The Design and Implementation of the Anykernel and Rump Kernels

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46 (some exceptions to the file system rule exist, such as Bluetooth and Ethernet interfaces which are accessed via sockets on NetBSD). To access a /dev file system node in a rump kernel, file systems must be supported. Despite file system access being the standard way to access a device, it is possible to architect an application where the device interfaces are called directly without going through file system code. Doing so means skipping the permission checks offered by file systems, calling private kernel interfaces and generally having to write more fragile code. Therefore, it is not recommended as the default approach, but if need be due to resource limitations, it is a possibility. For example, let us assume we have a rump kernel running a TCP/IP stack and we wish to use the BSD Packet Filter (BPF) [67]. Access through /dev is presented in Figure 2.2, while direct BPF access which does not use file system user interfaces is presented in Figure 2.3. You will notice the first example is similar to a regular application, while the latter is more complex. We will continue to refer to these examples in this chapter when we go over other concepts related to rump kernels. The faction divisions allow cutting down several hundred kilobytes of memory overhead and milliseconds in startup time per instance. While the saving per instance is not dramatic, the overall savings are sizeable in applications such as network testing [44] which require thousands of virtual instances. For example, as we will later measure in Chapter 4, a virtual TCP/IP stack without file system support is 40% smaller (400kB) than one which contains file system support. 2.1.3 Hosting A rump kernel accesses host resources through the rumpuser hypercall interface. The hypercall layer is currently implemented for POSIX hosts, but there is no reason why it could not be adapted to suit alternative hosting as well, such as microkernels. We analyze the requirements for the hypercall interface in more detail
47 in Section 3.2.3. Whenever discussing hosting and the hypercall interface we attempt to keep the discussion generic and fall back to POSIX terminology only when necessary. The host controls what resources the guest has access to. It is unnecessary to run rump kernels as root on POSIX systems — security-conscious people will regard it as unwise as well unless there is a very good reason for it. Accessing resources such as the host file system will be limited to whatever credentials the rump kernel runs with on the host. Other resources such as memory consumption may be limited by thehostaswell. 2.2 Rump Kernel Clients We define a rump kernel client to be an application that requests services from a rump kernel. Examples of rump kernel clients are an application that accesses the network through a TCP/IP stack provided by a rump kernel, or an application that reads files via a file system driver running in a rump kernel. Likewise, a test program that is used to test kernel code by means of running it in a rump kernel is a rump kernel client. The relationship between a rump kernel and a rump kernel client is an almost direct analogy to an application process executing on an operating system and requesting services from the host kernel. The difference is that a rump kernel client must explicitly request all services from the rump kernel, while a process receives some services such as scheduling and memory protection implicitly from the host. As mentioned in Chapter 1 there are several possible relationship types the client and rump kernel can have. Each of them have different implications on the client and kernel. The possibilities are: local, remote and microkernel. The configurations
Page 1: Department of Computer Science and
Page 11 and 12: 9 Preface Meet the new boss Same as
Page 13: 11 Then there is my dear Xi, who, s
Page 16 and 17: 14 2.3.3 InterruptsandPreemption...
Page 18 and 19: 16 4.1.1 Implementation Effort ....
Page 20 and 21: 18 Appendix C Patches to the 5.99.4
Page 22 and 23: 20 ISA LGPL LRU LWP MD MI MMU NIC O
Page 25 and 26: 23 List of Figures 2.1 Rumpkernelhi
Page 27: 25 4.14 Time to execute 5M system c
Page 31 and 32: 29 1 Introduction In its classic ro
Page 33 and 34: 31 and application-level drivers. T
Page 35 and 36: 33 We define an anykernel to be an
Page 37 and 38: 35 Our implementation supports rump
Page 39 and 40: 37 The project was done in small in
Page 41 and 42: 39 2 The Anykernel and Rump Kernels
Page 43 and 44: 41 building on top of the entities
Page 45 and 46: 43 Drivers in a rump kernel remain
Page 47: 45 Figure 2.1: Rump k
Page 51 and 52: 49 int rumpns_bpfopen(dev_t, int, i
Page 53 and 54: 51 Figure 2.4:
Page 55 and 56: 53 while the application logic stil
Page 57 and 58: 55 We must solve the lack of a rump
Page 59 and 60: 57 2.3.1 Kernel threads Up until no
Page 61 and 62: 59 void * pool_cache_get_paddr(pool
Page 63 and 64: 61 2.3.4 An Example We present an e
Page 65 and 66: 63 Figure 2.6: Prov
Page 67: 65 The straightforward use of exist
Page 70 and 71: 68 We identified three obstacles fo
Page 72 and 73: 70 for loadable kernel modules (dis
Page 74 and 75: 72 e.g. the routine for mapping a p
Page 76 and 77: 74 3.2.1 C Symbol Namespaces In the
Page 78 and 79: 76 the double underscore namespace
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Page 82 and 83: 80 The following rumpuser interface
Page 84 and 85: 82 The entry point rump_schedule()
Page 86 and 87: 84 3.3.1 CPU Scheduling Recall from
Page 88 and 89: 86 The fastpath is taken in cases w
Page 90 and 91: 88 Releasing a CPU requires the fol
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Page 94 and 95: 92 Hardware interrupt handlers are
Page 96 and 97: 94 Due to the design choice that a
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96 in. Therefore, we should critica
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98 Pager window create+access time
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100 A rump kernel can be configured
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102 Since all pages managed by the
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104 not in control of thread schedu
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106 synchronization part of the alg
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108 /* * Run a cross call to cycle
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110 kernel needs to do is make sure
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112 The kernel with uniprocessor lo
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114 the header file while open() c
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116 The same wrapper works both for
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118 5. Some calling conventions (e.
