[PATCH 14/28] elf: Enhance ld.so --help to print HWCAP subdirectories

[Adhemerval Zanella]

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

On 01/10/2020 13:33, Florian Weimer via Libc-alpha wrote:
> ---
>  elf/dl-usage.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
> 
> diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> index 20aa715cb1..9765d1b5c1 100644
> --- a/elf/dl-usage.c
> +++ b/elf/dl-usage.c
> @@ -22,6 +22,8 @@
>  #include <unistd.h>
>  #include "version.h"
>  
> +#include <dl-hwcaps.h>
> +
>  void
>  _dl_usage (const char *argv0, const char *wrong_option)
>  {
> @@ -101,6 +103,65 @@ print_search_path_for_help (struct dl_main_state *state)
>    print_search_path_for_help_1 (__rtld_search_dirs.dirs);
>  }
>  
> +/* Helper function for printing flags associated with a HWCAP name.  */
> +static void
> +print_hwcap_1 (bool *first, bool active, const char *label)
> +{
> +  if (active)
> +    {
> +      if (*first)
> +        {
> +          _dl_printf (" (");
> +          *first = false;
> +        }
> +      else
> +        _dl_printf (", ");
> +      _dl_printf ("%s", label);
> +    }
> +}
> +
> +/* Called after a series of print_hwcap_1 calls to emit the line
> +   terminator.  */
> +static void
> +print_hwcap_1_finish (bool *first)
> +{
> +  if (*first)
> +    _dl_printf ("\n");
> +  else
> +    _dl_printf (")\n");
> +}
> +
> +/* Write a list of hwcap subdirectories to standard output.  See
> + _dl_important_hwcaps in dl-hwcaps.c.  */
> +static void
> +print_legacy_hwcap_directories (void)
> +{
> +  _dl_printf ("\n\
> +Legacy HWCAP subdirectories under library search path directories:\n");
> +
> +  const char *platform = GLRO (dl_platform);
> +  if (platform != NULL)
> +    _dl_printf ("  %s (AT_PLATFORM)\n", platform);
> +
> +  _dl_printf ("  tls (supported, searched)\n");
> +
> +  uint64_t hwcap_mask = GET_HWCAP_MASK();
> +  uint64_t searched = GLRO (dl_hwcap) & hwcap_mask;
> +  for (int n = 63; n >= 0; --n)
> +    {
> +      uint64_t bit = 1ULL << n;

UINT64_C(1) maybe?

> +      if (HWCAP_IMPORTANT & bit)
> +        {
> +          _dl_printf ("  %s", _dl_hwcap_string (n));
> +          bool first = true;
> +          print_hwcap_1 (&first, GLRO (dl_hwcap) & bit, "supported");
> +          print_hwcap_1 (&first, !(hwcap_mask & bit), "masked");
> +          print_hwcap_1 (&first, searched & bit, "searched");
> +          print_hwcap_1_finish (&first);
> +        }
> +    }
> +}
> +

Ok.

>  void
>  _dl_help (const char *argv0, struct dl_main_state *state)
>  {
> @@ -136,5 +197,6 @@ This program interpreter self-identifies as: " RTLD "\n\
>  ",
>                argv0);
>    print_search_path_for_help (state);
> +  print_legacy_hwcap_directories ();
>    _exit (0);
>  }
> 

Ok.