DOCSLIB.ORG

Microkernels Meet Recursive Virtual Machines

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Microkernels Meet Recursive Virtual Machines Microkernels Meet Recursive Virtual Machines Bryan Ford Mike Hibler Jay Lepreau Patrick Tullmann Godmar Back Stephen Clawson Department of Computer Science, University of Utah Salt Lake City, UT 84112 [email protected] http://www.cs.utah.edu/projects/flux/ Abstract ªverticallyº by implementing OS functionalityin stackable virtual machine monitors, each of which exports a virtual Thispaper describes a novel approach to providingmod- machine interface compatible with the machine interface ular and extensible operating system functionality and en- on which it runs. Traditionally,virtual machines have been capsulated environments based on a synthesis of micro- implemented on and export existing hardware architectures kernel and virtual machine concepts. We have developed so they can support ªnaiveº operating systems (see Fig- a software-based virtualizable architecture called Fluke ure 1). For example, the most well-known virtual machine that allows recursive virtual machines (virtual machines system, VM/370 [28, 29], provides virtual memory and se- running on other virtual machines) to be implemented ef- curity between multiple concurrent virtual machines, all ®ciently by a microkernel running on generic hardware. exporting the IBM S/370 hardware architecture. Further- A complete virtual machine interface is provided at each more, special virtualizable hardware architectures [22, 35] level; ef®ciency derives from needing to implement only have been proposed, whose design goal is to allow virtual new functionality at each level. This infrastructure allows machines to be stacked much more ef®ciently. common OS functionality, such as process management, demand paging, fault tolerance, and debugging support, to This paper presents a new approach to OS extensibil- be provided by cleanly modularized, independent, stack- ity which combines both microkernel and virtual machine able virtual machine monitors, implemented as user pro- concepts in one system. We have designed a ªvirtualiz- cesses. It can also provide uncommon or unique OS fea- able architectureº that does not attempt to emulate an ac- tures, including the above features specialized for particu- tual hardware architecture closely, but is instead designed lar applications' needs, virtual machines transparently dis- along the lines of a traditional process model and is in- tributed cross-node, or security monitors that allow arbi- tended to be implemented in software by a microkernel. trary untrusted binaries to be executed safely. Our proto- The microkernel runs on the ªrawº hardware platform and type implementation of this model indicates that it is prac- exports our software-based virtualizable architecture (see tical to modularize operating systems this way. Some types Figure 2), which we will refer to as a virtualizable pro- of virtual machine layers impose almost no overhead at all, cess or nested process architecture to avoid confusion with while others impose some overhead (typically 0±35%),but traditional hardware-based architectures. The virtual ma- only on certain classes of applications. chine monitors designed to run on this software architec- ture, which we call nesters, can ef®ciently create additional recursive virtual machines or nested processes in which ar- 1 Introduction bitrary applications or other nesters can run. Increasing operating system modularity and extensibil- Although the Fluke architecture does not closely fol- ity without excessively hurting performance is a topic of low a traditional virtual machine architecture, it is de- much ongoingresearch [5, 9, 18, 36, 40]. Microkernels [4, signed to preserve certain highly useful properties of re- 24]attempt to decompose operatingsystems ªhorizontallyº cursive virtual machines. These properties are required to by moving traditionalkernel functionalityinto servers run- different degrees by different nesters that take advantage ning in user mode. Recursive virtual machines [23], on of the model. For example, demand paging and check- the other hand, allow operating systems to be decomposed pointing nesters require access to and control over the pro- gram state contained in their children, grandchildren, and This research was supported in part by the Defense Advanced Re- so on, whereas process management and security monitor- search Projects Agency,monitoredby the Departmentof the Army, under contract number DABT63±94±C±0058. The opinions and conclusions ing nesters primarilyrely onbeingable tomonitorand con- containedin thisdocumentarethoseof theauthorsandshould not be inter- trol IPC-based communication across the boundary sur- preted as representing of®cial views or policies of the U.S. Government. Application App App Nested Process Process Architecture Interface Process Process Checkpoint Operating Nester System Application Kernel App App Process Process Virtual Machine Demand Paging Application Debug Nester Nester Operating System Virtual Machine Kernel Monitor Process Mgmt Nester Virtual Machine Virtual Machine Virtual Machine Hardware Monitor Hardware Microkernel Interface Interface Bare Machine Bare Machine Figure 1: Traditional virtual machines based on hardware architec- Figure 2: Virtual machines based on an extended architecture imple- tures. Each shaded area is a separate virtual machine, and each virtual mented by a microkernel. The interface between the microkerneland the machine exports the same architecture as the base machine's architecture. bare machineis a traditionalhardware-basedmachinearchitecture,butthe common interface betweenall the other layers in the system is a software- based nested process architecture. Each