From owner-freebsd-hackers@freebsd.org Mon Jun 5 05:08:00 2017 Return-Path: Delivered-To: freebsd-hackers@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 69892BF6E2A for ; Mon, 5 Jun 2017 05:08:00 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: from asp.reflexion.net (outbound-mail-210-5.reflexion.net [208.70.210.5]) (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 1C8C670E9D for ; Mon, 5 Jun 2017 05:07:59 +0000 (UTC) (envelope-from markmi@dsl-only.net) Received: (qmail 8606 invoked from network); 5 Jun 2017 05:07:53 -0000 Received: from unknown (HELO mail-cs-01.app.dca.reflexion.local) (10.81.19.1) by 0 (rfx-qmail) with SMTP; 5 Jun 2017 05:07:53 -0000 Received: by mail-cs-01.app.dca.reflexion.local (Reflexion email security v8.40.0) with SMTP; Mon, 05 Jun 2017 01:07:53 -0400 (EDT) Received: (qmail 23400 invoked from network); 5 Jun 2017 05:07:53 -0000 Received: from unknown (HELO iron2.pdx.net) (69.64.224.71) by 0 (rfx-qmail) with (AES256-SHA encrypted) SMTP; 5 Jun 2017 05:07:53 -0000 Received: from [192.168.1.114] (c-76-115-7-162.hsd1.or.comcast.net [76.115.7.162]) by iron2.pdx.net (Postfix) with ESMTPSA id 706B8EC805D; Sun, 4 Jun 2017 22:07:52 -0700 (PDT) From: Mark Millard Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: 32-bit powerpc FreeBSD address 0x0-0xff content (physical addresses): What is the explanation? Message-Id: Date: Sun, 4 Jun 2017 22:07:51 -0700 To: Justin Hibbits , Nathan Whitehorn , FreeBSD PowerPC ML , freebsd-hackers@freebsd.org X-Mailer: Apple Mail (2.3273) X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 Jun 2017 05:08:00 -0000 I've been trying to get evidence for periodic/random panics in the likes of head -r317820 for 32-bit powerpc FreeBSD used on an old PowerMac G5 so-called "Quad Core". One thing that I've noticed that looks odd is that the vmcore.* files (debug.minidump=0) show content that looks like the following for physical address range 0x0..0xff (via a hacked-to-work-a-little kgdb for physical address access to such a vmcore.* file): (kgdb) x/128wx 0x0 0x0: 0x00000000 0x00000000 0x00000000 0x00000000 0x10: 0x00000000 0xffa35e50 0xffa35ee8 0x00000000 0x20: 0x00000000 0x00000000 0x00000000 0x00000000 0x30: 0x00000000 0x00000000 0x00000000 0x00000000 0x40: 0x00000000 0x00000000 0x00000000 0x00000000 0x50: 0x00000000 0x00000000 0x00000000 0x00000000 0x60: 0x00000000 0x00000000 0x00000000 0x00000000 0x70: 0x00000000 0x00000000 0x00000000 0x00000000 0x80: 0x00000090 0x7ff7c080 0x7fc9e7c8 0x00000000 0x90: 0x3c007ff7 0x6000c100 0x7c0903a6 0x4e800421 0xa0: 0x00000000 0x00000000 0x00000000 0x00000000 0xb0: 0x00000000 0x00000000 0x00000000 0x00000000 0xc0: 0x00000000 0x00000000 0x00000000 0x00000000 0xd0: 0x00000000 0x00000000 0x00000000 0x00000000 0xe0: 0x00000000 0x00000000 0x00000000 0x00000000 0xf0: 0x00000000 0x00000000 0x00000000 0x00000000 . . . Or viewed as instructions when the bit patterns fit such (with added NOTE's): (kgdb) x/128i 0x0 0x0: .long 0x0 0x4: .long 0x0 0x8: .long 0x0 0xc: .long 0x0 0x10: .long 0x0 0x14: .long 0xffa35e50 0x18: .long 0xffa35ee8 0x1c: .long 0x0 0x20: .long 0x0 0x24: .long 0x0 0x28: .long 0x0 0x2c: .long 0x0 0x30: .long 0x0 0x34: .long 0x0 0x38: .long 0x0 0x3c: .long 0x0 0x40: .long 0x0 0x44: .long 0x0 0x48: .long 0x0 0x4c: .long 0x0 0x50: .long 0x0 0x54: .long 0x0 0x58: .long 0x0 0x5c: .long 0x0 0x60: .long 0x0 0x64: .long 0x0 0x68: .long 0x0 0x6c: .long 0x0 0x70: .long 0x0 0x74: .long 0x0 0x78: .long 0x0 0x7c: .long 0x0 0x80: .long 0x90 0x84: .long 0x7ff7c080 0x88: .long 0x7fc9e7c8 0x8c: .long 0x0 0x90: lis r0,32759 (NOTE: 32759==0x7ff7) 0x94: ori r0,r0,49408 (NOTE: 49408==0xC100) 0x98: mtctr r0 (NOTE: So ctr==r0==0x7ff7C100) 0x9c: bctrl (NOTE: So to 0x7ff7C100 virtual address) 0xa0: .long 0x0 (NOTE: lr would end up pointing here.) 0xa4: .long 0x0 0xa8: .long 0x0 0xac: .long 0x0 0xb0: .long 0x0 0xb4: .long 0x0 0xb8: .long 0x0 0xbc: .long 0x0 0xc0: .long 0x0 0xc4: .long 0x0 0xc8: .long 0x0 0xcc: .long 0x0 0xd0: .long 0x0 0xd4: .long 0x0 0xd8: .long 0x0 0xdc: .long 0x0 0xe0: .long 0x0 0xe4: .long 0x0 0xe8: .long 0x0 0xec: .long 0x0 0xf0: .long 0x0 0xf4: .long 0x0 0xf8: .long 0x0 0xfc: .long 0x0 . . . Is this deliberate? If yes: What is it for? (I've not found what writes those bytes.) I do not make the claim that the above is tied to the periodic/random panics. It just seems unusual. === Mark Millard markmi at dsl-only.net