Thu Jun 16 14:25:22 1994 Eric Youngdale (ericy@cais.cais.com)

	* i386linux.c: Many new functions and definitions for linker
	support for Linux shared libraries.
	* bfd-in.h (bfd_linux_size_dynamic_sections): Declare.
	* bfd-in2.h: Rebuild.

1 files changed, 621 insertions, 0 deletions

diff --git a/bfd/i386linux.c b/bfd/i386linux.c
index 97fc6a0..5390b42 100644
--- a/bfd/i386linux.c
+++ b/bfd/i386linux.c
@@ -75,5 +75,626 @@ i386linux_write_object_contents (abfd)
 }
 
 #define MY_write_object_contents i386linux_write_object_contents
+
+/* Code to link against Linux a.out shared libraries.  */
+
+/* See if a symbol name is a reference to the global offset table.  */
+
+#ifndef GOT_REF_PREFIX
+#define	GOT_REF_PREFIX	"__GOT_"
+#endif
+
+#define IS_GOT_SYM(name) \
+  (strncmp (name, GOT_REF_PREFIX, sizeof GOT_REF_PREFIX - 1) == 0)
+
+/* See if a symbol name is a reference to the procedure linkage table.  */
+
+#ifndef PLT_REF_PREFIX
+#define	PLT_REF_PREFIX	"__PLT_"
+#endif
+
+#define IS_PLT_SYM(name) \
+  (strncmp (name, PLT_REF_PREFIX, sizeof PLT_REF_PREFIX - 1) == 0)
+
+/* This special symbol is a set vector that contains a list of
+   pointers to fixup tables.  It will be present in any dynamicly
+   linked file.  The linker generated fixup table should also be added
+   to the list, and it should always appear in the second slot (the
+   first one is a dummy with a magic number that is defined in
+   crt0.o).  */
+
+#ifndef SHARABLE_CONFLICTS
+#define SHARABLE_CONFLICTS "__SHARABLE_CONFLICTS__"
+#endif
+
+/* We keep a list of fixups.  The terminology is a bit strange, but
+   each fixup contains two 32 bit numbers.  A regular fixup contains
+   an address and a pointer, and at runtime we should store the
+   address at the location pointed to by the pointer.  A builtin fixup
+   contains two pointers, and we should read the address using one
+   pointer and store it at the location pointed to by the other
+   pointer.  Builtin fixups come into play when we have duplicate
+   __GOT__ symbols for the same variable.  The builtin fixup will copy
+   the GOT pointer from one over into the other.  */
+
+struct fixup
+{
+  struct fixup *next;
+  struct linux_link_hash_entry *h;
+  bfd_vma value;
+
+  /* Nonzero if this is a jump instruction that needs to be fixed,
+     zero if this is just a pointer */
+  char jump;
+
+  char builtin;
+};
+
+/* We don't need a special hash table entry structure, but we do need
+   to keep some information between linker passes, so we use a special
+   hash table.  */
+
+struct linux_link_hash_entry
+{
+  struct aout_link_hash_entry root;
+};
+
+struct linux_link_hash_table
+{
+  struct aout_link_hash_table root;
+
+  /* First dynamic object found in link.  */
+  bfd *dynobj;
+
+  /* Number of fixups.  */
+  size_t fixup_count;
+
+  /* Number of builtin fixups.  */
+  size_t local_builtins;
+
+  /* List of fixups.  */
+  struct fixup *fixup_list;
+};
+
+static struct bfd_hash_entry *linux_link_hash_newfunc
+  PARAMS ((struct bfd_hash_entry *, struct bfd_hash_table *, const char *));
+static struct bfd_link_hash_table *linux_link_hash_table_create
+  PARAMS ((bfd *));
+static struct fixup *new_fixup
+  PARAMS ((struct bfd_link_info *, struct linux_link_hash_entry *,
+	   bfd_vma, int));
+static boolean linux_link_create_dynamic_sections
+  PARAMS ((bfd *, struct bfd_link_info *));
+static boolean linux_add_one_symbol
+  PARAMS ((struct bfd_link_info *, bfd *, const char *, flagword, asection *,
+	   bfd_vma, const char *, boolean, boolean,
+	   struct bfd_link_hash_entry **));
+static boolean linux_tally_symbols
+  PARAMS ((struct linux_link_hash_entry *, PTR));
+static boolean linux_finish_dynamic_link
+  PARAMS ((bfd *, struct bfd_link_info *));
+
+/* Routine to create an entry in an Linux link hash table.  */
+
+static struct bfd_hash_entry *
+linux_link_hash_newfunc (entry, table, string)
+     struct bfd_hash_entry *entry;
+     struct bfd_hash_table *table;
+     const char *string;
+{
+  struct linux_link_hash_entry *ret = (struct linux_link_hash_entry *) entry;
+
+  /* Allocate the structure if it has not already been allocated by a
+     subclass.  */
+  if (ret == (struct linux_link_hash_entry *) NULL)
