[RFC] elf: Add elf checks for main executable

[Adhemerval Zanella]

On 18/11/2021 17:00, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> +static inline void
>> +_dl_check_ehdr (struct link_map *main_map)
>> +{
>> +  ElfW(Ehdr) *ehdr = (void *) main_map->l_map_start;
>> +  int err = _dl_elfhdr_check (ehdr);
>> +  if (err != DL_ELFHDR_OK)
>> +    _dl_fatal_printf ("program loading error: %s\n", _dl_elfhdr_errstr (err));
>> +}
> 
> I think you need to iterate through the load segments and see if there
> is one with p_offset == 0 and p_memsz > 0 (the ELF header is smaller
> than a page).  That's the one to use for this check.  If there is no
> such segment, we have to skip the check.

Hum, should we set the l_map_start as well only if we found such segment?