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Understanding Memory Layout for Process Stack Data Code

Explore the structure of memory for processes, focusing on stack, data, and code segments. Learn from CS 140 Lecture Notes about linkers, assembly, and creating executable files.

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Understanding Memory Layout for Process Stack Data Code

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  1. Memory Layout for Process ∞ Stack Data Code 0 CS 140 Lecture Notes: Linkers

  2. ∞ Stack Data Code 0 x.c y.c cc cc y.s x.s as as y.o x.o 101010101010101010101010101010101010101010101010 z.c cc z.s as z.o 101010101010101010101010101010101010101010101010 101010101010101010101010101010101010101010101010 101010101010101010101010101010101010101010101010 Creating a Process SourceCode Assembly Code Object Code Executable OS ld a.out Compiler Assembler Linker Loader CS 140 Lecture Notes: Linkers

  3. A Simple Example main.c stdio.c extern float sin(); extern printf(), scanf(); main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result); } intprintf(char *fmt, ...) { ... } intscanf(char *fmt, ...) { ... } math.c double sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x)… } return res; } CS 140 Lecture Notes: Linkers

  4. Object File main.c main.o extern float sin(); extern printf(), scanf(); main() { double x, result; printf("Type number: "); scanf("%f", &x); result = sin(x); printf("Sine is %f\n", result); } ... call printf ... call scanf ... call sin ... call printf def: main@T:0 ref: printf@T:20 ref: printf@T:56 ref: scanf@T:32 ref: sin@T:40 text section 20 32 40 56 symbols relocation “Store the final location of printfat offset 20 in the text section” CS 140 Lecture Notes: Linkers

  5. Object File math.c math.o double sin(double x) { static double res, lastx; if (x != lastx) { lastx = x; … compute sin(x) … } return res; } ... load lastx ... store lastx ... load res res: lastx: def: sin@T:0 def: lastx@D:8 def: res@D:0 ref: lastx@T:8 ref: lastx@T:20 ref: res@T:204 text section 8 20 204 0 8 data section symbols relocation CS 140 Lecture Notes: Linkers

  6. After Pass 1 Memory map: Symbol table: main: 0 sin: 64 lastx: 700 result: 708 printf: 314 scanf: 508 836 stdio.o data 708 math.o data 700 stdio.o text 276 math.o text 64 main.o text 0 CS 140 Lecture Notes: Linkers

  7. Relocation ... call 0 ... 40 text section in main.o ref: sin@T:40 relocation record in main.o sin: 64 symbol table ... call 64 ... 40 text section in a.out CS 140 Lecture Notes: Linkers

  8. CS 140 Lecture Notes: Linkers

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