+    ret = ((struct linux_link_hash_entry *)
+	   bfd_hash_allocate (table, sizeof (struct linux_link_hash_entry)));
+  if (ret == NULL)
+    return (struct bfd_hash_entry *) ret;
+
+  /* Call the allocation method of the superclass.  */
+  ret = ((struct linux_link_hash_entry *)
+	 NAME(aout,link_hash_newfunc) ((struct bfd_hash_entry *) ret,
+				       table, string));
+  if (ret != NULL)
+    {
+      /* Set local fields; there aren't any.  */
+    }
+
+  return (struct bfd_hash_entry *) ret;
+}
+
+/* Create a Linux link hash table.  */
+
+static struct bfd_link_hash_table *
+linux_link_hash_table_create (abfd)
+     bfd *abfd;
+{
+  struct linux_link_hash_table *ret;
+
+  ret = ((struct linux_link_hash_table *)
+	 malloc (sizeof (struct linux_link_hash_table)));
+  if (ret == (struct linux_link_hash_table *) NULL)
+    {
+      bfd_set_error (bfd_error_no_memory);
+      return (struct bfd_link_hash_table *) NULL;
+    }
+  if (! NAME(aout,link_hash_table_init) (&ret->root, abfd,
+					 linux_link_hash_newfunc))
+    {
+      free (ret);
+      return (struct bfd_link_hash_table *) NULL;
+    }
+
+  ret->dynobj = NULL;
+  ret->fixup_count = 0;
+  ret->local_builtins = 0;
+  ret->fixup_list = NULL;
+
+  return &ret->root.root;
+}
+
+/* Look up an entry in a Linux link hash table.  */
+
+#define linux_link_hash_lookup(table, string, create, copy, follow) \
+  ((struct linux_link_hash_entry *) \
+   aout_link_hash_lookup (&(table)->root, (string), (create), (copy),\
+			  (follow)))
+
+/* Traverse a Linux link hash table.  */
+
+#define linux_link_hash_traverse(table, func, info)			\
+  (aout_link_hash_traverse						\
+   (&(table)->root,							\
+    (boolean (*) PARAMS ((struct aout_link_hash_entry *, PTR))) (func),	\
+    (info)))
+
+/* Get the Linux link hash table from the info structure.  This is
+   just a cast.  */
+
+#define linux_hash_table(p) ((struct linux_link_hash_table *) ((p)->hash))
+
+/* Store the information for a new fixup.  */
+
+static struct fixup *
+new_fixup (info, h, value, builtin)
+     struct bfd_link_info *info;
+     struct linux_link_hash_entry *h;
+     bfd_vma value;
+     int builtin;
+{
+  struct fixup *f;
+
+  f = (struct fixup *) bfd_hash_allocate (&info->hash->table,
+					  sizeof (struct fixup));
+  if (f == NULL)
+    return f;
+  f->next = linux_hash_table (info)->fixup_list;
+  linux_hash_table (info)->fixup_list = f;
+  f->h = h;
+  f->value = value;
+  f->builtin = builtin;
+  f->jump = 0;
+  ++linux_hash_table (info)->fixup_count;
+  return f;
+}
+
+/* We come here once we realize that we are going to link to a shared
+   library.  We need to create a special section that contains the
+   fixup table, and we ultimately need to add a pointer to this into
+   the set vector for SHARABLE_CONFLICTS.  At this point we do not
+   know the size of the section, but that's OK - we just need to
+   create it for now.  */
+
+static boolean
+linux_link_create_dynamic_sections (abfd, info)
+     bfd *abfd;
+     struct bfd_link_info *info;
+{
+  flagword flags;
+  register asection *s;
+
+  /* Note that we set the SEC_IN_MEMORY flag.  */
+  flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY;
+
+  /* We choose to use the name ".dynamic" for the fixup table.  Why
+     not? */
+  s = bfd_make_section (abfd, ".dynamic");
+  if (s == NULL
+      || ! bfd_set_section_flags (abfd, s, flags)
+      || ! bfd_set_section_alignment (abfd, s, 2))
+    return false;
+  s->_raw_size = 0;
+  s->contents = 0;
+
+  return true;
+}
+
+/* Function to add a single symbol to the linker hash table.  This is
+   a wrapper around _bfd_generic_link_add_one_symbol which handles the
+   tweaking needed for dynamic linking support.  */
+
+static boolean
+linux_add_one_symbol (info, abfd, name, flags, section, value, string,
+		      copy, collect, hashp)
+     struct bfd_link_info *info;
+     bfd *abfd;
+     const char *name;
+     flagword flags;
+     asection *section;
+     bfd_vma value;
+     const char *string;
+     boolean copy;
+     boolean collect;
+     struct bfd_link_hash_entry **hashp;
+{
+  struct linux_link_hash_entry *h;
+  boolean insert;
+
+  /* Look up and see if we already have this symbol in the hash table.
