about summary refs log tree commit diff
path: root/sysdeps/i386
diff options
context:
space:
mode:
Diffstat (limited to 'sysdeps/i386')
-rw-r--r--sysdeps/i386/dl-machine.h169
-rw-r--r--sysdeps/i386/dl-runtime.c92
-rw-r--r--sysdeps/i386/elf/start.S86
3 files changed, 347 insertions, 0 deletions
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
new file mode 100644
index 0000000000..5e1ee2a413
--- /dev/null
+++ b/sysdeps/i386/dl-machine.h
@@ -0,0 +1,169 @@
+/* Machine-dependent ELF dynamic relocation inline functions.  i386 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.  */
+
+#define ELF_MACHINE_NAME "i386"
+
+#include <assert.h>
+#include <string.h>
+#include <link.h>
+
+
+/* Return nonzero iff E_MACHINE is compatible with the running host.  */
+static inline int
+elf_machine_matches_host (Elf32_Half e_machine)
+{
+  switch (e_machine)
+    {
+    case EM_386:
+    case EM_486:
+      return 1;
+    default:
+      return 0;
+    }
+}
+
+
+/* Return the run-time address of the _GLOBAL_OFFSET_TABLE_.
+   Must be inlined in a function which uses global data.  */
+static inline Elf32_Addr *
+elf_machine_got (void)
+{
+  register Elf32_Addr *got asm ("%ebx");
+  return got;
+}
+
+
+/* Return the run-time load address of the shared object.  */
+static inline Elf32_Addr
+elf_machine_load_address (void)
+{
+  Elf32_Addr addr;
+  asm ("	call here\n"
+       "here:	popl %0\n"
+       "	subl $here, %0"
+       : "=r" (addr));
+  return addr;
+}
+/* The `subl' insn above will contain an R_386_32 relocation entry
+   intended to insert the run-time address of the label `here'.
+   This will be the first relocation in the text of the dynamic linker;
+   we skip it to avoid trying to modify read-only text in this early stage.  */
+#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
+  ++(const Elf32_Rel *) (dynamic_info)[DT_REL]->d_un.d_ptr;
+
+/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
+   LOADADDR is the load address of the object; INFO is an array indexed
+   by DT_* of the .dynamic section info.  */
+
+static inline void
+elf_machine_rel (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
+		 const Elf32_Rel *reloc,
+		 Elf32_Addr sym_loadaddr, const Elf32_Sym *sym)
+{
+  Elf32_Addr *const reloc_addr = (Elf32_Addr *) reloc->r_offset;
+  const Elf32_Addr sym_value = sym_loadaddr + sym->st_value;
+
+  switch (ELF32_R_TYPE (reloc->r_info))
+    {
+    case R_386_COPY:
+      memcpy (reloc_addr, (void *) sym_value, sym->st_size);
+      break;
+    case R_386_GLOB_DAT:
+    case R_386_JMP_SLOT:
+      *reloc_addr = sym_value;
+      break;
+    case R_386_32:
+      *reloc_addr += sym_value;
+      break;
+    case R_386_RELATIVE:
+      *reloc_addr += loadaddr;
+      break;
+    case R_386_PC32:
+      *reloc_addr = sym_value - (Elf32_Addr) reloc_addr;
+      break;
+    default:
+      assert (! "unexpected dynamic reloc type");
+      break;
+    }
+}
+
+
+/* The i386 never uses Elf32_Rela relocations.  */
+static inline void
+elf_machine_rela (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
+		  const Elf32_Rela *reloc, 
+		  Elf32_Addr sym_loadaddr, const Elf32_Sym *sym)
+{
+  _dl_signal_error (0, "Elf32_Rela relocation requested -- unused on i386");
+}
+
+
+/* Set up the loaded object described by L so its unrelocated PLT
+   entries will jump to the on-demand fixup code in dl-runtime.c.  */
+
+static inline void
+elf_machine_runtime_setup (struct link_map *l)
+{
+  extern void _dl_runtime_resolve (Elf32_Word);
+  /* The GOT entries for functions in the PLT have not yet been filled
+     in.  Their initial contents will arrange when called to push an
+     offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
+     and then jump to _GLOBAL_OFFSET_TABLE[2].  */
+  Elf32_Addr *got = (Elf32_Addr *) l->l_info[DT_PLTGOT]->d_un.d_ptr;
+  got[1] = (Elf32_Addr) l;	/* Identify this shared object.  */
+  /* This function will get called to fix up the GOT entry indicated by
+     the offset on the stack, and then jump to the resolved address.  */
+  got[2] = (Elf32_Addr) &_dl_runtime_resolve;
+}
+
+
+/* Initial entry point code for the dynamic linker.
