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.

5 files changed, 62 insertions, 103 deletions

diff --git a/ChangeLog b/ChangeLog
index 4e65832..edca9f2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 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.
+
 	* gmon/Makefile (headers): Remove machine-gmon.h.
 	* sysdeps/stub/machine-gmon.h, sysdeps/i386/machine-gmon.h: Removed.
 	* gmon/mcount.c [! NO_UNDERSCORES] (_mcount): Specify "mcount" as
diff --git a/sysdeps/i386/dl-runtime.c b/elf/dl-runtime.c
index 5e4a289..7e554bc 100644
--- a/sysdeps/i386/dl-runtime.c
+++ b/elf/dl-runtime.c
@@ -1,5 +1,5 @@
-/* On-demand PLT fixup for shared objects.  i386 version.
-Copyright (C) 1995 Free Software Foundation, Inc.
+/* 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
@@ -20,28 +20,42 @@ Cambridge, MA 02139, USA.  */
 #include <link.h>
 #include "dynamic-link.h"
 
-/* This function is not called in the normal way.  The PLT jumps here, not
-   using a call.  The stack looks like this:
-
--->8(%esp)	address to return to the caller of the function in the PLT
-   4(%esp)	relocation offset for this PLT entry
-   0(%esp)	identifier for this shared object (struct link_map *)
-
-   The user expects the real function the PLT refers to to be entered
-   with 8(%esp) as the top of stack.  */
-
-void
-_dl_runtime_resolve (Elf32_Word reloc_offset)
+/* 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)
 {
-  __label__ return_insn;
-  struct link_map *l = (void *) (&reloc_offset)[-1];
-
   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 Elf32_Rel *const reloc
+  const PLTREL *const reloc
     = (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr +
 		      reloc_offset);
 
@@ -61,34 +75,26 @@ _dl_runtime_resolve (Elf32_Word reloc_offset)
     }
   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_rel (l, reloc, loadbase, definer);
+  elf_machine_relplt (l, reloc, loadbase, definer);
 
-  /* The top of the stack is the word we set L from; but this location
-     holds the address we will return to.  Store there the address of a
-     "ret" instruction, which will pop the stack and run the code at the
-     address in the next stack word.  */
-  (&reloc_offset)[-1] = (Elf32_Word) &&return_insn;
+  return *(Elf32_Addr *) (l->l_addr + reloc->r_offset);
+}
 
-  /* The next stack word is our argument RELOC_OFFSET; but that "ret" will
-     pop and jump to this location, and the next stack word is the user's
-     return address.  So store here the resolved address of the function
-     referred to by this PLT entry; once "ret" pops this address, the
-     function in the shared object will run with the stack arranged just as
-     when the user entered the PLT.  */
-  (&reloc_offset)[0] = *(Elf32_Word *) (l->l_addr + reloc->r_offset);
 
-  return;
+/* 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.  */
 
- return_insn: asm volatile ("ret");
-}
+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++;
     }
 
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 4ce4d4b..8f72073 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -157,8 +157,20 @@ elf_machine_runtime_setup (struct link_map *l, int lazy)
 	 the offset on the stack, and then jump to the resolved address.  */
       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
     }
-}
 
+  /* This code is used in dl-runtime.c to call the `fixup' function
+     and then redirect to the address it returns.  */
+#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
+	.globl _dl_runtime_resolve
+	.type _dl_runtime_resolve, @function
+_dl_runtime_resolve:
+	call fixup	# Args pushed by PLT.
+	addl $8, %esp	# Pop args.
+	jmp *%eax	# Jump to function address.
+");
+/* The PLT uses Elf32_Rel relocs.  */
+#define elf_machine_relplt elf_machine_rel
+}
 
 /* Mask identifying addresses reserved for the user program,
    where the dynamic linker should not map anything.  */
diff --git a/sysdeps/stub/dl-runtime.c b/sysdeps/stub/dl-runtime.c
deleted file mode 100644
index f660ef2..0000000
--- a/sysdeps/stub/dl-runtime.c
+++ /dev/null
@@ -1,64 +0,0 @@
-/* On-demand PLT fixup for shared objects.  Stub version.
-Copyright (C) 1995 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"
-
-/* This function is not called in the normal way.  The PLT jumps here, not
-   using a call.  */
-void
-_dl_runtime_resolve ()
-{
-  struct link_map *l = ???;
-  Elf32_Word reloc_offset = ???;
-
-  const Elf32_Sym *const symtab
-    = (const Elf32_Sym *) l->l_info[DT_SYMTAB]->d_un.d_ptr;
-  const char *strtab
-    = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
-
-  const Elf32_Rel *const reloc = (void *) (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_prev->l_next = real_next;
-      l->l_next = _dl_loaded;
-      scope = l;
-    }
-  else
-    scope = _dl_loaded;
-  
-  definer = &symtab[ELF32_R_SYM (reloc->r_info)];
-  loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, scope);
-  
-  /* Restore list frobnication done above for DT_SYMBOLIC.  */
-  l->l_next = real_next;
-  l->l_prev->l_next = l;
-
-  /* Apply the relocation with that value.  */
-  elf_machine_rel (l->l_addr, l->l_info, reloc, loadbase, definer);
-}