iAPX 286 Operating System Writers Guide 1983

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BINDING AND LOADING474849505152535455565758596061626364656667686970717273747576777879LARGE V1P0.STACK0,LARGE-V1P0.STACK1,LARGE-V1P0.STACK2) -) ,URTASK LDT (ENTRY=(URTASK)),CONSOLE LDT (ENTRY=(CONSOLE DRIVER, CONSOLE STACK0)),LOADER TASK LDT (ENTRY=(LOADER, LOADER STACK0)),IDT (ENTRY=(15:TIME_SLICE)); -TASKADAM (INITIAL, OBJECTLDTCONSOLE DEVICE (OBJECTLDTSTACKSLOADER TASK (OBJECTLDTSTACKSEXPORT #:F1:XOS.LB2 (KERNELXQ RESERVE SLOTS,XQ-RELINQUISH SLOTS,XQ-ALLOCATE, -XQ-FREE SEG,XQ-CREATE ALIAS,XQ-CHANGE-AR,XQ-WAIT SEMAPHORE,XQ-SIGNAL SEMAPHORE,XQ-SEND MESSAGE,XQ=RECEIVE_MESSAGE));ENDURTASK,URTASK LDT) ,CONSOLE DRIVER,CONSOLE-LDT,(CONSOLE STACK0)),LOADER,LOADER TASK LDT,(LOADER_STACK0));BUILD FILE PROCESSING COMPLETEDFigure 11-3. Builder Specifications for XOS (Cont'd.)These specifications do not illustrate all the features of Builder; refer to the iAPX 286 System BuilderUser's Guide for a complete description of Builder syntax.OVERVIEW OF LOADINGThe loader in a dynamic system is not only responsible for copying a program into main memory, butis also a step in the binding process. A loader installs the actual TSS and LDT for a task, therebymaking it possible for the processor to interpret the task's memory references.If all symbolic references are already resolved, a loader's work is simple. The iAPX 286 object moduleformat (OMF) organizes segment information to facilitate rapid loading with little decision-making bythe loader program.11-8 121960·001
BIND.ING AND LOADINGConverting a Program Into a Task'Before an operating system can switch control to a new task, these structures must be initialized:• The TSS (data the processor needs in order to run the task).• The task database (TOB) (data the operating system needs in order to run the task).Either the following structures must be present or some mechanism must be in place to make thempresent when necessary:• Stack segments for each privilege level at which the task runs. (A stack-fault handler couldautomatically allocate a stack the first time it is used.)• Executable and data segments. (A virtual memory system could make these present when referenced.)Most programs also need an LOT to contain descriptors for segments private to the task. An LOT isnot required, however, if all descriptors used by the task reside in the GOT.. The initial values in the CS:IP fields of the TSS should point to the entry point of the first procedureof the new task.STYLES OF LOADERSThere are several ways to structure a loader. The following are just a few examples:I. As a separate and permanent task. With such a structure the loader constructs data segments inthe format of the new task's TSS and LOT. To create the new task, it passes descriptors for thesesegments to privilege-level 0 CPL-O) procedures that convert them to system segments and startthe new task.2. As procedures that run within an existing task. This approach suits the UNIX EXECUTE function,where the FORK function creates the task in which the loader runs as a duplicate of the task thatcalled the FORK function. The loader deletes the descriptors it finds in the task's LOT (therebydeleting the associated segments unless aliases exist in other tasks) and creates new descriptorsfor the segments it loads.3. As procedures in a skeletal task created by the operating-system kernel. The loader has only toallocate an LOT and install descriptors for the segments it loads:For approaches 2 and 3, the procedures of the loader may have segment descriptors and gates in theGOT so as not to encumber the LOTS.KERNEL SUPPORTA loader normally funs at PLs 2 or3 because it uses of both kernel-level procedures (for example,ALLOCATE to create a segment for the new task) and PL-I procedures (for example, the I/O proceduresto read object modules from disk). However, task creation involves some functions that only11-9 121960-001
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LITERATUREIn addition to the produc
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Intel Corporation makes no warranty
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PREFACEExternal LiteratureMany aspe
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Table of ContentsCHAPTER 1PageINTRO
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TABLE OF CONTENTSCHAPTER 9PageVIRTU
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TABLE OF CONTENTSLIST OF FIGURESFig
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Introduction to Protected 1Multitas
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INTRODUCTION TO PROTECTED MULTITASK
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inter INTRODUCTION TO PROTECTED MUL
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111'eI INTRODUCTION TO PROTECTED MU
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Using Hardware2Protection Features
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USING HARDWARE PROTECTION,FEATURESs
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interUSING HARDWARE PROTECTION FEAT
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USING HARDWARE PROTECTION FEATURES(
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USING HARDWARE PROTECTION FEATURES
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USING HARDWARE PROTECTION FEATUREST
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USING HARDWARE PROTECTION FEATURESo
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USING HARDWARE PROTECTION FEATURESL
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USING HARDWARE PROTECTION FEATUREST
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USING HARDWARE PROTECTION FEATURESE
