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// To keep this in the first portion of the binary.
.section ".text.boot"
// Make _start global.
.globl _start
_start:
reset:
// disable core0,1,2.
mrc p15, #0, r1, c0, c0, #5
and r1, r1, #3
cmp r1, #0
bne io_halt
// set vector address.
ldr r0, =vector
mcr p15, 0, r0, c12, c0, 0
// save cpsr.
mrs r0, cpsr
// setup sp in IRQ mode.
bic r1, r0, #0x1f
orr r1, r1, #0x12
msr cpsr_c,r1
mov sp,#0x4000
// setup sp in FIQ mode.
bic r1, r0, #0x1f
orr r1, r1, #0x11
msr cpsr_c,r1
mov sp,#0x2000
// setup sp in UNDEF mode.
bic r1, r0, #0x1f
orr r1, r1, #0x1B
msr cpsr_c,r1
mov sp,#0x1000
// setup sp in ABORT mode.
bic r1, r0, #0x1f
orr r1, r1, #0x17
msr cpsr_c,r1
mov sp,#0x0800
// Setup sp in USR/SYS mode.
bic r1, r0, #0x1f
orr r1, r1, #0x1f
msr cpsr_c,r1
mov sp,#0x6000
// restore to SVC (in the case of a reset)
bic r1, r0, #0x1f
orr r1, r1, #0x13
msr cpsr_c, r1
//msr cpsr_c, r0
// setup the stack in SVC mode.
mov sp, #0x8000
// Clear out bss.
ldr r4, =__bss_start
ldr r9, =__bss_end
mov r5, #0
mov r6, #0
mov r7, #0
mov r8, #0
b 2f
1:
// store multiple at r4.
stmia r4!, {r5-r8}
// If we are still below bss_end, loop.
2:
cmp r4, r9
blo 1b
// Call kernel_main
ldr r3, =kernel_main
blx r3
irq:
push {r0,r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,lr}
bl c_irq_handler
pop {r0,r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,lr}
subs pc, lr, #4
.globl io_halt
io_halt:
wfi
b io_halt
// TODO: SETUP OTHER STACKS
undefined:
stmfd sp!, {r0-r12,lr}
ldr r0, [lr, #-4]
push {r0}
ldr r0, =undefined_msg
bl uart_string
pop {r0}
bl uart_hex
ldr r0, =undefined_at
bl uart_string
// Output lr
mov r1, #0x1000
ldr r0, [r1, #-4]
bl uart_hexn
// Skip instruction for now
// In future,
// ldmfd sp!, {r0-r12,lr} // Note the lack of ^ since subs will handle it
// subs pc, lr, #4
ldmfd sp!, {r0-r12,pc}^
svc:
stmfd sp!, {r0-r12,lr}
ldr r0, [lr, #-4]
bic r0, #0xFF000000
push {r0}
ldr r0, =svc_msg
bl uart_string
ldr r0, [sp]
bl uart_hexn
pop {r0}
// SVC #0 returns to supervisor mode
// TODO: Make supervisor mode return to a specific location
// (rather than to a user location) such as the kernel loop
cmp r0, #0
bne 1f
mrs r0, spsr
bic r0, #0x1f
// Return in supervisor mode
orr r0, #0x13
msr spsr, r0
1:
ldmfd sp!, {r0-r12,pc}^
io_halt_prefetch:
stmfd sp!, {r0-r12,lr}
ldr r0, =prefetch_msg
bl uart_string
ldmfd sp!, {r0-r12,pc}^
io_halt_data:
stmfd sp!, {r0-r12,lr}
ldr r0, =data_msg
bl uart_string
// Output return address
mov r1, #0x800
ldr r0, [r1, #-4]
sub r0, #8
bl uart_hexn
ldmfd sp!, {r0-r12,pc}^
io_halt_fiq:
ldr r0, =fiq_msg
push {lr}
bl uart_string
pop {lr}
b io_halt
.align 5
vector:
ldr pc, reset_handler
ldr pc, undefined_handler
ldr pc, svc_handler
ldr pc, prefetch_handler
ldr pc, data_handler
ldr pc, unused_handler
ldr pc, irq_handler
ldr pc, fiq_handler
reset_handler: .word reset
undefined_handler: .word undefined
svc_handler: .word svc
prefetch_handler: .word io_halt_prefetch
data_handler: .word io_halt_data
unused_handler: .word io_halt
irq_handler: .word irq
fiq_handler: .word io_halt_fiq
.section .data
undefined_msg: .asciz "Undefined Handler\nUNDEF "
undefined_at: .asciz " @ 0x"
svc_msg: .asciz "SVC Handler\nSVC #"
prefetch_msg: .asciz "Prefetch Handler\n"
data_msg: .asciz "Data Handler\n"
fiq_msg: .asciz "FIQ\n"
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