From owner-freebsd-arm@freebsd.org Thu Nov 30 23:03:46 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 AD5B9DEC29D for ; Thu, 30 Nov 2017 23:03:46 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (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 9AE537A932 for ; Thu, 30 Nov 2017 23:03:46 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id vAUN3kUT011482 for ; Thu, 30 Nov 2017 23:03:46 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-arm@FreeBSD.org Subject: [Bug 224008] UBLDR doesn't save registers correctly in start.S Date: Thu, 30 Nov 2017 23:03:46 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: arm X-Bugzilla-Version: 11.1-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: parakleta@darkreality.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-arm@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter attachments.created Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Nov 2017 23:03:46 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D224008 Bug ID: 224008 Summary: UBLDR doesn't save registers correctly in start.S Product: Base System Version: 11.1-RELEASE Hardware: arm OS: Any Status: New Severity: Affects Some People Priority: --- Component: arm Assignee: freebsd-arm@FreeBSD.org Reporter: parakleta@darkreality.org Created attachment 188440 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D188440&action= =3Dedit Save and Restore U-Boot registers. Using `ubldr.bin` I was getting intermittent behaviour depending on which options I compiled into U-Boot. Eventually I discovered that the issue is = that the entry point in `sys/boot/arm/uboot/start.S` is not correctly saving and restoring registers. Most importantly the r9 register is the base of the global data and this is not typically a callee-saved register, but must be = for U-Boot. There is a change to this file on April 2 by "ian" which saves the argument= and return address but it doesn't go far enough. My patch is to applied to the state before that patch. Essentially the important caller-saved registers are pushed (r0, r1, r9, lr) before the relocation call, and popped after. Then r8/r9 are saved as usual for the syscall trampoline, and lr is stored in r8 (now free) as a callee-s= aved value before calling into `main`. The call to `main` can no longer be a tail call because we must restore r9 especially after main returns (although since we have used r8 to hold lr we must also restore this). I don't know how this affects the ELF version, but this patch is critical f= or the correct functioning of the binary version of UBLDR. --=20 You are receiving this mail because: You are the assignee for the bug.=