[glibc.git] / sysdeps / i386 / dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  i386 version.
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.  */

#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; \
  (dynamic_info)[DT_RELSZ]->d_un.d_val -= sizeof (Elf32_Rel);

/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
   MAP is the object containing the reloc.  */

static inline void
elf_machine_rel (struct link_map *map,
		 const Elf32_Rel *reloc, const Elf32_Sym *sym,
		 Elf32_Addr (*resolve) (const Elf32_Sym **ref,
					Elf32_Addr reloc_addr,
					int noplt))
{
  Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
  Elf32_Addr loadbase;

  switch (ELF32_R_TYPE (reloc->r_info))
    {
    case R_386_COPY:
      loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
      memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
      break;
    case R_386_GLOB_DAT:
      loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
		  /* RESOLVE is null during bootstrap relocation.  */
		  map->l_addr);
      *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
      break;
    case R_386_JMP_SLOT:
      loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 1) :
		  /* RESOLVE is null during bootstrap relocation.  */
		  map->l_addr);
      *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
      break;
    case R_386_32:
      if (map->l_type == lt_interpreter)
	{
	  /* Undo the relocation done here during bootstrapping.  Now we will
	     relocate it anew, possibly using a binding found in the user
	     program or a loaded library rather than the dynamic linker's
	     built-in definitions used while loading those libraries.  */
	  const Elf32_Sym *const dlsymtab
	    = (void *) (map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
	  *reloc_addr -= (map->l_addr +
			  dlsymtab[ELF32_R_SYM (reloc->r_info)].st_value);
	}
      loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
      *reloc_addr += sym ? (loadbase + sym->st_value) : 0;
      break;
    case R_386_RELATIVE:
      if (map->l_type != lt_interpreter) /* Already done in dynamic linker.  */
	*reloc_addr += map->l_addr;
      break;
    case R_386_PC32:
      loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
      *reloc_addr += ((sym ? (loadbase + sym->st_value) : 0) -
		      (Elf32_Addr) reloc_addr);
      break;
    case R_386_NONE:		/* Alright, Wilbur.  */
      break;
    default:
      assert (! "unexpected dynamic reloc type");
      break;
    }
}

static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf32_Rel *reloc)
{
  Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
  switch (ELF32_R_TYPE (reloc->r_info))
    {
    case R_386_JMP_SLOT:
      *reloc_addr += map->l_addr;
      break;
    default:
      assert (! "unexpected PLT reloc type");
      break;
    }
}

/* Nonzero iff TYPE describes relocation of a PLT entry, so
   PLT entries should not be allowed to define the value.  */
#define elf_machine_pltrel_p(type) ((type) == R_386_JMP_SLOT)

/* The i386 never uses Elf32_Rela relocations.  */
#define ELF_MACHINE_NO_RELA 1


/* 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, int lazy)
{
  Elf32_Addr *got;
  extern void _dl_runtime_resolve (Elf32_Word);

  if (l->l_info[DT_JMPREL] && lazy)
    {
      /* 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].  */
      got = (Elf32_Addr *) (l->l_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;
    }

  /* 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.  */
#define ELF_MACHINE_USER_ADDRESS_MASK	0xf8000000UL


