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

Thomas Huth
2023-03-27T14:39:57Z

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@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