64 lines
2.1 KiB
ArmAsm
64 lines
2.1 KiB
ArmAsm
.intel_syntax noprefix
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.extern main
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.section .text
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.global _start
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_start:
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# On entry, the stack contains:
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# [rsp] = argc (argument count)
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# [rsp+8] = argv[0] (program name)
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# [rsp+16] = argv[1] (first argument)
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# ...
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# Get argc from stack
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mov rdi, [rsp] # rdi = argc
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# Calculate space needed for our array structure
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# We need: 8 bytes (length) + argc * 8 bytes (pointers)
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mov rax, rdi # rax = argc
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shl rax, 3 # rax = argc * 8 (each pointer is 8 bytes)
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add rax, 8 # rax = 8 + argc * 8 (add space for length)
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# Allocate space on stack (align to 16 bytes)
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add rax, 15 # Round up to nearest 16
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and rax, -16 # Align to 16 bytes
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sub rsp, rax # Allocate space
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# Store array length at beginning
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mov [rsp], rdi # Store argc as array length
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# Copy argv pointers to our array
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lea rsi, [rsp + 8] # rsi points to start of argv in stack
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lea rdi, [rsp + 8] # rdi points to our array data (after length)
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mov rcx, [rsp] # rcx = argc (loop counter)
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copy_loop:
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test rcx, rcx # Check if we're done
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jz done_copying
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mov rax, [rsi] # Load argv[i] pointer
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mov [rdi], rax # Store in our array
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add rsi, 8 # Move to next argv entry
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add rdi, 8 # Move to next array slot
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dec rcx # Decrement counter
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jmp copy_loop
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done_copying:
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# Now rsp points to our array: [length][ptr0][ptr1]...[ptrN-1]
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mov rdi, rsp # Pass array pointer to main
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call main
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# Clean up stack (restore original rsp)
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# Calculate how much we allocated
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mov rdi, [rsp] # Get argc back
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shl rdi, 3 # argc * 8
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add rdi, 8 # + 8 for length
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add rdi, 15 # Round up
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and rdi, -16 # Align
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add rsp, rdi # Restore stack
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# Exit with main's return value
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mov rdi, rax # rax contains main's return value
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mov rax, 60 # sys_exit
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syscall
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