Computer Systems Organization

Transcription

1 Computer Systems Organization 1

2 Outline 2

3 A software view User Interface 3

4 How it works 4

5 The gcc compilation system 5

6 The gcc compilation system hello.c (source code) Pre-processor (cpp) hello.i (modified source) Compiler (cc) Assembler (as) hello.s (assembly code) hello.o (object file) Linker (ld) hello (executable) 6

7 The Preprocessor: cpp First step: gcc compiler driver invokes cpp Output is expanded C source cpp does text substitution! Converts the C source file to another C source file! Expands #define #include #if! Output is another C source file 7

8 The Preprocessor: cpp 8

9 Macros Whitespace required Whitespace forbidden 9

10 Macros - Why the parens? Whitespace required Whitespace forbidden 10

11 Macros Just Textual Substitution Perfectly Okay No syntax error, after all! 11

12 Conditional Compilation 12

13 Compiler Assembler 13

14 Linker Libraries libc.a hello.o there.o Linker (ld) hello The executable file 14

15 The gcc compilation system hello.c (source code) Pre-processor (cpp) hello.i (modified source) Compiler (cc) Assembler (as) hello.s (assembly code) hello.o (object file) Linker (ld) hello (executable) 15

16 GCC variations default is a.out 16

17 GCC variations default is hello.i default is hello.s default is hello.o default is a.out 17

18 GCC variations default is hello.i default is hello.s default is hello.o default is a.out 18

19 GCC variations 19

20 The Virtual Address Space FFFFFFFF

21 The Virtual Address Space FFFFFFFF Program Code

22 The Virtual Address Space FFFFFFFF Constants Program Code

23 The Virtual Address Space FFFFFFFF Data Constants Program Code

24 The Virtual Address Space FFFFFFFF Stack Data Constants Program Code

25 The Virtual Address Space FFFFFFFF Stack Heap Data Constants Program Code

26 The Virtual Address Space FFFFFFFF Stack Memory Maped Pages Heap Data Constants Program Code

27 The Virtual Address Space FFFFFFFF Stack Memory Maped Pages Heap.data segment.text segment Read-Write Data Constants Read-Only Program Code

28 The Executable File FFFFFFFF Additional Info.data segment Read-Write.text segment Read-Only Header 28

29 Why Link? 29

30 The linking process (ld) 30

31 The Linking Process Header.text Header.data Additional Info main.o.text Header.text.data Additional Info foo.o.data Additional Info Executable File 31

32 Resolving External References Header.text Header.data Additional Info main.o.text Header.text.data Additional Info foo.o.data Additional Info Executable File 32

33 Example Virtual Address Space 0xffffffff 0xc Memory used by the kernel for this process invisible to user code stack %rsp (stack pointer) 0x memory mapped region for shared library functions shared by other processes 0x x run-time heap (managed by malloc) read/write segment (.data,.bss) read-only segment (.init,.text,.rodata) unused brk loaded from the executable file 33

34 Libraries and Linking 34

35 Three Kinds of Object Files (Modules) Relocatable object file (.o file) Contains code and data in a form that can be combined with other relocatable object files to form executable object file. Each.o file is produced from exactly one source (.c) file Executable object file (a.out file) Contains code and data in a form that can be copied directly into memory and then executed. Shared object file (.so file) Special type of relocatable object file that can be loaded into memory and linked dynamically, at either load time or runtime. Called Dynamic Link Libraries (DLLs) by Windows 35

36 The Complete Picture main.c foo.c Translators (cc1, as) main.o Translators (cc1, as) foo.o libwhatever.a Partially linked executable (on disk) Linker (ld) myprog libc.so Shared library of dynamically relocatable object files libm.so Loader / Dynamic Linker (ld-linux.so) Fully linked executable myprog (in memory) libc.so functions called by main.c and foo.c are loaded, linked, and (potentially) shared among processes. 36

37 The Operating System 37

38 Operating system functions 38

39 Operating system functions 39

40 Unix file system 40

41 Unix file systems 41

42 Process abstraction 42

43 How does a program get executed? 43

44 Loading Executable Binaries Executable object file for example program p ELF header Program header table (required for executables).text section 0 Process image init and shared lib segments Virtual addr 0x080483e0.data section.bss section.symtab.rel.text.rel.data.debug Section header table (required for relocatables).text segment (r/o).data segment (initialized r/w).bss segment (uninitialized r/w) 0x x0804a010 0x0804a3b0 44

45 Where are programs loaded in memory? 45

46 Where are programs loaded, cont d 46

47 Where are programs loaded, cont d 47

48 Modern linking and loading 48

49 The memory hierarchy 49

50 Memory heirarchy motivation 50

51 The memory heirarchy Smaller Faster More Expensive L1 L0 Registers Level 1 Cache On Chip Larger Slower Cheaper L3 L2 Level 2 Cache ( chip (off Main Memory L4 Local Secondary Storage L5 Remote Secondary Storage 51

52 Hardware organization CPU PC... Register File Bus Interface ALU System Bus I/O Bridge Memory Bus Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 52

53 Summary using hello.c 1. Shell process running, waiting for input CPU PC... Register File Bus Interface ALU System Bus I/O Bridge Memory Bus Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 53

54 Summary using hello.c 3. Command read into registers 4. Before sent to main memory before being read by shell process CPU Register File Memory Bus PC... Bus Interface ALU System Bus I/O Bridge Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 2. User types./hello 54

55 Summary using hello.c 5. Shell process creates new process through OS and initiates DMA of hello executable from disk to main memory CPU Register File Memory Bus PC... Bus Interface ALU System Bus I/O Bridge Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 55

56 Summary using hello.c 6. CPU executes hello code from main memory CPU PC... Register File Bus Interface ALU System Bus I/O Bridge Memory Bus Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 56

57 Summary using hello.c 7. CPU copies string hello, world\n from main memory to display CPU PC... Register File Bus Interface ALU System Bus I/O Bridge Memory Bus Main Memory I/O Bus USB Controller Graphics Controller... Disk Controller 57