From nobody Tue Oct 7 14:06:27 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F13ED239E9F; Wed, 9 Jul 2025 17:56:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752083804; cv=none; b=JNhHQ7m0KjL2MJX52OgBe2+O+KDSb/rrDr3AfhJ4vdplFCGj5H1/IgX+NY9vaiw+wzpSJBU/JJsbLwk267V7OFt4spXubXpOHVPxcmX357Bx2i8IpyvUhI2FAbf/zbPk3g3HEHssLgIkSH7fp6MJMGBIo/Cpb8yepvoh8aWNA0c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752083804; c=relaxed/simple; bh=AfS6TQQh82okS9DkGW8GQh9IptmjH99b08416Bg0FsU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=fGuh/2GKOhy6wELNE+11BK85wlfDiuyW1ZSKFF9j3PoK+wQ6hAFTKAYl8OS7Ugm8W3e5ECvTQUZTtqQiZo+EQ9FTs1ihVWZ5RcAhx/7Op9fOOm6vwPTl2XmYtADyuSujw1w3LAa3X9pPBcLbF3+H8pYOlAC7iiZPUUySfxVaDmk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=i3c90rMz; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=AE24LCm9; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="i3c90rMz"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="AE24LCm9" From: Nam Cao DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1752083800; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aa+pYL1S1rGVwB7K8u9n1mKPCXiF5HJyzw8bW7g2Blo=; b=i3c90rMz+GHCI3Fuj0nPXD/+/i4SeqCkj4CnwDWejIPlkAbpeYC63vxBE9CelT0MgSL0hL iF5izsTJ7SPjU/tsKUWa6lGi1iZognxcON81tIGgp9787Wxoq1SEjKd2tf/JWKo5N/Nnmw lmny83Kpt8mZov5vwTvt0VlHAM+26L38jldq3cvIEftR1lJKvvBz0L4koge1Sx9o2H2UYH RiWVTUfJKhAUSQx7dwXg9f92cBi2rsvYubJQR9rZ4jQDIFczeLnMXq65fIr/gExw/+NcsU 9xG0QKu8eLiRn2cfJ3d7Y0IA+gdA4rJqbw12DSlTErYuWRN1UMu/HE0Q5blarg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1752083800; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aa+pYL1S1rGVwB7K8u9n1mKPCXiF5HJyzw8bW7g2Blo=; b=AE24LCm9/NNOeAGpxA4GsnA+UjRyTrx5484+twAZRoZYTfufWVe2CFqbV13958ZIaM6Ues C6eWN+/yI/IU/ACw== To: Steven Rostedt , John Ogness , Masami Hiramatsu , Mathieu Desnoyers , Gabriele Monaco , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Nam Cao Subject: [PATCH v12 09/12] rv: Add rtapp_pagefault monitor Date: Wed, 9 Jul 2025 19:56:26 +0200 Message-Id: <0e5e682e21ee949fa3ac2e9a68347eadc0cbfeb7.1752082806.git.namcao@linutronix.de> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Reviewed-by: Gabriele Monaco Signed-off-by: Nam Cao --- kernel/trace/rv/Kconfig | 1 + kernel/trace/rv/Makefile | 1 + kernel/trace/rv/monitors/pagefault/Kconfig | 20 +++++ .../trace/rv/monitors/pagefault/pagefault.c | 88 +++++++++++++++++++ .../trace/rv/monitors/pagefault/pagefault.h | 64 ++++++++++++++ .../rv/monitors/pagefault/pagefault_trace.h | 14 +++ kernel/trace/rv/rv_trace.h | 1 + tools/verification/models/rtapp/pagefault.ltl | 1 + 8 files changed, 190 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 =20 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-$(CONFIG_RV_MON_SCPD) +=3D monitors/scpd/scpd.o obj-$(CONFIG_RV_MON_SNEP) +=3D monitors/snep/snep.o obj-$(CONFIG_RV_MON_SNCID) +=3D monitors/sncid/sncid.o obj-$(CONFIG_RV_MON_RTAPP) +=3D monitors/rtapp/rtapp.o +obj-$(CONFIG_RV_MON_PAGEFAULT) +=3D monitors/pagefault/pagefault.o # Add new monitors here obj-$(CONFIG_RV_REACTORS) +=3D rv_reactors.o obj-$(CONFIG_RV_REACT_PRINTK) +=3D reactor_printk.o diff --git a/kernel/trace/rv/monitors/pagefault/Kconfig b/kernel/trace/rv/m= onitors/pagefault/Kconfig new file mode 100644 index 000000000000..5e16625f1653 --- /dev/null +++ b/kernel/trace/rv/monitors/pagefault/Kconfig @@ -0,0 +1,20 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +config RV_MON_PAGEFAULT + depends on RV + select RV_LTL_MONITOR + depends on RV_MON_RTAPP + depends on X86 || RISCV + default y + select LTL_MON_EVENTS_ID + bool "pagefault monitor" + help + Monitor that real-time tasks do not raise page faults, causing + undesirable latency. + + If you are developing a real-time system and not entirely sure whether + the applications are designed correctly for real-time, you want to say + Y here. + + This monitor does not affect execution speed while it is not running, + therefore it is safe to enable this in production kernel. diff --git