+   The C function `_dl_start' is the real entry point;
+   its return value is the user program's entry point.  */
+
+#define RTLD_START asm ("\
+.text\n\
+.globl _start\n\
+_start:	call _dl_start\n\
+	# Save the user entry point address in %ebx.\n\
+	movl %eax, %ebx\n\
+	# Call _dl_init_next to return the address of an initializer\n\
+	# function to run.\n\
+0:	call _dl_init_next@PLT\n\
+	# Check for zero return, when out of initializers.\n\
+	testl %eax,%eax\n\
+	jz 1f\n\
+	# Call the shared object initializer function.\n\
+	# NOTE: We depend only on the registers (%ebx)\n\
+	# and the return address pushed by this call;\n\
+	# the initializer is called with the stack just\n\
+	# as it appears on entry, and it is free to move\n\
+	# the stack around, as long as it winds up jumping to\n\
+	# the return address on the top of the stack.\n\
+	call *%eax\n\
+	# Loop to call _dl_init_next for the next initializer.\n\
+	jmp 0b\n\
+	# Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
+1:	call 2f\n\
+2:	popl %eax\n\
+	addl $_GLOBAL_OFFSET_TABLE_+[.-2b], %eax\n\
+	leal _dl_fini@GOT(%eax), %edx\n\
+	# Jump to the user entry point.\n\
+	jmp *%ebx\n\
+");
diff --git a/sysdeps/i386/dl-runtime.c b/sysdeps/i386/dl-runtime.c
new file mode 100644
index 0000000000..897524fdd3
--- /dev/null
+++ b/sysdeps/i386/dl-runtime.c
@@ -0,0 +1,92 @@
+/* On-demand PLT fixup for shared objects.  i386 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.  */
+
+register void *sp asm ("%esp");
+
+#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
+   8(%esp) as the top of stack.  */
+
+void
+_dl_runtime_resolve (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_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);
+
+  /* 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;
+
+  /* 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 *) reloc->r_offset;
+
+  return;
+
+ return_insn: asm volatile ("ret");
+}
diff --git a/sysdeps/i386/elf/start.S b/sysdeps/i386/elf/start.S
new file mode 100644
index 0000000000..5c29ce412a
--- /dev/null
+++ b/sysdeps/i386/elf/start.S
@@ -0,0 +1,86 @@
+/* Startup code compliant to the ELF i386 ABI.
+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.  */
+
+/* This is the canonical entry point, usually the first thing in the text
+   segment.  The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
+   point runs, most registers' values are unspecified, except for:
+
+   %edx		Contains a function pointer to be registered with `atexit'.
+   		This is how the dynamic linker arranges to have DT_FINI
+		functions called for shared libraries that have been loaded
+		before this code runs.
+
+   %esp		The stack contains the arguments and environment:
+   		0(%esp)			argc
+		4(%esp)			argv[0]
+		...
+		(4*argc)(%esp)		NULL
+		(4*(argc+1))(%esp)	envp[0]
+		...
+					NULL
+*/
+
+	.text	
+	.globl _start
+_start:
+	/* Clear the frame pointer.  The ABI suggests this be done, to mark
+	   the outermost frame obviously.  */
+	movl $0, %ebp
+
+	/* %edx contains the address of the shared library termination
+	   function, which we will register with `atexit' to be called by
+	   `exit'.  I suspect that on some systems, and when statically
+	   linked, this will not be set by anything to any function
+	   pointer; hopefully it will be zero so we don't try to call
+	   random pointers.  */
+	testl %edx
+	jeq nofini
+	pushl %edx
+	call atexit
+	addl $4, %esp
+nofini:
+
+	/* Do essential libc initialization.  In statically linked
+	   programs under the GNU Hurd, this is what sets up the
+	   arguments on the stack for the code below.  */
+	call __libc_init_first
+
+	/* Extract the arguments and environment as encoded on the stack
+	   and set up the arguments for `main': argc, argv, envp.  */
+	popl %esi		/* Pop the argument count.  */
+	leal 4(%esp,%esi,4), %eax /* envp = &argv[argc + 1] */
+	movl %eax, _environ	/* Store it in the global variable.  */
+	pushl %eax		/* Push third argument: envp.  */
+	leal 4(%esp), %eax	/* argv starts just above that word.  */
+	pushl %eax		/* Push second argument: argv.  */
+	pushl %esi		/* Push first argument: argc.  */
+
+	/* Call `_init', which is the entry point to our own `.init'
+	   section; and register with `atexit' to have `exit' call
+	   `_fini', which is the entry point to our own `.fini' section.  */
+	call _init
+	pushl $_fini
+	call atexit
+	addl $4, %esp
+
+	/* Call the user's main function, and exit with its value.  */
+	call main
+	pushl %eax
+	call exit		/* This should never return.  */
+	hlt			/* Crash if somehow it does return.  */