國立政治大學資訊科學系 2014/4/30 Assembling Programs for Execution Assembly Programs Macro Processors 系統程式 Expanded Assembly Programs Core Assemblers Object Programs Chapter 3: Loaders and Linkers Linkers Libraries Loaders Executables 國立政治大學資訊科學系 Fundamental System Software Assembly Programs Assembler directives One-pass Symbolic operands Multi-pass Mnemonic op codes Fundamental System Software (2) Object Programs Assemblers SP.Chap3.2 Assembly Program 1 Object Program 1 Header records Text records Assembly Program 2 End records Literals Assemblers Object Program 2 Modification records Symbol-defining stmts Expressions Define records Program blocks Refer records Object Program 3 Assembly Program 3 Control sections 國立政治大學資訊科學系 SP.Chap3.3 Fundamental System Software (3) Object Prog 1 Object Prog 1 Assemblers Assembly Program 3 國立政治大學資訊科學系 Object Prog 2 Object Prog 3 Assembly Program 2 Linkers SP.Chap3.4 Fundamental System Software (4) Assembly Program 1 Assembly Program 1 Assembly Program 2 國立政治大學資訊科學系 Assemblers Object Prog 2 Linkers Loaders Loaders Linkers may combine multiple object codes into a single executable file. SP.Chap3.5 C/C++ ... Programs Compilers 國立政治大學資訊科學系 Object Progs A standardized format for the object codes allows linkers to combine object codes created by assemblers and compilers implemented by different providers. SP.Chap3.6 1 國立政治大學資訊科學系 2014/4/30 Fundamental System Software (5) Assembly Programs C/C++ ... Programs Assemblers Compilers Object Progs Object Progs Linkers Loaders Linkers and Loaders Loaders bring object programs into memory and start their execution. Linkers Libraries 國立政治大學資訊科學系 Since the format of object codes is standardized, linkers do not need to know the original computer languages that were used to implement the libraries. SP.Chap3.7 Simple Loaders In most cases all program translators on a particular system produce object programs in the same format. Discuss why 國立政治大學資訊科學系 SP.Chap3.8 Absolute Loader An absolute loader An absolute loader brings the object code to the memory location chosen by its programmer Use the algorithm shown in Figure 3.2 to review the operation of a simple loader with Figure 3.1. Explain the object code and actual object code. A bootstrap loader The bootstrap loader loads the first program to be run by the computer--usually an operating system. Algorithm shown on Figure 3.3 Bootstrap loaders in ROM (Section 3.4.3) 國立政治大學資訊科學系 SP.Chap3.9 Fetch-Decode-Execute Cycles 國立政治大學資訊科學系 SP.Chap3.10 A Simplified System ALU (Data Path) R A M address MEMORY data Registers control CPU I/O 1 Source: Charles S. Parker, Understanding Computers Today & Tomorrow, Dryden, 1998 國立政治大學資訊科學系 SP.Chap3.11 國立政治大學資訊科學系 Control Unit I/O 2 The CPU loads the very first program , including the bootstrap loader, to be executed from the ROM. R O M SP.Chap3.12 2 國立政治大學資訊科學系 2014/4/30 Bootstrap Loader BOOT START 0 Relocation and Linking GETC TD INPUT JEQ GETC RD INPUT COMP #4 EOF JEQ 80 COMP #48 ‘0’ JLT GETC SUB #48 <10 COMP #10 JLT RETURN SUB #7 A~F RETURN RSUB INPUT BYTE X’F1’ END LOOP CLEAR A LDX #128 LOOP JSUB GETC RMO A,S SHIFTL S,4 JSUB GETC ADDR S,A STCH 0,X TIXR X,X J LOOP 國立政治大學資訊科學系 A linkage loader, pp. 134-141 1110 0000 0000 0000 PROGA 0020 0023 0027 0040 REF1 REF2 REF3 LISTA . ENDA REF4 REF5 REF6 REF7 REF8 0054 0020 0023 0027 0040 REF1 REF2 REF3 LISTA . ENDA REF4 REF5 REF6 REF7 REF8 0054 0054 0057 005A 005D 0060 國立政治大學資訊科學系 START EXTDEF EXTREF . LDA +LDT LDX EQU EQU WORD WORD WORD WORD WORD SP.Chap3.14 START EXTDEF EXTREF . LDA +LDT LDX EQU EQU WORD WORD WORD WORD WORD 0 LISTA,ENDA LISTB, ENDB, LISTC, ENDC LISTA LISTB+4 #ENDA-LISTA * * ENDA-LISTA+LISTC ENDC-LISTC-10 ENDC-LISTC+LISTA-1 ENDA-LISTA-(ENDB-LISTB) LISTB-LISTA 國立政治大學資訊科學系 SP.Chap3.15 Program Linking PROGA The assembler does whatever it can do for address calculation. The loader will do the rest. 國立政治大學資訊科學系 0054 0057 005A 005D 0060 0000 required line change (Figure 3.7) Review Section 2.3.5 Program Linking ? 