[kvm-unit-tests v3 03/13] powerpc: Add some checking to exception handler install

[Thomas Huth]

On 27/03/2023 14.45, Nicholas Piggin wrote:
> Check to ensure exception handlers are not being overwritten or
> invalid exception numbers are used.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
> Since v2:
> - New patch
> 
>   lib/powerpc/processor.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
> index ec85b9d..70391aa 100644
> --- a/lib/powerpc/processor.c
> +++ b/lib/powerpc/processor.c
> @@ -19,11 +19,23 @@ static struct {
>   void handle_exception(int trap, void (*func)(struct pt_regs *, void *),
>   		      void * data)
>   {
> +	if (trap & 0xff) {

You could check for the other "invalid exception handler" condition here 
already, i.e. if (trap & ~0xf00) ...

I'd maybe simply do an "assert(!(trap & ~0xf00))" here.

> +		printf("invalid exception handler %#x\n", trap);
> +		abort();
> +	}
> +
>   	trap >>= 8;
>   
>   	if (trap < 16) {

... then you could get rid of the if-statement here and remove one level of 
indentation in the code below.

> +		if (func && handlers[trap].func) {
> +			printf("exception handler installed twice %#x\n", trap);
> +			abort();
> +		}
>   		handlers[trap].func = func;
>   		handlers[trap].data = data;
> +	} else {
> +		printf("invalid exception handler %#x\n", trap);
> +		abort();
>   	}
>   }
>   

  Thomas