/* 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\
.globl _dl_start_user\n\
_start:\n\
	call _dl_start\n\
_dl_start_user:\n\
	# Save the user entry point address in %edi.\n\
	movl %eax, %edi\n\
	# Point %ebx at the GOT.
	call 0f\n\
0:	popl %ebx\n\
	addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx\n\
	# See if we were run as a command with the executable file\n\
	# name as an extra leading argument.\n\
	movl _dl_skip_args@GOT(%ebx), %eax\n\
	movl (%eax),%eax\n\
	# Pop the original argument count.\n\
	popl %ecx\n\
	# Subtract _dl_skip_args from it.\n\
	subl %eax, %ecx\n\
	# Adjust the stack pointer to skip _dl_skip_args words.\n\
	leal (%esp,%eax,4), %esp\n\
	# Push back the modified argument count.\n\
	pushl %ecx\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 and %edi)\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\
1:	# Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
	movl _dl_fini@GOT(%ebx), %edx\n\
	# Jump to the user's entry point.\n\
	jmp *%edi\n\
");
Commit	Line	Data
d66e34cd	1	/* Machine-dependent ELF dynamic relocation inline functions. i386 version.
a2e1b046	2	Copyright (C) 1995, 1996 Free Software Foundation, Inc.
d66e34cd RM	3	This file is part of the GNU C Library.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Library General Public License as
	7	published by the Free Software Foundation; either version 2 of the
	8	License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Library General Public License for more details.
	14
	15	You should have received a copy of the GNU Library General Public
	16	License along with the GNU C Library; see the file COPYING.LIB. If
	17	not, write to the Free Software Foundation, Inc., 675 Mass Ave,
	18	Cambridge, MA 02139, USA. */
	19
	20	#define ELF_MACHINE_NAME "i386"
	21
	22	#include <assert.h>
	23	#include <string.h>
	24	#include <link.h>
	25
	26
	27	/* Return nonzero iff E_MACHINE is compatible with the running host. */
	28	static inline int
	29	elf_machine_matches_host (Elf32_Half e_machine)
	30	{
	31	switch (e_machine)
	32	{
	33	case EM_386:
	34	case EM_486:
	35	return 1;
	36	default:
	37	return 0;
	38	}
	39	}
	40
	41
	42	/* Return the run-time address of the _GLOBAL_OFFSET_TABLE_.
	43	Must be inlined in a function which uses global data. */
	44	static inline Elf32_Addr *
	45	elf_machine_got (void)
	46	{
	47	register Elf32_Addr *got asm ("%ebx");
	48	return got;
	49	}
	50
	51
	52	/* Return the run-time load address of the shared object. */
	53	static inline Elf32_Addr
	54	elf_machine_load_address (void)
	55	{
	56	Elf32_Addr addr;
	57	asm (" call here\n"
	58	"here: popl %0\n"
	59	" subl $here, %0"
	60	: "=r" (addr));
	61	return addr;
	62	}
	63	/* The `subl' insn above will contain an R_386_32 relocation entry
	64	intended to insert the run-time address of the label `here'.
	65	This will be the first relocation in the text of the dynamic linker;
	66	we skip it to avoid trying to modify read-only text in this early stage. */
67	#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
44c8d1a2	68	++(const Elf32_Rel *) (dynamic_info)[DT_REL]->d_un.d_ptr; \
a993273c	69	(dynamic_info)[DT_RELSZ]->d_un.d_val -= sizeof (Elf32_Rel);
d66e34cd RM	70
d66e34cd RM	71	/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
421f82e5	72	MAP is the object containing the reloc. */
d66e34cd RM	73
d66e34cd RM	74	static inline void
421f82e5	75	elf_machine_rel (struct link_map *map,
710f7bab RM	76	const Elf32_Rel reloc, const Elf32_Sym sym,
	77	Elf32_Addr (resolve) (const Elf32_Sym *ref,
	78	Elf32_Addr reloc_addr,
	79	int noplt))
d66e34cd	80	{
a1a9d215	81	Elf32_Addr const reloc_addr = (void ) (map->l_addr + reloc->r_offset);
710f7bab	82	Elf32_Addr loadbase;
d66e34cd RM	83
	84	switch (ELF32_R_TYPE (reloc->r_info))
	85	{
	86	case R_386_COPY:
710f7bab RM	87	loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
710f7bab RM	88	memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
d66e34cd RM	89	break;
d66e34cd RM	90	case R_386_GLOB_DAT:
710f7bab RM	91	loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
	92	/* RESOLVE is null during bootstrap relocation. */
	93	map->l_addr);
	94	*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
	95	break;
d66e34cd	96	case R_386_JMP_SLOT:
710f7bab RM	97	loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 1) :
	98	/* RESOLVE is null during bootstrap relocation. */
	99	map->l_addr);
	100	*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
d66e34cd RM	101	break;
d66e34cd RM	102	case R_386_32:
5bf62f2d RM	103	if (map->l_type == lt_interpreter)
	104	{
	105	/* Undo the relocation done here during bootstrapping. Now we will
	106	relocate it anew, possibly using a binding found in the user
	107	program or a loaded library rather than the dynamic linker's
	108	built-in definitions used while loading those libraries. */
	109	const Elf32_Sym *const dlsymtab
	110	= (void *) (map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
	111	*reloc_addr -= (map->l_addr +
	112	dlsymtab[ELF32_R_SYM (reloc->r_info)].st_value);
	113	}
710f7bab RM	114	loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
710f7bab RM	115	*reloc_addr += sym ? (loadbase + sym->st_value) : 0;
