Re: [Qemu-devel] [PATCH v2 3/3] m68k: fix usp processing on interrupt entry and exception exit

[Laurent Vivier <laurent@vivier.eu>]

Le 19/06/2015 15:43, gerg@uclinux.org a écrit :
> From: Greg Ungerer <gerg@uclinux.org>
> 
> The action to potentially switch sp register is not occurring at the correct
> point in the interrupt entry or exception exit sequences.
> 
> For the interrupt entry case the sp on entry is used to create the stack
> exception frame - but this may well be the user stack pointer, since we
> haven't done the switch yet. Re-order the flow to switch the sp regs then
> use the current sp to create the exception frame.
> 
> For the return from exception case the code is unwinding the sp after
> switching sp registers. But it should always unwind the supervisor sp
> first, then carry out any required sp switch.
> 
> Note that these problems don't effect operation unless the user sp bit is
> set in the CACR register. Only a single sp is used in the default power up
> state. Previously Linux only used this single sp mode. But modern versions
> of Linux use the user sp mode now, so we need correct behavior for Linux
> to work.
> 
> Signed-off-by: Greg Ungerer <gerg@uclinux.org>
> Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
> ---
>  target-m68k/op_helper.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

Reviewed-by: Laurent Vivier <laurent@vivier.eu>