elf_link_check_versioned_symbol
Alan Modra
amodra@bigpond.net.au
Sat Jun 22 03:41:00 GMT 2002
On Fri, Jun 21, 2002 at 09:40:23AM -0700, H . J . Lu wrote:
> You missed:
>
> if ((verstab[symidx] & 0x7fff)
> >= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
>
> An unversioned reference can be resolved by the oldest version. The
> rest of code is ok although I prefer to keep the error message instead
> of abort () just in case. If you want, I can submit a new working
> patch.
The code you use in your binutils doesn't check for multiple
VERSYM_HIDDEN symbols. That seems wrong to me, since as far as I can
see, ld.so will do so in certain cases.
I didn't exactly miss that code in elf/do-lookup.h; I looked at it
and chose to use the comparison against 2. On looking again, I see
that ld.so doesn't set DL_LOOKUP_RETURN_NEWEST, so the right thing to
do is return success on finding a version 2 sym, and count syms with
versions >= 3. That will make both your testcases work, and match
ld.so behaviour.
As far as error message vs abort, I prefer the abort as it should
never happen with any user input. ie. we're checking ld internal
consistency. The other thing you mentioned privately, the change
in elf_link_loaded_list order was deliberate. It a) is simpler
code, and b) the search order doesn't matter.
bfd/ChangeLog
* elf-bfd.h (elf_link_loaded_list): New structure.
(elf_link_hash_table): Add "loaded".
* elf.c (_bfd_elf_link_hash_table_init): Initialize "loaded".
* elflink.h (elf_link_check_versioned_symbol): New function.
(elf_link_output_extsym): Call elf_link_check_versioned_symbol.
Index: bfd/elf-bfd.h
===================================================================
RCS file: /cvs/src/src/bfd/elf-bfd.h,v
retrieving revision 1.79
diff -u -p -r1.79 elf-bfd.h
--- bfd/elf-bfd.h 7 Jun 2002 14:57:10 -0000 1.79
+++ bfd/elf-bfd.h 21 Jun 2002 05:28:38 -0000
@@ -223,6 +223,12 @@ struct elf_link_local_dynamic_entry
Elf_Internal_Sym isym;
};
+struct elf_link_loaded_list
+{
+ struct elf_link_loaded_list *next;
+ bfd *abfd;
+};
+
enum elf_link_info_type
{
ELF_INFO_TYPE_NONE,
@@ -297,6 +303,9 @@ struct elf_link_hash_table
/* Cached start, size and alignment of PT_TLS segment. */
struct elf_link_tls_segment *tls_segment;
+
+ /* A linked list of BFD's loaded in the link. */
+ struct elf_link_loaded_list *loaded;
};
/* Look up an entry in an ELF linker hash table. */
Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.147
diff -u -p -r1.147 elf.c
--- bfd/elf.c 9 Jun 2002 03:08:54 -0000 1.147
+++ bfd/elf.c 21 Jun 2002 05:28:43 -0000
@@ -1430,6 +1430,7 @@ _bfd_elf_link_hash_table_init (table, ab
table->bucketcount = 0;
table->needed = NULL;
table->runpath = NULL;
+ table->loaded = NULL;
table->hgot = NULL;
table->stab_info = NULL;
table->merge_info = NULL;
Index: bfd/elflink.h
===================================================================
RCS file: /cvs/src/src/bfd/elflink.h,v
retrieving revision 1.167
diff -u -p -r1.167 elflink.h
--- bfd/elflink.h 19 Jun 2002 10:07:36 -0000 1.167
+++ bfd/elflink.h 22 Jun 2002 10:20:29 -0000
@@ -2315,6 +2315,20 @@ elf_link_add_object_symbols (abfd, info)
}
}
+ if (is_elf_hash_table (info))
+ {
+ /* Add this bfd to the loaded list. */
+ struct elf_link_loaded_list *n;
+
+ n = ((struct elf_link_loaded_list *)
+ bfd_alloc (abfd, sizeof (struct elf_link_loaded_list)));
+ if (n == NULL)
+ goto error_return;
+ n->abfd = abfd;
+ n->next = hash_table->loaded;
+ hash_table->loaded = n;
+ }
+
return true;
error_return:
@@ -4536,6 +4550,8 @@ static boolean elf_link_output_extsym
PARAMS ((struct elf_link_hash_entry *, PTR));
static boolean elf_link_sec_merge_syms
PARAMS ((struct elf_link_hash_entry *, PTR));
+static boolean elf_link_check_versioned_symbol
+ PARAMS ((struct bfd_link_info *, struct elf_link_hash_entry *));
static boolean elf_link_input_bfd
PARAMS ((struct elf_final_link_info *, bfd *));
static boolean elf_reloc_link_order
@@ -6042,6 +6058,147 @@ elf_link_sec_merge_syms (h, data)
return true;
}
+/* For DSOs loaded in via a DT_NEEDED entry, emulate ld.so in
+ allowing an unsatisfied unversioned symbol in the DSO to match a
