371 lines
14 KiB
Markdown
371 lines
14 KiB
Markdown
---
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title: Instructions
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TARGET DECK: Obsidian::STEM
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FILE TAGS: x86-64
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tags:
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- x86-64
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---
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## Overview
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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.
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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.
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%%ANKI
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Basic
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x86-64 assembly comes in what two formats?
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Back: ATT and Intel.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313804-->
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END%%
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%%ANKI
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Basic
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Which x86-64 assembly format does Linux use?
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Back: ATT.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313810-->
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END%%
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%%ANKI
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Basic
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Which x86-64 assembly format does Microsoft use?
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Back: Intel.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313814-->
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END%%
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%%ANKI
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Basic
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What is the "most confusing" difference between ATT and Intel assembly?
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Back: Multiple operands in one are listed in reverse order relative to the other.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313818-->
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END%%
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%%ANKI
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Basic
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What term describes assembly lines with a leading `.`?
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Back: Directives.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313822-->
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END%%
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%%ANKI
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Basic
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Assembly directives are important for what two programs?
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Back: The assembler and the linker.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1710959313826-->
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END%%
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## Instruction Classes
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An x86-64 CPU contains a set of 16 general-purpose registers storing 64-bit values. They are used to store integers and pointers.
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1 Byte | 2 Bytes | 4 Bytes | 8 Bytes | Purpose
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------- | ------- | ------- | ------- | -------
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`%al` | `%ax` | `%eax` | `%rax` | Return value
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`%bl` | `%bx` | `%ebx` | `%rbx` | Callee saved
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`%cl` | `%cx` | `%ecx` | `%rcx` | 4th argument
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`%dl` | `%dx` | `%edx` | `%rdx` | 3rd argument
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`%sil` | `%si` | `%esi` | `%rsi` | 2nd argument
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`%dil` | `%di` | `%edi` | `%rdi` | 1st argument
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`%bpl` | `%bp` | `%ebp` | `%rbp` | Callee saved
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`%spl` | `%sp` | `%esp` | `%rsp` | Stack pointer
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`%r8b` | `%r8w` | `%r8d` | `%r8` | 5th argument
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`%r9b` | `%r9w` | `%r9d` | `%r9` | 6th argument
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`%r10b` | `%r10w` | `%r10d` | `%r10` | Caller saved
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`%r11b` | `%r11w` | `%r11d` | `%r11` | Caller saved
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`%r12b` | `%r12w` | `%r12d` | `%r12` | Callee saved
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`%r13b` | `%r13w` | `%r13d` | `%r13` | Callee saved
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`%r14b` | `%r14w` | `%r14d` | `%r14` | Callee saved
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`%r15b` | `%r15w` | `%r15d` | `%r15` | Callee saved
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%%ANKI
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Basic
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How many general-purpose registers are available to x86-64 instructions?
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Back: 16
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889856-->
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END%%
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%%ANKI
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Cloze
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The x86 64-bit registers all start with prefix {`%r`}.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889861-->
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END%%
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%%ANKI
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Cloze
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The x86 32-bit registers all start with prefix {`%e`}.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889864-->
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END%%
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%%ANKI
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Basic
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Instructions that generate 1-byte quantities do what to the remaining bytes of a register?
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Back: Leaves them alone.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889866-->
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END%%
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%%ANKI
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Basic
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Instructions that generate 2-byte quantities do what to the remaining bytes of a register?
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Back: Leaves them alone.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889869-->
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END%%
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%%ANKI
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Basic
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Instructions that generate 4-byte quantities do what to the remaining bytes of a register?
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Back: Zeroes them out.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889872-->
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END%%
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%%ANKI
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Basic
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Instructions that generate 8-byte quantities do what to the remaining bytes of a register?
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Back: N/A
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889874-->
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END%%
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There are three types of operands:
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* **Immediates**. These denote constant values. In ATT assembly, they are written with a `$` followed by an integer using standard C notation.
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* **Registers**. These denote the contents of a register.
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* **Memory**. These denote some memory location according to a computed address (i.e. the **effective address**).
