From nobody Sun Dec 14 18:12:30 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 65A55330B2B; Wed, 29 Oct 2025 10:23:40 +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=1761733423; cv=none; b=sPNt25zpwhE4Wb+pKVwMzrqAOFc8m3w20dlVMpzU5pIwgJNQsxA090rFtbu/4SI712H3vj5nFcwHvie+xFzjCWKdUJgz2J/HGLyfA/n79OMjTJWaoNGwWtUjdVmJW53mNdAsP63TiRSyXg0xD24qcYvkpBawkRQD68zCLDtMlyY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761733423; c=relaxed/simple; bh=9KAUuxbUlgJs8O75LTi+3jxReGldcdTjlGfXvKkktGI=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=PqaXFfvv1SWAsIudrjiDxYH5X8GBj06F5O1kBxxXOeUXa6DCwbx10407/NGMeuNGl1ZlYr/6f3CHsa6E43QukWogVaxEg23c8KFzmXaigSbDslzoK0BbI5tI/q3HWhmQckZr/h832dsCZOpps30ATEDwm9DTlTeNbN8wSQTzTW4= 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=KCDpJSzH; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=nZTR5GDD; 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="KCDpJSzH"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="nZTR5GDD" Date: Wed, 29 Oct 2025 10:23:35 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1761733416; 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=nXS9VSciu+t1rRiSmIIOdQ7Kv4/bAdxu6TJ2BX1A1dc=; b=KCDpJSzHEun8NQ1AA5EQ4OqC3nG9sifxtxjqsadg44p3ST6Akmu+Gs22c8DQ7g/TI137lY 1ziSIA7Ettx2o6gfEHb17z/Z9UG8cSYQ0fyP2pnqjbjTY9/hwsx4dsyRF73VUk14eUz3oX /m0Wkiz7REr6K4zRtJIqiANLYqiwumvsEoIZT5zelB2gz1rCfhit2O1TQL0TvtvbNDsBL9 1YpqNNHULL6TXGiEE/PeXgV7cUtVcbu9zMnTXaHNy+Z3k+IKcPKMjll4xEswxWaBoL4OOg FaVY/0jfARTis2hcWHl2gacGy8Kyfh2O0XBiQyOrGjVa96rz+hlhErz7Sl8Ozg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1761733416; 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=nXS9VSciu+t1rRiSmIIOdQ7Kv4/bAdxu6TJ2BX1A1dc=; b=nZTR5GDDSf3hTyaTTgmVuuKtWf+t3iF2xs2OqYxezig3QfJSAMMVjKp/XenP97oBMhL/Fy jROIh5Qh6UdI5NCA== 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)" , 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: <176173341514.2601451.16659594890035832293.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: 7315751a4e9e4c00278717c9f344a5929ca9898c Gitweb: https://git.kernel.org/tip/7315751a4e9e4c00278717c9f344a5929= ca9898c Author: Thomas Gleixner AuthorDate: Mon, 27 Oct 2025 09:45:10 +01:00 Committer: Peter Zijlstra CommitterDate: Wed, 29 Oct 2025 11:07:18 +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) 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 a526074..06c21f6 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 32d4ab7..4d7ba22 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 /*