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glibc/sysdeps/i386/dl-machine.h
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/* 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; \ | |
(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, | |
Elf32_Addr sym_loadaddr, const Elf32_Sym *sym) | |
{ | |
Elf32_Addr *const reloc_addr = (void *) (map->l_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: | |
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); | |
} | |
*reloc_addr += sym_value; | |
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: | |
*reloc_addr += sym_value - (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; | |
} | |
} | |
/* 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) | |
{ | |
Elf32_Addr *got; | |
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]. */ | |
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; | |
} | |
/* 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\ | |
"); |