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/* 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, undo;
weak_symbol (_dl_rtld_map); /* Defined in rtld.c, but not in libc.a. */
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 (resolve && map == &_dl_rtld_map)
/* 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. */
undo = map->l_addr + sym->st_value;
else
undo = 0;
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) - undo;
break;
case R_386_RELATIVE:
if (!resolve || map != &_dl_rtld_map) /* Already done in rtld itself. */
*reloc_addr += map->l_addr;
break;
case R_386_PC32:
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) -
(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\
pushl %esp\n\
call _dl_start\n\
popl %ebx\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\
# Push _dl_default_scope[2] as argument in _dl_init_next call below.\n\
movl _dl_default_scope@GOT(%ebx), %eax\n\
movl 8(%eax), %esi\n\
0: pushl %esi\n\
# Call _dl_init_next to return the address of an initializer\n\
# function to run.\n\
call _dl_init_next@PLT\n\
addl $4, %esp # Pop argument.\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, %esi 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\
");
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