Re: [PATCH 1/1] util/getauxval: Porting to FreeBSD getauxval feature

[Thomas Huth <thuth@redhat.com>]

On 24/05/2020 14.09, David CARLIER wrote:
> Hi here porting qemu_getauxval to FreeBSD. Thanks. Regards.
> 
> From 5be5e56a59631b28ed7b738d251dda252ba9b03e Mon Sep 17 00:00:00 2001
> From: David Carlier <devnexen@gmail.com>
> Date: Sun, 24 May 2020 13:03:32 +0100
> Subject: [PATCH] util/getauxval: FreeBSD has a similar auxilary vector API
> 
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
>  configure        | 6 ++++++
>  util/getauxval.c | 6 ++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/configure b/configure
> index 2fc05c4465..545fd2364f 100755
> --- a/configure
> +++ b/configure
> @@ -5824,7 +5824,13 @@ getauxval=no
>  cat > $TMPC << EOF
>  #include <sys/auxv.h>
>  int main(void) {
> +#if defined(__linux__)
>    return getauxval(AT_HWCAP) == 0;
> +#elif defined(__FreeBSD__)
> +  unsigned long a = 0;
> +  return elf_aux_info(AT_HWCAP, &a, sizeof(a)) == 0;
> +#endif
> +  return 1;
>  }
>  EOF
>  if compile_prog "" "" ; then

That configure check looks wrong. On other systems (i.e. non-Linux and
non-FreeBSD), this code snippet will now compile successfully and thus
the configure script sets getauxval=yes. I'd suggest you change it this
way instead:

 int main(void) {
+#if defined(__FreeBSD__)
+  unsigned long a = 0;
+  return elf_aux_info(AT_HWCAP, &a, sizeof(a)) == 0;
+#else
   return getauxval(AT_HWCAP) == 0;
+#endif
 }

... so that it still fails to compile by default on other systems.

 Thomas