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

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

On 08/02/2022 17:34, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>>> diff --git a/sysdeps/unix/sysv/linux/dl-parse_auxv.h b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
>>> new file mode 100644
>>> index 0000000000..f450c6c5ce
>>> --- /dev/null
>>> +++ b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
> 
>>> +typedef ElfW(Addr) dl_parse_auxv_t[AT_MINSIGSTKSZ + 1];
>>> +
>>> +/* Copy the auxiliary vector into AUX_VALUES and set up GLRO
>>> +   variables.  */
>>> +static inline
>>> +void _dl_parse_auxv (ElfW(auxv_t) *av, dl_parse_auxv_t auxv_values)
>>> +{
>>> +  auxv_values[AT_ENTRY] =  (ElfW(Addr)) ENTRY_POINT;
>>
>> Extra whitespace.
> 
> Fxied.
> 
>>> +  auxv_values[AT_PAGESZ] = EXEC_PAGESIZE;
>>> +  auxv_values[AT_FPUCW] = _FPU_DEFAULT;
>>> +
>>> +  /* NB: Default to a constant CONSTANT_MINSIGSTKSZ.  */
>>> +  _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
>>> +                  "CONSTANT_MINSIGSTKSZ is constant");
>>
>> Shouldn't it warn that CONSTANT_MINSIGSTKSZ is not a constant?
> 
> Sorry, would please rephrase?  Should I change this to
> ""CONSTANT_MINSIGSTKSZ is not constant"?

Yeah because on a the _Static_assert failure the resulting message seems
to the opposite of what triggered it.

> 
>>> +  auxv_values[AT_MINSIGSTKSZ] = CONSTANT_MINSIGSTKSZ;
>>> +
>>> +  for (; av->a_type != AT_NULL; av++)
>>> +    if (av->a_type <= AT_MINSIGSTKSZ)
>>> +      auxv_values[av->a_type] = av->a_un.a_val;
>>> +
>>> +  GLRO(dl_pagesize) = auxv_values[AT_PAGESZ];
>>> +  __libc_enable_secure = auxv_values[AT_SECURE];
>>> +  GLRO(dl_platform) = (void *) auxv_values[AT_PLATFORM];
>>> +  GLRO(dl_hwcap) = auxv_values[AT_HWCAP];
>>> +  GLRO(dl_hwcap2) = auxv_values[AT_HWCAP2];
>>> +  GLRO(dl_clktck) = auxv_values[AT_CLKTCK];
>>> +  GLRO(dl_fpu_control) = auxv_values[AT_FPUCW];
>>> +  _dl_random = (void *) auxv_values[AT_RANDOM];
>>> +  GLRO(dl_minsigstacksize) = auxv_values[AT_MINSIGSTKSZ];
>>> +  GLRO(dl_sysinfo_dso) = (void *) auxv_values[AT_SYSINFO_EHDR];
>>> +#ifdef NEED_DL_SYSINFO
>>
>> I think you can now assume NEED_DL_SYSINFO is always defined.
> 
> NEED_DL_SYSINFO is only defined by i386 and ia64, only
> NEED_DL_SYSINFO_DSO is always defined on Linux.

Indeed, my confusion here.

> 
> Thanks,
> Florian
>