shaded area is a separate process. rounding the nested environment. Our microkernel's API provides these properties ef®- ciently in several ways. Address spaces are composed from nel and most do not allow control over physical memory other address spaces using hierarchical memory remapping management, just backing store. Similarly, multiuser se- primitives. For CPU resources, the kernel provides primi- curity mechanisms are not always needed, since most per- tives that support hierarchical scheduling. To allow IPC- sonal computers are dedicated to the use of a single per- based communication to short-circuit the hierarchy safely, son, and even process management and job control features the kernel provides a global capability model that supports may not be needed in single-applicationsystems such as the selective interpositionon communication channels. On top proverbial ªInternet appliance.º Our system demonstrates of the microkernel API, well-de®ned IPC interfaces pro- decomposed paging and POSIX process management by videI/O and resource management functionalityat a higher implementing these traditionalkernel functions as optional level than in traditional virtual machines. These higher- nesters which can be used only when needed, and only for level interfaces are more suited to the needs of modern ap- the parts of a system for which they are desired. plications: e.g., they provide ®le handles instead of device Increasing the scope of existing mechanisms: There I/O registers. are algorithms and software packages available for com- This nested process architecture can be used to apply mon operating systems to provide features such as dis- existing algorithms and techniques in more ¯exible ways. tributed shared memory (DSM) [10, 32], checkpoint- Some examples we demonstrate in this paper include the ing [11], and security against untrusted applications [52]. following: However, these systems only cleanly support applications Decomposing the kernel: Some features of traditional running in a single logical protection domain. In a nested operating systems are usually so tightly integrated into the process model, any process can create further nested sub- kernel that it is dif®cult to eliminate them in situations processes which are completely encapsulated within the in which they are not needed. A striking example is de- parent. This design allows DSM, checkpointing, security, mand paging. Although it is often possible to disable it and other mechanisms to be applied just as easily to multi- in particular situations on particular regions (e.g., using process applications or even complete operating environ- POSIX's mlock()), all of the paging support is still in ments. Our system demonstrates this ¯exibility by provid- the kernel, occupying memory and increasing system over- ing a checkpointer, implemented as a nester, which can be head. Even systems that support ªexternal pagers,º such as transparently applied to arbitrary domains such as a single Mach, contain considerable paging-related code in the ker- application, a multi-process user environment containing a process manager and multiple applications, or even the en- sections. tire system. Composing OS features: The mechanisms mentioned 2.1 Traditional Virtual Machines above are generally dif®cult or impossibleto combine ¯ex- ibly. One might be able to run an application and check- A virtual machine simulator, such as the Java inter- point it, or to run an untrusted application in a secure en- preter [25], is a program that runs on one hardware ar- vironment, but existing software mechanisms are insuf®- chitecture and implements in software a virtual machine cient to run a checkpointed, untrusted application without conforming to a completely different architecture. In con- implementing a new, specialized program designed to pro- trast, a virtual machine monitor or hypervisor, such as vide both functions. A nested
Load more

Recommended publications
  • The Flask Security Architecture: System Support for Diverse Security Policies
    The Flask Security Architecture: System Support for Diverse Security Policies Ray Spencer Secure Computing Corporation Stephen Smalley, Peter Loscocco National Security Agency Mike Hibler, David Andersen, Jay Lepreau University of Utah http://www.cs.utah.edu/flux/flask/ Abstract and even many types of policies [1, 43, 48]. To be gen- erally acceptable, any computer security solution must Operating systems must be flexible in their support be flexible enough to support this wide range of security for security policies, providing sufficient mechanisms for policies. Even in the distributed environments of today, supporting the wide variety of real-world security poli- this policy flexibility must be supported by the security cies. Such flexibility requires controlling the propaga- mechanisms of the operating system [32]. tion of access rights, enforcing fine-grained access rights and supporting the revocation of previously granted ac- Supporting policy flexibility in the operating system is cess rights. Previous systems are lacking in at least one a hard problem that goes beyond just supporting multi- of these areas. In this paper we present an operating ple policies. The system must be capable of supporting system security architecture that solves these problems. fine-grained access controls on low-level objects used to Control over propagation is provided by ensuring that perform higher-level functions controlled by the secu- the security policy is consulted for every security deci- rity policy. Additionally, the system must ensure that sion. This control is achieved without significant perfor- the propagation of access rights is in accordance with mance degradation through the use of a security decision the security policy.
