From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 21 Jun 2013 18:00:04 +0200 (CEST) Received: from mail-pa0-f50.google.com ([209.85.220.50]:35990 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6825660Ab3FUP7nbVUEN (ORCPT ); Fri, 21 Jun 2013 17:59:43 +0200 Received: by mail-pa0-f50.google.com with SMTP id fb1so7929663pad.23 for ; Fri, 21 Jun 2013 08:59:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=91/K7eTujW7s7a6i5LL665CheCKUJgAnY0ByGn0uZVE=; b=CuBDgJANycaGLcAsPq295vSpGSEzlOIXBXFDQl7nfxDqZ65o6cqmelSFQbRVnGxk5S niZZEPKRFuuzUNwGmvybOS0bx5KcyaJfcxZLmVfzNMAuvL8D9RdS/GeG/clyqmmGCUwe umv/1V3LS0mPY8h1v/Mk7JFnUeLh9MX/qdQLu0kBPz9pMfYr43oYQpqjYVUUUHn2Scvn PaKxXQfZcc0bWcjgbDBf9zn7bXinCyAPDw2u+hg9Wfmlzpbe6p4EnrgdwniBF2FzDcLI 5yNUXPsMcRIeRBVJWSyWXx4xdt4tDQ3Y1rTsqA6Lg7bcTZhl09j7vJg8wfp1wMRJsn9g EKQA== X-Received: by 10.66.118.79 with SMTP id kk15mr16767755pab.193.1371830375720; Fri, 21 Jun 2013 08:59:35 -0700 (PDT) Received: from dl.caveonetworks.com (64.2.3.195.ptr.us.xo.net. [64.2.3.195]) by mx.google.com with ESMTPSA id at1sm5372126pbc.10.2013.06.21.08.59.33 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 21 Jun 2013 08:59:34 -0700 (PDT) Message-ID: <51C47864.9030200@gmail.com> Date: Fri, 21 Jun 2013 08:59:32 -0700 From: David Daney User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: James Hogan CC: linux-kernel@vger.kernel.org, Ralf Baechle , Al Viro , Andrew Morton , Oleg Nesterov , Kees Cook , David Daney , "Paul E. McKenney" , David Howells , Dave Jones , linux-mips@linux-mips.org Subject: Re: [PATCH v3] kernel/signal.c: fix BUG_ON with SIG128 (MIPS) References: <1371821962-9151-1-git-send-email-james.hogan@imgtec.com> In-Reply-To: <1371821962-9151-1-git-send-email-james.hogan@imgtec.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 37087 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ddaney.cavm@gmail.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On 06/21/2013 06:39 AM, James Hogan wrote: > MIPS has 128 signals, the highest of which has the number 128 (they > start from 1). The following command causes get_signal_to_deliver() to > pass this signal number straight through to do_group_exit() as the exit > code: > > strace sleep 10 & sleep 1 && kill -128 `pidof sleep` > > However do_group_exit() checks for the core dump bit (0x80) in the exit > code which matches in this particular case and the kernel panics: > > BUG_ON(exit_code & 0x80); /* core dumps don't get here */ > > Fundamentally the exit / wait status code cannot represent SIG128. In > fact it cannot represent SIG127 either as 0x7f represents a stopped > child. > > Therefore add sig_to_exitcode() and exitcode_to_sig() functions which > map signal numbers > 126 to exit code 126 and puts the remainder (i.e. > sig - 126) in higher bits. This allows WIFSIGNALED() to return true for > both SIG127 and SIG128, and allows WTERMSIG to be later updated to read > the correct signal number for SIG127 and SIG128. I really hate this approach. Can we just change the ABI to reduce the number of signals so that all the standard C library wait related macros don't have to be changed? Think about it, any user space program using signal numbers 127 and 128 doesn't work correctly as things exist today, so removing those two will be no great loss. David Daney > > Signed-off-by: James Hogan > Cc: Ralf Baechle > Cc: Al Viro > Cc: Andrew Morton > Cc: Oleg Nesterov > Cc: Kees Cook > Cc: David Daney > Cc: "Paul E. McKenney" > Cc: David Howells > Cc: Dave Jones > Cc: linux-mips@linux-mips.org > --- > v3: > > A slightly different approach this time, closer to the original patch I > sent. This is because reducing _NSIG to 127 (like v2) still leaves > incorrect exit status codes for SIG127. The only ABI this changes is the > wait/waitpid status code, and it's in such a way that old binaries, as > long as they use the macros defined in the wait manpage, should see a > process terminated by signal 126 for SIG127 and SIG128 rather than > !WIFSIGNALED(). Software rebuilt with updated libc wait status macros > would see the correct terminating signal number. > > kernel/signal.c | 32 +++++++++++++++++++++++++++++--- > 1 file changed, 29 insertions(+), 3 deletions(-) >