+     If we do, and the defining entry is from a shared library, we
+     need to create the dynamic sections.
+
+     FIXME: What if abfd->xvec != info->hash->creator?  We may want to
+     be able to link Linux a.out and ELF objects together, but serious
+     confusion is possible.  */
+
+  insert = false;
+
+  if (! info->relocateable
+      && linux_hash_table (info)->dynobj == NULL
+      && strcmp (name, SHARABLE_CONFLICTS) == 0)
+    {
+      if (! linux_link_create_dynamic_sections (abfd, info))
+	return false;
+      linux_hash_table (info)->dynobj = abfd;
+      insert = true;
+    }
+
+  if (section == &bfd_abs_section
+      && (IS_GOT_SYM (name) || IS_PLT_SYM (name)))
+    {
+      h = linux_link_hash_lookup (linux_hash_table (info), name, false,
+				  false, false);
+      if (h != NULL
+	  && h->root.root.type == bfd_link_hash_defined)
+	{
+	  if (new_fixup (info, h, value, ! IS_PLT_SYM(name)) == NULL)
+	    return false;
+	  return true;
+	}
+      if (hashp != NULL)
+	*hashp = (struct bfd_link_hash_entry *) h;
+    }
+
+  /* Do the usual procedure for adding a symbol.  */
+  if (! _bfd_generic_link_add_one_symbol (info, abfd, name, flags, section,
+					  value, string, copy, collect,
+					  hashp))
+    return false;
+
+  /* Insert a pointer to our table in the set vector.  The dynamic
+     linker requires this information */
+  if (insert)
+    {
+      asection *s;
+
+      /* Here we do our special thing to add the pointer to the
+	 dynamic section in the SHARABLE_CONFLICTS set vector.  */
+      s = bfd_get_section_by_name (linux_hash_table (info)->dynobj,
+				   ".dynamic");
+      BFD_ASSERT (s != NULL);
+
+      if (! (_bfd_generic_link_add_one_symbol
+	     (info, linux_hash_table (info)->dynobj, SHARABLE_CONFLICTS,
+	      BSF_GLOBAL | BSF_CONSTRUCTOR, s, 0, NULL, false, false, NULL)))
+	return false;
+    }
+
+  return true;
+}
+
+/* We will crawl the hash table and come here for every global symbol.
+   We will examine each entry and see if there are indications that we
+   need to add a fixup.  There are two possible cases - one is where
+   you have duplicate definitions of PLT or GOT symbols - these will
+   have already been caught and added as "builtin" fixups.  If we find
+   that the corresponding non PLT/GOT symbol is also present, we
+   convert it to a regular fixup instead.
