From: Alan Cox <alan@linux.intel.com>
Date: Fri, 4 May 2018 09:02:19 +0000 (+0100)
Subject: 6809: remove the old SAM hacks
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=df0629f4eecb7828a7c8c6f8cbd659bb7db9f7c2;p=FUZIX.git

6809: remove the old SAM hacks

It's a crazy way to run a system and it messes up stuff for everything else.
We don't use it since removing the original dragon hack kernel.
---

diff --git a/Kernel/lowlevel-6809.s b/Kernel/lowlevel-6809.s
index 6ca05478..e81e80b3 100644
--- a/Kernel/lowlevel-6809.s
+++ b/Kernel/lowlevel-6809.s
@@ -68,33 +68,18 @@
 ;
 ; Called by swi, which has already saved our CPU state for us
 ;
-; The lack of shared RAM leads to the rather ugly SAM_ macros needing to
-; be here for SAM based boxes as we have no valid stack at this point
-;
 unix_syscall_entry:
-	SAM_KERNEL	; stack now invalid
-
 	leax 14,s	; 12 stacked by the swi + return address of caller
 	ldy #U_DATA__U_ARGN
-	SAM_USER
 	ldd 4,s		; first argument in swi stacked X
-	SAM_KERNEL
 	std ,y++
-	SAM_USER
 	ldd ,x++	; second argument from caller's stack
-	SAM_KERNEL
 	std ,y++
-	SAM_USER
 	ldd ,x++ 	; third
-	SAM_KERNEL
 	std ,y++
-	SAM_USER
 	ldd ,x++ 	; fourth
-	SAM_KERNEL
 	std ,y++
-	SAM_USER
 	ldd 1,s		; stacked D register -> syscall number
-	SAM_KERNEL
 	stb U_DATA__U_CALLNO
         ; save process stack pointer (in user page)
         sts U_DATA__U_SYSCALL_SP
@@ -125,14 +110,11 @@ unix_syscall_entry:
 
         ; switch back to user stack
         lds U_DATA__U_SYSCALL_SP
-	; stack is no longer valid
 
-	SAM_USER
 	; stack is now valid but user stack
         ; check for signals, call the handlers
         jsr dispatch_process_signal
 
-	SAM_KERNEL
         ; check if error condition to be signalled on return
         ldd U_DATA__U_ERROR
 	beq not_error
@@ -145,18 +127,14 @@ not_error:
         ldx U_DATA__U_RETVAL
 unix_return:
 	; we never make a syscall from in kernel space
-	SAM_USER
 	stx 4,s		; replace stacked values before rti
 	std 1,s
 	rti
-
 ;
-;	In SAM land this function is called on the user stack with the user
-;	memory mapped, we must rts on the right bank !
+;	We must rts on the right bank !
 ;
 dispatch_process_signal:
         ; check if any signal outstanding
-	SAM_KERNEL
         ldb U_DATA__U_CURSIG
         beq dosigrts
         ; put number in X as the argument for the signal handler
@@ -165,9 +143,6 @@ dispatch_process_signal:
 	tfr d,x
 
 	lslb		;	2 bytes per entry
-;
-;	FIXME: must save Y for same ??
-;
         ; load the address of signal handler function
 	ldy #U_DATA__U_SIGVEC
 	ldu b,y		; now u = udata.u_sigvec[cursig]
@@ -183,7 +158,6 @@ dispatch_process_signal:
 	clr ,y
 
         ldy #signal_return
-	SAM_USER
         pshs y      ; push return address
 
         andcc #0xef
@@ -191,12 +165,7 @@ dispatch_process_signal:
 
 signal_return:
         orcc #0x10
-;
-;	FIXME: port over the Z80 loop and check for next signal
-;
 dosigrts:
-	; right stack for the rts instruction
-	SAM_USER
         rts
 
 _doexec:
@@ -215,7 +184,6 @@ _doexec:
 	; At this point the stack goes invalid
         lds U_DATA__U_ISP
 	andcc #0xef			; IRQs on
-	SAM_USER			; Stack valid, go to user code
         jmp ,x
 
 ;
@@ -223,18 +191,7 @@ _doexec:
 ;	poll ttys from it. The more logic we could move to common here the
 ;	better.
 ;
-;	For SAM based machines this involves some craziness as we have no
-;	common inter-bank RAM. In the SAM case we will always enter with
-;	the kernel mapped, but our stack on entry is likely to be invalid
-;
-;	Thus we have to have inlined SAM conditionals - bletch
-;
-;	Y is used for the SAM logic so preserve it always
-;
 interrupt_handler:
-	    SAM_SAVE		; loads Y
-	    SAM_KERNEL
-
 	    ; Do not use the stack before the switch...
 
 	    ; FIXME: add profil support here (need to keep profil ptrs
@@ -245,16 +202,12 @@ interrupt_handler:
 
             ; switch stacks
             sts istack_switched_sp
-	    ; Unlike Z80 even the istack is banked, it's only valid on some
-	    ; SAM based boxes when SAM_KERNEL is true
             lds #istack_top-2
 	    ; FIXME: check store/dec order might not need to be -2 here!!!!
 
 	    jsr map_save
 
-	    SAM_USER
 	    lda 0		; save address 0 contents for checking
-	    SAM_KERNEL
 
 	    ; preserves registers
 	    jsr map_kernel
@@ -286,9 +239,6 @@ in_kernel:
 	    ; _need_resched, and will only do so if the caller was in
 	    ; user space so has a free kernel stack
 
-	    ;
-	    ; Y is caller saves so we'll get the right Y back
-	    ; for our SAM_RESTORE
             jsr _platform_interrupt
 
             clr _inint
@@ -319,8 +269,6 @@ in_kernel:
 	    ; the user stack and map ourself in
 	    jsr map_process_always
 	    lds U_DATA__U_SYSCALL_SP
-	    ; do the map on the user stack (for SAM switching)
-	    SAM_USER
 	    bra intdone
 
 	    ; Not task switching - the easy and usual path
@@ -331,18 +279,15 @@ no_switch:
 	    ; pre-emption is handled differently...
 	    jsr map_restore
 	    lds istack_switched_sp
-	    SAM_USER
 
 intdone: 
             ; we're not in kernel mode, check for signals
-	    ; runs off the user stack so need user ram mapped on a SAM
-	    ; based platform
+	    ; runs off the user stack
 	    pshs y
             jsr dispatch_process_signal
 	    puls y
 
 interrupt_return:
-	    SAM_RESTORE			; uses the saved Y
             rti
 interrupt_return_x:
 	    tfr x,s
@@ -358,11 +303,9 @@ trap_signal:
 
 ;  Called from process context (hopefully)
 null_handler:
-	    SAM_KERNEL
 	    ; kernel jump to NULL is bad
 	    lda U_DATA__U_INSYS
 	    beq trap_illegal
-	    SAM_USER
 	    ; user is merely not good
 	    ; check order of push arguments !!
             ldx #7
@@ -394,7 +337,6 @@ nmimsg:     .ascii "[NMI]"
             .db 13,10,0
 
 nmi_handler:
-	SAM_KERNEL
 	lds #istack_top-2		; We aren't coming back so this is ok
 	jsr map_kernel
         ldx #nmimsg