23 KiB
| title | TARGET DECK | FILE TAGS | tags | |
|---|---|---|---|---|
| Procedures | Obsidian::STEM | x86-64 |
|
Overview
The x86-64 stack grows towards lower addresses. When a procedure is invoked, more spack on the top of the stack is allocated for that procedure to make use of. This portion of the stack is called a frame. The general shape of the stack looks as follows:
!
Note parts of this diagram are omitted when possible. For instance, a stack frame may not exist at all if all arguments to a leaf procedure can be passed through registers. A leaf procedure is a function that does not call another function.
%%ANKII Basic What ADT is used internally in procedure-calling mechanisms? Back: A stack. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. END%%
%%ANKII Cloze The x86-64 stack grows towards {lower} addresses. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. END%%
%%ANKI Basic What is a frame w.r.t. the x86-64 stack? Back: A region of the stack dedicated to a particular function call. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What instructions are used to store and retrieve from the x86-64 stack?
Back: pushq and popq.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What does the "stack pointer" refer to w.r.t. the x86-64 stack?
Back: Register %rsp.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How is the stack pointer manipulated to allocate space on the x86-64 stack?
Back: By decrementing %rsp by an appropriate amount.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How is the stack pointer manipulated to deallocate space on the x86-64 stack?
Back: By incrementing %rsp by an appropriate amount.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Suppose procedure P calls Q. What data sits at the end of P's frame?
Back: A return address.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Cloze A {leaf} procedure is a function that {does not call another function}. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Suppose procedure P calls Q. The return address belongs to who's frame?
Back: P
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Suppose procedure P calls Q. Why is the return address considered to be in P's frame?
Back: It is state relevant to P.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Q is about to call another procedure. What is the highlighted portion of its stack frame for?
!
Back: Callee-saved registers.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Q is about to call another procedure. What is the highlighted portion of its stack frame for?
!
Back: Local variables.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Q is about to call another procedure. What is the highlighted portion of its stack frame for?
!
Back: Additional integral arguments.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What must still be added to the stack before Q passes control to another procedure?
!
Back: The return address.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
CALL and RET
Like conditions#JMP instructions, call allows specifying a direct or indirect operand. call pushes the address of the instruction following it onto the stack and updates the PC to the operand. ret reverts these steps.
| Instruction | Operands | Description |
|---|---|---|
call |
Label | Procedure call |
call |
*Operand | Procedure call |
ret |
Return from call |
%%ANKI
Cloze
The {call} instruction is the counterpart to the {ret} instruction.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What two things does the call instruction do?
Back: It pushes the return address on the stack and updates the PC.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What two things does the ret instruction do?
Back: It pops the return address off the stack and updates the PC.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
The operand forms of call mirror what other instruction class?
Back: JMP
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
A call instruction pushes what address onto the stack?
Back: That of the instruction following the call instruction.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What return address is pushed onto the stack after call is run?
1: ...
2: callq .L1
3: ...
Back: 3
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What address is the PC updated to after call is run?
1: ...
2: callq .L1
3: ...
Back: That corresponding to label .L1.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register(s) does a call instruction update?
Back: %rsp and %rip.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register(s) does a ret instruction update?
Back: %rsp and %rip.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Local Storage
On the Stack
x86-64 employs 6 registers for passing integral (i.e. integer and pointer) arguments between caller and callee.
| Bits | Arg 1 | Arg2 | Arg3 | Arg4 | Arg5 | Arg6 |
|---|---|---|---|---|---|---|
| 64 | %rdi |
%rsi |
%rdx |
%rcx |
%r8 |
%r9 |
| 32 | %edi |
%esi |
%edx |
%ecx |
%r8d |
%r9d |
| 16 | %di |
%si |
%dx |
%cx |
%r8w |
%r9w |
| 8 | %dil |
%sil |
%dl |
%cl |
%r8b |
%r9b |
If more than 6 integral arguments are specified to a procedure, the surplus are placed onto the stack in the caller's frame. The 7th argument is placed closer to the top of the stack (i.e. with lower address) than subsequent arguments.
%%ANKI
Basic
How many registers are available for passing integral arguments between procedures?
Back: 6
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
By convention, register {%rdi} is used for {the first integral argument}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should the first integral argument of a procedure be placed in?
Back: %rdi
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
By convention, register {%rsi} is used for {the second integral argument}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should the second integral argument of a procedure be placed in?
Back: %rsi
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
From smallest to largest, list the four "second integral argument" registers.
Back: %sil, %si, %esi, and %rsi.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:%rdi} is to the {2:first} integral argument whereas {2:%rsi} is to the {1:second} integral argument.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
By convention, register {%rdx} is used for {the third integral argument}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should the third integral argument of a procedure be placed in?
