From nobody Sun Dec 14 18:04:30 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 ABC77311C09; Tue, 4 Nov 2025 08:17:11 +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=1762244234; cv=none; b=UkFsGld/4Po6WP6fFY3We8JqTs4oJNUbmKUiiqlr2sEM7+FGtlI8Lu+/vddBva46zbjyv3YIS6TnO+mD7Qq/wzHWP51I3mlNx719NA1Ygky2bC/kad3SbUqkLtvqhQhEkoo2knU1ZKt0LqvqoPQG3a/2iYzTB+LMlMgtLdS9CH0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762244234; c=relaxed/simple; bh=X7sDuz3ISeh2MhYFhGGfPkQJSOQYICibtgN6KV70nHI=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=O2pFe4z64Kx/57dibexocNEcuisf1JHwFyNqr7mTjzVY/1VsYQrTy1eoZC5f3Ug1m6p2hrYwtIiNN2m7HUiXt4GNac5QZ7OFtTZwf8b816CiS9xDqSvUsIkb5r+yyKNTXLjHNtDafjnZqZFCfOILVm1Jm7ZHnKv6xlq6hi3acMY= 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=n3DMVMB8; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=092ShYbq; 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="n3DMVMB8"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="092ShYbq" Date: Tue, 04 Nov 2025 08:17:08 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1762244230; 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=ZhwyM2vHZukDnZT+GEwxaHr/XreWhPgCixo02kbHQig=; b=n3DMVMB8im04z6H00uHQ4z3llVLzD8itlEb6cq6XLt2T7KZnY1z3m4JQ36l9dd0FR9accX RWeMcSI5sXiSvD2vKvgtCmWnPUW/pHNHWSyldGq4NSm+d+ky11B1871gRZUkeB4ebu+KSO 6qdgnk4dVR6rJgbond4tcRV6IFXMMeLdg42v6DcoTSSzsovHqg9HF4mevHY3UcI2Ja8RyR PSh1A1EDYrTAiSWSCTCD3vWcj+3trYknXpm/ZtBSkZUcBVatP9kQ1QbkRiiHfXrXoazeDD hEMSsafONJEk/o4J1ULyMcN78rv4x+3/4hXBH60xGNzanen1VFbGQQ9hXOJlsg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1762244230; 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=ZhwyM2vHZukDnZT+GEwxaHr/XreWhPgCixo02kbHQig=; b=092ShYbqqi/O3CFdI5ZBL06VsBcIU6d2frilv658aabiGYOveGtIkxjqn5ZjIaP8r8aiFM +IAqOFRcEn/KLnCQ== 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: Separate the signal delivery path Cc: Thomas Gleixner , "Peter Zijlstra (Intel)" , Ingo Molnar , Mathieu Desnoyers , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20251027084307.455429038@linutronix.de> References: <20251027084307.455429038@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176224422846.2601451.4229883174306540906.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: 9f6ffd4cebda86841700775de3213f22bb0ea22d Gitweb: https://git.kernel.org/tip/9f6ffd4cebda86841700775de3213f22b= b0ea22d Author: Thomas Gleixner AuthorDate: Mon, 27 Oct 2025 09:45:10 +01:00 Committer: Ingo Molnar CommitterDate: Tue, 04 Nov 2025 08:33:47 +01:00 rseq: Separate the signal delivery path Completely separate the signal delivery path from the notify handler as they have different semantics versus the event handling. The signal delivery only needs to ensure that the interrupted user context was not in a critical section or the section is aborted before it switches to the signal frame context. The signal frame context does not have the original instruction pointer anymore, so that can't be handled on exit to user space. No point in updating the CPU/CID ids as they might change again before the task returns to user space for real. The fast path optimization, which checks for the 'entry from user via interrupt' condition is only available for architectures which use the generic entry code. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Link: https://patch.msgid.link/20251027084307.455429038@linutronix.de --- include/linux/rseq.h | 21 ++++++++++++++++----- kernel/rseq.c | 30 ++++++++++++++++++++++-------- 2 files changed, 38 insertions(+), 13 deletions(-) diff --git a/include/linux/rseq.h b/include/linux/rseq.h index 92f9cd4..f5a4318 100644 --- a/include/linux/rseq.h +++ b/include/linux/rseq.h @@ -7,22 +7,33 @@ =20 #include =20 -void __rseq_handle_notify_resume(struct ksignal *sig, struct pt_regs *regs= ); +void __rseq_handle_notify_resume(struct pt_regs *regs); =20 static inline void rseq_handle_notify_resume(struct pt_regs *regs) { if (current->rseq.event.has_rseq) - __rseq_handle_notify_resume(NULL, regs); + __rseq_handle_notify_resume(regs); } =20 +void __rseq_signal_deliver(int sig, struct pt_regs *regs); + +/* + * Invoked from signal delivery to fixup based on the register context bef= ore + * switching to the signal delivery context. + */ static inline void rseq_signal_deliver(struct ksignal *ksig, struct pt_reg= s *regs) { - if (current->rseq.event.has_rseq) { - current->rseq.event.sched_switch =3D true; - __rseq_handle_notify_resume(ksig, regs); + if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY)) { + /* '&' is intentional to spare one conditional branch */ + if (current->rseq.event.has_rseq & current->rseq.event.user_irq) + __rseq_signal_deliver(ksig->sig, regs); + } else { + if (current->rseq.event.has_rseq) + __rseq_signal_deliver(ksig->sig, regs); } } =20 +/* Raised from context switch and exevce to force evaluation on exit to us= er */ static inline void rseq_sched_switch_event(struct task_struct *t) { if (t->rseq.event.has_rseq) { diff --git a/kernel/rseq.c b/kernel/rseq.c index 1e4f1d2..13faadc 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -250,13 +250,12 @@ efault: * respect to other threads scheduled on the same CPU, and with respect * to signal handlers. */ -void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *reg= s) +void __rseq_handle_notify_resume(struct pt_regs *regs) { struct task_struct *t =3D current; struct rseq_ids ids; u32 node_id; bool event; - int sig; =20 /* * If invoked from hypervisors before entering the guest via @@ -275,10 +274,7 @@ void __rseq_handle_notify_resume(struct ksignal *ksig,= struct pt_regs *regs) if (unlikely(t->flags & PF_EXITING)) return; =20 - if (ksig) - rseq_stat_inc(rseq_stats.signal); - else - rseq_stat_inc(rseq_stats.slowpath); + rseq_stat_inc(rseq_stats.slowpath); =20 /* * Read and clear the event pending bit first. If the task @@ -317,8 +313,26 @@ void __rseq_handle_notify_resume(struct ksignal *ksig,= struct pt_regs *regs) return; =20 error: - sig =3D ksig ? ksig->sig : 0; - force_sigsegv(sig); + force_sig(SIGSEGV); +} + +void __rseq_signal_deliver(int sig, struct pt_regs *regs) +{ + rseq_stat_inc(rseq_stats.signal); + /* + * Don't update IDs, they are handled on exit to user if + * necessary. The important thing is to abort a critical section of + * the interrupted context as after this point the instruction + * pointer in @regs points to the signal handler. + */ + if (unlikely(!rseq_handle_cs(current, regs))) { + /* + * Clear the errors just in case this might survive + * magically, but leave the rest intact. + */ + current->rseq.event.error =3D 0; + force_sigsegv(sig); + } } =20 /*