[PATCH glibc 3/9] Implement __libc_early_init

[Adhemerval Zanella]

On 24/04/2020 17:18, Carlos O'Donell via Libc-alpha wrote:
> On 4/24/20 2:22 PM, Florian Weimer wrote:
>> * Carlos O'Donell via Libc-alpha:
>>
>>> Please clarify or remove the comment related to libc_already_loaded.
>>
>> I have removed the initialization.  It is no longer relevant in the
>> current patch.  It may have been obsoleted by other dl_open_worker
>> changes earlier.
> 
> Thanks!
[...]
>> diff --git a/elf/dl-lookup-direct.c b/elf/dl-lookup-direct.c
>> new file mode 100644
>> index 0000000000..5637ae89de
>> --- /dev/null
>> +++ b/elf/dl-lookup-direct.c
>> @@ -0,0 +1,116 @@
>> +/* Look up a symbol in a single specified object.
>> +   Copyright (C) 1995-2020 Free Software Foundation, Inc.
>> +   This file is part of the GNU C Library.
>> +
>> +   The GNU C Library is free software; you can redistribute it and/or
>> +   modify it under the terms of the GNU Lesser General Public
>> +   License as published by the Free Software Foundation; either
>> +   version 2.1 of the License, or (at your option) any later version.
>> +
>> +   The GNU C Library is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> +   Lesser General Public License for more details.
>> +
>> +   You should have received a copy of the GNU Lesser General Public
>> +   License along with the GNU C Library; if not, see
>> +   <https://www.gnu.org/licenses/>.  */
>> +
>> +#include <ldsodefs.h>
>> +#include <string.h>
>> +#include <elf_machine_sym_no_match.h>
>> +#include <dl-hash.h>
>> +
>> +/* This function corresponds to do_lookup_x in elf/dl-lookup.c.  The
>> +   variant here is simplified because it requires symbol
>> +   versioning.  */
>> +static const ElfW(Sym) *
>> +check_match (const struct link_map *const map, const char *const undef_name,
>> +             const char *version, uint32_t version_hash,
>> +             const Elf_Symndx symidx)
>> +{
>> +  const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
>> +  const ElfW(Sym) *sym = &symtab[symidx];
>> +
>> +  unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
>> +  if (__glibc_unlikely ((sym->st_value == 0 /* No value.  */
>> +                         && sym->st_shndx != SHN_ABS
>> +                         && stt != STT_TLS)
>> +                        || elf_machine_sym_no_match (sym)))
>> +    return NULL;
>> +
>> +  /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
>> +     STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
>> +     code/data definitions.  */
>> +#define ALLOWED_STT \
>> +  ((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
>> +   | (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
>> +  if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
>> +    return NULL;
>> +
>> +  const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
>> +
>> +  if (strcmp (strtab + sym->st_name, undef_name) != 0)
>> +    /* Not the symbol we are looking for.  */
>> +    return NULL;
>> +
>> +  ElfW(Half) ndx = map->l_versyms[symidx] & 0x7fff;
>> +  if (map->l_versions[ndx].hash != version_hash
>> +      || strcmp (map->l_versions[ndx].name, version) != 0)
>> +    /* It's not the version we want.  */
>> +    return NULL;
>> +
>> +  return sym;
>> +}
> 
> OK.

The only reservation I have with this change it this code duplication,
could we refactor to have this patch in a common place?