+
+   This function is called via linux_link_hash_traverse.  */
+
+static boolean
+linux_tally_symbols (h, data)
+     struct linux_link_hash_entry *h;
+     PTR data;
+{
+  struct bfd_link_info *info = (struct bfd_link_info *) data;
+  struct fixup *f, *f1;
+  int is_plt;
+  struct linux_link_hash_entry *h1, *h2;
+
+  /* If this symbol is not a PLT/GOT, we do not even need to look at it */
+  is_plt = IS_PLT_SYM (h->root.root.root.string);
+
+  if (is_plt || IS_GOT_SYM (h->root.root.root.string))
+    {
+      /* Look up this symbol twice.  Once just as a regular lookup,
+	 and then again following all of the indirect links until we
+	 reach a real symbol.  */
+      h1 = linux_link_hash_lookup (linux_hash_table (info),
+				   (h->root.root.root.string
+				    + sizeof PLT_REF_PREFIX - 1),
+				   false, false, true);
+      /* h2 does not follow indirect symbols. */
+      h2 = linux_link_hash_lookup (linux_hash_table (info), 
+				   (h->root.root.root.string
+				    + sizeof PLT_REF_PREFIX - 1),
+				   false, false, false);
+
+      /* The real symbol must exist but if it is also an ABS symbol,
+	 there is no need to have a fixup.  This is because they both
+	 came from the same library.  If on the other hand, we had to
+	 use an indirect symbol to get to the real symbol, we add the
+	 fixup anyway, since there are cases where these symbols come
+	 from different shared libraries */
+      if (h1 != NULL
+	  && ((h1->root.root.type == bfd_link_hash_defined
+	       && h1->root.root.u.def.section != &bfd_abs_section)
+	      || h2->root.root.type == bfd_link_hash_indirect))
+	{
+	  f = new_fixup (info, h1, h->root.root.u.def.value, 0);
+	  if (f == NULL)
+	    {
+	      /* FIXME: No way to return error.  */
+	      abort ();
+	    }
+	  f->jump = is_plt;
+
+	  /* See if there is a "builtin" fixup already present
+	     involving this symbol.  If so, convert it to a regular
+	     fixup.  In the end, this relaxes some of the requirements
+	     about the order of performing fixups.  */
+	  for (f1 = linux_hash_table (info)->fixup_list;
+	       f1 != NULL;
+	       f1 = f1->next)
+	    {
+	      if (f1 == f)
+		continue;
+	      if (f1->h != h)
+		continue;
+	      f1->h = h1;
+	      f1->jump = is_plt;
+	      f1->builtin = 0;
+	    }
+	}
+
+      /* Quick and dirty way of stripping these symbols from the
+	 symtab. */
+      h->root.written = true;
+    }
+
+  return true;
+}
+
+/* This is called to set the size of the .dynamic section is.  It is
+   called by the Linux linker emulation before_allocation routine.  We
+   have finished reading all of the input files, and now we just scan
+   the hash tables to find out how many additional fixups are
+   required.  */
+
+boolean
+bfd_linux_size_dynamic_sections (output_bfd, info)
+     bfd *output_bfd;
+     struct bfd_link_info *info;
+{
+  struct fixup *f;
+  asection *s;
+
+  /* First find the fixups... */
+  linux_link_hash_traverse (linux_hash_table (info),
+			    linux_tally_symbols,
+			    (PTR) info);
+
+  /* If there are builtin fixups, leave room for a marker.  This is
+     used by the dynamic linker so that it knows that all that follow
+     are builtin fixups instead of regular fixups.  */
+  for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
+    {
+      if (f->builtin)
+	{
+	  ++linux_hash_table (info)->fixup_count;
+	  ++linux_hash_table (info)->local_builtins;
+	  break;
+	}
+    }
+
+  if (linux_hash_table (info)->dynobj == NULL)
+    {
+      if (linux_hash_table (info)->fixup_count > 0)
+	abort ();
+      return true;
+    }
+
+  /* Allocate memory for our fixup table.  We will fill it in later.  */
+  s = bfd_get_section_by_name (linux_hash_table (info)->dynobj, ".dynamic");
+  if (s != NULL)
+    {
+      s->_raw_size = 8 + linux_hash_table (info)->fixup_count * 8;
+      s->contents = (bfd_byte *) bfd_alloc (output_bfd, s->_raw_size);
+      if (s->contents == NULL)
+	{
+	  bfd_set_error (bfd_error_no_memory);
+	  return false;
+	}
+      memset (s->contents, 0, s->_raw_size);
+    }
+
+  return true;
+}
+
+/* We come here once we are ready to actually write the fixup table to
+   the output file.  Scan the fixup tables and so forth and generate
+   the stuff we need.  */
+
+static boolean
+linux_finish_dynamic_link (output_bfd, info)
+     bfd *output_bfd;
+     struct bfd_link_info *info;