    [Show full text]
  • All Computer Applications Need to Store and Retrieve Information
    MyFS: An Enhanced File System for MINIX A Dissertation Submitted in partial fulfillment of the requirement for the award of the degree of MASTER OF ENGINEERING ( COMPUTER TECHNOLOGY & APPLICATIONS ) By ASHISH BHAWSAR College Roll No. 05/CTA/03 Delhi University Roll No. 3005 Under the guidance of Prof. Asok De Department Of Computer Engineering Delhi College Of Engineering, New Delhi-110042 (University of Delhi) July-2005 1 CERTIFICATE This is to certify that the dissertation entitled “MyFS: An Enhanced File System for MINIX” submitted by Ashish Bhawsar in the partial fulfillment of the requirement for the award of degree of Master of Engineering in Computer Technology and Application, Delhi College of Engineering is an account of his work carried out under my guidance and supervision. Professor D. Roy Choudhury Professor Asok De Head of Department Head of Department Department of Computer Engineering Department of Information Technology Delhi College of Engineering Delhi College of Engineering Delhi Delhi 2 ACKNOWLEDGEMENT It is a great pleasure to have the opportunity to extent my heartiest felt gratitude to everybody who helped me throughout the course of this project. I would like to express my heartiest felt regards to Dr. Asok De, Head of the Department, Department of Information Technology for the constant motivation and support during the duration of this project. It is my privilege and owner to have worked under the supervision. His invaluable guidance and helpful discussions in every stage of this thesis really helped me in materializing this project. It is indeed difficult to put his contribution in few words. I would also like to take this opportunity to present my most sincere regards to Dr.
    [Show full text]
  • Composing Abstractions Using the Null-Kernel
    Composing Abstractions using the null-Kernel James Litton Deepak Garg University of Maryland Max Planck Institute for Software Systems Max Planck Institute for Software Systems [email protected] [email protected] Peter Druschel Bobby Bhattacharjee Max Planck Institute for Software Systems University of Maryland [email protected] [email protected] CCS CONCEPTS hardware, such as GPUs, crypto/AI accelerators, smart NICs/- • Software and its engineering → Operating systems; storage devices, NVRAM etc., and to efficiently support new Layered systems; • Security and privacy → Access control. application requirements for functionality such as transac- tional memory, fast snapshots, fine-grained isolation, etc., KEYWORDS that demand new OS abstractions that can exploit existing hardware in novel and more efficient ways. Operating Systems, Capability Systems At its core, the null-Kernel derives its novelty from being ACM Reference Format: able to support and compose across components, called Ab- James Litton, Deepak Garg, Peter Druschel, and Bobby Bhattachar- stract Machines (AMs) that provide programming interfaces jee. 2019. Composing Abstractions using the null-Kernel. In Work- at different levels of abstraction. The null-Kernel uses an ex- shop on Hot Topics in Operating Systems (HotOS ’19), May 13–15, 2019, Bertinoro, Italy. ACM, New York, NY, USA, 6 pages. https: tensible capability mechanism to control resource allocation //doi.org/10.1145/3317550.3321450 and use at runtime. The ability of the null-Kernel to support interfaces at different levels of abstraction accrues several 1 INTRODUCTION benefits: New hardware can be rapidly deployed using rela- tively low-level interfaces; high-level interfaces can easily Abstractions imply choice, one that OS designers must con- be built using low-level ones; and applications can benefit front when designing a programming interface to expose.
