matos/core/cpu_context_switch.S

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.file "cpu_context_switch.S"
.text
.globl cpu_context_switch
.type cpu_context_switch, @function
cpu_context_switch:
// arg2= to_context -- esp+68
// arg1= from_context -- esp+64
// caller ip -- esp+60
pushf // (eflags) esp+56
pushl %cs // (cs) esp+52
pushl $resume_pc // (ip) esp+48
pushl $0 // (error code) esp+44
pushal // (general reg) esp+12+8*4
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
/*
* Now that the original eax/ebx are stored, we can use them safely
*/
/* Store the address of the saved context */
movl 64(%esp), %ebx
movl %esp, (%ebx)
/* This is the proper context switch ! We change the stack here */
movl 68(%esp), %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 */
resume_pc:
// Same context as that when cpu_context_switch got called
// arg2= to_context -- esp+8
// arg1= from_context -- esp+4
// caller ip -- esp
ret
/* ------------------------- */
.globl cpu_context_exit_to
.type cpu_context_exit_to, @function
cpu_context_exit_to:
// arg3= reclaiming_arg -- esp+12
// arg2= reclaiming_func -- esp+8
// arg1= to_context -- esp+4
// caller ip -- esp
/* Store the current SP in a temporary register */
movl %esp, %eax
/* This is the proper context switch ! We change the stack here */
movl 4(%eax), %esp
/* Call the reclaiming function (remember: the old frame address
is stored in eax) */
pushl 12(%eax)
call *8(%eax)
addl $4, %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 */