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.globl irq_handler
irq_handler:
    mov    r13,r0
    sub    r0,lr,#4
    mov    lr,r1
    mrs    r1,spsr
    
    msr    cpsr_c, #(MODE_SYS | IRQ_FLAG )
    stmfd    sp!,{r0,r1}
    stmfd    sp,{r2-r12, lr}
    mov    r0,sp
    sub    sp,sp,#(13*4)
    
    msr    cpsr_c, #(MODE_IRQ | IRQ_FLAG )
    stmfd    r0!,{r13,r14}
    msr    cpsr_c, #(MODE_SYS | IRQ_FLAG )
    
    ldr    r0, =current_task
    ldr    r0,[r0]
    str    sp,[r0]
    
    ldr    r12, =call_irq
    mov    lr,pc
    bx    r12
    
    mov    sp, #0
    
    ldr    r0, =current_task
    ldr    r0,[r0]
    ldr    sp,[r0]

    msr    cpsr_c,#(MODE_SYS | IRQ_FLAG )
    mov    r0,sp
    add    sp,sp,#(15*4)
    
    msr    cpsr_c,#(MODE_IRQ | IRQ_FLAG )
    mov    sp, r0
    ldmfd    sp,{r0-r12}^
    nop
    add    sp, sp,#(13*4)
    
    ldr    lr,[sp, #4]
    msr    spsr_cxsf,lr

    ldr    lr,[sp]
    add    sp, sp,#(2*4)
    movs    pc,lr