Linux® Emulation in Freebsd
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Introduction to Debugging the Freebsd Kernel
Introduction to Debugging the FreeBSD Kernel John H. Baldwin Yahoo!, Inc. Atlanta, GA 30327 [email protected], http://people.FreeBSD.org/˜jhb Abstract used either directly by the user or indirectly via other tools such as kgdb [3]. Just like every other piece of software, the The Kernel Debugging chapter of the FreeBSD kernel has bugs. Debugging a ker- FreeBSD Developer’s Handbook [4] covers nel is a bit different from debugging a user- several details already such as entering DDB, land program as there is nothing underneath configuring a system to save kernel crash the kernel to provide debugging facilities such dumps, and invoking kgdb on a crash dump. as ptrace() or procfs. This paper will give a This paper will not cover these topics. In- brief overview of some of the tools available stead, it will demonstrate some ways to use for investigating bugs in the FreeBSD kernel. FreeBSD’s kernel debugging tools to investi- It will cover the in-kernel debugger DDB and gate bugs. the external debugger kgdb which is used to perform post-mortem analysis on kernel crash dumps. 2 Kernel Crash Messages 1 Introduction The first debugging service the FreeBSD kernel provides is the messages the kernel prints on the console when the kernel crashes. When a userland application encounters a When the kernel encounters an invalid condi- bug the operating system provides services for tion (such as an assertion failure or a memory investigating the bug. For example, a kernel protection violation) it halts execution of the may save a copy of the a process’ memory current thread and enters a “panic” state also image on disk as a core dump. -
Drilling Network Stacks with Packetdrill
Drilling Network Stacks with packetdrill NEAL CARDWELL AND BARATH RAGHAVAN Neal Cardwell received an M.S. esting and troubleshooting network protocols and stacks can be in Computer Science from the painstaking. To ease this process, our team built packetdrill, a tool University of Washington, with that lets you write precise scripts to test entire network stacks, from research focused on TCP and T the system call layer down to the NIC hardware. packetdrill scripts use a Web performance. He joined familiar syntax and run in seconds, making them easy to use during develop- Google in 2002. Since then he has worked on networking software for google.com, the ment, debugging, and regression testing, and for learning and investigation. Googlebot web crawler, the network stack in Have you ever had the experience of staring at a long network trace, trying to figure out what the Linux kernel, and TCP performance and on earth went wrong? When a network protocol is not working right, how might you find the testing. [email protected] problem and fix it? Although tools like tcpdump allow us to peek under the hood, and tools like netperf help measure networks end-to-end, reproducing behavior is still hard, and know- Barath Raghavan received a ing when an issue has been fixed is even harder. Ph.D. in Computer Science from UC San Diego and a B.S. from These are the exact problems that our team used to encounter on a regular basis during UC Berkeley. He joined Google kernel network stack development. Here we describe packetdrill, which we built to enable in 2012 and was previously a scriptable network stack testing. -
ARM Assembly Shellcode from Zero to ARM Assembly Bind Shellcode
Lab: ARM Assembly Shellcode From Zero to ARM Assembly Bind Shellcode HITBSecConf2018 - Amsterdam 1 Learning Objectives • ARM assembly basics • Writing ARM Shellcode • Registers • System functions • Most common instructions • Mapping out parameters • ARM vs. Thumb • Translating to Assembly • Load and Store • De-Nullification • Literal Pool • Execve() shell • PC-relative Addressing • Reverse Shell • Branches • Bind Shell HITBSecConf2018 - Amsterdam 2 Outline – 120 minutes • ARM assembly basics • Reverse Shell • 15 – 20 minutes • 3 functions • Shellcoding steps: execve • For each: • 10 minutes • 10 minutes exercise • Getting ready for practical part • 5 minutes solution • 5 minutes • Buffer[10] • Bind Shell • 3 functions • 25 minutes exercise HITBSecConf2018 - Amsterdam 3 Mobile and Iot bla bla HITBSecConf2018 - Amsterdam 4 It‘s getting interesting… HITBSecConf2018 - Amsterdam 5 Benefits of Learning ARM Assembly • Reverse Engineering binaries on… • Phones? • Routers? • Cars? • Intel x86 is nice but.. • Internet of Things? • Knowing ARM assembly allows you to • MACBOOKS?? dig into and have fun with various • SERVERS?? different device types HITBSecConf2018 - Amsterdam 6 Benefits of writing ARM Shellcode • Writing your own assembly helps you to understand assembly • How functions work • How function parameters are handled • How to translate functions to assembly for any purpose • Learn it once and know how to write your own variations • For exploit development and vulnerability research • You can brag that you can write your own shellcode instead -
