Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu>

	* sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE,
	elf_machine_relplt): New macros.
	* elf/dl-runtime.c: New file.
	* sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed.
	* sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE,
	elf_machine_relplt): New macros.
	* elf/dl-runtime.c: New file.
	* sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed.

2 files changed, 102 insertions, 2 deletions

diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
new file mode 100644
index 0000000..7e554bc
--- /dev/null
+++ b/elf/dl-runtime.c
@@ -0,0 +1,100 @@
+/* On-demand PLT fixup for shared objects.
+Copyright (C) 1995, 1996 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 Library General Public License as
+published by the Free Software Foundation; either version 2 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <link.h>
+#include "dynamic-link.h"
+
+/* Figure out the right type, Rel or Rela.  */
+#define elf_machine_rel 1
+#define elf_machine_rela 2
+#if elf_machine_relplt == elf_machine_rel
+#define PLTREL Elf32_Rel
+#elif elf_machine_relplt == elf_machine_rela
+#define PLTREL Elf32_Rela
+#else
+#error "dl-machine.h bug: elf_machine_relplt not rel or rela"
+#endif
+#undef elf_machine_rel
+#undef elf_machine_rela
+
+/* We need to define the function as a local symbol so that the reference
+   in the trampoline code will be a local PC-relative call.  Tell the
+   compiler not to worry that the function appears not to be called.  */
+
+static Elf32_Addr fixup (struct link_map *l, Elf32_Word reloc_offset)
+     __attribute__ ((unused));
+
+/* This function is called through a special trampoline from the PLT the
+   first time each PLT entry is called.  We must perform the relocation
+   specified in the PLT of the given shared object, and return the resolved
+   function address to the trampoline, which will restart the original call
+   to that address.  Future calls will bounce directly from the PLT to the
+   function.  */
+
+static Elf32_Addr
+fixup (struct link_map *l, Elf32_Word reloc_offset)
+{
+  const Elf32_Sym *const symtab
+    = (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr);
+  const char *strtab =
+    (const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
+
+  const PLTREL *const reloc
+    = (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr +
+		      reloc_offset);
+
+  const Elf32_Sym *definer;
+  Elf32_Addr loadbase;
+  struct link_map *scope, *real_next;
+
+  /* Look up the symbol's run-time value.  */
+
+  real_next = l->l_next;
+  if (l->l_info[DT_SYMBOLIC])
+    {
+      l->l_next = _dl_loaded;
+      if (l->l_prev)
+	l->l_prev->l_next = real_next;
+      scope = l;
+    }
+  else
+    scope = _dl_loaded;
+
+  definer = &symtab[ELF32_R_SYM (reloc->r_info)];
+  loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer,
+				scope, l->l_name, 0);
+
+  /* Restore list frobnication done above for DT_SYMBOLIC.  */
+  l->l_next = real_next;
+  if (l->l_prev)
+    l->l_prev->l_next = l;
+
+  /* Apply the relocation with that value.  */
+  elf_machine_relplt (l, reloc, loadbase, definer);
+
+  return *(Elf32_Addr *) (l->l_addr + reloc->r_offset);
+}
+
+
+/* This macro is defined in dl-machine.h to define the entry point called
+   by the PLT.  The `fixup' function above does the real work, but a little
+   more twiddling is needed to get the stack right and jump to the address
+   finally resolved.  */
+
+ELF_MACHINE_RUNTIME_TRAMPOLINE
diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index ed8d24c..38236ba 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -1,5 +1,5 @@
 /* Inline functions for dynamic linking.
-Copyright (C) 1995 Free Software Foundation, Inc.
+Copyright (C) 1995, 1996 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
@@ -43,7 +43,7 @@ elf_get_dynamic_info (Elf32_Dyn *dyn, Elf32_Dyn *info[DT_NUM + DT_PROCNUM])
 	       dyn->d_tag < DT_LOPROC + DT_PROCNUM)
 	info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn;
       else
-	assert (! "bad dynamic tag");	
+	assert (! "bad dynamic tag");
       dyn++;
     }