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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.
46 lines
1.4 KiB
ArmAsm
46 lines
1.4 KiB
ArmAsm
;
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; 2015-10-07, Greg King
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;
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.export moveinit
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.import __INIT_LOAD__, __INIT_RUN__, __INIT_SIZE__ ; Linker-generated
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.macpack cpu
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.macpack generic
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; Put this in the DATA segment because it is self-modifying code.
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.data
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; Move the INIT segment from where it was loaded (over the bss segments)
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; into where it must be run (over the BSS segment). The two areas might overlap;
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; and, the segment is moved upwards. Therefore, this code starts at the highest
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; address, and decrements to the lowest address. The low bytes of the starting
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; pointers are not sums. The high bytes are sums; but, they do not include the
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; carry. Both the low-byte sums and the carries will be done when the pointers
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; are indexed by the .Y register.
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moveinit:
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; First, move the last, partial page.
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; Then, move all of the full pages.
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ldy #<__INIT_SIZE__ ; size of partial page
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ldx #>__INIT_SIZE__ + (<__INIT_SIZE__ <> 0) ; number of pages, including partial
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L1: dey
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init_load:
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lda __INIT_LOAD__ + (__INIT_SIZE__ & $FF00) - $0100 * (<__INIT_SIZE__ = 0),y
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init_run:
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sta __INIT_RUN__ + (__INIT_SIZE__ & $FF00) - $0100 * (<__INIT_SIZE__ = 0),y
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tya
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bnz L1 ; page not finished
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dec init_load+2
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dec init_run+2
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dex
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bnz L1 ; move next page
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rts
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