From nobody Mon Dec 16 04:13:45 2024 X-Original-To: freebsd-hackers@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 4YBRQw6KTjz5gqrt; Mon, 16 Dec 2024 04:14:16 +0000 (UTC) (envelope-from darius@dons.net.au) Received: from midget.dons.net.au (midget.dons.net.au [IPv6:2403:580d:ae98:0:225:90ff:fe47:39b4]) by mx1.freebsd.org (Postfix) with ESMTP id 4YBRQw2HDNz4DZs; Mon, 16 Dec 2024 04:14:16 +0000 (UTC) (envelope-from darius@dons.net.au) Authentication-Results: mx1.freebsd.org; none Received: from smtpclient.apple (unknown [IPv6:2001:44b8:1d2:8900:1876:809f:8906:ef38]) by midget.dons.net.au (Postfix) with ESMTPSA id 15A57756308; Mon, 16 Dec 2024 14:44:03 +1030 (ACDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dons.net.au; s=default; t=1734322445; bh=mNVyqTmcw9SeJxg5bqR5OOr4IpOtPA32g9kQkL4xq7E=; h=Subject:From:In-Reply-To:Date:Cc:References:To; b=qf+kdrOLn9fj5YMvSR0GfCpP/ARmVg3EF1hOs7m60HWfJi7gAlB1RNAtdZzCm2cER Pp6YVYrdd6vkLveVnT86hpFQiDUQEhL9IoqlQGmu4jP0LxQzc3G0PmXrIfC5QoSjz1 bB1t7/lKvWf52y60LKt7RgEArey7jLSCOvAsCVGaQ4C86lkJ4OH+7Ss8HLVdggUchu bVorf8mwlhI8LEr+V4QtqamlrfB2+1wWy7ljgzFyb+tZYGjJmQv1A09jFTH9AAwj71 lHPbU939JW7GuviGQ5cuqe/V5NrVCPLPNsU6Hyl/+Mw72qi3EJj1AjHE5CM+4DR+1W 803T2nvrSQsdg== Content-Type: text/plain; charset=us-ascii List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@FreeBSD.org Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3826.200.121\)) Subject: Re: What kind of code might generate amd64 addressses like 0xFFFFF80000000007 or be based on 0xFFFFF80000000000 ? From: Daniel O'Connor In-Reply-To: <65B0673C-287A-47E5-A732-17CC5EEE3350@yahoo.com> Date: Mon, 16 Dec 2024 14:43:45 +1030 Cc: FreeBSD Current , FreeBSD-STABLE Mailing List , freebsd-hackers , freebsd-amd64@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: <8C32FA41-C0EC-4679-9E26-B7CC3C69ECE6@dons.net.au> References: <65B0673C-287A-47E5-A732-17CC5EEE3350.ref@yahoo.com> <65B0673C-287A-47E5-A732-17CC5EEE3350@yahoo.com> To: Mark Millard X-Mailer: Apple Mail (2.3826.200.121) X-Rspamd-Action: no action X-Rspamd-Server: midget.dons.net.au X-Spam-Status: No, score=-0.09 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:4764, ipnet:2403:5800::/27, country:AU] X-Rspamd-Queue-Id: 4YBRQw2HDNz4DZs X-Spamd-Bar: ---- Hi Mark, > On 16 Dec 2024, at 10:33, Mark Millard wrote: > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D267028 is for a = crash problem > someone has been having over more than 2 years. There are boot time = crashes > involved. >=20 > It appears that 0xFFFFF80000000007 is showing up in use and stored in = data > structures as a pointer value in fields/arguments that are pointers, = where such > a special value would not be expected. Later defrerencing does not go = well, at > least when the dererefenced data is then in-turn put to use. >=20 > The small offset from 0xFFFFF80000000000 suggests to me that the = special value likely > is inappropriately left around and somehow picked up and used. = 0xFFFFF80000000000 (or > near it) might be odd enough to have only a few known likely possible = usages. Such > notes in the bugzilla report would be good if such is the case. Thus = my question. That value (0xffffffff80000000) is kernbase (see sysctl = kern.base_address). However it is hard to think of why that value (or a small offset to it) = is getting put in places it shouldn't be.. -- Daniel O'Connor "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum