Hello World
First let’s present the program and then we’ll discuss it. This program works by making Linux system calls and like all Linux programs starts execution at the globally exported _start label. The program uses the Assembly directives specified in the GCC documentation.
#
# Risc-V Assembler program to print "Hello World!"
# to stdout.
#
# a0-a2 - parameters to linux function services
# a7 - linux function number
#
.global _start # Provide program starting address to linker
# Setup the parameters to print hello world
# and then call Linux to do it.
_start: addi a0, x0, 1 # 1 = StdOut
la a1, helloworld # load address of helloworld
addi a2, x0, 13 # length of our string
addi a7, x0, 64 # linux write system call
ecall # Call linux to output the string
# Setup the parameters to exit the program
# and then call Linux to do it.
addi a0, x0, 0 # Use 0 return code
addi a7, x0, 93 # Service command code 93 terminates
ecall # Call linux to terminate the program
.data
helloworld: .ascii "Hello World!\n"The ‘#’ character is the comment character and anything after it on a line is a comment.
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