Re: [kvm-unit-tests PATCH v2] powerpc: restore TOC pointer

[Thomas Huth <thuth@redhat.com>]

On 22.04.2016 13:12, Laurent Vivier wrote:
> As the TOC pointer can be corrupted by the main program,
> we must restore it in the exception handler.
> 
> As we know where we are loaded, we can now compute it easily.
> 
> To compute it only in the common part of the exception handler
> (call_handler), store the address of call_handler at an absolute
> address in memory to be able to call the handler from the exception
> table (as SLOF does).
> 
> Reported-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> v2: don't add SPAPR_KERNEL_LOAD_ADDR to r2 as
>     the TOC has been relocated and have directly the good
>     value. The problem has been reported by Thomas.

This seems to fix the issue with the emulator invalid-instruction test.
Thanks!

 Thomas


>  powerpc/cstart64.S | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> index c47b67d..2d66032 100644
> --- a/powerpc/cstart64.S
> +++ b/powerpc/cstart64.S
> @@ -13,6 +13,8 @@
>  
>  #include "spapr.h"
>  
> +#define P_HANDLER	0x2ff8
> +
>  .section .init
>  
>  /*
> @@ -46,6 +48,11 @@ start:
>  	add	r4, r4, r31
>  	bl	relocate
>  
> +	/* compute address of call_handler */
> +
> +	LOAD_REG_ADDR(r4, call_handler)
> +	std	r4, P_HANDLER(0)
> +
>  	/* relocate vector table to base address 0x0 (MSR_IP = 0) */
>  
>  	/* source: r4, dest end: r5, destination: r6 */
> @@ -166,6 +173,11 @@ call_handler:
>  	mfsrr1	r0
>  	std	r0, _MSR(r1)
>  
> +	/* restore TOC pointer */
> +
> +	LOAD_REG_IMMEDIATE(r31, SPAPR_KERNEL_LOAD_ADDR)
> +	ld	r2, (p_toc - start)(r31)
> +
>  	/* FIXME: build stack frame */
>  
>  	/* call generic handler */
> @@ -221,7 +233,7 @@ call_handler:
>  	mfctr	r0
>  	std	r0,_CTR(r1)
>  
> -	LOAD_REG_ADDR(r0, call_handler)
> +	ld	r0, P_HANDLER(0)
>  	mtctr	r0
>  
>  	li	r0,\vec
> @@ -245,3 +257,5 @@ VECTOR(0x900)
>  	.align 7
>  	.globl __end_interrupts
>  __end_interrupts:
> +	.org	P_HANDLER
> +	.llong	0
>