From nobody Sun Dec 14 18:11:36 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 198B5331A72; Wed, 29 Oct 2025 10:23:45 +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=1761733428; cv=none; b=unnMV6iXtqsZsnPZ7rddTe9Tvdav0ZgEIn41YMQKDqSlpRv5h9bX6a8m9ajDXJ4vAdAQ0Y8HlQhNLe1bizuaUsopT8FZAyzx7M9gAAAnuPCT0YEiMX64JD/lG8HVjQHotgte3ly4EIA++ZR9m087vmdSY6WwiLaHlOLQdMj+Oas= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761733428; c=relaxed/simple; bh=NUxHD7kKY6ljQ3w8iuT4JfTdXblNwqC1NA1Q0/X3ZMA=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=lMssqLk4zltSkACpzS4luroSOAXQRMsEhPGapy2iFbwU+agZ+8A9yf63qMxH8gFlaVz2tYGe3i9OZpaJWpr1PgP4xEJtW44TbwNa5GgI4UQ0oO04UU8nDC7Cgy778UBL9LELHuk4xKUYeVvTSVuCPYaQxlXSF9p4x2g02rmtVQg= 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=s1kViIYy; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=CSFot/JO; 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="s1kViIYy"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="CSFot/JO" Date: Wed, 29 Oct 2025 10:23:42 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1761733424; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=egWQNddlbTr4kXgM/8O/h+xPWuA9Mzt/2KhCwH0koqU=; b=s1kViIYyusKwISVtHQzLnaqW7i5yo0dQriiFVrBoz8BxJI8/mh2LUprErI/UG4pSptjHz9 BGGyHP6qmw15bQXJFnWvCj8OhHURCW48l5VY5R14iPzMWiDbCzVhiBJM8+MyNRpJyY/lWY Lr9JoZh4rg4oI2vPQZa+jxffdHYAsb94bNDG3NYOy65ujROMZzm37/2hn3MIFbUoDCSyan RPqmuSUFCdsiez0utdM6P1DqdOhDu4jeywuCeWMUYNbGwwl/tuDdWTca/pLcZnd39Z2Ioj Ql4BMgqMcXF44pW9/UCvKwqRJa6fQPXYHFyYqWdj9y//zOwS+1o7Q9Q3Y8gzug== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1761733424; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=egWQNddlbTr4kXgM/8O/h+xPWuA9Mzt/2KhCwH0koqU=; b=CSFot/JOAdMc8Z4d12a3qvBfqm0ZpX6uTfNCkxlLUvdTcqb21S8tjBkzgKz4Ri6j3ZNMxT fVoHD+vh/fnxfODQ== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/rseq] rseq: Provide static branch for runtime debugging Cc: Thomas Gleixner , "Peter Zijlstra (Intel)" , Mathieu Desnoyers , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20251027084307.089270547@linutronix.de> References: <20251027084307.089270547@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176173342275.2601451.12192719270073853345.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the core/rseq branch of tip: Commit-ID: 5885f2a4824dbf7628fc1fedce27f50657f7dbc8 Gitweb: https://git.kernel.org/tip/5885f2a4824dbf7628fc1fedce27f5065= 7f7dbc8 Author: Thomas Gleixner AuthorDate: Mon, 27 Oct 2025 09:44:55 +01:00 Committer: Peter Zijlstra CommitterDate: Wed, 29 Oct 2025 11:07:16 +01:00 rseq: Provide static branch for runtime debugging Config based debug is rarely turned on and is not available easily when things go wrong. Provide a static branch to allow permanent integration of debug mechanisms along with the usual toggles in Kconfig, command line and debugfs. Requested-by: Peter Zijlstra Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Mathieu Desnoyers Link: https://patch.msgid.link/20251027084307.089270547@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 4 +- include/linux/rseq_entry.h | 3 +- init/Kconfig | 14 +++- kernel/rseq.c | 73 +++++++++++++++- 4 files changed, 90 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 6c42061..e638274 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6500,6 +6500,10 @@ Memory area to be used by remote processor image, managed by CMA. =20 + rseq_debug=3D [KNL] Enable or disable restartable sequence + debug mode. Defaults to CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE. + Format: + rt_group_sched=3D [KNL] Enable or disable SCHED_RR/FIFO group scheduling when CONFIG_RT_GROUP_SCHED=3Dy. Defaults to !CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED. diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h index ff9080b..ed8e5f8 100644 --- a/include/linux/rseq_entry.h +++ b/include/linux/rseq_entry.h @@ -34,6 +34,7 @@ DECLARE_PER_CPU(struct rseq_stats, rseq_stats); #endif /* !CONFIG_RSEQ_STATS */ =20 #ifdef CONFIG_RSEQ +#include #include =20 #include @@ -64,6 +65,8 @@ static inline void rseq_trace_ip_fixup(unsigned long ip, = unsigned long start_ip, unsigned long offset, unsigned long abort_ip) { } #endif /* !CONFIG_TRACEPOINT */ =20 +DECLARE_STATIC_KEY_MAYBE(CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE, rseq_debug_enab= led); + static __always_inline void rseq_note_user_irq_entry(void) { if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY)) diff --git a/init/Kconfig b/init/Kconfig index f39fdfb..bde40ab 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1925,10 +1925,24 @@ config RSEQ_STATS =20 If unsure, say N. =20 +config RSEQ_DEBUG_DEFAULT_ENABLE + default n + bool "Enable restartable sequences debug mode by default" if EXPERT + depends on RSEQ + help + This enables the static branch for debug mode of restartable + sequences. + + This also can be controlled on the kernel command line via the + command line parameter "rseq_debug=3D0/1" and through debugfs. + + If unsure, say N. + config DEBUG_RSEQ default n bool "Enable debugging of rseq() system call" if EXPERT depends on RSEQ && DEBUG_KERNEL + select RSEQ_DEBUG_DEFAULT_ENABLE help Enable extra debugging checks for the rseq system call. =20 diff --git a/kernel/rseq.c b/kernel/rseq.c index c0dbe2e..679ab8e 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -95,6 +95,27 @@ RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL | \ RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE) =20 +DEFINE_STATIC_KEY_MAYBE(CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE, rseq_debug_enabl= ed); + +static inline void rseq_control_debug(bool on) +{ + if (on) + static_branch_enable(&rseq_debug_enabled); + else + static_branch_disable(&rseq_debug_enabled); +} + +static int __init rseq_setup_debug(char *str) +{ + bool on; + + if (kstrtobool(str, &on)) + return -EINVAL; + rseq_control_debug(on); + return 1; +} +__setup("rseq_debug=3D", rseq_setup_debug); + #ifdef CONFIG_TRACEPOINTS /* * Out of line, so the actual update functions can be in a header to be @@ -112,10 +133,11 @@ void __rseq_trace_ip_fixup(unsigned long ip, unsigned= long start_ip, } #endif /* CONFIG_TRACEPOINTS */ =20 +#ifdef CONFIG_DEBUG_FS #ifdef CONFIG_RSEQ_STATS DEFINE_PER_CPU(struct rseq_stats, rseq_stats); =20 -static int rseq_debug_show(struct seq_file *m, void *p) +static int rseq_stats_show(struct seq_file *m, void *p) { struct rseq_stats stats =3D { }; unsigned int cpu; @@ -140,14 +162,56 @@ static int rseq_debug_show(struct seq_file *m, void *= p) return 0; } =20 +static int rseq_stats_open(struct inode *inode, struct file *file) +{ + return single_open(file, rseq_stats_show, inode->i_private); +} + +static const struct file_operations stat_ops =3D { + .open =3D rseq_stats_open, + .read =3D seq_read, + .llseek =3D seq_lseek, + .release =3D single_release, +}; + +static int __init rseq_stats_init(struct dentry *root_dir) +{ + debugfs_create_file("stats", 0444, root_dir, NULL, &stat_ops); + return 0; +} +#else +static inline void rseq_stats_init(struct dentry *root_dir) { } +#endif /* CONFIG_RSEQ_STATS */ + +static int rseq_debug_show(struct seq_file *m, void *p) +{ + bool on =3D static_branch_unlikely(&rseq_debug_enabled); + + seq_printf(m, "%d\n", on); + return 0; +} + +static ssize_t rseq_debug_write(struct file *file, const char __user *ubuf, + size_t count, loff_t *ppos) +{ + bool on; + + if (kstrtobool_from_user(ubuf, count, &on)) + return -EINVAL; + + rseq_control_debug(on); + return count; +} + static int rseq_debug_open(struct inode *inode, struct file *file) { return single_open(file, rseq_debug_show, inode->i_private); } =20 -static const struct file_operations dfs_ops =3D { +static const struct file_operations debug_ops =3D { .open =3D rseq_debug_open, .read =3D seq_read, + .write =3D rseq_debug_write, .llseek =3D seq_lseek, .release =3D single_release, }; @@ -156,11 +220,12 @@ static int __init rseq_debugfs_init(void) { struct dentry *root_dir =3D debugfs_create_dir("rseq", NULL); =20 - debugfs_create_file("stats", 0444, root_dir, NULL, &dfs_ops); + debugfs_create_file("debug", 0644, root_dir, NULL, &debug_ops); + rseq_stats_init(root_dir); return 0; } __initcall(rseq_debugfs_init); -#endif /* CONFIG_RSEQ_STATS */ +#endif /* CONFIG_DEBUG_FS */ =20 #ifdef CONFIG_DEBUG_RSEQ static struct rseq *rseq_kernel_fields(struct task_struct *t)