Hardware-Driven Evolution in Storage Software by Zev Weiss A
Hardware-Driven Evolution in Storage Software by Zev Weiss A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Computer Sciences) at the UNIVERSITY OF WISCONSIN–MADISON 2018 Date of final oral examination: June 8, 2018 ii The dissertation is approved by the following members of the Final Oral Committee: Andrea C. Arpaci-Dusseau, Professor, Computer Sciences Remzi H. Arpaci-Dusseau, Professor, Computer Sciences Michael M. Swift, Professor, Computer Sciences Karthikeyan Sankaralingam, Professor, Computer Sciences Johannes Wallmann, Associate Professor, Mead Witter School of Music i © Copyright by Zev Weiss 2018 All Rights Reserved ii To my parents, for their endless support, and my cousin Charlie, one of the kindest people I’ve ever known. iii Acknowledgments I have taken what might be politely called a “scenic route” of sorts through grad school. While Ph.D. students more focused on a rapid graduation turnaround time might find this regrettable, I am glad to have done so, in part because it has afforded me the opportunities to meet and work with so many excellent people along the way. I owe debts of gratitude to a large cast of characters: To my advisors, Andrea and Remzi Arpaci-Dusseau. It is one of the most common pieces of wisdom imparted on incoming grad students that one’s relationship with one’s advisor (or advisors) is perhaps the single most important factor in whether these years of your life will be pleasant or unpleasant, and I feel exceptionally fortunate to have ended up iv with the advisors that I’ve had. -
Proceedings of the Linux Symposium
Proceedings of the Linux Symposium Volume One June 27th–30th, 2007 Ottawa, Ontario Canada Contents The Price of Safety: Evaluating IOMMU Performance 9 Ben-Yehuda, Xenidis, Mostrows, Rister, Bruemmer, Van Doorn Linux on Cell Broadband Engine status update 21 Arnd Bergmann Linux Kernel Debugging on Google-sized clusters 29 M. Bligh, M. Desnoyers, & R. Schultz Ltrace Internals 41 Rodrigo Rubira Branco Evaluating effects of cache memory compression on embedded systems 53 Anderson Briglia, Allan Bezerra, Leonid Moiseichuk, & Nitin Gupta ACPI in Linux – Myths vs. Reality 65 Len Brown Cool Hand Linux – Handheld Thermal Extensions 75 Len Brown Asynchronous System Calls 81 Zach Brown Frysk 1, Kernel 0? 87 Andrew Cagney Keeping Kernel Performance from Regressions 93 T. Chen, L. Ananiev, and A. Tikhonov Breaking the Chains—Using LinuxBIOS to Liberate Embedded x86 Processors 103 J. Crouse, M. Jones, & R. Minnich GANESHA, a multi-usage with large cache NFSv4 server 113 P. Deniel, T. Leibovici, & J.-C. Lafoucrière Why Virtualization Fragmentation Sucks 125 Justin M. Forbes A New Network File System is Born: Comparison of SMB2, CIFS, and NFS 131 Steven French Supporting the Allocation of Large Contiguous Regions of Memory 141 Mel Gorman Kernel Scalability—Expanding the Horizon Beyond Fine Grain Locks 153 Corey Gough, Suresh Siddha, & Ken Chen Kdump: Smarter, Easier, Trustier 167 Vivek Goyal Using KVM to run Xen guests without Xen 179 R.A. Harper, A.N. Aliguori & M.D. Day Djprobe—Kernel probing with the smallest overhead 189 M. Hiramatsu and S. Oshima Desktop integration of Bluetooth 201 Marcel Holtmann How virtualization makes power management different 205 Yu Ke Ptrace, Utrace, Uprobes: Lightweight, Dynamic Tracing of User Apps 215 J. -
“Out-Of-VM” Approach for Fine-Grained Process Execution Monitoring
Workshop for Frontiers of Cloud Computing, Dec 1, 2011, IBM T.J. Watson Research Center, NY Process Out-Grafting: An Efficient “Out-of-VM” Approach for Fine-Grained Process Execution Monitoring Deepa Srinivasan, Zhi Wang, Xuxian Jiang, Dongyan Xu * North Carolina State University, Purdue University* Malware Infection Trend New malware samples collected by McAfee Labs, by month* *Figure source: McAfee Threats Report: Second Quarter 2011, McAfee Labs 2 Anti-Malware Isolation Traditional anti-malware tools are not well-isolated Virtual Machine (VM) introspection Isolate tool by placing it outside a VM Analyze states and events externally User-mode Applications Monitor Virtual Machine … OS Kernel Hypervisor 3 Anti-Malware Isolation Traditional anti-malware tools are not well-isolated Virtual Machine (VM) introspection Isolate tool by placing it outside a VM Analyze states and events externally User-mode Applications Monitor VM Virtual Introspection Machine … OS Kernel Hypervisor 4 Out-of-VM Solutions Livewire (Garfinkel et al. , NDSS ‘03) XenAccess (Payne et al. , ACSAC ‘07) VMScope (Jiang et al. , RAID ‘07) Lares (Payne et al. , Oakland ‘08) … 5 Semantic Gap in Introspection What we want to observe High-level states and events (e.g. system calls, processes) What we can observe Low-level states and events (e.g. raw memory, interrupts) Internal User-mode Applications Monitor … External Monitor Semantic Virtual Machine Gap OS Kernel Hypervisor 6 Addressing the Semantic Gap Guest view casting VMWatcher (Jiang et al. , CCS -
