[PATCH] ppc: Don't do relative branches from relocated memory

[Andreas Färber]

On startup, OpenBIOS copies exception vectors to 0x00000000.
Therefore jumps cannot be performed relative to the compile-time address
to outside the relocated exception vectors.

QEMU's g3beige and mac99 did not run into this so far, but prep does.

Signed-off-by: Andreas Färber 
---
 arch/ppc/qemu/start.S |    4 +++-
 1 Datei geändert, 3 Zeilen hinzugefügt(+), 1 Zeile entfernt(-)

diff --git a/arch/ppc/qemu/start.S b/arch/ppc/qemu/start.S
index 5c86d74..66987a0 100644
--- a/arch/ppc/qemu/start.S
+++ b/arch/ppc/qemu/start.S
@@ -302,7 +302,9 @@ trap_error:
    bctr

VECTOR( 0x100, "SRE" ):
-        b       _entry
+    LOAD_REG_IMMEDIATE(r3, _entry)
+    mtctr r3
+    bctr

ILLEGAL_VECTOR( 0x200 )

[PATCH] ppc: Don't do relative branches from relocated memory

[Alexander Graf]

On 24.02.2013, at 23:32, Andreas Färber wrote:
> On startup, OpenBIOS copies exception vectors to 0x00000000.
> Therefore jumps cannot be performed relative to the compile-time address
> to outside the relocated exception vectors.
>
> QEMU's g3beige and mac99 did not run into this so far, but prep does.
>
> Signed-off-by: Andreas Färber

This sounds wrong. You shouldn't get to 0x100 in RAM. It's the reset vector!

Alex
> arch/ppc/qemu/start.S |    4 +++-
> 1 Datei geändert, 3 Zeilen hinzugefügt(+), 1 Zeile entfernt(-)
>
> diff --git a/arch/ppc/qemu/start.S b/arch/ppc/qemu/start.S
> index 5c86d74..66987a0 100644
> --- a/arch/ppc/qemu/start.S
> +++ b/arch/ppc/qemu/start.S
> @@ -302,7 +302,9 @@ trap_error:
>    bctr
>
> VECTOR( 0x100, "SRE" ):
>    b       _entry
> LOAD_REG_IMMEDIATE(r3, _entry)
> mtctr r3
> bctr
>
> ILLEGAL_VECTOR( 0x200 )