Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752128AbaKGMLo (ORCPT ); Fri, 7 Nov 2014 07:11:44 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:58937 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751435AbaKGMLk (ORCPT ); Fri, 7 Nov 2014 07:11:40 -0500 Date: Fri, 7 Nov 2014 12:11:19 +0000 From: Russell King - ARM Linux To: Arnd Bergmann Cc: Will Deacon , "linux-arm-kernel@lists.infradead.org" , AKASHI Takahiro , "roland@hack.frob.com" , "oleg@redhat.com" , "linaro-kernel@lists.linaro.org" , "keescook@chromium.org" , "linux-kernel@vger.kernel.org" , "dsaxena@linaro.org" Subject: Re: [RFC] ptrace: add generic SET_SYSCALL request Message-ID: <20141107121119.GQ4042@n2100.arm.linux.org.uk> References: <1415346443-28915-1-git-send-email-takahiro.akashi@linaro.org> <1977974.l97vvy7Y8b@wuerfel> <20141107115551.GC18916@arm.com> <1678531.AUssrM9PAs@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1678531.AUssrM9PAs@wuerfel> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 07, 2014 at 01:03:00PM +0100, Arnd Bergmann wrote: > On Friday 07 November 2014 11:55:51 Will Deacon wrote: > > We need this for arm64 and, since all architectures seem to have a mechanism > > for setting a system call via ptrace, moving it to generic code should make > > sense for new architectures too, no? > > It makes a little more sense now, but I still don't understand why you > need to set the system call number via ptrace. What is this used for, > and why doesn't any other architecture have this? All other architectures have a way. x86, for example, you set orig_eax (or orig_rax) to change the syscall number. On ARM, that doesn't work because we don't always pass the syscall number in a register. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/