d66e34cd RM	116	break;
d66e34cd RM	117	case R_386_RELATIVE:
5bf62f2d RM	118	if (map->l_type != lt_interpreter) /* Already done in dynamic linker. */
5bf62f2d RM	119	*reloc_addr += map->l_addr;
d66e34cd RM	120	break;
d66e34cd RM	121	case R_386_PC32:
710f7bab RM	122	loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
	123	*reloc_addr += ((sym ? (loadbase + sym->st_value) : 0) -
	124	(Elf32_Addr) reloc_addr);
d66e34cd	125	break;
86fe2915 RM	126	case R_386_NONE: /* Alright, Wilbur. */
86fe2915 RM	127	break;
d66e34cd RM	128	default:
	129	assert (! "unexpected dynamic reloc type");
	130	break;
	131	}
	132	}
	133
a1a9d215 RM	134	static inline void
	135	elf_machine_lazy_rel (struct link_map map, const Elf32_Rel reloc)
	136	{
	137	Elf32_Addr const reloc_addr = (void ) (map->l_addr + reloc->r_offset);
	138	switch (ELF32_R_TYPE (reloc->r_info))
	139	{
	140	case R_386_JMP_SLOT:
	141	*reloc_addr += map->l_addr;
	142	break;
	143	default:
	144	assert (! "unexpected PLT reloc type");
	145	break;
	146	}
	147	}
d66e34cd	148
6c03c2cf RM	149	/* Nonzero iff TYPE describes relocation of a PLT entry, so
	150	PLT entries should not be allowed to define the value. */
	151	#define elf_machine_pltrel_p(type) ((type) == R_386_JMP_SLOT)
	152
d66e34cd	153	/* The i386 never uses Elf32_Rela relocations. */
421f82e5	154	#define ELF_MACHINE_NO_RELA 1
d66e34cd RM	155
	156
	157	/* Set up the loaded object described by L so its unrelocated PLT
	158	entries will jump to the on-demand fixup code in dl-runtime.c. */
	159
	160	static inline void
a2e1b046	161	elf_machine_runtime_setup (struct link_map *l, int lazy)
d66e34cd	162	{
a1a9d215	163	Elf32_Addr *got;
d66e34cd	164	extern void _dl_runtime_resolve (Elf32_Word);
a1a9d215	165
a2e1b046 RM	166	if (l->l_info[DT_JMPREL] && lazy)
	167	{
	168	/* The GOT entries for functions in the PLT have not yet been filled
	169	in. Their initial contents will arrange when called to push an
	170	offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
	171	and then jump to _GLOBAL_OFFSET_TABLE[2]. */
	172	got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
	173	got[1] = (Elf32_Addr) l; /* Identify this shared object. */
	174	/* This function will get called to fix up the GOT entry indicated by
	175	the offset on the stack, and then jump to the resolved address. */
	176	got[2] = (Elf32_Addr) &_dl_runtime_resolve;
	177	}
d66e34cd	178
38334018 RM	179	/* This code is used in dl-runtime.c to call the `fixup' function
	180	and then redirect to the address it returns. */
	181	#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
	182	.globl _dl_runtime_resolve
	183	.type _dl_runtime_resolve, @function
	184	_dl_runtime_resolve:
	185	call fixup # Args pushed by PLT.
	186	addl $8, %esp # Pop args.
	187	jmp *%eax # Jump to function address.
	188	");
	189	/* The PLT uses Elf32_Rel relocs. */
	190	#define elf_machine_relplt elf_machine_rel
	191	}
d66e34cd	192
5bf62f2d RM	193	/* Mask identifying addresses reserved for the user program,
	194	where the dynamic linker should not map anything. */
	195	#define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
	196
	197
	198
d66e34cd RM	199	/* Initial entry point code for the dynamic linker.
	200	The C function `_dl_start' is the real entry point;
	201	its return value is the user program's entry point. */
	202
	203	#define RTLD_START asm ("\
	204	.text\n\
	205	.globl _start\n\
421f82e5 RM	206	.globl _dl_start_user\n\
	207	_start:\n\
	208	call _dl_start\n\
	209	_dl_start_user:\n\
	210	# Save the user entry point address in %edi.\n\
	211	movl %eax, %edi\n\
	212	# Point %ebx at the GOT.
a1a9d215 RM	213	call 0f\n\
	214	0: popl %ebx\n\
	215	addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx\n\
	216	# See if we were run as a command with the executable file\n\
	217	# name as an extra leading argument.\n\
24906b43	218	movl _dl_skip_args@GOT(%ebx), %eax\n\
a1a9d215	219	movl (%eax),%eax\n\
24906b43 RM	220	# Pop the original argument count.\n\
	221	popl %ecx\n\
	222	# Subtract _dl_skip_args from it.\n\
	223	subl %eax, %ecx\n\
	224	# Adjust the stack pointer to skip _dl_skip_args words.\n\
	225	leal (%esp,%eax,4), %esp\n\
	226	# Push back the modified argument count.\n\
	227	pushl %ecx\n\
d66e34cd RM	228	# Call _dl_init_next to return the address of an initializer\n\
	229	# function to run.\n\
	230	0: call _dl_init_next@PLT\n\
	231	# Check for zero return, when out of initializers.\n\
	232	testl %eax,%eax\n\
	233	jz 1f\n\
	234	# Call the shared object initializer function.\n\
a1a9d215	235	# NOTE: We depend only on the registers (%ebx and %edi)\n\
d66e34cd RM	236	# and the return address pushed by this call;\n\
	237	# the initializer is called with the stack just\n\
	238	# as it appears on entry, and it is free to move\n\
	239	# the stack around, as long as it winds up jumping to\n\
	240	# the return address on the top of the stack.\n\
	241	call *%eax\n\
	242	# Loop to call _dl_init_next for the next initializer.\n\
	243	jmp 0b\n\
a1a9d215 RM	244	1: # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
a1a9d215 RM	245	movl _dl_fini@GOT(%ebx), %edx\n\
421f82e5 RM	246	# Jump to the user's entry point.\n\
421f82e5 RM	247	jmp *%edi\n\
d66e34cd	248	");