Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755513Ab2JTNHC (ORCPT ); Sat, 20 Oct 2012 09:07:02 -0400 Received: from usmamail.tilera.com ([12.216.194.151]:19122 "EHLO USMAMAIL.TILERA.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754617Ab2JTNHA (ORCPT ); Sat, 20 Oct 2012 09:07:00 -0400 Message-ID: <5082A1F1.3080303@tilera.com> Date: Sat, 20 Oct 2012 09:06:57 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 To: Al Viro CC: , , Linus Torvalds , Benjamin Herrenschmidt , "David S. Miller" Subject: Re: [PATCH] tile: support GENERIC_KERNEL_THREAD and GENERIC_KERNEL_EXECVE References: <20121016223508.GR2616@ZenIV.linux.org.uk> <201210192041.q9JKf7jD003998@farm-0010.internal.tilera.com> <20121019213548.GR2616@ZenIV.linux.org.uk> In-Reply-To: <20121019213548.GR2616@ZenIV.linux.org.uk> X-Enigmail-Version: 1.4.5 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2879 Lines: 60 On 10/19/2012 5:35 PM, Al Viro wrote: > On Fri, Oct 19, 2012 at 04:25:12PM -0400, Chris Metcalf wrote: >> Also provide an optimized current_pt_regs() while we're at it. > Applied. BTW, are you sure you want to record parent's pid and not tid? By recording ->pid rather than ->pgid, we ARE recording the tid :-) > Anyway, here's a followup on top of this one (again, completely untested) - > switching to generic sys_execve(). Does that look right for you? It does look right, but it doesn't quite work as-is. But after some tweaks it did yield a kernel that booted up userspace correctly, so I think it's basically good. First, the compat_sys_execve() declaration provided in arch/tile/include/asm/compat.h isn't right, so I deleted that (you had only deleted the PTREGS_SYSCALL trampoline declaration, _compat_sys_execve). However, then arch/tile/kernel/compat.c failed to build, because is included before , and provides __ARCH_WANT_SYS_EXECVE, and so we end up with no declaration at all for compat_sys_execve. For most platforms this is no big deal, but on tile we use the __SYSCALL #define to provide the actual syscall table, and for that to work we need a declaration in scope for each syscall at the time we create the table. The best solution seems likely to be to copy the other place in where we need to do something configurable (that is, CONFIG_ARCH_WANT_OLD_COMPAT_IPC), and just convert __ARCH_WANT_SYS_EXECVE to be a Kconfig option. Another possibility is to pre-include in the tile compat.c before including . This requires adding some #undefs for _SC_3264, etc., in , since we'll need to include the header twice, once to satisfy , and then again to actually provide the body of the syscall array. If we go down this path, I suspect we should just make include , so it gets the __ARCH_WANT_SYS_EXECVE define provided. Otherwise we have the ugly requirement of requiring the C file to include specific headers in specific order for it to work right. > While > we are at it, I wonder if any of PTREGS_SYSCALL wrappers are needed - > current_pt_regs() would do just as well, won't it? It's a couple of > arithmetical operations vs. arith operation + branch; even if the latter > is somehow cheaper, can't be cheaper by much. And I'd expect it to be > costlier, actually, what with the icache effects. Yes, that's a good idea. I'll look at it when I'm back in the office next week. -- Chris Metcalf, Tilera Corp. http://www.tilera.com -- 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/