51 lines
1.3 KiB
ArmAsm
51 lines
1.3 KiB
ArmAsm
.text # section declaration
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msg:
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.string "needs a proper file name\n"
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len = . - msg # length of our dear string
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# we must export the entry point to the ELF linker or loader.
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# They convientionally recognize _start as their entry point.
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# Use ld -e main to override the default if you wish
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.global _start
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_start:
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# first check that we got the correct number of inputs
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pop %rax # Get the number of arguments
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pop %rdi # Get the program name
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pop %rdi # Get the actual argument
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# Check if we have the correct number of inputs
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cmp $2, %rax
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# Jump to Bail if the number is not correct
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jne Bail
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# Load our preferred mode
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mov $0755, %rsi
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# Load the syscall number for chmod
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mov $90, %rax
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# Call the kernel
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syscall
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Done:
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# program completed Successfully
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mov $0, %rdi # All is well
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mov $60, %rax # put the exit syscall number in eax
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syscall # Call it a good day
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Bail:
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# first let the user know what was wrong
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mov $len,%rdx # third argument: message length
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mov $msg,%rsi # second argument: pointer to message to write
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mov $1,%rdi # first argument: file handle (stdout)
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mov $1,%rax # system call number (sys_write)
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syscall # call kernel
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# Second terminate with an error
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mov $1, %rdi # there was an error
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mov $60, %rax # put the exit syscall number in eax
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syscall # bail out
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