From nobody Fri Jul 16 11:08:55 2021 X-Original-To: freebsd-arm@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 2E6498D49BD for ; Fri, 16 Jul 2021 11:09:00 +0000 (UTC) (envelope-from tuexen@freebsd.org) Received: from drew.franken.de (mail-n.franken.de [193.175.24.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.franken.de", Issuer "Sectigo RSA Domain Validation Secure Server CA" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4GR7lw0G7Zz4jQN for ; Fri, 16 Jul 2021 11:08:59 +0000 (UTC) (envelope-from tuexen@freebsd.org) Received: from smtpclient.apple (ip1f100e9c.dynamic.kabel-deutschland.de [31.16.14.156]) (Authenticated sender: macmic) by mail-n.franken.de (Postfix) with ESMTPSA id 22AD6721E282D; Fri, 16 Jul 2021 13:08:56 +0200 (CEST) Content-Type: text/plain; charset=utf-8 List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@freebsd.org Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.100.0.2.22\)) Subject: Re: register x18 From: tuexen@freebsd.org In-Reply-To: Date: Fri, 16 Jul 2021 13:08:55 +0200 Cc: freebsd-arm@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: <32C24DDC-C8A1-43CD-9220-8009B229E452@freebsd.org> References: <86EC9C12-F90C-4D0C-BFA3-41986C9F07B5@freebsd.org> To: Mark Millard X-Mailer: Apple Mail (2.3654.100.0.2.22) X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=disabled version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on mail-n.franken.de X-Rspamd-Queue-Id: 4GR7lw0G7Zz4jQN X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N > On 16. Jul 2021, at 04:06, Mark Millard wrote: >=20 >=20 >=20 > On 2021-Jul-15, at 17:40, Michael Tuexen = wrote: >=20 >> Dear all, >>=20 >> register x18 seems to be special. What is it used for in FreeBSD? >>=20 >> Best regards >> Michael >=20 > = https://developer.arm.com/documentation/den0024/a/The-ABI-for-ARM-64-bit-A= rchitecture/Register-use-in-the-AArch64-Procedure-Call-Standard/Parameters= -in-general-purpose-registers >=20 > reports: >=20 > QUOTE > =E2=80=A2 X18 is the platform register and is reserved for the = use of platform ABIs. This is an adional temporary register on platforms = that don't assign a special meaning to it. > END QUOTE >=20 > So, special, yes. But I do not know what the "platform ABI" usage > for it might be on FreeBSD. So, for the most part, this does not > well-answer your question. Sorry. Yepp, I found the above text. However, x18 seems to be used when = accessing global variables. I am looking at a panic, where the system panics on = accessing global variable, which can be controlled by sysctl. It seems that x18 does not have the expected value, but it is also not = set in the function... Best regards Michael >=20 > =3D=3D=3D > Mark Millard > marklmi at yahoo.com > ( dsl-only.net went > away in early 2018-Mar) >=20