The Design and Implementation of the Anykernel and Rump Kernels

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182 Anecdotal analysis For several weeks the author did his day-to-day web browsing with Firefox acting as a remote client for a rump kernel TCP/IP stack. There was no human-perceivable difference between the performance of a rump networking stack and the host networking stack, either in bulk downloads of speeds up to 10Mbps, flash content or interactive page loads. The only human-perceivable difference was the ability to reboot the TCP/IP stack from under the browser without having to close the browser first. Microbenchmarks show that remote system calls are orders of magnitude slower than local system calls especially due to copyin/out I/O. However, this“macrobenchmark” suggests that others factors in real application hugely mitigate this performance difference. We conclude that without a specific application use case any optimizations are premature. In the event of such use cases emerging, optimizations know from literature [14, 63] may be attempted. 3.13 Summary We began this chapter by describing the cornerstone techniques for how to convert an existing monolithic kernel codebase into an anykernel. To retain the existing properties of the monolithic kernel, we did not introduce any new technologies, and adjusted the codebase using the following techniques: code moving, function pointers and weak symbols. These techniques were enough to convert the NetBSD kernel into an anykernel with an independent base and orthogonal factions. We went over the various rump kernel implementation aspects such as implicit thread creation and the CPU scheduler. After that, we studied the effects that feature
183 relegation has on the implementation of the virtual memory subsystem and locking facilities. The rest of the chapter discussed various segments of the implementation, such as microkernel style file servers with rump kernel backends, USB hardware drivers and accessing rump kernels over the Internet. We found out that many of the adjustments we did to NetBSD pertaining to the subject matter had a wider benefit. One example was the addition of the ioconf and pseudo-root keywords to a config file. This improvement simplified creating kernel modules out of device drivers and has been used by dozens of non rump kernel drivers since. Another modification we did was the ability to disable builtin kernel modules. This modification made it possible to disable drivers with newly discovered vulnerabilities without having to immediately reboot the system. These out-of-band benefits show that not only were our modifications useful in addressing our problem set, but they also benefit the original monolithic kernel.
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Department of Computer Science and
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9 Preface Meet the new boss Same as
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11 Then there is my dear Xi, who, s
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14 2.3.3 InterruptsandPreemption...
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16 4.1.1 Implementation Effort ....
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18 Appendix C Patches to the 5.99.4
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20 ISA LGPL LRU LWP MD MI MMU NIC O
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23 List of Figures 2.1 Rumpkernelhi
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25 4.14 Time to execute 5M system c
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29 1 Introduction In its classic ro
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31 and application-level drivers. T
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33 We define an anykernel to be an
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35 Our implementation supports rump
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37 The project was done in small in
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39 2 The Anykernel and Rump Kernels
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41 building on top of the entities
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43 Drivers in a rump kernel remain
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45 Figure 2.1: Rump k
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47 in Section 3.2.3. Whenever discu
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49 int rumpns_bpfopen(dev_t, int, i
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51 Figure 2.4:
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53 while the application logic stil
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55 We must solve the lack of a rump
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57 2.3.1 Kernel threads Up until no
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59 void * pool_cache_get_paddr(pool
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61 2.3.4 An Example We present an e
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63 Figure 2.6: Prov
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65 The straightforward use of exist
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68 We identified three obstacles fo
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70 for loadable kernel modules (dis
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72 e.g. the routine for mapping a p
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74 3.2.1 C Symbol Namespaces In the
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76 the double underscore namespace
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78 since the representation might n
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80 The following rumpuser interface
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82 The entry point rump_schedule()
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84 3.3.1 CPU Scheduling Recall from
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86 The fastpath is taken in cases w
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88 Releasing a CPU requires the fol
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90 10 8 seconds 6 4 2 0 1CPU 2CPU n
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92 Hardware interrupt handlers are
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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+
Page 134 and 135: 132 into a rump kernel and the driv
Page 136 and 137: 134 sys/arch/x86/include/cpu.h: #de
Page 138 and 139: 136 3.8.4 Rump Component Init Routi
Page 140 and 141: 138 RUMP_COMPONENT(RUMP_COMPONENT_N
Page 142 and 143: 140 We have three distinct cases we
Page 144 and 145: 142 # ifconfig tap0 create # ifconf
Page 146 and 147: 144 Unprivileged use of host’s ne
Page 148 and 149: 146 DOMAIN_DEFINE(sockindomain); co
Page 150 and 151: 148 issue another write before the
Page 152 and 153: 150 using an interface called USBDI
Page 154 and 155: 152 The kernel device configuration
Page 156 and 157: 154 # $NetBSD: UMASS.ioconf,v 1.4 2
Page 158 and 159: 156 USB Host Controller Hub0 (root)
Page 160 and 161: 158 Figure 3.30: File s
Page 162 and 163: 160 in-kernel mount: /dev/sd0e /m/u
Page 164 and 165: 162 structure being created by rump
Page 166 and 167: 164 3.12.1 Client-Kernel Locators B
Page 168 and 169: 166 A tmpfs server listening on INA
Page 170 and 171: 168 Request Arguments Response Desc
Page 172 and 173: 170 Host syscall rump syscall 1. op
Page 174 and 175: 172 A client’s initial connection
Page 176 and 177: 174 their system calls to a rump ke
Page 178 and 179: 176 stdin/stdout, the new file desc
Page 180 and 181: 178 Supporting fork() Recall, the f
Page 182 and 183: 180 As with fork, most of the kerne
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Page 188 and 189: 186 SLOC 8000 7000 6000 5000 4000 3
Page 190 and 191: 188 Total commits to the kernel 9,6
Page 192 and 193: 190 120 build time (minutes) 100 80
Page 194 and 195: 192 4.2.2 makefs For a source tree
Page 196 and 197: 194 not include later debugging [76
Page 198 and 199: 196 the necessary tools such as mak
Page 200 and 201: 198 proach of supplying alternate c
Page 202 and 203: 200 are not out-of-the-box compatib
Page 204 and 205: 202 golem> mount -t msdos -o rump /
Page 206 and 207: 204 Full OS By a full OS we mean a
Page 208 and 209: 206 • Rapid prototyping: One of t
Page 210 and 211: 208 4.5.3 Testing: Case Studies We
Page 212 and 213: 210 static void scsitest_request(st
Page 214 and 215: 212 waits for the timeout and check
Page 216 and 217: 214 • We noticed that even in sup
Page 218 and 219: 216 which were discovered during wr
Page 220 and 221: 218 version swap no swap NetBSD 5.1
Page 222 and 223: 220 It needs to be stressed that Ta
Page 224 and 225: 222 Network clusters Bootstrapping
Page 226 and 227: 224 8 7 Standard components Self-co
Page 228 and 229: 226 Rump kernel calls, as expected,
Page 230 and 231: 228 Traditional FFS We measure the
Page 232 and 233: 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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The Design and Implementation of the Anykernel and Rump Kernels

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