Program Behaviour Program Behaviour semantics .c .c .c source - - PowerPoint PPT Presentation

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Program Behaviour Program Behaviour semantics .c .c .c source - - PowerPoint PPT Presentation

Aug 17, 2022 120 likes •1.06k views

Program Behaviour Program Behaviour semantics .c .c .c source program code inputs Program Behaviour semantics .c .c .c source program code inputs Next Talk: other things Program Behaviour semantics .c .c .c source program

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SLIDE 1
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SLIDE 2

Program Behaviour

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SLIDE 3

Program Behaviour

.c .c .c

source code semantics program inputs

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SLIDE 4

Program Behaviour

.c .c .c

source code semantics program inputs

Next Talk:

  • ther things
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SLIDE 5

Program Behaviour

.c .c .c

source code semantics program inputs

Next Talk:

  • ther things

This Talk: the linker

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SLIDE 6

.c .c .c .c

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SLIDE 7

.c .c .c .c .o .o

compile

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SLIDE 8

.c .c .c .c .o .o

exe

compile link

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SLIDE 9

.c .c .c .c .o .o

exe

.c

compile link concatenate

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SLIDE 10

.c .c .c .c .o .o

exe exe

.c

compile compile link concatenate

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SLIDE 11

.c .c .c .c .o .o

exe exe

.c

compile compile link concatenate

≠

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SLIDE 12

Correctness can depend on how the program was linked

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SLIDE 13

.c

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SLIDE 14

.c

compile

.o

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SLIDE 15

.c

compile

Sections

.o

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SLIDE 16

.c

compile

Sections

.text

.o

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SLIDE 17

.c

compile

Sections

.text .data

.o

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SLIDE 18

.c

compile

Sections

.text .data

.o

.debug

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SLIDE 19

.c

compile

Sections

.text .data

.o

.debug

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SLIDE 20

.c

compile

Sections

.text .data

.o

.debug

X R

W

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SLIDE 21

.data

.o

.debug .data

.o

.debug

.text .text

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SLIDE 22

link

.data

.o

.debug

.text

.data

.o

.debug

.data

.text .text

.o

.debug

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SLIDE 23

link

.data

.o

.debug

.text

.data

.o

.debug

.data

.text .text

.o

.debug

  • Join sections together
  • Resolve symbols
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SLIDE 24

Executable 0x0000

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SLIDE 25

Executable 0xb000

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SLIDE 26

Executable 0xb400

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SLIDE 27

Executable 0xc000

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SLIDE 28

Executable 0xca00

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SLIDE 29

Executable 0x0000 .text .text .data .data .debug .debug

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SLIDE 30

Executable 0x0000 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

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SLIDE 31

Executable 0x0000 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

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SLIDE 32

Executable .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

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SLIDE 33

Executable 0xb000 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

.text

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SLIDE 34

Executable 0xb000 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

.text

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SLIDE 35

Executable 0xb400 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

.text

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SLIDE 36

Executable 0xb400 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

.text

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SLIDE 37

Executable 0xd000 .text .text .data .data .debug .debug .text : { *(.text*) } . = . + 0x400 .data : { *(.data*) }

.text

.data

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SLIDE 38

Executable 0xd000

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 39

Executable 0xd000

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 40

Executable 0xd000

text_start

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 41

Executable 0xd000

text_start

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 42

Executable 0xd400

.text

0xd000

text_start

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 43

Executable 0xd400

.text

0xd000

text_start

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 44

Executable

.text

0xd000

text_start

0xd400

text_end

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 45

Executable

.text

0xd000

text_start

0xd400

text_end

.text : { text_start = . *(.text*) text_end = . } text_size = SIZEOF(.text)

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SLIDE 46

Executable

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

.text : { text_start = . *(.text*) text_end = . }

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SLIDE 47

Executable

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

extern char text_size[], text_start[], text_end[]; int main() { assert(&text_size == (char*)0x400); assert(&text_start == (char*)0xd000); }

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SLIDE 48

Executable

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 49

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 50

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 51

Symbol Table foo bar ... text_start text_size 12 ... ??? ???

