Re: [PATCH 5/7] tunables: Use glibc.tune.hwcap_mask tunable instead of _dl_hwcap_mask

[Siddhesh Poyarekar <siddhesh at gotplt dot org>]

On Wednesday 17 May 2017 08:58 PM, Adhemerval Zanella wrote:
> I would recommend to incorporate the fix for LD_HWCAP_MASK on tst-end-setuid
> you sent before [1] to avoid this fail on some configuration (mine for
> instance).  Also I think we should open a bugzilla to iron out the
> elf/dl-hwcaps.c allocation scheme which is triggering this issue.
> 
> [1] https://sourceware.org/ml/libc-alpha/2017-05/msg00340.html

Pushed fix to the test case:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=ce79740bdbccea312df6cfcf70689efb57792fc9

and reported bug:

https://sourceware.org/bugzilla/show_bug.cgi?id=21502

Siddhesh

> 
> 
>> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
>> index f26a8b2..695ac24 100644
>> --- a/sysdeps/generic/ldsodefs.h
>> +++ b/sysdeps/generic/ldsodefs.h
>> @@ -515,8 +515,10 @@ struct rtld_global_ro
>>    /* Mask for hardware capabilities that are available.  */
>>    EXTERN uint64_t _dl_hwcap;
>>  
>> +#if !HAVE_TUNABLES
>>    /* Mask for important hardware capabilities we honour. */
>>    EXTERN uint64_t _dl_hwcap_mask;
>> +#endif
>>  
>>  #ifdef HAVE_AUX_VECTOR
>>    /* Pointer to the auxv list supplied to the program at startup.  */
>> diff --git a/sysdeps/sparc/sparc32/dl-machine.h b/sysdeps/sparc/sparc32/dl-machine.h
>> index cf7272f..6923e47 100644
>> --- a/sysdeps/sparc/sparc32/dl-machine.h
>> +++ b/sysdeps/sparc/sparc32/dl-machine.h
>> @@ -39,7 +39,12 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
>>        /* XXX The following is wrong!  Dave Miller rejected to implement it
>>  	 correctly.  If this causes problems shoot *him*!  */
>>  #ifdef SHARED
>> -      return GLRO(dl_hwcap) & GLRO(dl_hwcap_mask) & HWCAP_SPARC_V9;
>> +# if HAVE_TUNABLES
>> +      uint64_t hwcap_mask = TUNABLE_GET (glibc, tune, hwcap_mask);
> 
> You are missing '#include <elf/dl-tunables.h>' and the final type argument for
> TUNABLE_GET (it fails to build for sparcv9 with tunable enabled).
> 
>> +# else
>> +      uint64_t hwcap_mask = GLRO(dl_hwcap_mask);
>> +# endif
>> +      return GLRO(dl_hwcap) & hwcap_mask & HWCAP_SPARC_V9;
>>  #else
>>        return GLRO(dl_hwcap) & HWCAP_SPARC_V9;
>>  #endif
>> diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
>> index b481f50..4fe58bf 100644
>> --- a/sysdeps/x86/cpu-features.c
>> +++ b/sysdeps/x86/cpu-features.c
>> @@ -316,7 +316,11 @@ no_cpuid:
>>    /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86.  */
>>    GLRO(dl_platform) = NULL;
>>    GLRO(dl_hwcap) = 0;
>> +#if !HAVE_TUNABLES
>> +  /* The glibc.tune.hwcap_mask tunable is initialized already, so no need to do
>> +     this.  */
>>    GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
>> +#endif
>>  
>>  # ifdef __x86_64__
>>    if (cpu_features->kind == arch_kind_intel)
>>