國立政治大學資訊科學系 multiprogramming, libraries,... Using modification record may not be good for all machine architectures. (Figure 3.6) Relocation bits and bit masks SP.Chap3.13 Relocation Masks 1111 1111 1100 Why relocation? SP.Chap3.16 Program Linking - PROGB 0 LISTA,ENDA LISTB, ENDB, LISTC, ENDC 0000 LISTA LISTB+4 #ENDA-LISTA * 0036 REF1 003A REF2 003D REF3 0060 0070 * ENDA-LISTA+LISTC ENDC-LISTC-10 ENDC-LISTC+LISTA-1 ENDA-LISTA-(ENDB-LISTB) LISTB-LISTA 0070 0073 0076 0079 007C SP.Chap3.17 PROGB LISTB . ENDB REF4 REF5 REF6 REF7 REF8 國立政治大學資訊科學系 START EXTDEF EXTREF . LDA +LDT LDX EQU EQU WORD WORD WORD WORD WORD 0 LISTB,ENDB LISTA, ENDA, LISTC, ENDC LISTA LISTB+4 #ENDA-LISTA * * ENDA-LISTA+LISTC ENDC-LISTC-10 ENDC-LISTC+LISTA-1 ENDA-LISTA-(ENDB-LISTB) LISTB-LISTA SP.Chap3.18 3 國立政治大學資訊科學系 2014/4/30 Program Linking - PROGB 0000 PROGB START EXTDEF EXTREF . LDA +LDT LDX EQU 0036 REF1 003A REF2 003D REF3 0060 0070 0070 0073 0076 0079 007C LISTB . ENDB REF4 REF5 REF6 REF7 REF8 EQU WORD WORD WORD WORD WORD Program Linking - PROGC 0 LISTB,ENDB LISTA, ENDA, LISTC, ENDC 0000 LISTA LISTB+4 #ENDA-LISTA * 0018 REF1 001C REF2 0020 REF3 0030 0042 * ENDA-LISTA+LISTC ENDC-LISTC-10 ENDC-LISTC+LISTA-1 ENDA-LISTA-(ENDB-LISTB) LISTB-LISTA 國立政治大學資訊科學系 0042 0045 0048 004B 004E SP.Chap3.19 PROGADDR CSADDR CSLTH ESTAB EQU WORD WORD WORD WORD WORD 0 LISTC,ENDC LISTA, ENDA, LISTB, ENDB LISTA LISTB+4 #ENDA-LISTA * * ENDA-LISTA+LISTC ENDC-LISTC-10 ENDC-LISTC+LISTA-1 ENDA-LISTA-(ENDB-LISTB) LISTB-LISTA 國立政治大學資訊科學系 Control section Pass 2 H and D records Data structure LISTC . ENDC REF4 REF5 REF6 REF7 REF8 START EXTDEF EXTREF . LDA +LDT LDX EQU SP.Chap3.20 ESTAB A Two-Pass Linking Loader Pass 1 PROGC Load maps E and M records Data structure Symbol name Address Length 4000 0063 LISTA 4040 ENDA 4056 LISTB 40C3 ENDB 40D3 LISTC 4112 ENDC 4124 PROGA PROGB PROGADDR CSADDR 4063 PROGC EXECADDR CSLTH What are the R records for? 40E2 007F 0051 reducing the number of table search operations... 國立政治大學資訊科學系 SP.Chap3.21 Reference number H^PROGA ^000000^.. D^LISTA ^000040…. R^LISTB ^ENDB ^LISTC ^ENDC …… M^000024^05^+LISTB M^000054^06^+LISTC M^000057^06^+ENDC M^000057^06^-LISTC 國立政治大學資訊科學系 國立政治大學資訊科學系 SP.Chap3.22 Optional Loader Features H^PROGA ^000000^.. D^LISTA ^000040…. R^02LISTB ^03ENDB ^04LISTC ^05ENDC …… M^000024^05^+02 M^000054^06^+04 M^000057^06^+05 M^000057^06^-04 SP.Chap3.23 Automatic library search What? How? Enter referred symbols into ESTAB Search libraries for undefined symbols at the end of pass 1 (and continue the search if necessary) Issue error messages if undefined symbols still exist 國立政治大學資訊科學系 SP.Chap3.24 4 國立政治大學資訊科學系 2014/4/30 Optional Loader Features Linkage Editor Loader options INCLUDE program-name(library-name) DELETE csect-name CHANGE name1, name2 LIBRARY MYLIB NOCALL STDDEV, PLOT, CORREL Linking loaders vs. linkage editors 國立政治大學資訊科學系 SP.Chap3.25 Frequency of reassembling matters. 國立政治大學資訊科學系 SP.Chap3.26 Dynamic Linking The linked program reserves the information for resolving external references. Edition of linked programs (page 154) Creation of packages (pp. 154-155) Timing for linking library functions (page 155) 國立政治大學資訊科學系 SP.Chap3.27 aka. dynamic loading and load on call Link the subroutines when they are called Advantages Processes share one copy of a subroutine or library. Processes always use the up-to-dated objects. Subroutines are loaded only when necessary. How? Figure 3.14 on page 157 Binding: the association of an actual addresses with symbolic names 國立政治大學資訊科學系 SP.Chap3.28 MS-DOS and Windows MS-DOS Most MS-DOS compilers and assemblers produce modules. MS-DOS LINK is a linkage editor. MS-DOS object module (Figure 3.15) Windows 國立政治大學資訊科學系 SP.Chap3.29 *.DLL files 國立政治大學資訊科學系 SP.Chap3.30 5 國立政治大學資訊科學系 2014/4/30 SunOS Linkers Link-editor and run-time linker Link-editor linker Relocation and linking operations are specified using a set of processor-specific codes. Symbolic references Library search: archives Shared objects: dynamic linking Run-time linker: dynamic linking 國立政治大學資訊科學系 SP.Chap3.31 6
© Copyright 2024 ExpyDoc