+{
+  asection *s, *os, *is;
+  bfd_byte *fixup_table;
+  struct linux_link_hash_entry *h;
+  struct fixup *f;
+  unsigned int new_addr;
+  int section_offset;
+  int fixups_written;
+
+  if (linux_hash_table (info)->dynobj == NULL)
+    return true;
+
+  s = bfd_get_section_by_name (linux_hash_table (info)->dynobj, ".dynamic");
+  BFD_ASSERT (s != NULL);
+  os = s->output_section;
+  fixups_written = 0;
+
+#ifdef LINUX_LINK_DEBUG
+  printf ("Fixup table file offset: %x  VMA: %x\n", 
+	  os->filepos + s->output_offset,
+	  os->vma + s->output_offset);
+#endif
+
+  fixup_table = s->contents;
+  bfd_put_32 (output_bfd, linux_hash_table (info)->fixup_count, fixup_table);
+  fixup_table += 4;
+
+  /* Fill in fixup table.  */
+  for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
+    {
+      if (f->builtin)
+	continue;
+
+      if (f->h->root.root.type != bfd_link_hash_defined)
+	{
+	  /* FIXME!  */
+	  fprintf (stderr,
+		   "Symbol %s not defined for fixups\n",
+		   f->h->root.root.root.string);
+	  continue;
+	}
+
+      is = f->h->root.root.u.def.section;
+      section_offset = is->output_section->vma + is->output_offset;
+      new_addr = f->h->root.root.u.def.value + section_offset;
+
+#ifdef LINUX_LINK_DEBUG
+      printf ("Fixup(%d) %s: %x %x\n",f->jump, f->h->root.root.string,
+	      new_addr, f->value);
+#endif
+
+      if (f->jump)
+	{
+	  /* Relative address */
+	  new_addr = new_addr - (f->value + 5); 
+	  bfd_put_32 (output_bfd, new_addr, fixup_table);
+	  fixup_table += 4;
+	  bfd_put_32 (output_bfd, f->value + 1, fixup_table);
+	  fixup_table += 4;
+	}
+      else
+	{
+	  bfd_put_32 (output_bfd, new_addr, fixup_table);
+	  fixup_table += 4;
+	  bfd_put_32 (output_bfd, f->value, fixup_table);
+	  fixup_table += 4;
+	}
+      ++fixups_written;
+    }
+
+  if (linux_hash_table (info)->local_builtins != 0)
+    {
+      /* Special marker so we know to switch to the other type of fixup */
+      bfd_put_32 (output_bfd, 0, fixup_table);
+      fixup_table += 4;
+      bfd_put_32 (output_bfd, 0, fixup_table);
+      fixup_table += 4;
+      ++fixups_written;
+      for (f = linux_hash_table (info)->fixup_list; f != NULL; f = f->next)
+	{
+	  if (! f->builtin)
+	    continue;
+
+	  if (f->h->root.root.type != bfd_link_hash_defined)
+	    {
+	      /* FIXME!  */
+	      fprintf (stderr,
+		       "Symbol %s not defined for fixups\n",
+		       f->h->root.root.root.string);
+	      continue;
+	    }
+
+	  is = f->h->root.root.u.def.section;
+	  section_offset = is->output_section->vma + is->output_offset;
+	  new_addr = f->h->root.root.u.def.value + section_offset;
+
+#ifdef LINUX_LINK_DEBUG
+	  printf ("Fixup(B) %s: %x %x\n", f->h->root.root.string,
+		  new_addr, f->value);
+#endif
+
+	  bfd_put_32 (output_bfd, new_addr, fixup_table);
+	  fixup_table += 4;
+	  bfd_put_32 (output_bfd, f->value, fixup_table);
+	  fixup_table += 4;
+	  ++fixups_written;
+	}
+  }
+
+  if (linux_hash_table (info)->fixup_count != fixups_written)
+    {
+      /* FIXME!  */
+      fprintf (stderr, "Warning: fixup count mismatch\n");
+      while (linux_hash_table (info)->fixup_count > fixups_written)
+	{
+	  bfd_put_32 (output_bfd, 0, fixup_table);
+	  fixup_table += 4;
+	  bfd_put_32 (output_bfd, 0, fixup_table);
+	  fixup_table += 4;
+	  ++fixups_written;
+	}
+    }
+
+  h = linux_link_hash_lookup (linux_hash_table (info), 
+			      "__BUILTIN_FIXUPS__",
+			      false, false, false);
+
+  if (h != NULL && h->root.root.type == bfd_link_hash_defined)
+    {
+      is = h->root.root.u.def.section;
+      section_offset = is->output_section->vma + is->output_offset;
+      new_addr = h->root.root.u.def.value + section_offset;
+
+#ifdef LINUX_LINK_DEBUG
+      printf ("Builtin fixup table at %x\n", new_addr);
+#endif
+
+      bfd_put_32 (output_bfd, new_addr, fixup_table);
+    }
+  else
+    bfd_put_32 (output_bfd, 0, fixup_table);
+
+  if (bfd_seek (output_bfd, os->filepos + s->output_offset, SEEK_SET) != 0)
+    return false;
+
+  if (bfd_write ((PTR) s->contents, 1, s->_raw_size, output_bfd)
+      != s->_raw_size)
+    return false;
+
+  return true;
+}
+
+#define MY_bfd_link_hash_table_create linux_link_hash_table_create
+#define MY_add_one_symbol linux_add_one_symbol
+#define MY_finish_dynamic_link linux_finish_dynamic_link
 
 #include "aout-target.h"