[PATCH v2 19/22] rv: Add rtapp_pagefault monitor

[Nam Cao]

Userspace real-time applications may have design flaws that they raise
page faults in real-time threads, and thus have unexpected latencies.

Add an linear temporal logic monitor to detect this scenario.

Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
---
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Alexandre Ghiti <alex@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
---
 kernel/trace/rv/Kconfig                       |  1 +
 kernel/trace/rv/Makefile                      |  1 +
 kernel/trace/rv/monitors/pagefault/Kconfig    | 11 +++
 .../trace/rv/monitors/pagefault/pagefault.c   | 83 +++++++++++++++++++
 .../trace/rv/monitors/pagefault/pagefault.h   | 57 +++++++++++++
 .../rv/monitors/pagefault/pagefault_trace.h   | 14 ++++
 kernel/trace/rv/rv_trace.h                    |  1 +
 tools/verification/models/rtapp/pagefault.ltl |  1 +
 8 files changed, 169 insertions(+)
 create mode 100644 kernel/trace/rv/monitors/pagefault/Kconfig
 create mode 100644 kernel/trace/rv/monitors/pagefault/pagefault.c
 create mode 100644 kernel/trace/rv/monitors/pagefault/pagefault.h
 create mode 100644 kernel/trace/rv/monitors/pagefault/pagefault_trace.h
 create mode 100644 tools/verification/models/rtapp/pagefault.ltl

diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig
index 5c407d291661..6f86d8501e87 100644
--- a/kernel/trace/rv/Kconfig
+++ b/kernel/trace/rv/Kconfig
@@ -42,6 +42,7 @@ source "kernel/trace/rv/monitors/scpd/Kconfig"
 source "kernel/trace/rv/monitors/snep/Kconfig"
 source "kernel/trace/rv/monitors/sncid/Kconfig"
 source "kernel/trace/rv/monitors/rtapp/Kconfig"
+source "kernel/trace/rv/monitors/pagefault/Kconfig"
 # Add new monitors here
 
