Increasing Addresses Grows Stack Down Stack Pointer: %rsp Stack - PDF document

Procedure Call Registers %rax %r8 %eax %r8d Return Arg 5 %rbx %r9 %ebx %r9d Arg 6 %rcx %r10 %ecx %r10d Arg 4 %rdx %r11 %edx %r11d Arg 3 %rsi %r12 %esi %r12d Arg 2 %rdi %r13 %edi %r13d Arg 1 %rsp %r14 %esp %r14d Stack ptr %rbp %r15 %ebp %r15d Sean Barker 1 Call Stack Stack “Bo;om” Increasing Addresses Grows Stack Down Stack Pointer: %rsp Stack “Top” Sean Barker 2

Stack Operations Stack “Bo8om” Stack “Bo;om” Increasing Increasing Addresses Addresses Grows Stack Grows Stack Down Stack Pointer: %rsp Down +8 Stack Pointer: %rsp -8 Stack “Top” Stack “Top” pushq Src popq Dest Sean Barker 3 Procedure Call Example (1) • Stack Grows • 0x130 0000000000400540 <foo>: Down • 0x128 • • 0x120 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • %rsp 0x120 • %rip 0x400544 0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq Sean Barker 4

Procedure Call Example (2) • Stack Grows • 0x130 0000000000400540 <foo>: Down • 0x128 • • 0x120 400544: callq 400550 <bar> 0x118 0x400549 400549: mov %rax,(%rbx) • %rsp 0x118 • %rip 0x400550 0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq Sean Barker 5 Procedure Call Example (3) • Stack Grows • 0x130 0000000000400540 <foo>: Down • 0x128 • • 0x120 400544: callq 400550 <bar> 0x118 0x400549 400549: mov %rax,(%rbx) • %rsp 0x118 • %rip 0x400557 0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq Sean Barker 6

Procedure Call Example (4) • Stack Grows • 0x130 0000000000400540 <foo>: Down • 0x128 • • 0x120 400544: callq 400550 <bar> 400549: mov %rax,(%rbx) • %rsp 0x120 • %rip 0x400549 0000000000400550 <bar>: 400550: mov %rdi,%rax • • 400557: retq Sean Barker 7 Passing Data Registers Stack ¢ First 6 arguments • • • %rdi Arg n %rsi Stack Grows %rdx Down • • • %rcx Arg 8 %r8 Arg 7 %r9 Stack “Top” ¢ Return value %rax Sean Barker 8

Stack Frames Previous Frame Frame Pointer: %rbp (Op:onal) x Frame for proc Stack Pointer: %rsp Stack “Top” Sean Barker 9 Call Chain Example Example Call Chain yoo(…) { yoo • • who(…) who(); who { • • • • • amI(); amI(…) amI amI } • • • { amI(); • amI • • • • } amI(); • amI • } Procedure amI() is recursive Sean Barker 10

Stack Frame Allocation (1) Stack yoo yoo(…) %rbp { yoo yoo • who %rsp • who(); amI amI • • } amI amI Sean Barker 11 Stack Frame Allocation (2) Stack yoo(…) yoo who(…) { yoo yoo { • who • • • • %rbp amI(); who(); who • • • • amI amI %rsp amI(); • • • • } amI } amI Sean Barker 12

Stack Frame Allocation (3) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); • who • • • • amI amI • amI(); • amI(); %rbp • • • } • amI amI } • %rsp } amI Recurse! Sean Barker 13 Stack Frame Allocation (4) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); amI(…) • who • • • • amI amI { • amI(); • • amI(); • • • } • • amI amI } amI(); • • } %rbp • amI amI } %rsp Recurse! Sean Barker 14

Stack Frame Allocation (5) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); amI(…) • who • • • • amI amI { • amI(); amI(…) • • amI(); • • • { } • • amI amI } • amI(); • • • } amI(); • amI amI • } • %rbp } amI Base %rsp Case Sean Barker 15 Stack Frame Allocation (6) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); amI(…) • who • • • • amI amI { • amI(); • • amI(); • • • } • • amI amI } amI(); • • } %rbp • amI amI } %rsp Sean Barker 16

Stack Frame Allocation (7) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); • who • • • • amI amI • amI(); • amI(); %rbp • • • } • amI amI } • %rsp } amI Sean Barker 17 Stack Frame Allocation (8) Stack yoo(…) yoo who(…) { yoo yoo { • who • • • • %rbp amI(); who(); who • • • • amI amI %rsp amI(); • • • • } amI } amI Sean Barker 18

Stack Frame Allocation (9) Stack yoo(…) yoo who(…) { yoo yoo { • amI(…) who • • • • { amI(); who(); • who • • • • amI amI • amI(); • amI(); %rbp • • • } • amI amI } • %rsp } amI Base Case Sean Barker 19 Stack Frame Allocation (10) Stack yoo(…) yoo who(…) { yoo yoo { • who • • • • %rbp amI(); who(); who • • • • amI amI %rsp amI(); • • • • } amI } amI Sean Barker 20