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120 int rump_pub_lwproc_rfork(int a
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122 By convention, file system devi
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124 ule directory tree from /stand
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126 After these steps have been per
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128 Host Dynamic Linker Using the h
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130 for (i = 0; i < SYS_NSYSENT; i+
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132 into a rump kernel and the driv
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134 sys/arch/x86/include/cpu.h: #de
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136 3.8.4 Rump Component Init Routi
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138 RUMP_COMPONENT(RUMP_COMPONENT_N
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140 We have three distinct cases we
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142 # ifconfig tap0 create # ifconf
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144 Unprivileged use of host’s ne
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146 DOMAIN_DEFINE(sockindomain); co
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148 issue another write before the
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150 using an interface called USBDI
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152 The kernel device configuration
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154 # $NetBSD: UMASS.ioconf,v 1.4 2
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156 USB Host Controller Hub0 (root)
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158 Figure 3.30: File s
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160 in-kernel mount: /dev/sd0e /m/u
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162 structure being created by rump
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164 3.12.1 Client-Kernel Locators B
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166 A tmpfs server listening on INA
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168 Request Arguments Response Desc
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170 Host syscall rump syscall 1. op
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172 A client’s initial connection
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174 their system calls to a rump ke
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176 stdin/stdout, the new file desc
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178 Supporting fork() Recall, the f
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180 As with fork, most of the kerne
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182 Anecdotal analysis For several
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184
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186 SLOC 8000 7000 6000 5000 4000 3
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188 Total commits to the kernel 9,6
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190 120 build time (minutes) 100 80
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192 4.2.2 makefs For a source tree
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194 not include later debugging [76
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196 the necessary tools such as mak
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198 proach of supplying alternate c
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200 are not out-of-the-box compatib
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202 golem> mount -t msdos -o rump /
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204 Full OS By a full OS we mean a
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206 • Rapid prototyping: One of t
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208 4.5.3 Testing: Case Studies We
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210 static void scsitest_request(st
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212 waits for the timeout and check
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214 • We noticed that even in sup
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216 which were discovered during wr
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218 version swap no swap NetBSD 5.1
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220 It needs to be stressed that Ta
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222 Network clusters Bootstrapping
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224 8 7 Standard components Self-co
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226 Rump kernel calls, as expected,
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228 Traditional FFS We measure the
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230 80 70 60 seconds 50 40 30 20 10
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232 The results are presented in Fi
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234 behavior is required by the act
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236
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238 Rialto [29] is an operating sys
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240 One argument for partitioned op
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242 View OS The View OS [37] approa
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244 OSKit Instead of making system
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246 discussing the type incompatibi
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248 difference to the abovementione
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250 At runtime, a rump kernel can a
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252 For testing and development we
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254
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256 Art of Virtualization. In: Proc
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258 [30] Adam Dunkels. 2001. Design
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260 [47] Galen C. Hunt and James R.
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262 [67] Steven McCanne and Van Jac
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264 [87] NetBSD Project. URL http:/
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266 of the 6th Workshop on Programm
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268
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A-2 RUMP.DHCPCLIENT(1) NetBSD Gener
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A-4 RUMP.HALT(1) NetBSD General Com
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A-6 RUMP_SERVER(1) NetBSD General C
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A-8 RUMP_SERVER(1) NetBSD General C
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A-10 SHMIF_DUMPBUS(1) NetBSD Genera
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A-12 P2K(3) NetBSD Library Function
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A-14 P2K(3) NetBSD Library Function
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A-16 RUMP(3) NetBSD Library Functio
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A-18 RUMP(3) NetBSD Library Functio
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A-20 RUMP_ETFS(3) NetBSD Library Fu
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A-22 RUMP_ETFS(3) NetBSD Library Fu
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A-24 RUMP_LWPROC(3) NetBSD Library
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A-26 RUMP_LWPROC(3) NetBSD Library
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A-28 RUMPCLIENT(3) NetBSD Library F
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A-30 RUMPCLIENT(3) NetBSD Library F
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A-32 RUMPHIJACK(3) NetBSD Library F
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A-38 UKFS(3) NetBSD Library Functio
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A-48 SHMIF(4) NetBSD Kernel Interfa
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A-50 RUMP_SP(7) NetBSD Miscellaneou
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A-52 RUMP_SP(7) NetBSD Miscellaneou
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B-2 TCP connections use standard TC
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B-4 rump clients. This means that j
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B-6 ponents. That can be done simpl
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B-8 Our goal is to add another part
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B-10 golem> export RUMP_SERVER=unix
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B-12 golem> rump.dd if=/dev/rcgd0d
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B-14 demogorgon# cgdconfig cgd0 /de
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B-16 rump_server -lrumpnet -lrumpne
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B-18 golem> rump.ifconfig virt0 cre
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B-20 Congratulations, that’s it.
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B-22 purely in userspace, it does n
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B-24 We then proceed to create a mo
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B-26 Then, the only thing left is t
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B-28 -d key=/dk,hostpath=${NFSX}/ff
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B-30 configuration. golem> sh rumpn
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B-32
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C-2 This is a quick fix for making
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C-4 This fixes the conditionally co
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Aalto-DD 171/2012 9HSTFMG*aejbgi+ I
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