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| Type | Form | Operand Value | Name |
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| --------- | ----------------- | ---------------------------------- | ------------------- |
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| Immediate | $\textdollar Imm$ | $Imm$ | Immediate |
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| Register | $r_a$ | $R[r_a]$ | Register |
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| Memory | $Imm$ | $M[Imm]$ | Absolute |
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| Memory | $(r_a)$ | $M[R[r_a]]$ | Indirect |
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| Memory | $Imm(r_b)$ | $M[Imm + R[r_b]]$ | Base + displacement |
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| Memory | $(r_b, r_i)$ | $M[R[r_b] + R[r_i]]$ | Indexed |
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| Memory | $Imm(r_b, r_i)$ | $M[Imm + R[r_b] + R[r_i]]$ | Indexed |
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| Memory | $(,r_i,s)$ | $M[R[r_i] \cdot s]$ | Scaled indexed |
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| Memory | $Imm(,r_i,s)$ | $M[Imm + R[r_i] \cdot s]$ | Scaled indexed |
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| Memory | $(r_b,r_i,s)$ | $M[R[r_b] + R[r_i] \cdot s]$ | Scaled indexed |
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| Memory | $Imm(r_b,r_i,s)$ | $M[Imm + R[r_b] + R[r_i] \cdot s]$ | Scaled indexed |
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%%ANKI
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Basic
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What are the three types of operands instructions can act on?
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Back: Immediates, registers, and memory addresses.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889877-->
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END%%
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%%ANKI
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Basic
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What are the types of source operands instructions can specify?
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Back: Immediates, registers, and memory addresses.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889887-->
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END%%
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%%ANKI
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Basic
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What are the types of destination operands instructions can specify?
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Back: Registers and memory addresses.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889894-->
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END%%
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%%ANKI
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Basic
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What does an immediate operand denote?
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Back: A constant value.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889897-->
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END%%
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%%ANKI
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Basic
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In ATT syntax, how is an immediate written?
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Back: As a `$$` followed by an integer using standard C notation.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889901-->
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END%%
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%%ANKI
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Basic
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In ATT syntax, how is a register written?
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Back: As a `%` followed by the name of the register.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889905-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $\textdollar Imm$?
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Back: $Imm$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889909-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $r_a$?
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Back: $R[r_a]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889912-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $Imm$?
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Back: $M[Imm]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889916-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $(r_a)$?
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Back: $M[R[r_a]]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889920-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $Imm(r_b)$?
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Back: $M[Imm + R[r_b]]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889923-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $(r_b, r_i)$?
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Back: $M[R[r_b] + R[r_i]]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889927-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $Imm(r_b, r_i)$?
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Back: $M[Imm + R[r_b] + R[r_i]]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889930-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $(,r_i,s)$?
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Back: $M[R[r_i] \cdot s]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889933-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $Imm(,r_i,s)$?
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Back: $M[Imm + R[r_i] \cdot s]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889937-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $(r_b,r_i,s)$?
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Back: $M[R[r_b] + R[r_i] \cdot s]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889941-->
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END%%
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%%ANKI
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Basic
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What is the operand value of form $Imm(r_b,r_i,s)$?
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Back: $M[Imm + R[r_b] + R[r_i] \cdot s]$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889945-->
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END%%
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%%ANKI
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Basic
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What distinguishes operand value $r_a$ from $(r_a)$?
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Back: The former denotes the register value. The latter denotes the value in memory at the address stored in $r_a$.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889949-->
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END%%
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%%ANKI
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Basic
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What values can $s$ take on in operand form $Imm(r_b,r_i,s)$?
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Back: $1$, $2$, $4$, or $8$.
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713212889952-->
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END%%
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%%ANKI
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Basic
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What operand form is named "immediate"?
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Back: $\textdollar Imm$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168875-->
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END%%
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%%ANKI
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Basic
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What operand form is named "register"?
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Back: $r_a$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168878-->
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END%%
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%%ANKI
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Basic
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What operand form is named "absolute"?
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Back: $Imm$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168881-->
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END%%
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%%ANKI
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Basic
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What operand form is named "indirect"?
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Back: $(r_a)$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168884-->
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END%%
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%%ANKI
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Basic
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What operand form is named "base + displacement"?
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Back: $Imm(r_b)$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168887-->
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END%%
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%%ANKI
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Basic
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What is the most general operand form named "indexed" (*not* "scaled indexed")?
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Back: $Imm(r_b, r_i)$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168890-->
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END%%
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%%ANKI
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Basic
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What is the most general operand form named "scaled indexed" (*not* indexed)?
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Back: $Imm(r_b, r_i, s)$
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Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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<!--ID: 1713213168894-->
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END%%
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## Bibliography
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* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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