[RFCv3] PPC: Mimic Apple's OpenFirmware behaviour if a divide by zero occurs.

[Mark Cave-Ayland]

As reported by Amadeusz Sławiński using a real Mac, if anything is divided by
zero then we should return zero:

0 > 2 0 /  ok
1 > u. 0  ok

This resolves a bug in BootX which (un)intentionally divides by zero during
boot.

Signed-off-by: Mark Cave-Ayland 
---
 openbios-devel/arch/ppc/qemu/init.c  |    8 ++++++++
 openbios-devel/arch/ppc/qemu/start.S |    1 -
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/openbios-devel/arch/ppc/qemu/init.c b/openbios-devel/arch/ppc/qemu/init.c
index dfc201f..a8fc320 100644
--- a/openbios-devel/arch/ppc/qemu/init.c
+++ b/openbios-devel/arch/ppc/qemu/init.c
@@ -59,6 +59,14 @@ unexpected_excep(int vector)
     }
 }

+extern void __divide_error(void);
+
+void
+__divide_error(void)
+{
+    return;
+}
+
 enum {
     ARCH_PREP = 0,
     ARCH_MAC99,
diff --git a/openbios-devel/arch/ppc/qemu/start.S b/openbios-devel/arch/ppc/qemu/start.S
index 77ced18..5c86d74 100644
--- a/openbios-devel/arch/ppc/qemu/start.S
+++ b/openbios-devel/arch/ppc/qemu/start.S
@@ -295,7 +295,6 @@ call_isi_exception:
 exception_return:
    EXCEPTION_EPILOGUE

-_GLOBAL(__divide_error):
 trap_error:
    mflr	r3
    LOAD_REG_FUNC(r4, unexpected_excep)