[PATCH] Fix static-binary lazy FPU context allocation

[Carlos O'Donell]

On 08/22/2013 03:12 PM, Maciej W. Rozycki wrote:
>  No regressions in mips-linux-gnu testing, o32, n64 and n32 ABIs.  OK to 
> apply?

What existing test case checks for this?

Could you please add a static test that verifies this is set correctly?

> 2013-08-22  Maciej W. Rozycki  <macro@codesourcery.com>
> 
> 	* csu/init-first.c (_init): Remove the !SHARED condition around
> 	FPU control word initialization.
> 	* elf/dl-support.c (_dl_fpu_control): New variable.
> 	(_dl_aux_init) <AT_FPUCW>: Initialize it.
> 
>   Maciej
> 
> glibc-static-fpucw.diff
> Index: glibc-fsf-trunk-quilt/csu/init-first.c
> ===================================================================
> --- glibc-fsf-trunk-quilt.orig/csu/init-first.c	2013-05-07 22:59:41.000000000 +0100
> +++ glibc-fsf-trunk-quilt/csu/init-first.c	2013-08-22 19:46:48.168109470 +0100
> @@ -61,11 +61,8 @@ _init (int argc, char **argv, char **env
>    if (!__libc_multiple_libcs)
>      {
>        /* Set the FPU control word to the proper default value if the
> -	 kernel would use a different value.  (In a static program we
> -	 don't have this information.)  */
> -#ifdef SHARED
> +	 kernel would use a different value.  */
>        if (__fpu_control != GLRO(dl_fpu_control))
> -#endif
>  	__setfpucw (__fpu_control);
>      }
>  
> Index: glibc-fsf-trunk-quilt/elf/dl-support.c
> ===================================================================
> --- glibc-fsf-trunk-quilt.orig/elf/dl-support.c	2013-08-20 15:18:10.000000000 +0100
> +++ glibc-fsf-trunk-quilt/elf/dl-support.c	2013-08-21 20:07:55.169669153 +0100
> @@ -167,6 +167,8 @@ size_t _dl_phnum;
>  uint64_t _dl_hwcap __attribute__ ((nocommon));
>  uint64_t _dl_hwcap2 __attribute__ ((nocommon));
>  

This needs a detailed comment here explaining the behaviour of this
internal variable. I would also welcome an expounding of the semantics
of __fpu_control and the behaviour for static and dynamic applications.

> +fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
> +
>  /* This is not initialized to HWCAP_IMPORTANT, matching the definition
>     of _dl_important_hwcaps, below, where no hwcap strings are ever
>     used.  This mask is still used to mediate the lookups in the cache
> @@ -253,6 +255,9 @@ _dl_aux_init (ElfW(auxv_t) *av)
>        case AT_HWCAP2:
>  	GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
>  	break;
> +      case AT_FPUCW:
> +	GLRO(dl_fpu_control) = av->a_un.a_val;
> +	break;
>  #ifdef NEED_DL_SYSINFO
>        case AT_SYSINFO:
>  	GL(dl_sysinfo) = av->a_un.a_val;
> 

In summary:
- Test case.
- Comment for _dl_fpu_control.

Cheers,
Carlos.