Sean Barker

Procedure Call Registers

1

%rax %eax

%rbx %ebx

%rdx %edx

%rcx %ecx

%rsi %esi

%rdi %edi

%rbp %ebp

%rsp %esp

%r8 %r8d

%r9 %r9d

%r11 %r11d

%r10 %r10d

%r12 %r12d

%r13 %r13d

%r15 %r15d

%r14 %r14d

Return

Arg 4

Arg 3

Arg 2

Arg 1

Stack ptr

Arg 5

Arg 6

Sean Barker

Call Stack

2

StackPointer:%rsp

StackGrows Down

Increasing Addresses

Stack“Top”

Stack“Bo;om”

Sean Barker

Stack Operations

3

-8

StackGrows Down

Increasing Addresses

Stack“Bo8om”

StackPointer:%rsp

Stack“Top”

StackPointer:%rsp

StackGrows Down

Increasing Addresses

Stack“Top”

Stack“Bo;om”

+8

popq Dest pushq Src

Sean Barker

Procedure Call Example (1)

4

0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq

0000000000400540 <foo>: • • 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • •

0x400544

0x120

•••

%rsp

0x120

0x128

0x130

%rip

Sean Barker

Procedure Call Example (2)

5

0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq

0000000000400540 <foo>: • • 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • •

0x400550

0x118

0x400549

•••

%rsp

0x120

0x128

0x130

0x118

%rip

Sean Barker

Procedure Call Example (3)

6

0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq

0000000000400540 <foo>: • • 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • •

0x400557

0x118

0x400549

•••

%rsp

0x120

0x128

0x130

0x118

%rip

Sean Barker

Procedure Call Example (4)

7

0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq

0000000000400540 <foo>: • • 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • •

0x400549

0x120

•••

%rsp

0x120

0x128

0x130

%rip

Sean Barker

Passing Data

8

Registers¢  First6arguments

¢  Returnvalue

Stack

%rdi

%rsi

%rdx

%rcx

%r8

%r9

%rax

Arg7

• • •

Arg8

Argn

• • •

Sean Barker

Stack Frames

9

FramePointer:%rbp

StackPointer:%rsp

Stack“Top”

PreviousFrame

Frameforproc

(Op:onal) x

Sean Barker

Call Chain Example

10

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

yoo

who

amI

amI

amI

Example CallChain

amI

ProcedureamI()isrecursive

Sean Barker

Stack Frame Allocation (1)

11

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo yoo(…) { • • who(); • • }

Sean Barker

Stack Frame Allocation (2)

12

yoo(…) { • • who(); • • }

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

who(…) { • • • amI(); • • • amI(); • • • }

Sean Barker

Stack Frame Allocation (3)

13

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (4)

14

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

amI

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (5)

15

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

amI

amI

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

amI(…) { • • amI(); • • }

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (6)

16

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

amI

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (7)

17

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (8)

18

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

Sean Barker

Stack Frame Allocation (9)

19

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

amI

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

amI(…) { • • amI(); • • }

Sean Barker

Stack Frame Allocation (10)

20

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo

who

yoo(…) { • • who(); • • }

who(…) { • • • amI(); • • • amI(); • • • }

Sean Barker

Stack Frame Allocation (11)

21

yoo

who

amI

amI

amI

amI

yoo

%rbp

%rsp

Stack

yoo yoo(…) { • • who(); • • }

Sean Barker

Stack Frame Components

22

ReturnAddr

SavedRegisters

+Local

Variables

ArgumentBuild

(Op<onal)

Old%rbp

Arguments7+

Caller Frame

Framepointer%rbp

Stackpointer %rsp

(Op<onal)

Sean Barker

Stack Example: incr

23

long incr(long *p, long val) { long x = *p; long y = x + val; *p = y; return x; }

incr: movq (%rdi), %rax addq %rax, %rsi movq %rsi, (%rdi) ret

Register Use(s)

%rdi Argumentp

%rsi Argumentval,y

%rax x,Returnvalue

Sean Barker

Using the Stack (1)

24

call_incr: subq $16, %rsp movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax addq $16, %rsp ret

long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; }

%rsp

Ini$alStackStructure

...

Rtnaddress

15213 Unused %rsp

Resul$ngStackStructure

...

