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.file "context-switch.s"
.text
.align 2
.global kerent
.type kerent, %function
kerent:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 1, uses_anonymous_args = 0
@movs pc, lr
@ debug print
@@mov r0, #1
@@mov r1, #123
@@bl bwputr(PLT)
@ save spsr to r1
mrs r1, spsr
@ switch to sysmode
msr cpsr_c, #0xdf
@ save user status
stmfd sp!, {r3-r12,r14,r1}
@ copy sp to r2 for later saving
mov r2, sp
@ move sp downward by 1
sub sp, sp, #4
@ switch to svc mode
msr cpsr_c, #0xd3
@ store lr_svc onto sp_usr
stmfd r2!, {lr}
@ move Args to r1
mov r1, r0
@ get swi number into r0
ldr r0, [lr, #-4]
@ mask off high bits
bic r0, r0, #0xff000000
@ pop kernels stack
ldmfd sp!, {r3-r12,pc}
.size kerent, .-kerent
.align 2
.global kerxit
.type kerxit, %function
kerxit:
@ this is equi to activate, an entry point in the kernel to which it goes
@ when its ready to restart the active task
@ args = 0, pretend = 0, frame = 8
@ frame_needed = 1, uses_anonymous_args = 0
@ push kernel's registers
stmfd sp!, {r3-r12, r14}
@ stmfd sp_svc!, {r0-r14} TODO
@ switching to system mode
msr cpsr_c, #0xdf
@ get task->sp_usr from arg 0
mov sp, r0
@ load spsr to r0, lr_svc to r2
ldmfd sp!, {r0, r2}
@ move sp up 2 slot
add sp, sp, #8
@ switch back to svc mode
msr cpsr_c, #0xd3
@ set spsr to r0
msr spsr, r0
@ set lr_svc to r2
mov lr, r2
@switch back to sys mode
msr cpsr_c, #0xdf
@ restore user's registers
ldmfd sp!, {r3-r12, r14}
@get back to svc mode
msr cpsr_c, #0xd3
@load return value into r0
mov r0, r1
@ go to usr program
movs pc, lr
.size kerxit, .-kerxit
.ident "GCC: (GNU) 4.0.2"