    [Show full text]
  • The Flask Security Architecture: System Support for Diverse Security Policies
    The Flask Security Architecture: System Support for Diverse Security Policies Ray Spencer Secure Computing Corporation Stephen Smalley, Peter Loscocco National Security Agency Mike Hibler, David Andersen, Jay Lepreau University of Utah http://www.cs.utah.edu/flux/flask/ Abstract and even many types of policies [1, 43, 48]. To be gen­ erally acceptable, any computer security solution must Operating systems must be flexible in their support be flexible enough to support this wide range of security for security policies, providing sufficient mechanisms for policies. Even in the distributed environments of today, supporting the wide variety of real-world security poli­ this policy flexibility must be supported by the security cies. Such flexibility requires controlling the propaga­ mechanisms of the operating system [32]. tion of access rights, enforcing fine-grained access rights and supporting the revocation of previously granted ac­ Supporting policy flexibility in the operating system is cess rights. Previous systems are lacking in at least one a hard problem that goes beyond just supporting multi­ of these areas. In this paper we present an operating ple policies. The system must be capable of supporting system security architecture that solves these problems. fine-grained access controls on low-level objects used to Control over propagation is provided by ensuring that perform higher-level functions controlled by the secu­ the security policy is consulted for every security deci­ rity policy. Additionally, the system must ensure that sion. This control is achieved without significant perfor­ the propagation of access rights is in accordance with mance degradation through the use of a security decision the security policy.
    [Show full text]
  • Harvard Cs252r Fa'13
    Type Enforcement & Pluggable MAC Harvard CS252r Fa’13 Tuesday, October 22, 13 1 Practical Domain and Type Enforcement for UNIX • Badger, et al. 1995 • Trusted Information Systems Tuesday, October 22, 13 2 Domain and Type Enforcement • Every Subject is associated with a Domain • Every Object is associated with a Type Tuesday, October 22, 13 3 Boebart and Kain ’85 [7], page 23 introduces this a given user could have multiple subjects operating in diferent domains dynamically, it seems a subject and an object are associated with just one, statically: could be anything Domain and Type Enforcement • Domain Definition Table • Domain’s Access Rights to each Type • read, write, etc. • Domain Interaction Table • Domain’s Access Rights to other Domains • signal, create, destroy, etc. Tuesday, October 22, 13 4 Domain and Type Enforcement • Strict Superset of Lattice-Expressible Security Policies Tuesday, October 22, 13 5 Domain and Type Enforcement Manager budget designs Accountant Engineer salary Tuesday, October 22, 13 6 DTEL Domain and Type Enforcement Language • Encompasses Existing Security Policies • Hierarchical Types • Simple, Declarative Language Tuesday, October 22, 13 7 DTEL Operating System Entities File Hierarchy Process Hierarchy Figure 1: Mismatch Between Policy Concepts and System Structures trol configurations. A DTE specification includes ration: the type statement, the domain statement, the security attribute associations such as typelfile tnitial-domain statement, and the assign statement.’ associations as well as other access control in- The purpose of this section is not to fully document Tuesday,formation. October 22, 13 The language provides a high-level DTEL, but to demonstrate through a small example 8 view of information traditionally enurnerated in that a meaningful DTEL policy can be expressed com- type enforcement tables and includes facilities pletely in a form simple and concise enough to be ad- for superimposing security attribute bindings and ministered at reasonable cost.
