From: Alan Cox <alan@linux.intel.com>
Date: Tue, 2 Jan 2018 21:03:23 +0000 (+0000)
Subject: 65c816: Fixes for non bank 0
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=3f9d24482c9f3434de95d85f25a29b8098366678;p=FUZIX.git

65c816: Fixes for non bank 0

With this fixed the large mode seems to work (not heavily tested) and
an 8MB boot works to a shell prompt and some test commands at least.
---

diff --git a/Kernel/lib/65c816.s b/Kernel/lib/65c816.s
index e11d3946..4f12020b 100644
--- a/Kernel/lib/65c816.s
+++ b/Kernel/lib/65c816.s
@@ -21,6 +21,7 @@
 	.import _runticks
 	.import outcharhex
 	.import outstring
+	.import kstack_base
 
 
 	.code
@@ -80,6 +81,9 @@ slow_path:
 	.a8
 	lda	U_DATA__U_PAGE
 	sta	f:KERNEL_CODE_FAR+switch_patch_1+1		; target bank of save
+.if ( KERNEL_BANK )
+	sta	f:KERNEL_CODE_FAR+switch_patch_2+1		; target bank of save
+.endif
 	rep	#$30
 	.i16
 	.a16
@@ -89,6 +93,20 @@ slow_path:
 	phb
 switch_patch_1:
 	mvn	0,KERNEL_BANK		; save stack and udata
+
+.if ( KERNEL_BANK )
+	;
+	;	Big (non bank 0) kernels by necessity split off the
+	;	kstack into bank 0.
+	;
+	;	FIXME: some day split the user ZP to be half ZP half Kstack
+	;
+	lda	#$FF
+	ldx	#kstack_base
+switch_patch_2:
+	mvn	0,0
+
+.endif
 	plb
 	sep #$30
 	stz	_inint
@@ -115,7 +133,10 @@ _switchin:
 	; If this is zero we need swapping so the swapper checks go here
 	; FIXME
 
-	sta	f:KERNEL_CODE_FAR+switch_patch_2+2	; source bank of retrieve
+	sta	f:KERNEL_CODE_FAR+switch_patch_3+2	; source bank of retrieve
+.if ( KERNEL_BANK )
+	sta	f:KERNEL_CODE_FAR+switch_patch_4+2	; source bank of retrieve
+.endif
 	rep	#$30
 	.i16
 	.a16
@@ -125,19 +146,41 @@ _switchin:
 	ldx	#U_DATA_STASH
 	ldy	#U_DATA
 	lda	#U_DATA__TOTALSIZE-1
-switch_patch_2:
+switch_patch_3:
 	mvn	KERNEL_BANK,0
-	;	after the MVN our data bank is KERNEL_DATA
+
+.if ( KERNEL_BANK )
+	;
+	;	Big kernel - recover kstack into bank 0
+	;
+	ldy	#kstack_base
+	lda	#$FF
+switch_patch_4:
+	mvn	0,0
+
+.endif
+
+	;	Bank may be invalid but we don't have a stack we can use
+	;	so force a far access
+	;	after this our data bank is KERNEL_DATA
 	;	Our stack is now valid and we may use it again, our UDATA
 	;	is for the new process
-	ldx	U_DATA__U_SP			; correct stack pointer
+	lda	f:KERNEL_FAR+U_DATA__U_SP	; correct stack pointer
+	tax
 	txs
+	;	Now our stack is valid fix the bank register
+
+	sep	#$20
+	.a8
+	lda	#KERNEL_BANK
+	pha
+	plb
+
 	ldx	U_DATA__U_PTAB
 	cpx	ptr1
 	bne	switchinfail	;	wrong process !!
 	stz	_runticks
-	sep	#$20
-	.a8
+
 	lda	#P_RUNNING
 	sta	a:P_TAB__P_STATUS_OFFSET,x
 	;	This will only be needed once we swap, and we will need to
@@ -181,6 +224,9 @@ _dofork:
 	lda	U_DATA__U_PAGE
 	sta	f:KERNEL_CODE_FAR+fork_patch+2	 ; source bank (parent)
 	sta	f:KERNEL_CODE_FAR+fork_patch_2+1 ; destination udata stash
+.if ( KERNEL_BANK )
+	sta	f:KERNEL_CODE_FAR+fork_patch_3+1 ; destination udata stash
+.endif
 	asl	a
 	adc	#STACK_BANKOFF
 	sta	ptr2+1			; source for S and DP
@@ -210,7 +256,7 @@ _dofork:
 	; Our context is now a valid stack frame so we can save stuff
 	ldx	#0
 	txy
-	lda	#MAP_SIZE	; 64K - udata shadow
+	lda	#MAP_SIZE-1	; 64K - udata shadow
 	phb
 fork_patch:
 	mvn	0,0		; copy the entire bank below the save
@@ -219,12 +265,25 @@ fork_patch:
 	lda	#U_DATA__TOTALSIZE-1
 fork_patch_2:
 	mvn	0,KERNEL_BANK
-	plb			; back to kernel bank
-
-	ldx	ptr2
-	ldy	ptr3
+.if ( KERNEL_BANK )
+	;
+	;	For big kernels copy the kstack separately as it's in
+	;	bank 0 but the C stack and udata are in kernel data.
+	;
+	ldx	#kstack_base
+	lda	#$FF
+fork_patch_3:
+	mvn	0,0
+.endif
+	;
+	;	Clone DP and stack between parent and child
+	;
+	ldx	ptr2		; in DP
+	ldy	ptr3		; in DP
 	lda	#$01FF		; DP and stack
+
 	mvn	0,0
+	plb			; back to corect bank register
 