 config RV_REACTORS
diff --git a/kernel/trace/rv/Makefile b/kernel/trace/rv/Makefile
index 9b28c2419995..353ecf939d0e 100644
--- a/kernel/trace/rv/Makefile
+++ b/kernel/trace/rv/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_RV_MON_SCPD) += monitors/scpd/scpd.o
 obj-$(CONFIG_RV_MON_SNEP) += monitors/snep/snep.o
 obj-$(CONFIG_RV_MON_SNCID) += monitors/sncid/sncid.o
 obj-$(CONFIG_RV_MON_RTAPP) += monitors/rtapp/rtapp.o
+obj-$(CONFIG_RV_MON_PAGEFAULT) += monitors/pagefault/pagefault.o
 # Add new monitors here
 obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
 obj-$(CONFIG_RV_REACT_PRINTK) += reactor_printk.o
diff --git a/kernel/trace/rv/monitors/pagefault/Kconfig b/kernel/trace/rv/monitors/pagefault/Kconfig
new file mode 100644
index 000000000000..b31dee208459
--- /dev/null
+++ b/kernel/trace/rv/monitors/pagefault/Kconfig
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+config RV_MON_PAGEFAULT
+	depends on RV
+	select RV_LTL_MONITOR
+	depends on RV_MON_RTAPP
+	default y
+	select LTL_MON_EVENTS_ID
+	bool "pagefault monitor"
+	help
+	  Monitor that real-time tasks do not raise page faults
diff --git a/kernel/trace/rv/monitors/pagefault/pagefault.c b/kernel/trace/rv/monitors/pagefault/pagefault.c
new file mode 100644
index 000000000000..9f7a4cba39a1
--- /dev/null
+++ b/kernel/trace/rv/monitors/pagefault/pagefault.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/ftrace.h>
+#include <linux/tracepoint.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rv.h>
+#include <rv/instrumentation.h>
+
+#define MODULE_NAME "pagefault"
+
+#include <rv_trace.h>
+#include <trace/events/exceptions.h>
+#include <monitors/rtapp/rtapp.h>
+
+#include "pagefault.h"
+#include <rv/ltl_monitor.h>
+
+static void ltl_atoms_fetch(struct task_struct *task, struct ltl_monitor *mon)
+{
+	ltl_atom_set(mon, LTL_RT, rt_task(task));
+}
+
+static void ltl_atoms_init(struct task_struct *task, struct ltl_monitor *mon, bool task_creation)
+{
+	if (task_creation)
+		ltl_atom_set(mon, LTL_PAGEFAULT, false);
+}
+
+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);
+}
+
+static int enable_pagefault(void)
+{
+	int retval;
+
+	retval = ltl_monitor_init();
+	if (retval)
+		return retval;
+
+	rv_attach_trace_probe("pagefault", page_fault_kernel, handle_page_fault);
+	rv_attach_trace_probe("pagefault", page_fault_user, handle_page_fault);
+
+	return 0;
+}
+
+static void disable_pagefault(void)
+{
+	rv_pagefault.enabled = 0;
+
+	rv_detach_trace_probe("rtapp_pagefault", page_fault_kernel, handle_page_fault);
+	rv_detach_trace_probe("rtapp_pagefault", page_fault_user, handle_page_fault);
+
+	ltl_monitor_destroy();
+}
+
+static struct rv_monitor rv_pagefault = {
+	.name = "pagefault",
+	.description = "Monitor that RT tasks do not raise page faults",
+	.enable = enable_pagefault,
+	.disable = disable_pagefault,
+};
+
+static int __init register_pagefault(void)
+{
+	rv_register_monitor(&rv_pagefault, &rv_rtapp);
+	return 0;
+}
+
+static void __exit unregister_pagefault(void)
+{
+	rv_unregister_monitor(&rv_pagefault);
+}
+
+module_init(register_pagefault);
+module_exit(unregister_pagefault);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Nam Cao <namcao@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("pagefault: Monitor that RT tasks do not raise page faults");
diff --git a/kernel/trace/rv/monitors/pagefault/pagefault.h b/kernel/trace/rv/monitors/pagefault/pagefault.h
new file mode 100644
index 000000000000..f4535c83f7d1
--- /dev/null
+++ b/kernel/trace/rv/monitors/pagefault/pagefault.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/rv.h>
+
+#define MONITOR_NAME pagefault
+
+enum ltl_atom {
+	LTL_PAGEFAULT,
+	LTL_RT,
+	LTL_NUM_ATOM
+};
+static_assert(LTL_NUM_ATOM <= RV_MAX_LTL_ATOM);
+
+static const char *ltl_atom_str(enum ltl_atom atom)
+{
+	static const char *const names[] = {
+		"p",
+		"r",
+	};
+
+	return names[atom];
+}
+
+enum ltl_buchi_state {
+	S0,
+	RV_NUM_BA_STATES
+};
+static_assert(RV_NUM_BA_STATES <= RV_MAX_BA_STATES);
+
+static void ltl_start(struct task_struct *task, struct ltl_monitor *mon)
+{
+	bool pagefault = test_bit(LTL_PAGEFAULT, mon->atoms);
+	bool val3 = !pagefault;
+	bool rt = test_bit(LTL_RT, mon->atoms);
+	bool val1 = !rt;
+	bool val4 = val1 || val3;
+
+	if (val4)
+		__set_bit(S0, mon->states);
+}
+
+static void
+ltl_possible_next_states(struct ltl_monitor *mon, unsigned int state, unsigned long *next)
+{
+	bool pagefault = test_bit(LTL_PAGEFAULT, mon->atoms);
+	bool val3 = !pagefault;
+	bool rt = test_bit(LTL_RT, mon->atoms);
+	bool val1 = !rt;
+	bool val4 = val1 || val3;
+
+	switch (state) {
+	case S0:
+		if (val4)
+			__set_bit(S0, next);
+		break;
+	}
+}
diff --git a/kernel/trace/rv/monitors/pagefault/pagefault_trace.h b/kernel/trace/rv/monitors/pagefault/pagefault_trace.h
new file mode 100644
index 000000000000..fe1f82597b1a
--- /dev/null
+++ b/kernel/trace/rv/monitors/pagefault/pagefault_trace.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Snippet to be included in rv_trace.h
+ */
+
+#ifdef CONFIG_RV_MON_PAGEFAULT
+DEFINE_EVENT(event_ltl_monitor_id, event_pagefault,
+	     TP_PROTO(struct task_struct *task, char *states, char *atoms, char *next),
+	     TP_ARGS(task, states, atoms, next));
+DEFINE_EVENT(error_ltl_monitor_id, error_pagefault,
+	     TP_PROTO(struct task_struct *task),
+	     TP_ARGS(task));
+#endif /* CONFIG_RV_MON_PAGEFAULT */
diff --git a/kernel/trace/rv/rv_trace.h b/kernel/trace/rv/rv_trace.h
index f9fb848bae91..02c906c9745b 100644
--- a/kernel/trace/rv/rv_trace.h
+++ b/kernel/trace/rv/rv_trace.h
@@ -172,6 +172,7 @@ TRACE_EVENT(error_ltl_monitor_id,
 
 	TP_printk("%s[%d]: violation detected", __get_str(comm), __entry->pid)
 );
+#include <monitors/pagefault/pagefault_trace.h>
 // Add new monitors based on CONFIG_LTL_MON_EVENTS_ID here
 #endif /* CONFIG_LTL_MON_EVENTS_ID */
 #endif /* _TRACE_RV_H */
diff --git a/tools/verification/models/rtapp/pagefault.ltl b/tools/verification/models/rtapp/pagefault.ltl
new file mode 100644
index 000000000000..d7ce62102733
--- /dev/null
+++ b/tools/verification/models/rtapp/pagefault.ltl
@@ -0,0 +1 @@
+RULE = always (RT imply not PAGEFAULT)
-- 
2.39.5