Practical and Effective Sandboxing for Non-Root Users
Practical and effective sandboxing for non-root users Taesoo Kim and Nickolai Zeldovich MIT CSAIL Abstract special tools. More importantly, all use cases neither re- quire root privilege nor require modification to the OS MBOX is a lightweight sandboxing mechanism for non- kernel and applications. root users in commodity OSes. MBOX’s sandbox usage model executes a program in the sandbox and prevents Overview MBOX aims to make running a program in a the program from modifying the host filesystem by layer- sandbox as easy as running the program itself. For exam- ing the sandbox filesystem on top of the host filesystem. ple, one can sandbox a program (say wget) by running as At the end of program execution, the user can examine below: changes in the sandbox filesystem and selectively com- mit them back to the host filesystem. MBOX implements $ mbox -- wget google.com ... this by interposing on system calls and provides a variety Network Summary: of useful applications: installing system packages as a > [11279] -> 173.194.43.51:80 > [11279] Create socket(PF_INET,...) non-root user, running unknown binaries safely without > [11279] -> a00::2607:f8b0:4006:803:0 network accesses, checkpointing the host filesystem in- ... Sandbox Root: stantly, and setting up a virtual development environment > /tmp/sandbox-11275 without special tools. Our performance evaluation shows > N:/tmp/index.html [c]ommit, [i]gnore, [d]iff, [l]ist, [s]hell, [q]uit ?> that MBOX imposes CPU overheads of 0.1–45.2% for var- ious workloads. In this paper, we present MBOX’s design, wget is a utility to download files from the web. -
Porting the QEMU Virtualization Software to MINIX 3
Porting the QEMU virtualization software to MINIX 3 Master's thesis in Computer Science Erik van der Kouwe Student number 1397273 [email protected] Vrije Universiteit Amsterdam Faculty of Sciences Department of Mathematics and Computer Science Supervised by dr. Andrew S. Tanenbaum Second reader: dr. Herbert Bos 12 August 2009 Abstract The MINIX 3 operating system aims to make computers more reliable and more secure by keeping privileged code small and simple. Unfortunately, at the moment only few major programs have been ported to MINIX. In particular, no virtualization software is available. By isolating software environments from each other, virtualization aids in software development and provides an additional way to achieve reliability and security. It is unclear whether virtualization software can run efficiently within the constraints of MINIX' microkernel design. To determine whether MINIX is capable of running virtualization software, I have ported QEMU to it. QEMU provides full system virtualization, aiming in particular at portability and speed. I find that QEMU can be ported to MINIX, but that this requires a number of changes to be made to both programs. Allowing QEMU to run mainly involves adding standardized POSIX functions that were previously missing in MINIX. These additions do not conflict with MINIX' design principles and their availability makes porting other software easier. A list of recommendations is provided that could further simplify porting software to MINIX. Besides just porting QEMU, I also investigate what performance bottlenecks it experiences on MINIX. Several areas are found where MINIX does not perform as well as Linux. The causes for these differences are investigated. -
Postmodern Strace Dmitry Levin
Postmodern strace Dmitry Levin Brussels, 2020 Traditional strace [1/30] Printing instruction pointer and timestamps print instruction pointer: -i option print timestamps: -r, -t, -tt, -ttt, and -T options Size and format of strings string size: -s option string format: -x and -xx options Verbosity of syscall decoding abbreviate output: -e abbrev=set, -v option dereference structures: -e verbose=set print raw undecoded syscalls: -e raw=set Traditional strace [2/30] Printing signals print signals: -e signal=set Dumping dump the data read from the specified descriptors: -e read=set dump the data written to the specified descriptors: -e write=set Redirecting output to files or pipelines write the trace to a file or pipeline: -o filename option write traces of processes to separate files: -ff -o filename Traditional strace [3/30] System call filtering trace only the specified set of system calls: -e trace=set System call statistics count time, calls, and errors for each system call: -c option sort the histogram printed by the -c option: -S sortby option Tracing control attach to existing processes: -p pid option trace child processes: -f option Modern strace [4/30] Tracing output format pathnames accessed by name or descriptor: -y option network protocol associated with descriptors: -yy option stack of function calls: -k option System call filtering pathnames accessed by name or descriptor: -P option regular expressions: -e trace=/regexp optional specifications: -e trace=?spec new syscall classes: %stat, %lstat, %fstat, %statfs, %fstatfs, %%stat, %%statfs -