+ versioned symbol that would normally require an explicit version,
+ if we find exactly one matching versioned symbol. */
+
+static boolean
+elf_link_check_versioned_symbol (info, h)
+ struct bfd_link_info *info;
+ struct elf_link_hash_entry *h;
+{
+ bfd *undef_bfd = h->root.u.undef.abfd;
+ struct elf_link_loaded_list *loaded;
+ Elf_External_Sym *buf;
+ Elf_External_Versym *extversym;
+
+ if ((undef_bfd->flags & DYNAMIC) == 0
+ || info->hash->creator->flavour != bfd_target_elf_flavour
+ || elf_dt_soname (h->root.u.undef.abfd) == NULL)
+ return false;
+
+ for (loaded = elf_hash_table (info)->loaded;
+ loaded != NULL;
+ loaded = loaded->next)
+ {
+ bfd *input;
+ Elf_Internal_Shdr *hdr;
+ bfd_size_type symcount;
+ bfd_size_type extsymcount;
+ bfd_size_type extsymoff;
+ Elf_Internal_Shdr *versymhdr;
+ Elf_External_Versym *ever;
+ Elf_External_Sym *esym;
+ Elf_External_Sym *esymend;
+ bfd_size_type count;
+ file_ptr pos;
+ int num_versions = 0;
+
+ input = loaded->abfd;
+
+ /* We check each DSO for a possible hidden versioned definition. */
+ if (input == undef_bfd
+ || (input->flags & DYNAMIC) == 0
+ || elf_dynversym (input) == 0)
+ continue;
+
+ hdr = &elf_tdata (input)->dynsymtab_hdr;
+
+ symcount = hdr->sh_size / sizeof (Elf_External_Sym);
+ if (elf_bad_symtab (input))
+ {
+ extsymcount = symcount;
+ extsymoff = 0;
+ }
+ else
+ {
+ extsymcount = symcount - hdr->sh_info;
+ extsymoff = hdr->sh_info;
+ }
+
+ if (extsymcount == 0)
+ continue;
+
+ count = extsymcount * sizeof (Elf_External_Sym);
+ buf = (Elf_External_Sym *) bfd_malloc (count);
+ if (buf == NULL)
+ return false;
+
+ /* Read in the symbol table. */
+ pos = hdr->sh_offset + extsymoff * sizeof (Elf_External_Sym);
+ if (bfd_seek (input, pos, SEEK_SET) != 0
+ || bfd_bread ((PTR) buf, count, input) != count)
+ goto error_ret;
+
+ /* Read in any version definitions. */
+ versymhdr = &elf_tdata (input)->dynversym_hdr;
+ extversym = (Elf_External_Versym *) bfd_malloc (versymhdr->sh_size);
+ if (extversym == NULL)
+ goto error_ret;
+
+ if (bfd_seek (input, versymhdr->sh_offset, SEEK_SET) != 0
+ || (bfd_bread ((PTR) extversym, versymhdr->sh_size, input)
+ != versymhdr->sh_size))
+ {
+ free (extversym);
+ error_ret:
+ free (buf);
+ return false;
+ }
+
+ ever = extversym + extsymoff;
+ esymend = buf + extsymcount;
+ for (esym = buf; esym < esymend; esym++, ever++)
+ {
+ const char *name;
+ Elf_Internal_Sym sym;
+ Elf_Internal_Versym iver;
+
+ elf_swap_symbol_in (input, esym, NULL, &sym);
+ if (ELF_ST_BIND (sym.st_info) == STB_LOCAL
+ || sym.st_shndx == SHN_UNDEF)
+ continue;
+
+ name = bfd_elf_string_from_elf_section (input,
+ hdr->sh_link,
+ sym.st_name);
+ if (strcmp (name, h->root.root.string) != 0)
+ continue;
+
+ _bfd_elf_swap_versym_in (input, ever, &iver);
+
+ if ((iver.vs_vers & VERSYM_HIDDEN) == 0)
+ {
+ /* If we have a non-hidden versioned sym, then it should
+ have provided a definition for the undefined sym. */
+ abort ();
+ }
+
+ if ((iver.vs_vers & VERSYM_VERSION) == 2)
+ {
+ /* This is the oldest (default) sym. We can use it. */
+ free (extversym);
+ free (buf);
+ return true;
+ }
+
+ if ((iver.vs_vers & VERSYM_VERSION) > 2)
+ {
+ /* We found one we can use if there's only one such sym. */
+ num_versions++;
+ }
+ }
+
+ free (extversym);
+ free (buf);
+ if (num_versions == 1)
+ return true;
+ }
+
+ return false;
+}
+
/* Add an external symbol to the symbol table. This is called from
the hash table traversal routine. When generating a shared object,
we go through the symbol table twice. The first time we output
@@ -6091,7 +6248,8 @@ elf_link_output_extsym (h, data)
&& ! finfo->info->shared
&& h->root.type == bfd_link_hash_undefined
&& (h->elf_link_hash_flags & ELF_LINK_HASH_REF_DYNAMIC) != 0
- && (h->elf_link_hash_flags & ELF_LINK_HASH_REF_REGULAR) == 0)
+ && (h->elf_link_hash_flags & ELF_LINK_HASH_REF_REGULAR) == 0
+ && ! elf_link_check_versioned_symbol (finfo->info, h))
{
if (! ((*finfo->info->callbacks->undefined_symbol)
(finfo->info, h->root.root.string, h->root.u.undef.abfd,
--
Alan Modra
IBM OzLabs - Linux Technology Centre
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