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0ee9b2e446
So far the INIT segment was run from the later heap+stack. Now the INIT segment is run from the later BSS. The background is that so far the INIT segment was pretty small (from $80 to $180 bytes). But upcoming changes will increase the INIT segment in certain scenarios up to ~ $1000 bytes. So programs with very limited heap+stack might just not been able to move the INIT segment to its run location. But moving the INIT segment to the later BSS allows it to occupy the later BSS+heap+stack. In order to allow that the constructors are _NOT_ allowed anymore to access the BSS. Rather they must use the DATA segment or the new INITBSS segment. The latter isn't cleared at any point so the constructors may use it to expose values to the main program. However they must make sure to always write the values as they are not pre-initialized.
44 lines
698 B
ArmAsm
44 lines
698 B
ArmAsm
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; Ullrich von Bassewitz, 1998-09-17, 2005-02-26.
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;
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; Zero the bss segment.
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;
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.export zerobss
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.import __BSS_RUN__, __BSS_SIZE__
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.importzp ptr1
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.code
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zerobss:
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lda #<__BSS_RUN__
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sta ptr1
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lda #>__BSS_RUN__
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sta ptr1+1
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lda #0
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tay
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; Clear full pages
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L1: ldx #>__BSS_SIZE__
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beq L3
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L2: sta (ptr1),y
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iny
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bne L2
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inc ptr1+1
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dex
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bne L2
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; Clear remaining page (y is zero on entry)
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L3: cpy #<__BSS_SIZE__
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beq L4
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sta (ptr1),y
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iny
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bne L3
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; Done
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L4: rts
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