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inl:el~USING HARDWARE PROTECTION FE
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IntelUSING HARDWARE PROTECTION FEAT
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IntelU~ING HARDWARE PROTECTION FEAT
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lSLDTFORMATRt;;SERV~~"O~iA~~.~ijij
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CHAPTER 3REAL MEMORY MANAGEMENTIn d
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REAL MEMORY MANAGEMENTIALLOCATEGATE
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interREAL MEMORY MANAGEMENTBEFOREAF
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REAL MEMORY MANAGEMENTGLOBAL DESCRI
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REAL MEMORY MANAGEMENTTable 3-1. Ac
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REAL MEMORY MANAGEMENTBEFOREI "FREE
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REAL MEMORY MANAGEMENTBEFOREI "FREE
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REAL MEMORY MANAGEMENTPL/M-286 COMP
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IIIIIIIIIIIIIIIIIIIIII
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II I telTASK MANAGEMENTCPUTASK REGI
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TASK MANAGEMENTIf the proc~sser, wh
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TASK MANAGEMENTUsually, termination
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TASK MANAGEMENTTASK XTSS TSS TSS TS
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TASK MANAGEMENTSCHEDULING POLICIEST
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TASK MANAGEMENTThe example in figur
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TASK MANAGEMENTREADY QUEUESBY PRIOR
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IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
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CHAPTER 5DATA SHARING, ALIASING, AN
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DATA SHARING, ALIASING, AND SYNCHRO
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interDATA SHARING, ALIASING, AND SV
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CHAPTER 6SIGNALS AND INTERRUPTSInte
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interSIGNALS AND INTERRUPTSlOTGOTTS
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SIGNALS AND INTERRUPTSTable 6-1. In
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SIGNALS AND INTERRUPTSSend interrup
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SIGNALS AND INTERRUPTSprocedure suc
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Handling Exception Conditions 7
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HANDLING EXCEPTION CONDITIONSError
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HANDLING EXCEPTION CONDITIONSAn exc
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Page 143 and 144: CHAPTER 8INPUT /OUTPUTMany of the c
Page 145 and 146: INPUT /OUTPUTYou can still take adv
Page 147 and 148: INPUT /OUTPUT• Only the operating
Page 149: INPUT /OUTPUTtask the I/0 procedure
Page 153 and 154: CHAPTER 9VIRTUAL MEMORYThe memory l
Page 155 and 156: VIRTUAL MEMORYthose segments that a
Page 157 and 158: VIRTUAL MEMORY• Return the RAM sp
Page 159 and 160: VIRTUAL MEMORYReplacementThe operat
Page 161 and 162: System Initialization10
Page 163 and 164: CHAPTER 10SYSTEM INITIALIZATIONThe
Page 165 and 166: SYSTEM INITIALIZATIONStarting the f
Page 167 and 168: iAPX286 "ACRO ASSEMBLERLOCOBJEnter
Page 169 and 170: iAPX286 MACRO ASSEMBLEtEnter Protec
Page 171 and 172: iAPX286 MACRO ASSEMBLER·· Enter ~
Page 173 and 174: iAPX286 'UCRO USE148LER Ente,. P,.o
Page 175 and 176: iAPX286 MACRO ASSEMBLEREnt9~ P~otec
Page 177: iAPX286 MACRO ASSEMBLE~ INITIAL TAS
Page 181 and 182: CHAPTER 11BINDING AND LOADINGBindin
Page 183 and 184: BINDING AND LOADINGNamingThe names
Page 185 and 186: BINDING AND LOADING$ COMPACT (NUCLE
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Page 191 and 192: BINDING AND LOADINGThe OMF of each
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Page 195 and 196: BINDING AND LOADINGPL/M-2B6 COMPILE
Page 197 and 198: BINDING AND LOADI.NGPL/M-286 COMPIL
Page 199 and 200: BINDING AND LOADINGPL/M-286 COMPILE
Page 201 and 202: BINDING AND LOADINGPL/M-2B6 COMPILE
Page 203 and 204: BINDING AND LOAD.INGPL/M-286 COMPIL
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Page 207 and 208: BINDING AND LOADINGPL/M-286 COMPILE
Page 209: Numerics Processor Extension 12
Page 212 and 213: NUMERICS PROCESSOR EXTENSIONMath Pr
Page 214 and 215: interNUMERICS PROCESSOR EXTENSION
Page 217: Extended Protection13
Page 220 and 221: EXTENDED PROTECTIONIndirect NamingT
Page 222 and 223: EXTENDED PROTECTIONanother procedur
Page 225: Glossary
Page 228 and 229: GLOSSARYbootloadable module: a modu
Page 230 and 231: GLOSSARYexception: a processor-dete
Page 232 and 233: GLOSSARYintersegment reference: a r
Page 234 and 235: GLOSSARYoutward call: the attempt t
Page 236 and 237: GLOSSARYscheduling state: one of se
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GLOSSARYvirtual address: an address
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INDEXES register, 2-17, 2-18, 2-21,
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INDEXpresent bit, 2-2, 2-3, 2-9, 5-
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interu.s. SALES OFFICESALAIWIA IlEQ
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interu.s. DISTRIBUTORSNEW YORK (C"n
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intJINTEL INTERNATIONAL SALES OFFIC
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iAPX 286 Operating System Writers Guide 1983

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