53 lines
1.2 KiB
ArmAsm
53 lines
1.2 KiB
ArmAsm
.text
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.balign 4
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.global _start
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_start:
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seth sp, #shigh(_stack)
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add3 sp, sp, #low(_stack)
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ldi fp, #0
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# Clear the BSS. Do it in two parts for efficiency: longwords first
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# for most of it, then the remaining 0 to 3 bytes.
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seth r2, #shigh(__bss_start)
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add3 r2, r2, #low(__bss_start); R2 = start of BSS
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seth r3, #shigh(_end)
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add3 r3, r3, #low(_end) ; R3 = end of BSS + 1
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sub r3, r2 ; R3 = BSS size in bytes
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mv r4, r3
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srli r4, #2 ; R4 = BSS size in longwords (rounded down)
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ldi r1, #0 ; clear R1 for longword store
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addi r2, #-4 ; account for pre-inc store
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beqz r4, .Lendloop1 ; any more to go?
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.Lloop1:
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st r1, @+r2 ; yep, zero out another longword
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addi r4, #-1 ; decrement count
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bnez r4, .Lloop1 ; go do some more
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.Lendloop1:
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and3 r4, r3, #3 ; get no. of remaining BSS bytes to clear
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addi r2, #4 ; account for pre-inc store
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beqz r4, .Lendloop2 ; any more to go?
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.Lloop2:
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stb r1, @r2 ; yep, zero out another byte
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addi r2, #1 ; bump address
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addi r4, #-1 ; decrement count
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bnez r4, .Lloop2 ; go do some more
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.Lendloop2:
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# Run code in the .init section.
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# This will queue the .fini section to be run with atexit.
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bl __init
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# Call main, then exit.
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bl main
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bl exit
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# If that fails just loop.
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.Lexit:
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bra .Lexit
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