24 KiB
| title | TARGET DECK | FILE TAGS | tags | |
|---|---|---|---|---|
| Instructions | Obsidian::STEM | x86-64 |
|
Overview
x86-64 instructions are designed so that commonly used instructions and those with fewer operands are encoded in a smaller number of bytes. Instructions range in length from 1 to 15 bytes.
x86-64 assembly comes in two flavors: ATT and Intel. ATT is most common in Linux systems so I focus on that. The most important distinction between the two is operand ordering: Intel syntax lists multiple operands in reverse order compared to ATT.
%%ANKI Basic x86-64 assembly comes in what two formats? Back: ATT and Intel. 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 x86-64 assembly format does Linux use? Back: ATT. 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 x86-64 assembly format does Microsoft use? Back: Intel. 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 the "most confusing" difference between ATT and Intel assembly? Back: Multiple operands in one are listed in reverse order relative to the other. 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 term describes assembly lines with a leading .?
Back: Directives.
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 Assembly directives are important for what two programs? Back: The assembler and the linker. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Instruction Classes
An x86-64 CPU contains a set of 16 general-purpose registers storing 64-bit values. They are used to store integers and pointers.
| 1 Byte | 2 Bytes | 4 Bytes | 8 Bytes | Purpose |
|---|---|---|---|---|
%al |
%ax |
%eax |
%rax |
Return value |
%bl |
%bx |
%ebx |
%rbx |
Callee saved |
%cl |
%cx |
%ecx |
%rcx |
4th argument |
%dl |
%dx |
%edx |
%rdx |
3rd argument |
%sil |
%si |
%esi |
%rsi |
2nd argument |
%dil |
%di |
%edi |
%rdi |
1st argument |
%bpl |
%bp |
%ebp |
%rbp |
Callee saved |
%spl |
%sp |
%esp |
%rsp |
Stack pointer |
%r8b |
%r8w |
%r8d |
%r8 |
5th argument |
%r9b |
%r9w |
%r9d |
%r9 |
6th argument |
%r10b |
%r10w |
%r10d |
%r10 |
Caller saved |
%r11b |
%r11w |
%r11d |
%r11 |
Caller saved |
%r12b |
%r12w |
%r12d |
%r12 |
Callee saved |
%r13b |
%r13w |
%r13d |
%r13 |
Callee saved |
%r14b |
%r14w |
%r14d |
%r14 |
Callee saved |
%r15b |
%r15w |
%r15d |
%r15 |
Callee saved |
%%ANKI Basic How many general-purpose registers are available to x86-64 instructions? Back: 16 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
The x86 64-bit registers all start with prefix {%r}.
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
The x86 32-bit registers all start with prefix {%e}.
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 Instructions that generate 1-byte quantities do what to the remaining bytes of a register? Back: Leaves them alone. 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 Instructions that generate 2-byte quantities do what to the remaining bytes of a register? Back: Leaves them alone. 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 Instructions that generate 4-byte quantities do what to the remaining bytes of a register? Back: Zeroes them out. 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 Instructions that generate 8-byte quantities do what to the remaining bytes of a register? Back: N/A Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
There are three types of operands:
- Immediates. These denote constant values. In ATT assembly, they are written with a
$followed by an integer using standard C notation. - Registers. These denote the contents of a register.
- Memory. These denote some memory location according to a computed address (i.e. the effective address).
| Type | Form | Operand Value | Name |
|---|---|---|---|
| Immediate | \textdollar Imm |
Imm |
Immediate |
| Register | r_a |
R[r_a] |
Register |
| Memory | Imm |
M[Imm] |
Absolute |
| Memory | (r_a) |
M[R[r_a]] |
Indirect |
| Memory | Imm(r_b) |
M[Imm + R[r_b]] |
Base + displacement |
| Memory | (r_b, r_i) |
M[R[r_b] + R[r_i]] |
Indexed |
| Memory | Imm(r_b, r_i) |
M[Imm + R[r_b] + R[r_i]] |
Indexed |
| Memory | (,r_i,s) |
M[R[r_i] \cdot s] |
Scaled indexed |
| Memory | Imm(,r_i,s) |
M[Imm + R[r_i] \cdot s] |
Scaled indexed |
| Memory | (r_b,r_i,s) |
M[R[r_b] + R[r_i] \cdot s] |
Scaled indexed |
| Memory | Imm(r_b,r_i,s) |
M[Imm + R[r_b] + R[r_i] \cdot s] |
Scaled indexed |
%%ANKI Basic What are the three types of operands instructions can act on? Back: Immediates, registers, and memory 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 are the types of source operands instructions can specify? Back: Immediates, registers, and memory 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 are the types of destination operands instructions can specify? Back: Registers and memory 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 does an immediate operand denote? Back: A constant value. 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
In ATT syntax, how is an immediate written?
