汇编AMD64梯度错误

Question

我不确定我的错误在哪里，我正在尝试从0-255水平红色和0-255绿色垂直输出渐变图案。我知道链接文件正常工作，因为它们经过了彻底的测试。任何帮助都将非常感激。

global _start
global start
extern writeRGB
extern writeHeader

_start:
        call start

sys_write:  equ 1
sys_open:   equ 2
sys_close:  equ 3
sys_exit:   equ 60

newLine : equ 10

section .data
filename:       db "gradient.ppm", 0

section .bss

buffer: resb 4096

section .text

start:

        push r12
        push r13
        push r14
        push r15
        push rbx
        push rbp

        mov rax, sys_open       ; setup to open file
        mov rdi, filename       ; move filename
        mov rsi, 577            ; given
        mov rdx, 0o644          ; given
        syscall                 ; open file

        cmp rax, 0              ; check status
        jl end

        mov r12, 0              ; red
        mov r13, 0              ; green  
        mov r14, rax            ; opened file
        mov r15, buffer         ; buffer
        mov rbx, 0              ; buffer counter

        lea rdi, [r15+rbx]      ; setup for writeheader call
        mov rsi, 256
        mov rdx, 256
        call writeHeader
        add rbx, rax            ; add buffer space used by writeheader
        call makeRGB            ; create 0 0 0 rgb
        lea rdi, [r15+rbx]      ; setup for writeRGB
        call writeRGB
        add rbx, rax            ; add buffer space used by writeRGB
        call incRed 

incRed:
        call addSpace
        inc r12                 ; red++
        call makeRGB            ; convert to RBG
        lea rdi, [r15+rbx]      ; setup for writeRGB call
        call writeRGB           
        add rbx, rax            ; add buffer space used by writeRGB
        cmp r12, 255            ; check to see if end of row
        jl incRed               ; if not end of row repeat
        je incGreen             ; if end of row start new row

incGreen:
        cmp r13, 255            ; if last line is written move to end
        je write
        call addNewLine
        mov r12, 0              ; reset red to 0
        inc r13                 ; green++
        call makeRGB            ; convert to RGB
        lea rdi, [r15+rbx]      ; setup for writeRGB call
        call writeRGB
        add rbx, rax            ; add buffer space used by writeRGB
        call addSpace
        jmp incRed              ; ret to incRed

makeRGB:
        mov r12, rsi            ; mov red into rsi
        shl rsi, 8              ; shift left 8 to make room for green
        add rsi, r13            ; add green
        shl rsi, 8              ; shift left to set blue to 0
        ret

addSpace:
        mov al, ' '             ; insert space
        mov [r15+rbx], al
        inc rbx
        ret

addNewLine:
        mov al, newLine         ; insert newline
        mov [r15+rbx], al
        inc rbx 
        ret

write:
        mov rax, sys_write
        mov rdi, r14            ; move opened file into rdi
        mov rsi, r15            ; buffer location
        mov rdx, rbx            ; load buffer size
        syscall                 ; write to file
        mov rbp, rax            ; status stored in rbp
        cmp rbp, 0              ; check status
        jl end

        mov rdi, r14            ; move opened file into rdi
        mov rax, sys_close      ; close file
        syscall

        call end                ; end

end:
        pop rbp
        pop rbx
        pop r15
        pop r14
        pop r13
        pop r12

        mov rdi, rax            ; prepare to exit
        mov rax, sys_exit       
        syscall                 ; exit