matos/core/irq_pit.S

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.file "irq_pit.S"
.text
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.extern switchKthread
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.globl pit_handler
.type pit_handler, @function
pit_handler: // already got eflags, cs and eip on stack thanks to CPU
pushl $0 // err_code esp+12+8*4=44
pushal // (general reg) esp+12
subl $2, %esp // (alignment) esp+10
pushw %ss // esp+8
pushw %ds // esp+6
pushw %es // esp+4
pushw %fs // esp+2
pushw %gs // esp
/* Send EOI to PIC */
movb $0x20, %al
outb %al, $0x20
pushl %esp
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call switchKthread
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movl %eax,%esp
/* Restore the CPU context */
popw %gs
popw %fs
popw %es
popw %ds
popw %ss
addl $2,%esp
popal
addl $4, %esp /* Ignore "error code" */
/* This restores the eflags, the cs and the eip registers */
iret /* equivalent to: popfl ; ret */