User-Level Infrastructure for System Call Interposition: a Platform for Intrusion Detection and Confinement
User-Level Infrastructure for System Call Interposition: A Platform for Intrusion Detection and Confinement K. Jain R. Sekar Iowa State University State University of New York Ames, IA 50014 Stony Brook, NY 11794 [email protected] [email protected] Abstract attacks launched remotely via the Internet. Such attacks may utilize a variety of techniques, e.g., exploit software er- Several new approaches for detecting malicious attacks rors in privileged programs to gain root privilege, exploit on computer systems and/or confining untrusted or ma- vulnerabilities in system configuration to access confiden- licious applications have emerged over the past several tial data, or rely on a legitimate system user to download years. These techniques often rely on the fact that when and run a legitimate-looking Trojan Horse program that in- a system is attacked from a remote location over a network, flicts damage. Intrusion detection refers to a broad range of damage can ultimately be inflicted only via system calls techniques that have been developed over the past several made by processes running on the target system. This factor years to protect against malicious attacks. A majority of has lead to a surge of interest in developing infrastructures these techniques take the passive approach of offline moni- that enable secure interception and modification of system toring of system (or user) activities to identify those activ- calls made by processes running on the target system. Most ities that deviate from the norm [1, 26, 10, 12, 17, 21] or known approaches for solving this problem have relied on are otherwise indicative of attacks [14, 18, 22]. -
Comparing Solaris to Redhat Enterprise And
THESE ARE TRYING TIMES IN SOLARIS- land. The Oracle purchase of Sun has caused PETER BAER GALVIN many changes both within and outside of Sun. These changes have caused some soul- Pete’s all things Sun: searching among the Solaris faithful. Should comparing Solaris to a system administrator with strong Solaris skills stay the course, or are there other RedHat Enterprise and operating systems worth learning? The AIX decision criteria and results will be different for each system administrator, but in this Peter Baer Galvin is the chief technologist for Corporate Technologies, a premier systems column I hope to provide a little input to integrator and VAR (www.cptech.com). Before that, Peter was the systems manager help those going down that path. for Brown University’s Computer Science Department. He has written articles and columns for many publications and is co- Based on a subjective view of the industry, I opine author of the Operating Systems Concepts that, apart from Solaris, there are only three and Applied Operating Systems Concepts worthy contenders: Red Hat Enterprise Linux (and textbooks. As a consultant and trainer, Peter teaches tutorials and gives talks on security its identical twins, such as Oracle Unbreakable and system administration worldwide. Peter Linux), AIX, and Windows Server. In this column blogs at http://www.galvin.info and twitters I discuss why those are the only choices, and as “PeterGalvin.” start comparing the UNIX variants. The next [email protected] column will contain a detailed comparison of the virtualization features of the contenders, as that is a full topic unto itself. -
Advanced Debugging in the Linux Environment
Advanced Debugging in the Linux Environment Stephen Rago NEC Laboratories America Tracing is an important debugging technique, especially with nontrivial applications, because it often isn’t clear how our programs interact with the operating system environment. For example, when you’re developing a C program, it is common to add printf statements to your program to trace its execution. This approach is the most basic of debugging techniques, but it has several drawbacks: you need to mod- ify and recompile your program, you might need to do so repeatedly as you gain moreinformation about what your program is doing, and you can’t put printf statements in functions belonging to libraries for which you don’t have source code. The Linux operating system provides morepowerful tools that make debugging easier and can overcome these limitations. This article provides a survey of these tools. We’ll start with a simple C program and see how some of these tools can help find bugs in the pro- gram. The program shown in Figure1includes three bugs, all marked by comments. #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #define BSZ 128 /* input buffer size */ #define MAXLINE 100000 /* lines stored */ char *lines[MAXLINE]; char buf[32]; /* BUG FIX #2: change 32 to BSZ */ int nlines; char * append(const char *str1, const char *str2) { int n = strlen(str1) + strlen(str2) + 1; char *p = malloc(n); if (p != NULL) { strcpy(p, str1); strcat(p, str2); } return(p); } void printrandom() { long idx = random() % nlines; fputs(lines[idx],