[OpenBIOS] [PATCH] arch/ppc/qemu: Moved exception handlers from beginning of RAM

[BALATON Zoltan]

Do not put exception handler routines between 0x00-0xff as some OSes
use this area for their own purposes and can corrupt them. (In
particular MorphOS writes to 0x80 during boot). This patch frees up
this area by moving the routines that were there higher.

Signed-off-by: BALATON Zoltan <balaton at eik.bme.hu>
---

This replaces my previous attempt (Use exception vectors from ROM
instead of copying them to page zero) as that relied on the MSR[IP]
bit that was found not to be generally available.

Index: openbios-devel/arch/ppc/qemu/start.S
===================================================================
--- openbios-devel/arch/ppc/qemu/start.S	(revision 1304)
+++ openbios-devel/arch/ppc/qemu/start.S	(working copy)
@@ -280,21 +280,9 @@ GLOBL(__vectors):
 1:	nop			//
 	b	1b
 
-call_dsi_exception:
-	LOAD_REG_FUNC(r3, dsi_exception)
-	mtctr	r3
-	bctrl
-	b	exception_return
+VECTOR( 0x100, "SRE" ):
+        b       _entry
 
-call_isi_exception:
-	LOAD_REG_FUNC(r3, isi_exception)
-	mtctr	r3
-	bctrl
-	b	exception_return
-
-exception_return:
-	EXCEPTION_EPILOGUE
-
 trap_error:
 	lis	r1, 0x8000			/* r1=0x80000000 */
 	add.	r1,r1,r1			/* r1=r1+r1 (high 32bit !0) */
@@ -309,9 +297,6 @@ trap_error:
 	mtctr r4
 	bctr
 
-VECTOR( 0x100, "SRE" ):
-        b       _entry
-
 ILLEGAL_VECTOR( 0x200 )
 
 VECTOR( 0x300, "DSI" ):
@@ -373,11 +358,16 @@ VECTOR( 0x2200, "ISI_64" ):
 
 real_dsi:
 	EXCEPTION_PREAMBLE
-	b	call_dsi_exception
+	LOAD_REG_FUNC(r3, dsi_exception)
+	b call_exception_handler
 
 real_isi:
 	EXCEPTION_PREAMBLE
-	b	call_isi_exception
+	LOAD_REG_FUNC(r3, isi_exception)
+call_exception_handler:
+	mtctr	r3
+	bctrl
+	EXCEPTION_EPILOGUE
 
 GLOBL(__vectors_end):