Re: [PATCH] target/s390x/tcg: SPX: check validity of new prefix

[David Hildenbrand]

On 27.06.22 15:12, Janis Schoetterl-Glausch wrote:
> According to the architecture, SET PREFIX must try to access the new
> prefix area and recognize an addressing exception if the area is not
> accessible.
> For qemu this check prevents a crash in cpu_map_lowcore after an
> inaccessible prefix area has been set.

I don't think that's possible. Our memory increments are 1 MiB and one
would have to cross a 1~MiB range with the second page to trigger that.
IIRC that's impossible with SPX address alignment requirements?


> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
> 
> 
> Is there a stricter check to see if the memory is accessible?
> 
> 
>  target/s390x/tcg/misc_helper.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target/s390x/tcg/misc_helper.c b/target/s390x/tcg/misc_helper.c
> index aab9c47747..c8447b36fc 100644
> --- a/target/s390x/tcg/misc_helper.c
> +++ b/target/s390x/tcg/misc_helper.c
> @@ -158,6 +158,10 @@ void HELPER(spx)(CPUS390XState *env, uint64_t a1)
>      if (prefix == old_prefix) {
>          return;
>      }
> +    if (!mmu_absolute_addr_valid(prefix, true) ||
> +        !mmu_absolute_addr_valid(prefix + TARGET_PAGE_SIZE, true)) {
> +        tcg_s390_program_interrupt(env, PGM_ADDRESSING, GETPC());
> +    }
>  
>      env->psa = prefix;
>      HELPER_LOG("prefix: %#x\n", prefix);
> 
> base-commit: 3a821c52e1a30ecd9a436f2c67cc66b5628c829f


-- 
Thanks,

David / dhildenb