 	;
 	;	Final hairy detail - the child S value needs to be shifted
diff --git a/Kernel/platform-v65c816-big/README b/Kernel/platform-v65c816-big/README
index cecbb9a8..2bfbee1e 100644
--- a/Kernel/platform-v65c816-big/README
+++ b/Kernel/platform-v65c816-big/README
@@ -49,13 +49,6 @@ make
 
 TODO
 ----
-- Fix task switching: on big model our udata is in bank 2 and our kstack
-  ring 0 so we can't save them as single 512 byte xfer but as we know we
-  won't be using nearly all the 512 bytes of C stack we can save udata and
-  most of C stack just fine.
 - See 65c816 port for general notes
 - Save jmpvec+1/2 in seg 2 on IRQ entry and restore on exit
 
-Optimisations We Need To Do
---------------------------------------------------------------
-- Only copy the needed memory when forking, not 64K ?
diff --git a/Kernel/platform-v65c816-big/commonmem.s b/Kernel/platform-v65c816-big/commonmem.s
index 1fcdcb41..1f25fc48 100644
--- a/Kernel/platform-v65c816-big/commonmem.s
+++ b/Kernel/platform-v65c816-big/commonmem.s
@@ -6,6 +6,7 @@
         .export _ub
         .export _udata
         .export kstack_top
+	.export kstack_base
 	.export kstackc_top
         .export istack_top
 	.export istackc_top
@@ -23,8 +24,8 @@
 ;	stack and a small CPU stack in the banking
 ;
 ;	Our current layout is
-;	[udata][C stack]		256 bytes
-;	[C stack]			256 
+;	[udata]				~256 bytes (279 with L2)
+;	[C stack]			256  (or thereabouts)
 ;
 ;	There is a separate IRQ DP, stack and C stack.
 ;
@@ -33,6 +34,7 @@ _udata:
 kstackc_base:
 	.res 512,0
 kstackc_top:
+	; and our saved area follows this by a copy of kstack
 
 ;
 ;	We have a single istack so we can stuff that anywhere we like
diff --git a/Kernel/platform-v65c816-big/config.h b/Kernel/platform-v65c816-big/config.h
index e64dde5a..48e2c001 100644
--- a/Kernel/platform-v65c816-big/config.h
+++ b/Kernel/platform-v65c816-big/config.h
@@ -26,8 +26,8 @@
  */
 #define CONFIG_BANK_65C816
 #define KERNEL_BANK	2
-#define MAX_MAPS 	125
-#define MAP_SIZE    0xFC00  /* 0-FBFF */
+#define MAX_MAPS	125
+#define MAP_SIZE    0xFB00  /* 0-FAFF */
 
 /* 0xEE because our first bank is 1 and 0xEE + 2 * 1 = 0xF0 */
 #define STACK_BANKOFF	0x00	/* 0400-FDFF */
@@ -36,7 +36,7 @@
 #define MAPBASE	    0x0000  /* We map from 0 */
 #define PROGBASE    0x0100  /* also data base */
 #define PROGLOAD    0x0100
-#define PROGTOP     0xFC00  /* Top of program. If we fixed a few things we
+#define PROGTOP     0xFB00  /* Top of program. If we fixed a few things we
                                could go to FE00 */
 
 #define BOOT_TTY 513        /* Set this to default device for stdio, stderr */
diff --git a/Kernel/platform-v65c816-big/kernel.def b/Kernel/platform-v65c816-big/kernel.def
index 338eaa22..b657e536 100644
--- a/Kernel/platform-v65c816-big/kernel.def
+++ b/Kernel/platform-v65c816-big/kernel.def
@@ -4,7 +4,7 @@
 U_DATA                  .set $0100	; avoid ZP
 ; 256+256		(U, kstack copy, k C stack copy)
 U_DATA__TOTALSIZE       .set $0200
-U_DATA_STASH		.set $FC00	; leaves FFxx for vectors and stubs
+U_DATA_STASH		.set $FB00	; leaves FFxx for vectors and stubs
 
 PROGLOAD		.set $0100
 ZPBASE			.set $0
@@ -21,6 +21,6 @@ STACK_BANKOFF		.set $FE	; 0400-FDFF
 IRQ_DP			.set $FF80	; FF80-FFBF
 KERNEL_DP		.set $00	; We use the real ZP for kernel DP
 
-MAP_SIZE		.set $FC00
+MAP_SIZE		.set $FB00
 
 PROGBASE		.set $0100
diff --git a/Kernel/platform-v65c816/README b/Kernel/platform-v65c816/README
index 2ba03d85..3be44e5c 100644
--- a/Kernel/platform-v65c816/README
+++ b/Kernel/platform-v65c816/README
@@ -36,7 +36,6 @@ the emulator.
 
 TODO
 ----
-- Test revized brk() checking
 - Add swap logic
 - Relocatable binaries
 - cc65 stubs optimized for 65c816
@@ -48,3 +47,10 @@ TODO
 Optimisations We Need To Do
 --------------------------------------------------------------
 - Only copy the needed memory when forking, not 64K ?
+- Can we keep udata in kernel ZP (at least for level 1). Would need to
+  audit that we don't take pointers to ZP but might be faster and we
+  need to do the same audit for some cases with 68K etc anyway
+- Can we put the kernel per process CPU stack (kstack) into the upper half
+  of ZP for each process. We don't need 256 bytes of ZP per process
+- Can we trim down to say 64 bytes ZP + 256 stack per process so we can go
+  above 8MB - do we care ??