Stack Frame Allocation (11) Stack yoo %rbp yoo(…) yoo { yoo who %rsp • • who(); amI amI • • amI } amI Sean Barker 21 Stack Frame Components Caller Frame Arguments 7+ Return Addr Frame pointer %rbp Old %rbp (Op<onal) Saved Registers + Local Variables Argument Stack pointer Build (Op<onal) %rsp Sean Barker 22

Stack Example: incr long incr(long *p, long val) { long x = *p; long y = x + val; *p = y; return x; } incr: Register Use(s) movq (%rdi), %rax Argument p %rdi addq %rax, %rsi Argument val , y movq %rsi, (%rdi) %rsi ret x , Return value %rax Sean Barker 23 Using the Stack (1) Ini$al Stack Structure long call_incr() { long v1 = 15213; . . . long v2 = incr(&v1, 3000); return v1+v2; } Rtn address %rsp call_incr: subq $16, %rsp Resul$ng Stack Structure movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi . . . call incr addq 8(%rsp), %rax Rtn address addq $16, %rsp %rsp+8 15213 ret Unused %rsp Sean Barker 24

Using the Stack (2) Stack Structure long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); . . . return v1+v2; } Rtn address %rsp+8 15213 Unused %rsp call_incr: subq $16, %rsp Register Use(s) movq $15213, 8(%rsp) movl $3000, %esi %rdi &v1 leaq 8(%rsp), %rdi %rsi 3000 call incr addq 8(%rsp), %rax addq $16, %rsp ret Sean Barker 25 Using the Stack (3) Stack Structure long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); . . . return v1+v2; } Rtn address %rsp+8 18213 Unused %rsp call_incr: subq $16, %rsp Register Use(s) movq $15213, 8(%rsp) movl $3000, %esi %rdi &v1 leaq 8(%rsp), %rdi %rsi 3000 call incr addq 8(%rsp), %rax addq $16, %rsp incr: ret movq (%rdi), %rax addq %rax, %rsi movq %rsi, (%rdi) ret Sean Barker 26

Using the Stack (4) Stack Structure long call_incr() { . . . long v1 = 15213; long v2 = incr(&v1, 3000); return v1+v2; Rtn address } %rsp+8 18213 Unused %rsp call_incr: Register Use(s) subq $16, %rsp Return value %rax movq $15213, 8(%rsp) movl $3000, %esi Updated Stack Structure leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax . . . addq $16, %rsp ret Rtn address %rsp Sean Barker 27 Using the Stack (5) Updated Stack Structure long call_incr() { long v1 = 15213; long v2 = incr(&v1, 3000); . . . return v1+v2; } Rtn address %rsp call_incr: Register Use(s) subq $16, %rsp Return value %rax movq $15213, 8(%rsp) movl $3000, %esi Final Stack Structure leaq 8(%rsp), %rdi call incr addq 8(%rsp), %rax . . . addq $16, %rsp %rsp ret Sean Barker 28

Stack Frame Components Caller Frame Arguments 7+ Return Addr Frame pointer %rbp Old %rbp (Op<onal) Saved Registers + Local Variables Argument Stack pointer Build (Op<onal) %rsp Sean Barker 29 Register Conventions Return value %rax (caller-saved) %rbx %rdi %r12 %rsi Callee-saved %r13 %rdx Arguments Temporaries (caller-saved) %r14 %rcx %r15 %r8 %rbp %r9 Special %rsp %r10 Caller-saved temporaries %r11 Sean Barker 30

Callee-Saved Example (1) Ini$al Stack Structure long call_incr2(long x) { long v1 = 15213; . . . long v2 = incr(&v1, 3000); return x+v2; } Rtn address %rsp call_incr2: pushq %rbx Resul$ng Stack Structure subq $16, %rsp movq %rdi, %rbx movq $15213, 8(%rsp) . . . movl $3000, %esi leaq 8(%rsp), %rdi Rtn address call incr addq %rbx, %rax Saved %rbx addq $16, %rsp %rsp+8 15213 popq %rbx Unused %rsp ret Sean Barker 31 Callee-Saved Example (2) Resul3ng Stack Structure long call_incr2(long x) { . . . long v1 = 15213; long v2 = incr(&v1, 3000); return x+v2; Rtn address } Saved %rbx %rsp+8 15213 call_incr2: Unused %rsp pushq %rbx subq $16, %rsp movq %rdi, %rbx Pre-return Stack Structure movq $15213, 8(%rsp) movl $3000, %esi leaq 8(%rsp), %rdi . . . call incr addq %rbx, %rax addq $16, %rsp Rtn address %rsp popq %rbx ret Sean Barker 32