_stop(void *data, struct task_struct *task)
diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index cfe950fef3b4..edb10812f296 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -142,6 +142,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <kunit/static_stub.h>
 
 #ifdef CONFIG_RV_MON_EVENTS
 #define CREATE_TRACE_POINTS
@@ -893,4 +894,11 @@ void rv_clear_testing(struct kunit_suite *suite)
 	mutex_unlock(&rv_interface_lock);
 }
 EXPORT_SYMBOL_IF_KUNIT(rv_clear_testing);
+
+struct task_struct *rv_get_current(void)
+{
+	KUNIT_STATIC_STUB_REDIRECT(rv_get_current);
+	return current;
+}
+EXPORT_SYMBOL_GPL(rv_get_current);
 #endif
diff --git a/kernel/trace/rv/rv_monitors_test.c b/kernel/trace/rv/rv_monitors_test.c
index 2145c85d4c9a..2108973383b2 100644
--- a/kernel/trace/rv/rv_monitors_test.c
+++ b/kernel/trace/rv/rv_monitors_test.c
@@ -106,6 +106,13 @@ struct task_struct *rv_kunit_alloc_mock_task(struct kunit *test)
 	return tsk;
 }
 
+static struct task_struct *stub_rv_get_current(void)
+{
+	if (active_ctx && active_ctx->curr)
+		return active_ctx->curr;
+	return current;
+}
+
 static int rv_mon_test_init(struct kunit *test)
 {
 	struct rv_kunit_ctx *ctx;
@@ -115,6 +122,8 @@ static int rv_mon_test_init(struct kunit *test)
 
 	test->priv = ctx;
 
+	kunit_activate_static_stub(test, rv_get_current, stub_rv_get_current);
+
 	return 0;
 }
 
-- 
2.55.0