From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1HT7lO-0001uF-Hj for user-mode-linux-devel@lists.sourceforge.net; Sun, 18 Mar 2007 19:38:23 -0700 Received: from mail153.messagelabs.com ([216.82.253.51]) by mail.sourceforge.net with smtp (Exim 4.44) id 1HT7lN-0004tr-0X for user-mode-linux-devel@lists.sourceforge.net; Sun, 18 Mar 2007 19:38:22 -0700 Received: from il06exr02.mot.com (il06exr02.mot.com [129.188.137.132]) by motgate8.mot.com (8.12.11/Motorola) with ESMTP id l2J2cJNF019375 for ; Sun, 18 Mar 2007 19:38:19 -0700 (MST) Received: from ZMY16EXM67.ds.mot.com (zmy16exm67.ap.mot.com [10.179.4.27]) by il06exr02.mot.com (8.13.1/8.13.0) with ESMTP id l2J2cHoJ017836 for ; Sun, 18 Mar 2007 21:38:18 -0500 (CDT) Content-class: urn:content-classes:message MIME-Version: 1.0 Date: Mon, 19 Mar 2007 10:38:27 +0800 Message-ID: <0A01463223B8164194908CAC85B66A1201AD3E2E@ZMY16EXM67.ds.mot.com> From: "Krishnappa Abhijith-A21204" Subject: [uml-devel] Regarding System call virtualization List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============1118191339==" Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: user-mode-linux-devel@lists.sourceforge.net This is a multi-part message in MIME format. --===============1118191339== Content-class: urn:content-classes:message Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C769CF.A514CAF8" This is a multi-part message in MIME format. ------_=_NextPart_001_01C769CF.A514CAF8 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hi, Is the below flow correct for UML (TT mode) =20 1. UML process wants to execute a sys call say open(). 2. UML TT comes to know this annuls with getpid(), and UML TT executes open() on behalf of UML process. 3. UML process executes the getpid() and returns and signals TT. 4. By this time UML TT has finished executing the system call open and has returned back, so TT fills in the registers of UML process. 5. Now UML process executes normally with the open file descriptor. =20 If the above steps are correct, then How does UML protects host kernel. because even here TT will ask for host kernel services which may corrupt host kernel ?=20 Is there any method by which it is prevented ? =20 Thanks a lot. Abhi ------_=_NextPart_001_01C769CF.A514CAF8 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hi,

=20 Is the below flow correct for UML = (TT=20 mode)

1. UML=20 process wants to execute a sys call say open().

2. UML TT=20 comes to know this annuls with getpid(), and UML TT executes open() on = behalf of=20 UML process.

3. UML=20 process executes the getpid() and returns and signals = TT.

4. By this=20 time UML TT has finished executing the system call open and has returned = back,=20 so TT fills in the registers of UML process.

5. Now UML=20 process executes normally with the open file = descriptor.

If the=20 above steps are correct, then How does UML protects host=20 kernel.

because=20 even here TT will ask for host kernel services which may corrupt host = kernel ?=20

Is there=20 any method by which it is prevented ?

Thanks a=20 lot.

Abhi

------_=_NextPart_001_01C769CF.A514CAF8-- --===============1118191339== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV --===============1118191339== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel --===============1118191339==-- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1HTLoZ-0005iu-Lg for user-mode-linux-devel@lists.sourceforge.net; Mon, 19 Mar 2007 10:38:37 -0700 Received: from saraswathi.solana.com ([198.99.130.12]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1HTLoS-00085c-Mt for user-mode-linux-devel@lists.sourceforge.net; Mon, 19 Mar 2007 10:38:35 -0700 Date: Mon, 19 Mar 2007 13:36:29 -0400 From: Jeff Dike Message-ID: <20070319173629.GA11790@c2.user-mode-linux.org> References: <0A01463223B8164194908CAC85B66A1201AD3E2E@ZMY16EXM67.ds.mot.com> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: <0A01463223B8164194908CAC85B66A1201AD3E2E@ZMY16EXM67.ds.mot.com> Subject: Re: [uml-devel] Regarding System call virtualization List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Krishnappa Abhijith-A21204 Cc: user-mode-linux-devel@lists.sourceforge.net On Mon, Mar 19, 2007 at 10:38:27AM +0800, Krishnappa Abhijith-A21204 wrote: > Is the below flow correct for UML (TT mode) Maybe, maybe not - your terminology is somewhat confusing. > 1. UML process wants to execute a sys call say open(). > 2. UML TT comes to know this By having PTRACE_SYSCALL on the host return status SIGTRAP | 0x80 from wait(). > annuls with getpid(), and UML TT executes > open() on behalf of UML process. If UML TT refers to the tracing thread, this is wrong. The TT ptraces a set of (UML) kernel register values into the process, and it (not the TT) executes the open. > 3. UML process executes the getpid() and returns and signals TT. This happened before step 2. > 4. By this time UML TT has finished executing the system call open and > has returned back, so TT fills in the registers of UML process. The system-call-making process finished executing in the UML kernel, and signals the TT (by sending itself a signal, which will bump the TT out of wait()) that it should return to userspace. > 5. Now UML process executes normally with the open file descriptor. > > If the above steps are correct, then How does UML protects host kernel. > because even here TT will ask for host kernel services which may corrupt > host kernel ? The *host* kernel is protected by hardware. UML is a normal process with no more access to the host kernel than ls. There is a related, good question here, which is how is the UML kernel protected, given that it is present, and not protected, in the process address space. The answer is that it isn't, at least not without severe performance penalties. This is largely what led to the skas modes. Jeff -- Work email - jdike at linux dot intel dot com ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel