Re: SIGSEGV in ld at elflink.h:5500

[Alan Modra <amodra at bigpond dot net dot au>]

On Thu, Jul 25, 2002 at 12:22:53AM -0400, John David Anglin wrote:
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x400000000004f604 in L$2249 () at ../../src/bfd/elflink.h:5500
> 
> > OK, so it's a section symbol from a removed linkonce section.
> > 
> > I think elf64-hppa.c needs to check for this case before calling
> > _bfd_elf64_link_record_local_dynamic_symbol, with something like
> > 
> > ((sec->flags & SEC_LINK_ONCE) != 0
> >  && bfd_is_abs_section (sec->output_section))
> 
> I traced back the value of "e" associated with the SIGSEGV and find
> that it is added in allocate_dynrel_entries.  I don't think the other
> functions that call _bfd_elf64_link_record_local_dynamic_symbol are
> a problem but I am not entirely certain.
> 
> The approach outlined above doesn't work.  It requires the input section
> for the symbol.  What we have is the owner and input index.  rent->sec->name
> is .eh_frame.  Any thoughts on an easy way to get the input section
> for the symbol?

The standard way is to read and swap in the symbol using
bfd_elf_get_elf_syms, then call bfd_section_from_elf_index on
sym.st_shndx.  However, I'm about to check in the following which
ought to make it easy for you.  In fact, you may not need to change
elf64-hppa.c at all.

Using bfd_elf_get_elf_syms in elf_link_record_local_dynamic_symbol
means we have no structures that change size between ELF32 and ELF64,
so the function can move to elflink.c.

bfd/ChangeLog
	* elf-bfd.h (_bfd_elf32_link_record_local_dynamic_symbol): Define
	as elf_link_record_local_dynamic_symbol.
	(_bfd_elf64_link_record_local_dynamic_symbol): Likewise.
	(elf_link_record_local_dynamic_symbol): Declare.  Now returns int.
	* elflink.h (elf_link_record_local_dynamic_symbol): Move to..
	* elflink.c: .. here.  Use bfd_elf_get_elf_syms.  Check whether an
	attempt is made to record a symbol in a discarded section, and
	return `2' in that case.

Committing to mainline.  This can go to the branch (assuming no
objections) when the elf64-hppa problem is proven fixed.

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Index: bfd/elf-bfd.h
===================================================================
RCS file: /cvs/src/src/bfd/elf-bfd.h,v
retrieving revision 1.84
diff -u -p -r1.84 elf-bfd.h
--- bfd/elf-bfd.h	23 Jul 2002 11:15:06 -0000	1.84
+++ bfd/elf-bfd.h	25 Jul 2002 06:41:20 -0000
@@ -1558,10 +1558,12 @@ extern Elf_Internal_Rela *_bfd_elf64_lin
 #define bfd_elf64_link_record_dynamic_symbol \
   _bfd_elf_link_record_dynamic_symbol
 
-extern boolean _bfd_elf32_link_record_local_dynamic_symbol
-  PARAMS ((struct bfd_link_info *, bfd *, long));
-extern boolean _bfd_elf64_link_record_local_dynamic_symbol
+extern int elf_link_record_local_dynamic_symbol
   PARAMS ((struct bfd_link_info *, bfd *, long));
+#define _bfd_elf32_link_record_local_dynamic_symbol \
+  elf_link_record_local_dynamic_symbol
+#define _bfd_elf64_link_record_local_dynamic_symbol \
+  elf_link_record_local_dynamic_symbol
 
 extern boolean _bfd_elf_close_and_cleanup
   PARAMS ((bfd *));
Index: bfd/elflink.c
===================================================================
RCS file: /cvs/src/src/bfd/elflink.c,v
retrieving revision 1.26
diff -u -p -r1.26 elflink.c
--- bfd/elflink.c	4 Jul 2002 14:40:25 -0000	1.26
+++ bfd/elflink.c	25 Jul 2002 06:41:27 -0000
@@ -302,6 +302,98 @@ _bfd_elf_link_record_dynamic_symbol (inf
   return true;
 }
 
+/* Record a new local dynamic symbol.  Returns 0 on failure, 1 on
+   success, and 2 on a failure caused by attempting to record a symbol
+   in a discarded section, eg. a discarded link-once section symbol.  */
+
+int
+elf_link_record_local_dynamic_symbol (info, input_bfd, input_indx)
+     struct bfd_link_info *info;
+     bfd *input_bfd;
+     long input_indx;
+{
+  bfd_size_type amt;
+  struct elf_link_local_dynamic_entry *entry;
+  struct elf_link_hash_table *eht;
+  struct elf_strtab_hash *dynstr;
+  unsigned long dynstr_index;
+  char *name;
+  Elf_External_Sym_Shndx eshndx;
+  char esym[sizeof (Elf64_External_Sym)];
+
+  if (! is_elf_hash_table (info))
+    return 0;
+
+  /* See if the entry exists already.  */
+  for (entry = elf_hash_table (info)->dynlocal; entry ; entry = entry->next)
+    if (entry->input_bfd == input_bfd && entry->input_indx == input_indx)
+      return 1;
+
+  amt = sizeof (*entry);
+  entry = (struct elf_link_local_dynamic_entry *) bfd_alloc (input_bfd, amt);
+  if (entry == NULL)
+    return 0;
+
+  /* Go find the symbol, so that we can find it's name.  */
+  if (!bfd_elf_get_elf_syms (input_bfd, &elf_tdata (input_bfd)->symtab_hdr,
+			     (size_t) 1, (size_t) input_indx,
+			     &entry->isym, esym, &eshndx))
+    {
+      bfd_release (input_bfd, entry);
+      return 0;
+    }
+
+  if (entry->isym.st_shndx != SHN_UNDEF
+      && (entry->isym.st_shndx < SHN_LORESERVE
+	  || entry->isym.st_shndx > SHN_HIRESERVE))
+    {
+      asection *s;
+
+      s = bfd_section_from_elf_index (input_bfd, entry->isym.st_shndx);
+      if (s == NULL || bfd_is_abs_section (s->output_section))
+	{
+	  /* We can still bfd_release here as nothing has done another
+	     bfd_alloc.  We can't do this later in this function.  */
+	  bfd_release (input_bfd, entry);
+	  return 2;
+	}
+    }
+
+  name = (bfd_elf_string_from_elf_section
+	  (input_bfd, elf_tdata (input_bfd)->symtab_hdr.sh_link,
+	   entry->isym.st_name));
+
+  dynstr = elf_hash_table (info)->dynstr;
+  if (dynstr == NULL)
+    {
+      /* Create a strtab to hold the dynamic symbol names.  */
+      elf_hash_table (info)->dynstr = dynstr = _bfd_elf_strtab_init ();
+      if (dynstr == NULL)
+	return 0;
+    }
+
+  dynstr_index = _bfd_elf_strtab_add (dynstr, name, false);
+  if (dynstr_index == (unsigned long) -1)
+    return 0;
+  entry->isym.st_name = dynstr_index;
+
+  eht = elf_hash_table (info);
+
+  entry->next = eht->dynlocal;
+  eht->dynlocal = entry;
+  entry->input_bfd = input_bfd;
+  entry->input_indx = input_indx;
+  eht->dynsymcount++;
+
+  /* Whatever binding the symbol had before, it's now local.  */
+  entry->isym.st_info
+    = ELF_ST_INFO (STB_LOCAL, ELF_ST_TYPE (entry->isym.st_info));
+
+  /* The dynindx will be set at the end of size_dynamic_sections.  */
+
+  return 1;
+}
+
 /* Return the dynindex of a local dynamic symbol.  */
 
 long
Index: bfd/elflink.h
===================================================================
RCS file: /cvs/src/src/bfd/elflink.h,v
retrieving revision 1.178
diff -u -p -r1.178 elflink.h
--- bfd/elflink.h	23 Jul 2002 04:38:17 -0000	1.178
+++ bfd/elflink.h	25 Jul 2002 06:41:35 -0000
@@ -2448,93 +2448,6 @@ elf_add_dynamic_entry (info, tag, val)
 
   return true;
 }
-
-/* Record a new local dynamic symbol.  */
-
-boolean
-elf_link_record_local_dynamic_symbol (info, input_bfd, input_indx)
-     struct bfd_link_info *info;
-     bfd *input_bfd;
-     long input_indx;
-{
-  struct elf_link_local_dynamic_entry *entry;
-  struct elf_link_hash_table *eht;
-  struct elf_strtab_hash *dynstr;
-  Elf_External_Sym esym;
-  Elf_External_Sym_Shndx eshndx;
-  Elf_External_Sym_Shndx *shndx;
-  unsigned long dynstr_index;
-  char *name;
-  file_ptr pos;
-  bfd_size_type amt;
-
-  if (! is_elf_hash_table (info))
-    return false;
-
-  /* See if the entry exists already.  */
-  for (entry = elf_hash_table (info)->dynlocal; entry ; entry = entry->next)
-    if (entry->input_bfd == input_bfd && entry->input_indx == input_indx)
-      return true;
-
-  entry = (struct elf_link_local_dynamic_entry *)
-    bfd_alloc (input_bfd, (bfd_size_type) sizeof (*entry));
-  if (entry == NULL)
-    return false;
-
-  /* Go find the symbol, so that we can find it's name.  */
-  amt = sizeof (Elf_External_Sym);
-  pos = elf_tdata (input_bfd)->symtab_hdr.sh_offset + input_indx * amt;
-  if (bfd_seek (input_bfd, pos, SEEK_SET) != 0
-      || bfd_bread ((PTR) &esym, amt, input_bfd) != amt)
-    return false;
-  shndx = NULL;
-  if (elf_tdata (input_bfd)->symtab_shndx_hdr.sh_size != 0)
-    {
-      amt = sizeof (Elf_External_Sym_Shndx);
-      pos = elf_tdata (input_bfd)->symtab_shndx_hdr.sh_offset;
-      pos += input_indx * amt;
-      shndx = &eshndx;
-      if (bfd_seek (input_bfd, pos, SEEK_SET) != 0
-	  || bfd_bread ((PTR) shndx, amt, input_bfd) != amt)
-	return false;
-    }
-  elf_swap_symbol_in (input_bfd, (const PTR) &esym, (const PTR) shndx,
-		      &entry->isym);
-
-  name = (bfd_elf_string_from_elf_section
-	  (input_bfd, elf_tdata (input_bfd)->symtab_hdr.sh_link,
-	   entry->isym.st_name));
-
-  dynstr = elf_hash_table (info)->dynstr;
-  if (dynstr == NULL)
-    {
-      /* Create a strtab to hold the dynamic symbol names.  */
-      elf_hash_table (info)->dynstr = dynstr = _bfd_elf_strtab_init ();
-      if (dynstr == NULL)
-	return false;
-    }
-
-  dynstr_index = _bfd_elf_strtab_add (dynstr, name, false);
-  if (dynstr_index == (unsigned long) -1)
-    return false;
-  entry->isym.st_name = dynstr_index;
-
-  eht = elf_hash_table (info);
-
-  entry->next = eht->dynlocal;
-  eht->dynlocal = entry;
-  entry->input_bfd = input_bfd;
-  entry->input_indx = input_indx;
-  eht->dynsymcount++;
-
-  /* Whatever binding the symbol had before, it's now local.  */
-  entry->isym.st_info
-    = ELF_ST_INFO (STB_LOCAL, ELF_ST_TYPE (entry->isym.st_info));
-
-  /* The dynindx will be set at the end of size_dynamic_sections.  */
-
-  return true;
-}
 
 /* Read and swap the relocs from the section indicated by SHDR.  This
    may be either a REL or a RELA section.  The relocations are