Rtnaddress

%rsp+8

Sean Barker

Using the Stack (2)

25

call_incr: subq $16, %rsp movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax addq $16, %rsp ret

long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; }

15213 Unused %rsp

StackStructure

...

Rtnaddress

%rsp+8

Register Use(s)

%rdi &v1

%rsi 3000

Sean Barker

Using the Stack (3)

26

call_incr: subq $16, %rsp movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax addq $16, %rsp ret

long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; }

18213

Unused %rsp

StackStructure

...

Rtnaddress

%rsp+8

Register Use(s)

%rdi &v1

%rsi 3000

incr: movq (%rdi), %rax addq %rax, %rsi movq %rsi, (%rdi) ret

Sean Barker

Using the Stack (4)

27

call_incr: subq $16, %rsp movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax addq $16, %rsp ret

long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; } 18213

Unused %rsp

StackStructure

...

Rtnaddress

%rsp+8

Register Use(s)

%rax Returnvalue

%rsp

UpdatedStackStructure

...

Rtnaddress

Sean Barker

Using the Stack (5)

28

call_incr: subq $16, %rsp movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax addq $16, %rsp ret

long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; }

Register Use(s)

%rax Returnvalue

%rsp

UpdatedStackStructure

...

Rtnaddress

%rsp

FinalStackStructure

...

Sean Barker

Stack Frame Components

29

ReturnAddr

SavedRegisters

+Local

Variables

ArgumentBuild

(Op<onal)

Old%rbp

Arguments7+

Caller Frame

Framepointer%rbp

Stackpointer %rsp

(Op<onal)

Sean Barker

Register Conventions

30

%rax

%rdx %rcx

Returnvalue(caller-saved)

%r8 %r9 %r10 %r11

%rdi %rsi

Arguments(caller-saved)

Caller-savedtemporaries

%rbx

%rsp

Callee-saved Temporaries

Special%rbp

%r12 %r13 %r14 %r15

Sean Barker

Callee-Saved Example (1)

31

call_incr2: pushq %rbx subq $16, %rsp movq %rdi, %rbx movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq %rbx, %rax addq $16, %rsp popq %rbx ret

long call_incr2(long x) { long v1 = 15213; long v2 = incr(&v1, 3000); return x+v2; } %rsp

Ini$alStackStructure

...

Rtnaddress

15213 Unused %rsp

Resul$ngStackStructure

...

Rtnaddress

%rsp+8 Saved%rbx

Sean Barker

Callee-Saved Example (2)

32

call_incr2: pushq %rbx subq $16, %rsp movq %rdi, %rbx movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi call incr addq %rbx, %rax addq $16, %rsp popq %rbx ret

long call_incr2(long x) { long v1 = 15213; long v2 = incr(&v1, 3000); return x+v2; }

%rsp

Pre-returnStackStructure

...

Rtnaddress

15213 Unused %rsp

Resul3ngStackStructure

...

Rtnaddress

%rsp+8 Saved%rbx

Sean Barker

Stack Frame Components

33

ReturnAddr

SavedRegisters

+Local

Variables

ArgumentBuild

(Op<onal)

Old%rbp

Arguments7+

Caller Frame

Framepointer%rbp

Stackpointer %rsp

(Op<onal)

Sean Barker

Recursion Example

34

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Sean Barker

Recursion Base Case

35

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rdi x Argument

%rax Returnvalue Returnvalue

Sean Barker

Recursion Register Save

36

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rdi x Argument

%rsp

...

Rtnaddress

Saved%rbx

Sean Barker

Recursion Call Setup

37

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rdi x >> 1 Rec.argument

%rbx x & 1 Callee-saved

Sean Barker

Recursive Call

38

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rbx x & 1 Callee-saved

%rax Recursivecallreturnvalue

Sean Barker

Recursion Result

39

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rbx x & 1 Callee-saved

%rax Returnvalue

Sean Barker

Recursion Result

40

/* Recursive popcount */ long pcount_r(unsigned long x) { if (x == 0) return 0; else return (x & 1) + pcount_r(x >> 1); }

pcount_r: movl $0, %eax testq %rdi, %rdi je .L6 pushq %rbx movq %rdi, %rbx andl $1, %ebx shrq %rdi call pcount_r addq %rbx, %rax popq %rbx .L6: rep; ret

Register Use(s) Type

%rax Returnvalue Returnvalue

%rsp ...