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.section ".text"
.globl schedule
.macro preserve_ctx
cps #0x1f // Sys mode
// Store Usr regs
stmfd sp!, {r0-r12}
stmfd sp!, {lr}
ldr r3, =scheduler // struct Scheduler
ldr r2, [r3, #0] // struct Thread* rthread
str lr, [r2, #0] // svc_lr -> void* pc
str sp, [r2, #4] // svc_lr -> void* sp
cps #0x10 // Svc mode
.endm
.macro restore_ctx
ldr r3, =scheduler // struct Scheduler
ldr r2, [r3, #0] // struct Thread* rthread
ldr lr, [r2, #0] // void* pc -> lr_svc
ldr r0, [r2, #4] // void* sp -> r0
cps #0x1f // Sys mode
mov sp, r0 // Set stack pointer
// Restore Usr regs
ldmfd sp!, {lr}
ldmfd sp!, {r0-r12}
cps #0x10 // Svc mode
.endm
// Assumption: Enter in SVC mode
schedule:
preserve_ctx
ldr r1, =irqlr
ldr r0, [r1]
cmp r0, #0
beq 1f
// Replace LR with IRQ's LR
mov lr, r0
// Clear IRQ's LR
mov r0, #0
str r0, [r1]
1:
// bl get_next_thread // next_thread -> r0
ldr r3, =scheduler
ldr r2, [r3, #0] // struct Thread* current
cmp r0, r2 // current = next?
beq 2f
str r0, [r3, #0] // next -> rthread
2:
restore_ctx
movs pc, lr
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