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 52

linker_syms.h char text_start[]; &text_start = 0xd000; char text_size[]; &text_size = 0x400;

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 53

linker_syms.h char text_start[]; &text_start = 0xd000; char text_size[]; &text_size = 0x400;

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *)&text_start, (size_t)&text_size); }

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SLIDE 54

linker_syms.h size_t text_start; text_start = 0xd000; size_t text_size; text_size = 0x400;

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *) text_start, (size_t) text_size); }

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SLIDE 55

linker_syms.h size_t text_start; text_start = 0xd000; size_t text_size; text_size = 0x400;

extern char text_size[], text_start[], text_end[]; int main() { memcpy( buf, (void *) text_start, (size_t) text_size); }

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SLIDE 56

Symbol Table foo bar ... text_start text_size 12 ...

.ld

exe

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SLIDE 57

OOPSLA'16

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SLIDE 58

OOPSLA'16

.o

.ld

.o

exe

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SLIDE 59

OOPSLA'16

.o

.ld

.o

exe

.ld

exe

text_start text_size 0xd 0xc

Symbol Table

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SLIDE 60

Four Functions

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SLIDE 61

Four Functions addrS addrE : ident ⇀ ℕ symbS symbE : ident ⇀ ident

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SLIDE 62

Four Functions addrS addrE : ident ⇀ ℕ

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

symbS symbE : ident ⇀ ident

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SLIDE 63

Four Functions addrS addrE : ident ⇀ ℕ

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

symbS symbE : ident ⇀ ident

symbS = .text ↦ text_start symbE = .text ↦ text_end

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SLIDE 64

Four Functions addrS addrE : ident ⇀ ℕ

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

symbS symbE : ident ⇀ ident

addrS = .text ↦ 0xd000 text_size ↦ 0x400 text_end ↦ 0xd400 text_start ↦ 0xd000

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SLIDE 65

Four Functions addrS addrE : ident ⇀ ℕ

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

symbS symbE : ident ⇀ ident

addrE = .text ↦ 0xd400

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SLIDE 66

Grammar

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SLIDE 67

Grammar

MEMORY { } Memory Directives

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SLIDE 68

Grammar

MEMORY { } SECTIONS { } Memory Directives Section Directives

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SLIDE 69

Grammar

MEMORY { } SECTIONS { } Memory Directives Section Directives Global Assignments

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SLIDE 70

Grammar

MEMORY { } SECTIONS { }

.text : { text_start = .; *(.text*) text_end = .; }

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SLIDE 71

Grammar

MEMORY { } SECTIONS { }

text_size = SIZEOF(.text);

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SLIDE 72

Grammar

MEMORY { } SECTIONS { }

rom : ORIGIN = 0x2000, LENTGH = 0x400;

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SLIDE 73

Expressions

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SLIDE 74

Expressions

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SLIDE 75

Expressions

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SLIDE 76

Expressions

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SLIDE 77

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

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SLIDE 78

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀

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SLIDE 79

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀

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SLIDE 80

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀

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SLIDE 81

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀

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SLIDE 82

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀

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SLIDE 83

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀ ⇀ ⇀

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SLIDE 84

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀

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SLIDE 85

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀

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SLIDE 86

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀

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SLIDE 87

Interpretation addrS

MEMORY { } SECTIONS { }

symbS addrE symbE

⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀ ⇀

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SLIDE 88
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SLIDE 89
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SLIDE 90

.text

0x400 text_size 0xd000

text_start

0xd400

text_end

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SLIDE 91

CAV'18

Implemented in CBMC

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SLIDE 92
  • Static analysers need to understand

program behaviour

  • Linker scripts introduce information

unavailable to static analyser

  • Solution: parse linker scripts, integrate

into static analysis