    [Show full text]
  • Capability Myths Demolished
    Capability Myths Demolished Mark S. Miller Ka-Ping Yee Jonathan Shapiro Combex, Inc. University of California, Berkeley Johns Hopkins University [email protected] [email protected] [email protected] ABSTRACT The second and third myths state false limitations on We address three common misconceptions about what capability systems can do, and have been capability-based systems: the Equivalence Myth (access propagated by a series of research publications over the control list systems and capability systems are formally past 20 years (including [2, 3, 7, 24]). They have been equivalent), the Confinement Myth (capability systems cited as reasons to avoid adopting capability models cannot enforce confinement), and the Irrevocability and have even motivated some researchers to augment Myth (capability-based access cannot be revoked). The capability systems with extra access checks [7, 13] in Equivalence Myth obscures the benefits of capabilities attempts to fix problems that do not exist. The myths as compared to access control lists, while the Confine- about what capability systems cannot do continue to ment Myth and the Irrevocability Myth lead people to spread, despite formal results [22] and practical see problems with capabilities that do not actually exist. systems [1, 9, 18, 21] demonstrating that they can do these supposedly impossible things. The prevalence of these myths is due to differing inter- pretations of the capability security model. To clear up We believe these severe misunderstandings are rooted the confusion, we examine three different models that in the fact that the term capability has come to be have been used to describe capabilities, and define a set portrayed in terms of several very different security of seven security properties that capture the distinctions models.
    [Show full text]
  • What Have We Learnt in 20 Years of L4 Microkernels?
    Lecture 6 From L3 to seL4: What Have We Learnt in 20 Years of L4 Microkernels? Kevin Elphinstone and Gernot Heiser Operating Systems Practical 12 November, 2014 OSP Lecture 6, L4 Microkernels 1/42 Contents Introduction and design principles Brief history of microkernels L4: Basic abstractions L4: Design and implementation choices Keywords Questions OSP Lecture 6, L4 Microkernels 2/42 Outline Introduction and design principles Brief history of microkernels L4: Basic abstractions L4: Design and implementation choices Keywords Questions OSP Lecture 6, L4 Microkernels 3/42 Context and terminology I Operating system I Kernel I Monolithic kernel I Microkernel OSP Lecture 6, L4 Microkernels 4/42 Operating system I abbrv. OS I Software (collection) to interface hardware with user I Components: I Kernel: Linux, FreeBSD, Windows NT, XNU, L4, ::: I Services/daemons: sysvinit, CUPS print server, udev, ::: I Utilities: ls, Windows Commander, top I Other applications OSP Lecture 6, L4 Microkernels 5/42 Kernel I Components directly interfacing with hardware I Examples? I \Core" of OS I No general definition of \core" OSP Lecture 6, L4 Microkernels 6/42 Monolithic vs. Micro-kernel Application Syscall User VFS "ode Uni File Server Device Server IPC, file system Application Driver Scheduler, virtual memory !ernel "ode Device drivers, dispatcher IPC, virtual memory IPC Hardware Hardware Source: http://www.cse.unsw.edu.au/ OSP Lecture 6, L4 Microkernels 7/42 Monolithic vs. Micro-kernel Monolithic kernel Microkernel I IPC, scheduling, I IPC, scheduling, memory management memory management I File systems I API closer to the I Drivers hardware I Higher-level API OSP Lecture 6, L4 Microkernels 8/42 Microkernel principles: minimality I If it's not critical, leave it out of the kernel I Pros: I Small code base I Easy to debug I Trusted Computing Base, feasible for formal verification I Cons: I Harder to find the \right" API design I Harder to optimize for high-performance OSP Lecture 6, L4 Microkernels 9/42 Microkernel principles: user-level services I Drivers, file systems, etc.
