From owner-freebsd-arm@freebsd.org Tue Feb 14 17:18:01 2017 Return-Path: Delivered-To: freebsd-arm@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 24269CDF089 for ; Tue, 14 Feb 2017 17:18:01 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: from asp.reflexion.net (outbound-mail-210-70.reflexion.net [208.70.210.70]) (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 CA2EE1C9A for ; Tue, 14 Feb 2017 17:18:00 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: (qmail 15483 invoked from network); 14 Feb 2017 17:17:58 -0000 Received: from unknown (HELO rtc-sm-01.app.dca.reflexion.local) (10.81.150.1) by 0 (rfx-qmail) with SMTP; 14 Feb 2017 17:17:58 -0000 Received: by rtc-sm-01.app.dca.reflexion.local (Reflexion email security v8.30.0) with SMTP; Tue, 14 Feb 2017 12:17:58 -0500 (EST) Received: (qmail 11758 invoked from network); 14 Feb 2017 17:17:58 -0000 Received: from unknown (HELO iron2.pdx.net) (69.64.224.71) by 0 (rfx-qmail) with (AES256-SHA encrypted) SMTP; 14 Feb 2017 17:17:58 -0000 Received: from [192.168.1.111] (c-67-170-167-181.hsd1.or.comcast.net [67.170.167.181]) by iron2.pdx.net (Postfix) with ESMTPSA id EFA15EC86D9; Tue, 14 Feb 2017 09:17:57 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 10.2 \(3259\)) Subject: Re: A potential fix for arm64's: sh`forkshell child-process path after fork sometimes has a bad stack pointer value From: Mark Millard In-Reply-To: <20170214165644.15dedf6e@zapp> Date: Tue, 14 Feb 2017 09:17:57 -0800 Cc: Shawn Webb , Tom Vijlbrief , freebsd-arm Content-Transfer-Encoding: 7bit Message-Id: <6EED2BFF-CAFB-4F58-8D0D-8E060319278C@dsl-only.net> References: <2D04FF37-DEC8-42CE-961D-AE8CD58A0EAA@dsl-only.net> <93064627-5F72-4167-90B1-0A98ABF4C99C@dsl-only.net> <3BC697B9-4A3E-49FF-AB11-1106E2EF8399@dsl-only.net> <20170214165644.15dedf6e@zapp> To: Andrew Turner X-Mailer: Apple Mail (2.3259) X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Feb 2017 17:18:01 -0000 On 2017-Feb-14, at 8:56 AM, Andrew Turner wrote: On Tue, 14 Feb 2017 08:35:54 -0800 > Mark Millard wrote: > >> The following change has let my test run for 8.5 hours so far without >> a fork-failure in sh`forkshell : >> >> # svnlite diff /usr/src/sys/arm64/arm64/swtch.S >> Index: /usr/src/sys/arm64/arm64/swtch.S >> =================================================================== >> --- /usr/src/sys/arm64/arm64/swtch.S (revision 312982) >> +++ /usr/src/sys/arm64/arm64/swtch.S (working copy) >> @@ -241,6 +241,12 @@ >> mov fp, #0 /* Stack traceback stops here. */ >> bl _C_LABEL(fork_exit) >> >> + /* >> + * Disable interrupts to avoid >> + * overwriting sp_el0 and spsr_el1 by an IRQ exception. >> + */ >> + msr daifset, #2 >> + >> /* Restore sp and lr */ >> ldp x0, x1, [sp] >> msr sp_el0, x0 >> @@ -263,12 +269,6 @@ >> ldp x28, x29, [sp, #TF_X + 28 * 8] >> /* Skip x30 as it was restored above as lr */ >> >> - /* >> - * Disable interrupts to avoid >> - * overwriting spsr_el1 by an IRQ exception. >> - */ >> - msr daifset, #2 >> - >> /* Restore elr and spsr */ >> ldp x0, x1, [sp, #16] >> msr elr_el1, x0 >> >> I'm going to switch to attempting a self-hosted buildworld >> buildkernel again. > > Can you try the patch in https://reviews.freebsd.org/D9593. It moves > loading of sp_el0 until after interrupts have been disabled. > > Andrew Sure. I'll stop the self-hosted buildworld buildkernel and switch over to your source. One minor point: /* Skip x30 as it was restored above as lr */ now should say something like: /* Skip x30 as it is restored below as lr */ === Mark Millard markmi at dsl-only.net