From owner-freebsd-ppc@freebsd.org Sun Jan 31 13:55:23 2016 Return-Path: Delivered-To: freebsd-ppc@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B3F59A732C2 for ; Sun, 31 Jan 2016 13:55:23 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: from asp.reflexion.net (outbound-mail-210-2.reflexion.net [208.70.210.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 50E28F35 for ; Sun, 31 Jan 2016 13:55:22 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: (qmail 18677 invoked from network); 31 Jan 2016 13:55:33 -0000 Received: from unknown (HELO mail-cs-01.app.dca.reflexion.local) (10.81.19.1) by 0 (rfx-qmail) with SMTP; 31 Jan 2016 13:55:33 -0000 Received: by mail-cs-01.app.dca.reflexion.local (Reflexion email security v7.80.0) with SMTP; Sun, 31 Jan 2016 08:55:27 -0500 (EST) Received: (qmail 10903 invoked from network); 31 Jan 2016 13:55:26 -0000 Received: from unknown (HELO iron2.pdx.net) (69.64.224.71) by 0 (rfx-qmail) with SMTP; 31 Jan 2016 13:55:26 -0000 X-No-Relay: not in my network X-No-Relay: not in my network X-No-Relay: not in my network X-No-Relay: not in my network Received: from [192.168.1.8] (c-76-115-7-162.hsd1.or.comcast.net [76.115.7.162]) by iron2.pdx.net (Postfix) with ESMTPSA id 288161C43D5; Sun, 31 Jan 2016 05:55:19 -0800 (PST) From: Mark Millard Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Subject: 3 quick questions about stack alignment for powerpc (32-bit) signal handlers Date: Sun, 31 Jan 2016 05:55:20 -0800 Message-Id: <517B7923-5166-42D0-8FA8-52C05F956F06@dsl-only.net> Cc: FreeBSD PowerPC ML , FreeBSD Toolchain To: Nathan Whitehorn , Justin Hibbits Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) X-Mailer: Apple Mail (2.2104) X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 31 Jan 2016 13:55:23 -0000 3 quick FreeBSD for powerpc (32-bit) questions: A) For PowerPC (32-bit) what is the stack alignment requirement by the = ABI(s) that FreeBSD targets? B) Are signal handlers supposed to be given that alignment? I ask because signal handlers are at times begin given just 4-byte = alignment but clang 3.8.0 powerpc's code generation can depend on the = alignment being more than 4. clang 3.8.0 can calculate addresses by, for example, masking in a 0x4 = relative to what would need to be an aligned address with alignment 8 or = more instead of adding 0x4 to a more arbitrary address. So far I've only seen less than 8 byte stack alignment via signal = handler activity. C) Which should be blamed for problems here: clang's code generation, = FreeBSD's stack alignment handling for signals, or both? =3D=3D=3D Mark Millard markmi at dsl-only.net