Formal Models of Operating System Kernels phần 6 pptx

... most signiﬁcant aspect of this chapter’s model is that it actsas an existence proof. It is possible to deﬁne a formal model of an operating system kernel and to prove some of its properties. In ... of the current kernel.5.2 RequirementsThe requirement is to model an operating system kernel that is based uponthe exchange of messages between processes. The kernel should be an example of ... cannot be used. Indeed, it is of a complexity not far from that of thetiny kernels used for embedded and some real-time systems. The µC/OS [18]is a good example of such a kernel.The kernel...

Formal Models of Operating System Kernels phần 10 pot

... 252PagingDiskProcessINIT 263 OnPageRequest 266 PageIsOnDisk 265 RemoveProcessFromPagingDisk 266 RetrievePageFromDisk 265 StorePageOnDisk 265 ProcessCreation:createASystemProcess 194createAUserProcess ... 166 MarkAsInStore 166 MarkAsSwappedOut 166 NextProcessToSwapIn 172ProcessStoreSize 168 ReadyProcessChildren 169 RemoveProcessStoreInfo 168 SetProcessStartResidencyTime 167 SetProcessStartSwappedOutTime 167 UpdateAllStorageTimes ... 77, 1 76, 211deallocation, 3 06 descriptor, 39, 51, 67 , 1 06 destruction, 84device, 1 06, 127idle, 40, 68 , 103, 127reference, 42, 56, 103management, 103null, 40, 68 , 103reference, 42, 56, 103page...

Formal Models of Operating System Kernels phần 9 potx

... counter are:BIT == {0, 1}N2 56 == 0 255(N2 56 is just the naturals 0 2 16 − 1—i.e., a 16- bit unsigned.)The computation of the counter value forms part of the predicate of schemaComputeHitCounts. ... Npgallocstart =0The value of 0 is completely arbitrary, as is now explained.Some systems map a virtual copy of the operating system onto the vir-tual address space of each user space (and some ... discussion of optimisation out of the way, it is possible to returnto the main theme. There follow some propositions dealing with the properties of the logical (Z) model of page faults. 6. 3 Virtual...

Formal Models of Operating System Kernels phần 8 pot

... comprising the system- call library all send and receivemessages. Therefore, the rest of the proof must be in terms of the properties of the message-passing subsystem.The message-passing subsystem is ... of sharedpages(p)(sg), for some p and sg.Proof. Similar to the previous proof. ✷Proposition 134. IsLockedPage iﬀ lpno? is a locked page; that is, iﬀ lpno?is an element of lockedpages.Proof. ... PHYSICALPAGENO → PAGEPAGE == PAGEOFFSET → PSUThe empty page is deﬁned as follows:NullPage : PAGENullPage =(λ i : PAGEOFFSET • 0)It is a page (vector of bytes), PAGEOFFSET bytes long, with each...

Formal Models of Operating System Kernels phần 7 doc

... •msgmgr.RcvMessage[/src?,/dest?, m/m!]∧ DoDiskSwap)5 .6 Kernel InterfaceSome readers will have been wondering why a proper system interface hasnot been deﬁned in any of the models so far. The ﬁrst kernel merits ... message contains the identiﬁer of the sending process. Italso contains two natural numbers (elements of N). They denote the size of the data area and the size of the stack area that are, respectively, ... prove some fairly general properties of themessage-passing system. Proposition 112. The message-passing mechanism is synchronous.Proof. By the predicates of SendMessage and RcvMessage.If the...

Formal Models of Operating System Kernels phần 5 pps

... to determine all the children of a parent process.4.8 General ResultsThis ﬁnal section contains the proof of a number of propositions that dealwith properties of the kernel.The propositions ... an idea of some of the other things that might need to be handled during termination).If a process is on disk when it is terminated (say, because of system ter-mination or because of some error ... enabling it to be represented withinthe system. As part of this, a test (proctab.CanGenPId)ismadeastowhetherthe system has reached its maximum number of processes. The schema is com-plicated...

Formal Models of Operating System Kernels phần 4 pot

... descendant of the ancestor of the process just blocked.Proof. This requires the proof of the following lemma.Lemma 16. For any process, p, BlockProcessChildren implies that there areno children of ... closure of the childof relation; the complete set of descendants of a given process are represented by childof+(|{p?}|) for any process identiﬁerp?. In BlockProcessChildren, ps is the set of descendants ... p,BlockProcessChildren ⇒ (∀ p1: APREF | childof (p1, p) • p ∈ ran userqueue )Proof. The predicate of BlockProcessChildren contains an instance of MakeUnready inside the scope of the universal quantiﬁer. The...

Formal Models of Operating System Kernels phần 3 ppt

... •parentof (p1, p?))RemoveProcessFromParent∆(parentof )parent?, child?:APREFparentof= parentof \{(parent?, child?)}ParentOfProcessp?:APREFparent!:APREF(∃ p1: APREF •parentof (p1, ... priority of process,p. If p is an element of q, then MakeUnready[p/pid?] implies that p is notan element of q.Proof. There are two cases to consider:Case 1. Process p is the head of q. The ... ⊆ known procs ∧ dom childof ⊆ known procsran childof ⊆ known procs ∧ ran childof = ran parentchildof∼= parentof ∧ code owners ⊆ dom parentof(∀ p1, p2: APREF •p1∈ dom blockswaiting...

Formal Models of Operating System Kernels phần 2 pps

... performed, the inclusion of IdleProcRef and the ex-clusion of NullProcRef are of some importance. They determine the range of possible values for the domains of the components of process descriptors. ... execution of a piece of code. They are used as a kind of low-level mutual exclusion mechanism.4.3 Common Structures 101Proof. By a previous Lemma (Lemma 5), | scnt| =#elts.ByLemma6andinduction, ... the idle process, of course.Proof. The components of the process description, pstate, pkind, pstack,pregs, etc., all have identical domains by the ﬁrst part of the invariant of PROCESSES.Thatis:dom...

Formal Models of Operating System Kernels phần 1 pdf

... 2285 .6 KernelInterface 231 6 Virtual Storage 239 6. 1 Introduction 239 6. 2 Outline 239 6. 3 VirtualStorage 240 6. 3.1 The Paging Disk Process 263 6. 3.2 Placement:Demand Paging andLRU 267 6. 3.3 ... the upper layers of an operating system. OS Kit is a software kit, not a formal speciﬁcation or modellingtool.Iain D. Craig Formal Models of Operating System Kernels ContentsPreface vii1 ... a real help—I have used formal models as a way of trying out new software ideas since the late 1980s). Of course, I hope that people from formal methods and operating systems,as well as computer...

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