Back: As a $$ followed by an integer using standard C notation.
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
In ATT syntax, how is a register written?
Back: As a % followed by the name of the register.
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 the operand value of form \textdollar Imm?
Back: Imm
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 the operand value of form r_a?
Back: R[r_a]
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 the operand value of form Imm?
Back: M[Imm]
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 the operand value of form (r_a)?
Back: M[R[r_a]]
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 the operand value of form Imm(r_b)?
Back: M[Imm + R[r_b]]
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 the operand value of form (r_b, r_i)?
Back: M[R[r_b] + R[r_i]]
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 the operand value of form Imm(r_b, r_i)?
Back: M[Imm + R[r_b] + R[r_i]]
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 the operand value of form (,r_i,s)?
Back: M[R[r_i] \cdot 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
What is the operand value of form Imm(,r_i,s)?
Back: M[Imm + R[r_i] \cdot 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
What is the operand value of form (r_b,r_i,s)?
Back: M[R[r_b] + R[r_i] \cdot 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
What is the operand value of form Imm(r_b,r_i,s)?
Back: M[Imm + R[r_b] + R[r_i] \cdot 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
What distinguishes operand value r_a from (r_a)?
Back: The former denotes the register value. The latter denotes the value in memory at the address stored in r_a.
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 values can s take on in operand form Imm(r_b,r_i,s)?
Back: 1, 2, 4, or 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
What operand form is named "immediate"?
Back: \textdollar Imm
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 operand form is named "register"?
Back: r_a
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 operand form is named "absolute"?
Back: Imm
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 operand form is named "indirect"?
Back: (r_a)
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 operand form is named "base + displacement"?
Back: Imm(r_b)
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 the most general operand form named "indexed" (not "scaled indexed")?
Back: Imm(r_b, r_i)
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 the most general operand form named "scaled indexed" (not indexed)?
Back: Imm(r_b, r_i, s)
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
MOV
%%ANKI
Basic
What four variants does MOV instructions take on in x86-64?
Back: movb, movw, movl, movq
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 bytes does a movb instruction operate on?
Back: One.
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 bytes does a movw instruction operate on?
Back: Two.
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 bytes does a movl instruction operate on?
Back: Four.
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 bytes does a movq instruction operate on?
Back: Eight.
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 combination of source and destination types is prohibited in MOV instructions?
Back: A source and destination memory 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
Basic
What is the result of %rax after instruction movl $0x4050,%eax?
Back: Upper 32-bits is 0 and lower 32-bits is 0x4050.
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 the result of %rax after instruction movq $0x4050,%rax?
Back: The 64-bit value is 0x4050.
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 the result of %rax after instruction movw $0x4050,%ax?
Back: The upper 48 bits are unchanged and the lower 16 bits are 0x4050.
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 the result of %rax after instruction movb $0x4050,%al?
Back: The upper 56 bits are unchanged and the lower 8 bits are 0x50.
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 the result of %rax after instruction movw $0x4050,%al?
Back: N/A. Invalid operand for 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 caveat is applied to the source operand of movq?
Back: Immediates are 32-bit two's-complement numbers sign extended to 64-bits.
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 mov instruction is needed when working with 64-bit immediate sources?
Back: movabsq
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 purpose does movabsq solve that movq does not?
Back: movabsq can have an arbitrary 64-bit immediate source.
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $-1, %al
Back: 0x00112233445566FF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movw $-1, %ax
Back: 0x001122334455FFFF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movl $-1, %eax
Back: 0x00000000FFFFFFFF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movq $-1, %rax
Back: 0xFFFFFFFFFFFFFFFF
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 the MOVZ instruction class?
Back: MOV instructions that zero extend the source to fit into the destination.
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 the MOVS instruction class?
Back: MOV instructions that sign extend the source to fit into the destination.
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 movzbw instruction do?
Back: Moves a zero-extended byte to a word.
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 movslq instruction do?
Back: Moves a sign-extended double word to a quad word.
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 movslb instruction do?
Back: N/A. This instruction does not exist.
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 combinatorial argument explains the number of MOVS instructions?
Back: There exists an instruction for each smaller declaration to larger declaration.
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 MOVZ instruction is "missing"?
Back: movzlq
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
Why does there not exist a movzlq instruction?
Back: Because movl already zeros out the upper bits of a destination register.
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movb %dl,%al
Back: 0x00112233445566AA
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movsbq %dl,%rax
Back: 0xFFFFFFFFFFFFFFAA
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movzbq %dl,%rax
Back: 0x00000000000000AA
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.