Compilation basic syntax

The assembler consists of three parts:

Data segment BSS paragraph text

Data segment:

Used to declare data segments that initialize data or constants, this data does not change at run time.

syntax for declaring data segments:

Section. Data

BSS segment:

The BSS segment declares the variable.

Declaration syntax:

Section. BSS

Text segment:

Save the actual code.

The required declaration at the beginning of this paragraph global_start: tell the kernel program to start executing the code.

Declaring text snippet Syntax:

Section. Text

Global _start

_start:

Comments:

Comments with semicolons:;

Assembly language Statements:

Three different types:

Executable instructions: Tell the processor what to do

Assembly directives: telling the compilation of various aspects of the assembly process

Macro: Text substitution

Assembly language Syntax:

[lable] mnemonic [operands] [; Comment]

assembly Language Output Hello World:

Input content:

　　

　　vim hello.asm ; Create a hello.asm file

　　nasm-f elf hello.asm ; assemble the program to form a hello.o file

　　ld-m elf_i386-s-o hello hello.o ; link and create an executable hello

　　./hello ; Execution procedure

Content of Hello.asm:

　　

Section . Text    global _start_start:    mov Edx,len     mov ecx,msg     mov ebx,1    mov eax,4    int  0x80     mov eax,1    int  0x80section. Data    'Hello, World', 0xa    len equ $-Msg

Section.Text, declared here as a paragraphGlobal_startThis section must be declared to tell the kernel program to start executing_start: ;Tell the linker here to program entry Movedx,Len;Information length MOVECX,Msg;Write the information movebx,1 ; Document descriptionMoveax,4 ;System call number(Sys_write) Int0x80 call kernel moveax,1 ;< Span class= "PLN" >system call number  (sys_exit int0x80call kernelsection. ' Hello, world! ' , 0xa  information len equ $ -  msg ; information length  
         

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Compilation basic syntax