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20be72dbf9
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da62a80b0e
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.global _start
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//exposes a symbol called start to the assembler
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.intel_syntax noprefix
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//See: https://www.youtube.com/watch?v=6S5KRJv-7RU
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//See: https://blog.rchapman.org/posts/Linux_System_Call_Table_for_x86_64/
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_start:
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//write call (sys_write)
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mov rax,1
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//sys_write system call
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mov rdi, 1
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//unsigned int fd = 1 (stdout)
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lea rsi,[hello_world]
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//load effective address (lea) into rsi of hello_world data
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mov rdx, 14
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//size_t count excluding null terminator
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syscall
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//exit call
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mov rax, 60
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mov rdi, 33
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//return result (must be "rdi" not "rdx" - how are these registers named?)
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syscall
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//apprently int 80h interrupt is also syscall?
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hello_world:
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.asciz "Hello, World!\n"
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@ -1,24 +0,0 @@
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https://www.youtube.com/watch?v=6S5KRJv-7RU
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rdi
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rsi
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r8
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r - 64 bit pointer
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mov rdi,8
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mov rdi,rsi
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memory operations
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mov rdi, qword ptr[rsi] values from memory into register
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mov qword ptr[rsi], rdi store into memory operation
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https://blog.rchapman.org/posts/Linux_System_Call_Table_for_x86_64/
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Compilation:
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as -c assemblyexample1.asm -o assemblyexample1.o
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gcc assemblyexample1.o -o assemblyexample1 -nostdlib -static
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Check error code:
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echo $?
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