Back: %rdx
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
By convention, register {%rcx} is used for {the fourth integral argument}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should the fourth integral argument of a procedure be placed in?
Back: %rcx
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should Q use to access value 1?
void P() {
Q(1, 2, 3, 4, 5, 6);
}
Back: %rdi
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should Q use to access value 2?
void P() {
Q(1, 2, 3, 4, 5, 6);
}
Back: %rsi
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should Q use to access value 3?
void P() {
Q(1, 2, 3, 4, 5, 6);
}
Back: %rdx
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Which register should Q use to access value 4?
void P() {
Q(1, 2, 3, 4, 5, 6);
}
Back: %rcx
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Let S denote %rsp before pushing parameter int a onto the stack. What is %rsp now?
Back: S - 8
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Let S denote %rsp before pushing parameter short a onto the stack. What is %rsp now?
Back: S - 8
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Let S denote %rsp before pushing parameter bool a onto the stack. What is %rsp now?
Back: S - 8
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
After calling Q, how much space do local parameters occupy in P's stack frame?
void P() {
Q(1, 2, 3, 4, 5, 6);
}
Back: 0 bytes. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
After calling Q, how much space do local parameters occupy in P's stack frame?
void P() {
Q(1, 2, 3, 4, 5, 6, 7, 8);
}
Back: 16 bytes. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
After calling Q, how much space do local parameters occupy in P's stack frame?
void P() {
Q(1, 2, 3, 4, 5, 6, true, 8);
}
Back: 16 bytes. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Basic Which frame contains the 7th argument?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7);
...
}
Back: P's frame.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI Basic Which frame contains the return address?
void P() {
...
Q(1, 2, 3);
...
}
Back: P's frame.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI Basic Which of the 7th or 8th argument has lower address?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7, 8);
...
}
Back: The 7th argument. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI Basic Which of the 7th or 8th argument is nearer the stack's top?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7, 8);
...
}
Back: The 7th argument. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI Basic Which arguments are placed onto the stack?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7, 8);
...
}
Back: Arguments 7 and 8. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI Basic Which of the 6th or 7th argument is nearer the stack's top?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7);
...
}
Back: N/A. Argument 6 isn't placed onto the stack at all. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI Basic Which of the 7th argument or the return address is nearer the stack's top?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7);
...
}
Back: The return address. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
In some cases, integral values still need to be placed onto the stack. For example, operator & is applied to a local variable and hence we must be able to generate an address for it.
%%ANKI
Cloze
In the following, P is the {caller} and Q is the {callee}.
int P() { Q(); }
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI
Basic
Why doesn't P have to allocate any local variables on the stack?
void P() {
int a = 100;
Q(a);
}
Back: A register can be set to immediate $100 for Q to access.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI
Basic
Why doesn't P have to allocate any local variables on the stack?
void P() {
int a = 100;
Q(&a);
}
Back: N/A. It does since we need an address for a to supply to Q.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI
Basic
Is P's local stack variables or arguments to Q nearer the stack's top?
void P() {
...
Q(1, 2, 3, 4, 5, 6);
...
}
Back: N/A. P does not have any arguments passed to Q on the stack.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI
Basic
Is P's local stack variables or arguments to Q nearer the stack's top?
void P() {
...
Q(1, 2, 3, 4, 5, 6, 7);
...
}
Back: The arguments to Q.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: c17
END%%
%%ANKI
Basic
Which registers are designated for argument passing?
Back: %rdi, %rsi, %rdx, %rcx, and %r8-%r9.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
In Registers
x86-64 employs 6 registers as callee-saved registers. If procedure P calls procedure Q, Q must preserve the values of these registers. That is, if Q were to modify these registers, Q is also responsible for restoring these values before returning back to P.
| Bits | ||||||
|---|---|---|---|---|---|---|
| 64 | %rbx |
%rbp |
%r12 |
%r13 |
%r14 |
%r15 |
| 32 | %ebx |
%ebp |
%r12d |
%r13d |
%r14d |
%r15d |
| 16 | %bx |
%bp |
%r12w |
%r13w |
%r14w |
%r15w |
| 8 | %bl |
%bpl |
%r12b |
%r13b |
%r14b |
%15b |
%%ANKI
Basic
Which registers are designated as callee-saved?
Back: %rbx, %rbp, and %r12-%r15.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Basic How many registers are designated as callee-saved? Back: 6. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI Basic What is a callee-saved register? Back: A register whose value must be preserved by a callee on return. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
By convention, register %rbp is used for {callee-saved values}.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Suppose P calls Q. Callee-saved registers are in which stack frame?
Back: Q's.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
Suppose P calls Q with 8 integral arguments. Which of P's callee-saved values or arguments to Q are nearer the stack's top?
Back: P's arguments to Q.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Bibliography
- Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.