a/kernel/trace/rv/monitors/pagefault/pagefault.c b/kernel/trace/= rv/monitors/pagefault/pagefault.c new file mode 100644 index 000000000000..9fe6123b2200 --- /dev/null +++ b/kernel/trace/rv/monitors/pagefault/pagefault.c @@ -0,0 +1,88 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define MODULE_NAME "pagefault" + +#include +#include +#include + +#include "pagefault.h" +#include + +static void ltl_atoms_fetch(struct task_struct *task, struct ltl_monitor *= mon) +{ + /* + * This includes "actual" real-time tasks and also PI-boosted + * tasks. A task being PI-boosted means it is blocking an "actual" + * real-task, therefore it should also obey the monitor's rule, + * otherwise the "actual" real-task may be delayed. + */ + ltl_atom_set(mon, LTL_RT, rt_or_dl_task(task)); +} + +static void ltl_atoms_init(struct task_struct *task, struct ltl_monitor *m= on, 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 =3D ltl_monitor_init(); + if (retval) + return retval; + + rv_attach_trace_probe("rtapp_pagefault", page_fault_kernel, handle_page_f= ault); + rv_attach_trace_probe("rtapp_pagefault", page_fault_user, handle_page_fau= lt); + + return 0; +} + +static void disable_pagefault(void) +{ + rv_detach_trace_probe("rtapp_pagefault", page_fault_kernel, handle_page_f= ault); + rv_detach_trace_probe("rtapp_pagefault", page_fault_user, handle_page_fau= lt); + + ltl_monitor_destroy(); +} + +static struct rv_monitor rv_pagefault =3D { + .name =3D "pagefault", + .description =3D "Monitor that RT tasks do not raise page faults", + .enable =3D enable_pagefault, + .disable =3D disable_pagefault, +}; + +static int __init register_pagefault(void) +{ + return rv_register_monitor(&rv_pagefault, &rv_rtapp); +} + +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 "); +MODULE_DESCRIPTION("pagefault: Monitor that RT tasks do not raise page fau= lts"); diff --git a/kernel/trace/rv/monitors/pagefault/pagefault.h b/kernel/trace/= rv/monitors/pagefault/pagefault.h new file mode 100644 index 000000000000..c580ec194009 --- /dev/null +++ b/kernel/trace/rv/monitors/pagefault/pagefault.h @@ -0,0 +1,64 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +/* + * C implementation of Buchi automaton, automatically generated by + * tools/verification/rvgen from the linear temporal logic specification. + * For further information, see kernel documentation: + * Documentation/trace/rv/linear_temporal_logic.rst + */ + +#include + +#define MONITOR_NAME pagefault + +enum ltl_atom { + LTL_PAGEFAULT, + LTL_RT, + LTL_NUM_ATOM +}; +static_assert(LTL_NUM_ATOM <=3D RV_MAX_LTL_ATOM); + +static const char *ltl_atom_str(enum ltl_atom atom) +{ + static const char *const names[] =3D { + "pa", + "rt", + }; + + return names[atom]; +} + +enum ltl_buchi_state { + S0, + RV_NUM_BA_STATES +}; +static_assert(RV_NUM_BA_STATES <=3D RV_MAX_BA_STATES); + +static void ltl_start(struct task_struct *task, struct ltl_monitor *mon) +{ + bool pagefault =3D test_bit(LTL_PAGEFAULT, mon->atoms); + bool val3 =3D !pagefault; + bool rt =3D test_bit(LTL_RT, mon->atoms); + bool val1 =3D !rt; + bool val4 =3D val1 || val3; + + if (val4) + __set_bit(S0, mon->states); +} + +static void +ltl_possible_next_states(struct ltl_monitor *mon, unsigned int state, unsi= gned long *next) +{ + bool pagefault =3D test_bit(LTL_PAGEFAULT, mon->atoms); + bool val3 =3D !pagefault; + bool rt =3D test_bit(LTL_RT, mon->atoms); + bool val1 =3D !rt; + bool val4 =3D 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 fd3111ad1d51..98eee8ec96e4 100644 --- a/kernel/trace/rv/rv_trace.h +++ b/kernel/trace/rv/rv_trace.h @@ -172,6 +172,7 @@ DECLARE_EVENT_CLASS(error_ltl_monitor_id, =20 TP_printk("%s[%d]: violation detected", __get_str(comm), __entry->pid) ); +#include // 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/verifica= tion/models/rtapp/pagefault.ltl new file mode 100644 index 000000000000..d7ce62102733 --- /dev/null +++ b/tools/verification/models/rtapp/pagefault.ltl @@ -0,0 +1 @@ +RULE =3D always (RT imply not PAGEFAULT) --=20 2.39.5