lowlevel-z80: set insys when pre-empting, fix a scribble in some modes

We must update the udata before mapping process memory as we are not
guaranteed that won't vanish the udata.

Set u_insys so that the following case cannot occur once we begin loosening
irq disabled areas

IRQ
	pre-empt
	ei
	swapper()

	IRQ
		pre-empt
		*boom*

diff --git a/Kernel/lowlevel-z80-banked.s b/Kernel/lowlevel-z80-banked.s
index 95c72ed..a323d34 100644 (file)
--- a/Kernel/lowlevel-z80-banked.s
+++ b/Kernel/lowlevel-z80-banked.s
@@ -516,6 +516,14 @@ preemption:
 
        ;
 intret2:call map_kernel
+
+       ;
+       ; Semantically we are doing a null syscall for pre-empt. We need
+       ; to record ourselves as in a syscall so we can't be recursively
+       ; pre-empted when switchout re-enables interrupts.
+       ;
+       ld a, #1
+       ld (U_DATA__U_INSYS), a
        ;
        ; Process status is offset 0
        ;
@@ -523,15 +531,17 @@ intret2:call map_kernel
        ld (hl), #P_READY
        call _switchout
        ;
+       ; We are no longer in an interrupt or a syscall
+       ;
+       xor a
+       ld (U_DATA__U_ININTERRUPT), a
+       ld (U_DATA__U_INSYS), a
+       ;
        ; We have been rescheduled, remap ourself and go back to user
        ; space via signal handling
        ;
        call map_process_always ; Get our user mapping back
 
-       ; We are no longer in an interrupt
-       xor a
-       ld (U_DATA__U_ININTERRUPT), a
-
        ; We were pre-empted but have now been rescheduled
        ; User stack
        ld sp, (U_DATA__U_SYSCALL_SP)

diff --git a/Kernel/lowlevel-z80.s b/Kernel/lowlevel-z80.s
index f8499bf..094787e 100644 (file)
--- a/Kernel/lowlevel-z80.s
+++ b/Kernel/lowlevel-z80.s
@@ -508,6 +508,14 @@ preemption:
 
        ;
 intret2:call map_kernel
+
+       ;
+       ; Semantically we are doing a null syscall for pre-empt. We need
+       ; to record ourselves as in a syscall so we can't be recursively
+       ; pre-empted when switchout re-enables interrupts.
+       ;
+       ld a, #1
+       ld (U_DATA__U_INSYS), a
        ;
        ; Process status is offset 0
        ;
@@ -515,14 +523,17 @@ intret2:call map_kernel
        ld (hl), #P_READY
        call _switchout
        ;
+       ; We are no longer in an interrupt or a syscall
+       ;
+       xor a
+       ld (U_DATA__U_ININTERRUPT), a
+       ld (U_DATA__U_INSYS), a
+       ;
        ; We have been rescheduled, remap ourself and go back to user
        ; space via signal handling
        ;
        call map_process_always ; Get our user mapping back
 
-       ; We are no longer in an interrupt
-       xor a
-       ld (U_DATA__U_ININTERRUPT), a
 
        ; We were pre-empted but have now been rescheduled
        ; User stack