Re: [PATCH v2 08/17] exec: Add support for TARGET_TAGGED_ADDRESSES

[Peter Maydell]

On Fri, 5 Jun 2020 at 05:17, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The AArch64 Linux ABI has always enabled TBI, but has historically
> required that pointer tags be removed before a syscall.  This has
> changed in the lead-up to ARMv8.5-MTE, in a way that affects the
> ABI generically and not specifically to MTE.
>
> This patch allows the target to indicate that (1) there are tags
> and (2) whether or not they should be taken into account at the
> syscall level.
>
> Adjust g2h, guest_addr_valid, and guest_range_valid to ignore
> pointer tags, similar to how TIF_TAGGED_ADDR alters __range_ok
> in the arm64 kernel source.
>
> The prctl syscall is not not yet updated, so this change by itself
> has no visible effect.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/exec/cpu_ldst.h | 22 ++++++++++++++++++----
>  target/arm/cpu-param.h  |  3 +++
>  bsd-user/main.c         |  5 +++++
>  linux-user/main.c       |  5 +++++
>  4 files changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
> index 066cf33f70..d84847dc70 100644
> --- a/include/exec/cpu_ldst.h
> +++ b/include/exec/cpu_ldst.h
> @@ -69,17 +69,31 @@ typedef uint64_t abi_ptr;
>  #define TARGET_ABI_FMT_ptr "%"PRIx64
>  #endif
>
> +#ifdef TARGET_TAGGED_ADDRESSES
> +extern abi_ptr untagged_addr_mask;
> +static inline abi_ptr untagged_addr(abi_ptr x)
> +{
> +    return x & untagged_addr_mask;
> +}
> +#else
> +static inline abi_ptr untagged_addr(abi_ptr x) { return x; }
> +#endif
> +
>  /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
> -#define g2h(x) ((void *)((unsigned long)(abi_ptr)(x) + guest_base))
> +static inline void *g2h(abi_ptr x)
> +{
> +    return (void *)(uintptr_t)(untagged_addr(x) + guest_base);
> +}
>
>  static inline bool guest_addr_valid(abi_ptr x)
>  {
> -    return x <= GUEST_ADDR_MAX;
> +    return untagged_addr(x) <= GUEST_ADDR_MAX;
>  }
>
> -static inline int guest_range_valid(unsigned long start, unsigned long len)
> +static inline bool guest_range_valid(abi_ptr start, abi_ulong len)

More type changes...

>  {
> -    return len - 1 <= GUEST_ADDR_MAX && start <= GUEST_ADDR_MAX - len + 1;
> +    return len - 1 <= GUEST_ADDR_MAX &&
> +           untagged_addr(start) <= GUEST_ADDR_MAX - len + 1;
>  }
>
>  #define h2g_valid(x)  ((uintptr_t)(x) - guest_base <= GUEST_ADDR_MAX)

otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM