Re: [Qemu-devel] [PATCH] cpu-all.h: Don't accidentally sign extend in g2h()

[Anthony Liguori]

On 03/09/2012 08:33 AM, Peter Maydell wrote:
> Cast the argument of the g2h() macro to a target_ulong so that
> it isn't accidentally sign-extended if it is a signed 32 bit
> type and long is a 64 bit type. In particular, this fixes a
> bug where it would return the wrong value for 32 bit guests
> on 64 bit hosts when passed in one of the arg* values from
> do_syscall() [which are all abi_long and thus signed types].
> This could result in spurious failure of mlock(), among others.
>
> Signed-off-by: Peter Maydell<address@hidden>
> ---

Applied.  Thanks.

Regards,

Anthony Liguori

> This should be committed before Alex's patch to make mmap allocate
> downwards (http://patchwork.ozlabs.org/patch/144476/) because that
> hugely increases the chances that g2h will get passed a pointer
> that has the high bit set.
>
>   cpu-all.h |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/cpu-all.h b/cpu-all.h
> index 80e6d42..a174532 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -197,7 +197,7 @@ extern unsigned long reserved_va;
>   #endif
>
>   /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
> -#define g2h(x) ((void *)((unsigned long)(x) + GUEST_BASE))
> +#define g2h(x) ((void *)((unsigned long)(target_ulong)(x) + GUEST_BASE))
>
>   #if HOST_LONG_BITS<= TARGET_VIRT_ADDR_SPACE_BITS
>   #define h2g_valid(x) 1