From: Alan Cox <alan@linux.intel.com>
Date: Fri, 17 Jul 2015 22:27:53 +0000 (+0100)
Subject: lowlevel-z80: set insys when pre-empting, fix a scribble in some modes
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=3984cf3d985f5e615c5438943b08020af14a5b17;p=FUZIX.git

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 95c72ed3..a323d344 100644
--- 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 f8499bf4..094787e4 100644
--- 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