    [Show full text]
  • Microkernel OS Evolution
    COMP9242 Advanced OS S2/2018 W01: Introduction to seL4 @GernotHeiser Copyright Notice These slides are distributed under the Creative Commons Attribution 3.0 License • You are free: – to share—to copy, distribute and transmit the work – to remix—to adapt the work • under the following conditions: – Attribution: You must attribute the work (but not in any way that suggests that the author endorses you or your use of the work) as follows: “Courtesy of Gernot Heiser, UNSW Sydney” The complete license text can be found at http://creativecommons.org/licenses/by/3.0/legalcode 2 COMP9242 S2/2018 W01 © 2017 Gernot Heiser. Distributed under CC Attribution License Reducing Trusted Computing Base: Microkernels • Idea of microkernel: IPC performance – Flexible, minimal platform is critical! – Mechanisms, not policies – Actual OS functionality provided by user-mode servers – Servers invoked by kernel-provided message-passing mechanism (IPC) – Goes back to Nucleus [Brinch Hansen’70] Application Syscall VFS User Unix File Mode Server Device Server IPC, file system Application Driver Kernel Scheduler, virtual memory Mode Device drivers, dispatcher IPC, virtual memory IPC Hardware Hardware 3 COMP9242 S2/2018 W01 © 2017 Gernot Heiser. Distributed under CC Attribution License Monolithic vs Microkernel OS Evolution Monolithic OS Microkernel OS • New features add code kernel • Features add usermode code • New policies add code kernel • Policies replace usermode code • Kernel complexity grows • Kernel complexity is stable • Adaptable • Dependable Application • Highly optimised Syscall VFS User Unix File Mode Server Device Server IPC, file system Application Driver Kernel Scheduler, virtual memory Mode Device drivers, dispatcher IPC, virtual memory IPC Hardware Hardware 4 COMP9242 S2/2018 W01 © 2017 Gernot Heiser.
    [Show full text]
  • Formal Verification of a Component Platform Matthew Fernandez
    Formal Verification of a Component Platform Matthew Fernandez A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy School of Computer Science and Engineering Faculty of Engineering March, 2016 Abstract The function of software used to be calculation; mechanising what was previously done by hand. Now it runs our communication networks, mass transportation and medical support. Yet we still build large software systems as if they were small, easily compre- hensible tools. The right to manage our safety and security should not be handed over lightly. When a program has the ability to compromise our security or injure us, we should demand evidence of its correctness. Formal software verification has demonstrated how to re- liably and repeatedly build safe and secure high-assurance systems, to a standard not achievable using other techniques. Yet it remains underused due to perceptions that it is expensive and time intensive to apply. In this thesis we demonstrate how to scale formal software verification beyond its current limits using component-based software engineering. By leveraging the strong isolation boundaries made possible by the CAmkES component platform operating on the seL4 microkernel, we decompose system verification along lines that correspond to the sys- tem architecture. The parallels between proof obligations and system architecture aid the designer’s intuition and allow easing verification challenges through architectural refactoring. To uphold the engineering abstraction that a component platform provides, we demonstrate a fully automated process for verifying functional correctness of platform- generated code and the correct initialisation of a CAmkES system. The system designer no longer needs to trust that the platform’s mechanisms do what they claim, as is the case with other existing component platforms.
    [Show full text]
  • Dynamic Data Models: an Application of MOP-Based Persistence in Common Lisp 1 Introduction
    Dynamic data models: an application of MOP-based persistence in Common Lisp Pierre Thierry Simon E.B. Thierry Ph.D. candidate Independent developer LSIIT, UMR CNRS-ULP 7005 Thierry Technologies Pôle API, BP 10413 Illkirch Cedex France [email protected] [email protected] Abstract The data model of an application, the nature and format of data stored across executions, is typically a very rigid part of its early specication, even when prototyping, and changing it after code that relies on it was written can prove quite expensive and error-prone. Code and data in a running Lisp image can be dynamically modied. A MOP-based persistence library can bring this dynamicity to the data model. This enables to extend the easy prototyping way of development to the storage of data and helps avoiding interruptions of service. This article presents the conditions to do this portably and transparently. 1 Introduction Many applications provide a continuous service but cannot guarantee that they will run continuously. These applications must serialize and write part of their state to be able to restore it when they are executed again. Some of these applications are designed to run continuously but one cannot avoid to shut them down occasionally, e.g. because of hardware failure, maintenance or software updates, like network servers. Others are only needed part of the time and are designed to be executed only then, like accounting software. Occasionally an application is designed to be executed in a short time and only handle user input and hardcoded data but, as the use conditions evolve, it becomes necessary to stop its execution and be able to resume it later.
