From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752797AbcHKOuO (ORCPT ); Thu, 11 Aug 2016 10:50:14 -0400 Received: from foss.arm.com ([217.140.101.70]:54558 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbcHKOuJ (ORCPT ); Thu, 11 Aug 2016 10:50:09 -0400 Date: Thu, 11 Aug 2016 15:50:00 +0100 From: Catalin Marinas To: Arnd Bergmann Cc: "Zhangjian (Bamvor)" , Yury Norov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arch@vger.kernel.org, libc-alpha@sourceware.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, pinskia@gmail.com, broonie@kernel.org, joseph@codesourcery.com, christoph.muellner@theobroma-systems.com, szabolcs.nagy@arm.com, klimov.linux@gmail.com, Nathan_Lynch@mentor.com, agraf@suse.de, Prasun.Kapoor@caviumnetworks.com, kilobyte@angband.pl, geert@linux-m68k.org, philipp.tomsich@theobroma-systems.com, manuel.montezelo@gmail.com, linyongting@huawei.com, maxim.kuvyrkov@linaro.org, davem@davemloft.net, Andrew Pinski , Andrew Pinski , Bamvor Jian Zhang , Hanjun Guo Subject: Re: [PATCH 05/19] arm64: rename COMPAT to AARCH32_EL0 in Kconfig Message-ID: <20160811145000.GB18366@e104818-lin.cambridge.arm.com> References: <1466207668-10549-1-git-send-email-ynorov@caviumnetworks.com> <1466207668-10549-6-git-send-email-ynorov@caviumnetworks.com> <57AC2AA5.1030808@huawei.com> <3043310.yXUR8Er0VK@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3043310.yXUR8Er0VK@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 Thu, Aug 11, 2016 at 10:53:01AM +0200, Arnd Bergmann wrote: > On Thursday, August 11, 2016 3:35:01 PM CEST Zhangjian (Bamvor) wrote: > > On 2016/6/18 7:54, Yury Norov wrote: > > > From: Andrew Pinski > > > > > > In this patchset ILP32 ABI support is added. Additionally to AARCH32, > > > which is binary-compatible with ARM, ILP32 is (mostly) ABI-compatible. > > > > > > From now, AARCH32_EL0 (former COMPAT) config option means the support of > > > AARCH32 userspace, ARM64_ILP32 - support of ILP32 ABI (see next patches), > > > and COMPAT indicates that one of them, or both, is enabled. > > > > > > Where needed, CONFIG_COMPAT is changed over to use CONFIG_AARCH32_EL0 instead > > > > > > Reviewed-by: David Daney > > > Signed-off-by: Andrew Pinski > > > Signed-off-by: Philipp Tomsich > > > Signed-off-by: Christoph Muellner > > > Signed-off-by: Bamvor Jian Zhang > > > Signed-off-by: Yury Norov > > ... > > > diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c > > > index c173d32..af200a8 100644 > > > --- a/arch/arm64/kernel/cpuinfo.c > > > +++ b/arch/arm64/kernel/cpuinfo.c > > > @@ -134,15 +134,17 @@ static int c_show(struct seq_file *m, void *v) > > > */ > > > seq_puts(m, "Features\t:"); > > > if (compat) { > > > -#ifdef CONFIG_COMPAT > > > - for (j = 0; compat_hwcap_str[j]; j++) > > > - if (compat_elf_hwcap & (1 << j)) > > > - seq_printf(m, " %s", compat_hwcap_str[j]); > > > - > > > - for (j = 0; compat_hwcap2_str[j]; j++) > > > - if (compat_elf_hwcap2 & (1 << j)) > > > - seq_printf(m, " %s", compat_hwcap2_str[j]); > > > -#endif /* CONFIG_COMPAT */ > > > +#ifdef CONFIG_AARCH32_EL0 > > I saw that compat_hwcap_str and compat_hwcap2_str is defined when > > "CONFIG_COMPAT" is true. Why we only change it to CONFIG_AARCH32_EL0 > > in c show()? > > > + if (personality(current->personality) == PER_LINUX32) { > > And "compat" is "personality(current->personality) == PER_LINUX32;", > > it seems that there is no need to add this twice. > > I think it would be best to remove the #ifdef here completely, > the PER_LINUX32 concept is not strictly tied to the emulation > of ARM binaries, it literally just changes the output of > /proc/cpuinfo and 'uname', It's not strictly related to ARM binaries, however it is related to AArch32 CPU features being supported and detected by the kernel. Currently, with CONFIG_COMPAT disabled, we won't have access to a (meaningful) compat_elf_hwcap. > and you can have ARM binaries with > PER_LINUX (using the arm64 uname) just like you can have > arm64 binaries running with PER_LINUX32. I was actually looking to enforce the 32-bit binaries to only see PER_LINUX32, though with a risk of breaking the ABI. OTOH, people are abusing this and write 32-bit apps relying on the 64-bit /proc/cpuinfo: http://lkml.kernel.org/g/1464706504-25224-3-git-send-email-catalin.marinas@arm.com (you were summoned on that discussion couple of times ;)) -- Catalin