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heap.s
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heap.s
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AREA |.text|, CODE, READONLY, ALIGN=2
THUMB
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; System Call Table
HEAP_TOP EQU 0x20001000
HEAP_BOT EQU 0x20004FE0
MAX_SIZE EQU 0x00004000 ; 16KB = 2^14
MIN_SIZE EQU 0x00000020 ; 32B = 2^5
MCB_TOP EQU 0x20006800 ; 2^10B = 1K Space
MCB_BOT EQU 0x20006BFE
MCB_ENT_SZ EQU 0x00000002 ; 2B per entry
MCB_TOTAL EQU 512 ; 2^9 = 512 entries
INVALID EQU -1 ; an invalid id
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Memory Control Block Initialization
EXPORT _heap_init
_heap_init
_kinit
;; Implement by yourself
PUSH {R1-R11, LR}
LDR R0, =MCB_TOP
LDR R1, =MCB_BOT
EOR R2, R2, R2
_kinit_loop
CMP R1, R0
BEQ _kinit_end
STRB R2, [R1]
SUB R1, R1, #1
_kinit_end
LDR R2, =MAX_SIZE
STR R2, [R0]
POP {R1-R11, PC}
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Kernel Memory Allocation
; void* _k_alloc( int size )
EXPORT _kalloc
_kalloc
;; Implement by yourself
push {r1-r12, lr}
mov r0, r8
ldr r1, =MCB_TOP
ldr r2, =MCB_BOT
BL _ralloc
MOVW r4, #0x5000
MOVT r4, #0x2000
STR r0, [r4]
pop {r1-r12, pc}
_ralloc
push {r4, lr}
mov r3, r1
ldr r4, =MIN_SIZE
cmp r0, r4
it lt
movlt r0, r4
ldr r4, =MCB_BOT
cmp r4, r2
it eq
addeq r2, r2, #2
subs r2, r2, r3
asrs r2, r2, #1
ldrsh r1, [r3]
cmp r1, r0
blt _ralloc_Lrange
tst r1, #1
bne _ralloc_Lrange
cmp r1, r0
beq _ralloc_range
cmp r0, r1, lsl #1
ble _ralloc_hit
_ralloc_range
orr r1, r1, #1
strh r1, [r3]
ldr r1, =MCB_TOP
subs r1, r3, r1
ldr r0, =HEAP_TOP
add r0, r0, r1, lsl #4
b _ralloc_end
_ralloc_hit
asrs r1, r1, #1
strh r1, [r3]
strh r1, [r2, r3]
add r2, r2, r3
mov r1, r3
bl _ralloc
b _ralloc_end
_ralloc_Lrange
ldr r2, =MAX_SIZE
cmp r2, r1
it ne
cmpne r4, r3
it le
movle r0, #0
bgt _ralloc_Rrange
_ralloc_end
pop {r4, pc}
_ralloc_Rrange
asrs r2, r1, #4
adds r1, r2, r3
ldrsh r2, [r2, r3]
add r2, r1, r2, asr #4
bl _ralloc
b _ralloc_end
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Kernel Memory De-allocation
; void free( void *ptr )
EXPORT _kfree
_kfree
;; Implement by yourself
MOV r0, r8
LDR r2, =HEAP_TOP
cmp r2, r0
BGT _kfree_null
LDR r1, =HEAP_BOT
PUSH {r4, lr}
MOV r4, r0
CMP r1, r0
BLT _kfree_end
LDR r0, =MCB_TOP
SUBS r2, r4, r2
ADD r0, r0, r2, asr #4
BL _rfree
CBZ r0, _kfree_end
MOV r0, r4
POP {r4, pc}
_kfree_end
EOR r0, r0, r0
POP {r4, pc} ; return from rfree( )
_kfree_null
EOR r0, r0, r0
BX lr
_rfree
push {r1-r11,lr}
mov r5, r0
mov r8, #0
ldr r6, =MCB_TOP
ldr r7, =MCB_BOT
sub r9, r0, r6
_rfree_body_logic
ldrsh r4, [r5]
mov r0, r9
bic r4, r4, #1
strh r4, [r5]
asrs r4, r4, #4
mov r1, r4
bl _rdiv_
ands r0, r0, #1
add r3, r5, r4
it ne
subne r3, r5, r4
cmp r6, r3
bgt _rfree_end
cmp r7, r3
blt _rfree_end
ldrsh r1, [r3]
mvns r2, r1
cmp r1, #0
ite eq
moveq r2, #0
andne r2, r2, #1
cbz r2, _rfree_end
cbz r0, _rfree_left
strh r8, [r5]
sub r9, r3, r6
mov r5, r3
ldrsh r2, [r3]
lsls r2, r2, #1
strh r2, [r3]
b _rfree_body_logic
_rfree_left
strh r0, [r3]
ldrsh r3, [r5]
lsls r3, r3, #1
strh r3, [r5]
b _rfree_body_logic
_rfree_end
pop {r1-r11, pc}
_rdiv_
udiv r0, r0, r1
bx lr
END