Re: [PATCH v2 5/5] Linux: Consolidate auxiliary vector parsing

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 11/02/2022 09:31, Szabolcs Nagy via Libc-alpha wrote:
> this broke aarch64 static binaries:
> 
> The 02/03/2022 12:08, Florian Weimer via Libc-alpha wrote
>>  void
>>  _dl_aux_init (ElfW(auxv_t) *av)
>>  {
>> -  int seen = 0;
>> -  uid_t uid = 0;
>> -  gid_t gid = 0;
>> -
>>  #ifdef NEED_DL_SYSINFO
>>    /* NB: Avoid RELATIVE relocation in static PIE.  */
>>    GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
>>  #endif
>>  
>>    _dl_auxv = av;
>> -  for (; av->a_type != AT_NULL; ++av)
>> -    switch (av->a_type)
>> -      {
>> -      case AT_PAGESZ:
>> -	if (av->a_un.a_val != 0)
>> -	  GLRO(dl_pagesize) = av->a_un.a_val;
>> -	break;
>> -      case AT_CLKTCK:
>> -	GLRO(dl_clktck) = av->a_un.a_val;
>> -	break;
>> -      case AT_PHDR:
>> -	GL(dl_phdr) = (const void *) av->a_un.a_val;
>> -	break;
>> -      case AT_PHNUM:
>> -	GL(dl_phnum) = av->a_un.a_val;
>> -	break;
>> -      case AT_PLATFORM:
>> -	GLRO(dl_platform) = (void *) av->a_un.a_val;
>> -	break;
>> -      case AT_HWCAP:
>> -	GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
>> -	break;
>> -      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;
>> -	break;
>> -#endif
>> -#ifdef NEED_DL_SYSINFO_DSO
>> -      case AT_SYSINFO_EHDR:
>> -	GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
>> -	break;
>> -#endif
>> -      case AT_UID:
>> -	uid ^= av->a_un.a_val;
>> -	seen |= 1;
>> -	break;
>> -      case AT_EUID:
>> -	uid ^= av->a_un.a_val;
>> -	seen |= 2;
>> -	break;
>> -      case AT_GID:
>> -	gid ^= av->a_un.a_val;
>> -	seen |= 4;
>> -	break;
>> -      case AT_EGID:
>> -	gid ^= av->a_un.a_val;
>> -	seen |= 8;
>> -	break;
>> -      case AT_SECURE:
>> -	seen = -1;
>> -	__libc_enable_secure = av->a_un.a_val;
>> -	__libc_enable_secure_decided = 1;
>> -	break;
>> -      case AT_RANDOM:
>> -	_dl_random = (void *) av->a_un.a_val;
>> -	break;
>> -      case AT_MINSIGSTKSZ:
>> -	_dl_minsigstacksize = av->a_un.a_val;
>> -	break;
>> -      DL_PLATFORM_AUXV
>> -      }
>> -  if (seen == 0xf)
>> -    {
>> -      __libc_enable_secure = uid != 0 || gid != 0;
>> -      __libc_enable_secure_decided = 1;
>> -    }
>> +  dl_parse_auxv_t auxv_values = { 0, };
>> +  _dl_parse_auxv (av, auxv_values);
> 
> this seems to use memset now on aarch64 before irelative
> relocs are resolved in static binaries.
> 
> which causes infinite loops in the iplt (i've also seen
> segfaults in the build log).
> 
> i wonder what is a clean fix...
> 

Maybe add inhibit_loop_to_libcall to avoid the memset call.