From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 9373142882C for ; Fri, 10 Jul 2026 12:53:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783688003; cv=none; b=jaqAuyvN8Wyrvk5OE85DntNSR/fJ24RJhV2URXcUBwRJ3EU0M0r++ya2PF6ejD1q59n0nfr80Avs2YKOc8/u7e/G2C6jYj8BSqXFEJxOshKLb/veXMthsKjS0NfVoB+UrBsO84wHsiADEsXxeEcoVTlTpbqciWYiOAa7dnKcNz8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783688003; c=relaxed/simple; bh=sxv6a13OPgrK6TOsUQ/kBJYeYtA4hSsjpL/QVUw8MJI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ff14UT4OBEjLXP1iVEMS6o7Z2ggesijQ06mJlFwQgjzpI6FOgUHEu6iTGPo4YpP/+qT/sWBQlud64sQzyMBxKjHQaL4XHYoRQvGBrY55pEP103Sq5H3bRJLP8PwJuIruqFVFTM+pSFV5cdDWq2GOJi46VxS1B9drH1bynbRNoVU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=O2AA42wc; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="O2AA42wc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783688000; h=from:from: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=XTxMckJ71iKdcnC625lbZ9WJQgTp+gyXuVTaxsSZYeA=; b=O2AA42wc0EFpHFaeTcNaA+5w2Vxj2dLQZ00YjfR5A3+JB1y4OPtfyeY1VNKeuyYVDjlqoy TzMenwjfF9q+zFqyZXi8XP+H48JHs7nMPojLVdTC4UG6U94iupybkM9uqpYd1CMMtl1uyc pySLQjyn0zU5XCWVDK7TvBD50TiZKnw= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-640-duefXCb_NOaqJcpTJsNlCw-1; Fri, 10 Jul 2026 08:53:17 -0400 X-MC-Unique: duefXCb_NOaqJcpTJsNlCw-1 X-Mimecast-MFC-AGG-ID: duefXCb_NOaqJcpTJsNlCw_1783687991 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AAE061801379; Fri, 10 Jul 2026 12:53:07 +0000 (UTC) Received: from fedora (unknown [10.44.49.164]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 8AEF2180029C; Fri, 10 Jul 2026 12:52:47 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 10 Jul 2026 14:53:07 +0200 (CEST) Date: Fri, 10 Jul 2026 14:52:40 +0200 From: Oleg Nesterov To: Michal =?iso-8859-1?Q?Such=E1nek?= Cc: Thomas Gleixner , LKML , Peter Zijlstra , Michael Ellerman , Shrikanth Hegde , linuxppc-dev@lists.ozlabs.org, Kees Cook , Huacai Chen , loongarch@lists.linux.dev, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Sven Schnelle , linux-s390@vger.kernel.org, x86@kernel.org, Mark Rutland , Jinjie Ruan , Andy Lutomirski , Richard Henderson , Russell King , Catalin Marinas , Guo Ren , Geert Uytterhoeven , Thomas Bogendoerfer , Helge Deller , Yoshinori Sato , Richard Weinberger , Chris Zankel , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-um@lists.infradead.org, Arnd Bergmann , Vineet Gupta , Will Deacon , Brian Cain , Michal Simek , Dinh Nguyen , "David S. Miller" , Andreas Larsson , linux-snps-arc@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-openrisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org Subject: Re: [patch 13/18] entry: Make trace_syscall_enter() return type bool Message-ID: References: <20260707181957.433213175@kernel.org> <20260707190254.338083894@kernel.org> <87se5tqkyp.ffs@fw13> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On 07/10, Michal Suchánek wrote: > > On Fri, Jul 10, 2026 at 01:40:43PM +0200, Oleg Nesterov wrote: > > > > I can only say that ptrace users do want to skip the syscall and set the > > return value on entry. > > > > See > > [PATCH v5 1/2] ptrace: add PTRACE_SET_SYSCALL_INFO syscall skipping support > > https://lore.kernel.org/all/20260709100949.94345-2-renzo@cs.unibo.it/ > > > > The changelog explains that currently this doesn't work because > > among the arches which define HAVE_ARCH_TRACEHOOK (at least) arch/mips is > > broken in this regard. > > Or it could be documented that setting the return value has to be done > in the exit trace, and that would than work on any architecture AFAICT. Well, ptrace users know the problem. And this what they have to do currently. > With ppc and s390 using the same register for the syscall number and > syscall return value it's very much impossible to poke the return value > on entry into a register using the generic register access function. As > of now there is no place to store the value ot of the return value > outside of the registers, either. I know nothing about ppc and s390. Can't comment right now. > And the current PTRACE_SET_SYSCALL_INFO indeed sets the syscall nr and > arguments on entry and the syscall return value on exit, that > disctincion is implemented. > > Not sure how the patchset you point out is relevant, it only adds > changes in the exit case. No. It allows to skip-and-set-retval on PTRACE_EVENT_SECCOMP. But ENTRY -> EXIT transition is not yet allowed due to the problems above. Oleg.