From: Alan Cox <alan@etchedpixels.co.uk>
Date: Sat, 15 Nov 2014 13:55:38 +0000 (+0000)
Subject: z80pack, tricks: update bankfork
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=2440d8be06f99346716edc400f22aa413f1a40da;p=FUZIX.git

z80pack, tricks: update bankfork

We now use all but 4K for base memory so we may need to copy more space.
Without this fix programs with large or no chmem crashes in fork()
---

diff --git a/Kernel/platform-z80pack/tricks.s b/Kernel/platform-z80pack/tricks.s
index a987439f..41694f59 100644
--- a/Kernel/platform-z80pack/tricks.s
+++ b/Kernel/platform-z80pack/tricks.s
@@ -221,15 +221,18 @@ _dofork:
         add hl, de
         ; load p_page
         ld c, (hl)
-	ld hl, (U_DATA__U_PAGE)
-	ld a, l
+	; load existing page ptr
+	push af
+	ld a, c
+	call outcharhex
+	pop af
+	ld a, (U_DATA__U_PAGE)
 
 	call bankfork			;	do the bank to bank copy
 
 	; Copy done
 
-	ld hl, (U_DATA__U_PAGE)	; parent memory
-        ld a, l
+	ld a, (U_DATA__U_PAGE)	; parent memory
 	out (21), a		; Switch context to parent
 
 	; We are going to copy the uarea into the parents uarea stash
@@ -239,6 +242,7 @@ _dofork:
 	ld de, #U_DATA_STASH	; target process
 	ld bc, #U_DATA__TOTALSIZE
 	ldir
+	; Return to the kernel mapping
 	xor a
 	out (21), a
         ; now the copy operation is complete we can get rid of the stuff
@@ -279,9 +283,9 @@ _swapstack:
 ;	Assumption - fits into a fixed number of whole 256 byte blocks
 ;
 bankfork:
-;	ld bc, #(0xC000 - 768)		;	48K minus the uarea stash
+;	ld bc, #(0xF000 - 768)		;	60K minus the uarea stash
 
-	ld b, #0xBD		; C0 x 256 minus 3 sets for the uarea stash
+	ld b, #0xED		; F0 x 256 minus 3 sets for the uarea stash
 	ld hl, #0		; base of memory to fork (vectors included)
 bankfork_1:
 	push bc			; Save our counter and also child offset
@@ -292,7 +296,7 @@ bankfork_1:
 	ldir			; copy into the bounce buffer
 	pop de			; recover source of copy to bounce
 				; as destination in new bank
-	pop bc			; recover child port number
+	pop bc			; recover child page number
 	push bc
 	ld b, a			; save the parent bank id
 	ld a, c			; switch to the child
@@ -303,7 +307,7 @@ bankfork_1:
 	ldir			; copy into the child
 	pop bc			; recover the bank pointers
 	ex de, hl		; destination is now source for next bank
-	ld a, b			; parent back is wanted in a
+	ld a, b			; parent bank is wanted in a
 	pop bc
 	djnz bankfork_1		; rinse, repeat
 	ret