    [Show full text]
  • Statistics for Brynosaurus.Com (2004)
    Statistics for brynosaurus.com (2004) Statistics for: brynosaurus.com Last Update: 26 Sep 2006 − 03:56 Reported period: Year 2004 When: Monthly history Days of month Days of week Hours Who: Countries Full list Hosts Full list Last visit Unresolved IP Address Robots/Spiders visitors Full list Last visit Navigation: Visits duration File type Viewed Full list Entry Exit Operating Systems Versions Unknown Browsers Versions Unknown Referers: Origin Refering search engines Refering sites Search Search Keyphrases Search Keywords Others: Miscellaneous HTTP Status codes Pages not found Summary Reported period Year 2004 First visit 01 Jan 2004 − 00:04 Last visit 31 Dec 2004 − 23:57 Unique visitors Number of visits Pages Hits Bandwidth <= 40525 47088 85260 726872 20.63 GB Viewed traffic * Exact value not available in (1.16 visits/visitor) (1.81 pages/visit) (15.43 hits/visit) (459.33 KB/visit) 'Year' view Not viewed traffic * 56661 78092 1.91 GB * Not viewed traffic includes traffic generated by robots, worms, or replies with special HTTP status codes. Monthly history Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 2004 Month Unique visitors Number of visits Pages Hits Bandwidth Jan 2004 3254 3542 5336 34926 1.06 GB Feb 2004 3721 4080 7997 68946 1.83 GB Mar 2004 5103 5842 9661 116080 2.89 GB Apr 2004 3761 4306 7697 69176 1.86 GB May 2004 3796 4415 7466 71072 1.96 GB Jun 2004 2664 3143 6283 49758 1.40 GB Jul 2004 2470 2908 5066 40287 1.18 GB Aug 2004 2279 2836 5394 40026 1.14 GB Sep 2004 2955
    [Show full text]
  • Lxds: Towards Isolation of Kernel Subsystems
    LXDs: Towards Isolation of Kernel Subsystems Vikram Narayanan Abhiram Balasubramanian∗ Charlie Jacobsen∗ University of California, Irvine University of Utah University of Utah Sarah Spall† Scott Bauer‡ Michael Quigley§ Aftab Hussain University of Utah University of Utah University of Utah University of California, Irvine Abdullah Younis¶ Junjie Shen University of California, Irvine University of California, Irvine Moinak Bhattacharyya Anton Burtsev University of California, Irvine University of California, Irvine Abstract and inherent complexity (typical kernel code adheres to mul- Modern operating systems are monolithic. Today, however, tiple allocation, synchronization, access control, and object lack of isolation is one of the main factors undermining se- lifetime conventions) bugs and vulnerabilities are routinely curity of the kernel. Inherent complexity of the kernel code introduced into the kernel code. In 2018, the Common Vul- and rapid development pace combined with the use of unsafe, nerabilities and Exposures database lists 176 Linux kernel low-level programming language results in a steady stream vulnerabilities that allow for privilege escalation, denial-of- of errors. Even after decades of efforts to make commodity service, and other exploits [20]. This number is the lowest kernels more secure, i.e., development of numerous static and across several years [19]. dynamic approaches aimed to prevent exploitation of most Even though a number of static and dynamic mechanisms common errors, several hundreds of serious kernel vulnerabil- have been invented to protect execution of the low-level kernel ities are reported every year. Unfortunately, in a monolithic code, e.g., modern kernels deploy stack guards [18], address kernel a single exploitable vulnerability potentially provides space layout randomization (ASLR) [45], and data execution an attacker with access to the entire kernel.
    [Show full text]