From owner-freebsd-current@FreeBSD.ORG Mon Aug 20 13:49:49 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4B854106564A; Mon, 20 Aug 2012 13:49:49 +0000 (UTC) (envelope-from monthadar@gmail.com) Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.freebsd.org (Postfix) with ESMTP id 19BCF8FC0C; Mon, 20 Aug 2012 13:49:48 +0000 (UTC) Received: by pbbrp2 with SMTP id rp2so7362304pbb.13 for ; Mon, 20 Aug 2012 06:49:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=FNSChAwdg/d23OASFliW0+j93Aqu3UnhOw9Qdy0A7vw=; b=HsSAlmbmVXDQ54PiWdWXr5mQiKC/q4YjaNcJnk2Lp3dGjzYVttFulEaoQpgG9ojTKL Iuzw7pL7THr/Urctw0R+fVjAmCPUMpyLZJ/or8Qam2ezhmwAsq1PeOEUTsEbigWk9Gzd nxA6H4mtLChYhIHNpSC3Xeb9efrWP2/5JcOCb5kWIsVzLa4LCUg3SUphMpZnwVpimYFQ DjZUW6SEv8MvzVc7WS6FqlMyZ1fZmodmfYflnfcYUZpGfTrMA6kYhVV44HKQdhD1tV2u a4jkU/JBFs6qL1FF1bhfGNxfOaMg/IhcnwsPuf9iEMWCLMwT3r/i1HuxFpNrzjnkBvqt 6IMQ== MIME-Version: 1.0 Received: by 10.66.87.66 with SMTP id v2mr29711977paz.71.1345470588217; Mon, 20 Aug 2012 06:49:48 -0700 (PDT) Received: by 10.68.32.197 with HTTP; Mon, 20 Aug 2012 06:49:48 -0700 (PDT) In-Reply-To: <201208200804.31932.jhb@freebsd.org> References: <201208200804.31932.jhb@freebsd.org> Date: Mon, 20 Aug 2012 15:49:48 +0200 Message-ID: From: Monthadar Al Jaberi To: John Baldwin Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-current@freebsd.org Subject: Re: kernel page fult for a valid pointer? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 Aug 2012 13:49:49 -0000 On Mon, Aug 20, 2012 at 2:04 PM, John Baldwin wrote: > On Saturday, August 18, 2012 2:29:26 pm Monthadar Al Jaberi wrote: >> Hi, >> >> I am wondering is there a reason for getting "Fatal trap 12: page >> fault while in kernel mode" "supervisor read, page not present" for an >> address used to be valid in kernel space? >> >> I dont really understand why I am getting this, I added a hardware >> watchpoint on the address, and when I got to the debuger I could read >> the memory content and dump for that address. But when I continue from >> the debugger I get the panic and now when I try to read the memory >> content I get *** error reading from address ce733000 ***. > > Whatever memory was there might have been unmapped? For example, > memory pointed to by I/O buffers (struct buf/bio) use transient > mappings that are only valid while an I/O request is in progress. Thank you the for the reply, so if a struct gets freed will the page it was on get un-mapped, so that I cant dump it in debugger? Even VirtualBox debugger cant dump the memory giving "VERR_PAGE_TABLE_NOT_PRESENT: Reading memory at...". In my case it is a struct ieee80211_node which gets freed, but where does the page get unmaped? I tried doubling the memory in VirtualBox. br, > > -- > John Baldwin -- Monthadar Al Jaberi