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Table of Contents

  1. Sections
  2. Symbols

Sections

Generic Section Directives

The following Directives create or select a section named like the Directive with default Attributes.

Directive Description Type Flags
.text Code SHT_PROGBITS SHF_ALLOC SHF_EXECINSTR
.data Initialized Data SHT_PROGBITS SHF_ALLOC SHF_WRITE
.rodata Initialized Data SHT_PROGBITS SHF_ALLOC
.bss Zero Initialized Data SHT_NOBITS SHF_ALLOC SHF_WRITE

.section

The .section Directive creates or selects a Section with specified Name, Type and Flags.
If the Name starts with a generic Section name (for example .text.mysectionname),
the Type and Flags can be omitted and the Default will be selected.

Valid Syntax

.section .text.mysectionname
.section .text.mysectionname, "<flags>"
.section .text.mysectionname, "<flags>", <type>
.section .mysectionname, "<flags>", <type>

Field Descriptions

  • "<flags>" : Any Combination of a w x in Parenthesis. For Example: "awx"
  • <type> : @progbits or @nobits

Symbols

There are several directives that create or modify Symbols.

Label Directive

Syntax: <symbolname>:
This is the only one that sets the value and the section index.
Those values are then locked into place.
There will be an error if another Label Directive tries to change the value or the shndx.

The Default Attributes are:

  • Size: 0
  • Type: STT_NOTYPE
  • Bind: STB_LOCAL
  • Visibility: STV_DEFAULT

Other Symbol Directives

All the other Symbol Directives only modify the relevant Attributes or create Placeholder Symbols

Directive Modified Field Type Bind Visibility Size
.extern <name> None Notype Local Default 0
.type <name>, @function Type STT_FUNC Local Default 0
.type <name>, @object Type STT_OBJECT Local Default 0
.type <name>, @notype Type STT_NOTYPE Local Default 0
.global <name> Bind Notype STB_GLOBAL Default 0
.globl <name> Bind Notype STB_GLOBAL Default 0
.local <name> Bind Notype STB_LOCAL Default 0
.weak <name> Bind Notype STB_WEAK Default 0
.hidden_name <name> Visibility Notype Local STV_HIDDEN 0
.internal <name> Visibility Notype Local STV_INTERNAL 0
.protected <name> Visibility Notype Local STV_PROTECTED 0
.size <name>, <size> Size Notype Local Default <size>

Misc Directives

.align

.set

.equ

Data

.string

.ascii

.zero

.byte

.half

.word

.2byte

.4byte

.incbin

Bss

.space

RiscV

Registers

Integer Registers

Float Registers

CSR Regasters

Relocations

Instructions

RiscV32I

Lui - Load Upper Immediate
lui rd, number
lui rd, symbol
lui rd, %hi(symbol)
Auipc - Add Upper Immediate to Program Counter
auipc rd, number
auipc rd, symbol
auipc rd, %pcrel_hi(symbol)
auipc rd, %got_pcrel_hi(symbol)
Load Store
lw rd, (rs1)
lw rd, offset(rs1)
lw rd, %lo(symbol)(rs1)
lw rd, %pcrel_lo(symbol)(rs1)

sw rs2, (rs1)
sw rs2, offset(rs1)
sw rs2, %lo(symbol)(rs1)
sw rs2, %pcrel_lo(symbol)(rs1)
Jalr
jalr rd, (rs1)
jalr rd, offset(rs1)
jalr rd, %lo(symbol)(rs1)
jalr rd, %pcrel_lo(symbol)(rs1)
Jal - Jump And Link
jal rd, symbol
Branch
beq rs1, rs2, symbol
bne rs1, rs2, symbol
blt rs1, rs2, symbol
bge rs1, rs2, symbol
bltu rs1, rs2, symbol
bgeu rs1, rs2, symbol