386 lines
12 KiB
C
386 lines
12 KiB
C
/* Machine-dependent ELF dynamic relocation inline functions. i386 version.
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Copyright (C) 1995, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef dl_machine_h
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#define dl_machine_h
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#define ELF_MACHINE_NAME "i386"
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#include <sys/param.h>
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/* Return nonzero iff ELF header is compatible with the running host. */
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static inline int __attribute__ ((unused))
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elf_machine_matches_host (const Elf32_Ehdr *ehdr)
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{
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return ehdr->e_machine == EM_386;
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}
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/* Return the link-time address of _DYNAMIC. Conveniently, this is the
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first element of the GOT. This must be inlined in a function which
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uses global data. */
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static inline Elf32_Addr __attribute__ ((unused))
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elf_machine_dynamic (void)
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{
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register Elf32_Addr *got asm ("%ebx");
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return *got;
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}
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/* Return the run-time load address of the shared object. */
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static inline Elf32_Addr __attribute__ ((unused))
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elf_machine_load_address (void)
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{
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Elf32_Addr addr;
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asm ("leal _dl_start@GOTOFF(%%ebx), %0\n"
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"subl _dl_start@GOT(%%ebx), %0"
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: "=r" (addr) : : "cc");
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return addr;
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}
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#if !defined PROF && !__BOUNDED_POINTERS__
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/* We add a declaration of this function here so that in dl-runtime.c
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the ELF_MACHINE_RUNTIME_TRAMPOLINE macro really can pass the parameters
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in registers.
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We cannot use this scheme for profiling because the _mcount call
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destroys the passed register information. */
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/* GKM FIXME: Fix trampoline to pass bounds so we can do
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without the `__unbounded' qualifier. */
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static ElfW(Addr) fixup (struct link_map *__unbounded l, ElfW(Word) reloc_offset)
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__attribute__ ((regparm (2), unused));
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static ElfW(Addr) profile_fixup (struct link_map *l, ElfW(Word) reloc_offset,
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ElfW(Addr) retaddr)
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__attribute__ ((regparm (3), unused));
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#endif
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/* Set up the loaded object described by L so its unrelocated PLT
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entries will jump to the on-demand fixup code in dl-runtime.c. */
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static inline int __attribute__ ((unused))
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elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
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{
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Elf32_Addr *got;
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extern void _dl_runtime_resolve (Elf32_Word);
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extern void _dl_runtime_profile (Elf32_Word);
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if (l->l_info[DT_JMPREL] && lazy)
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{
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/* The GOT entries for functions in the PLT have not yet been filled
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in. Their initial contents will arrange when called to push an
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offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
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and then jump to _GLOBAL_OFFSET_TABLE[2]. */
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got = (Elf32_Addr *) D_PTR (l, l_info[DT_PLTGOT]);
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got[1] = (Elf32_Addr) l; /* Identify this shared object. */
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/* The got[2] entry contains the address of a function which gets
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called to get the address of a so far unresolved function and
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jump to it. The profiling extension of the dynamic linker allows
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to intercept the calls to collect information. In this case we
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don't store the address in the GOT so that all future calls also
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end in this function. */
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if (__builtin_expect (profile, 0))
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{
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got[2] = (Elf32_Addr) &_dl_runtime_profile;
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if (_dl_name_match_p (_dl_profile, l))
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/* This is the object we are looking for. Say that we really
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want profiling and the timers are started. */
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_dl_profile_map = l;
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}
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else
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/* This function will get called to fix up the GOT entry indicated by
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the offset on the stack, and then jump to the resolved address. */
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got[2] = (Elf32_Addr) &_dl_runtime_resolve;
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}
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return lazy;
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}
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/* This code is used in dl-runtime.c to call the `fixup' function
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and then redirect to the address it returns. */
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#if !defined PROF && !__BOUNDED_POINTERS__
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# define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
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.text
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.globl _dl_runtime_resolve
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.type _dl_runtime_resolve, @function
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.align 16
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_dl_runtime_resolve:
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pushl %eax # Preserve registers otherwise clobbered.
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pushl %ecx
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pushl %edx
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movl 16(%esp), %edx # Copy args pushed by PLT in register. Note
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movl 12(%esp), %eax # that `fixup' takes its parameters in regs.
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call fixup # Call resolver.
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popl %edx # Get register content back.
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popl %ecx
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xchgl %eax, (%esp) # Get %eax contents end store function address.
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ret $8 # Jump to function address.
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.size _dl_runtime_resolve, .-_dl_runtime_resolve
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.globl _dl_runtime_profile
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.type _dl_runtime_profile, @function
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.align 16
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_dl_runtime_profile:
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pushl %eax # Preserve registers otherwise clobbered.
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pushl %ecx
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pushl %edx
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movl 20(%esp), %ecx # Load return address
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movl 16(%esp), %edx # Copy args pushed by PLT in register. Note
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movl 12(%esp), %eax # that `fixup' takes its parameters in regs.
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call profile_fixup # Call resolver.
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popl %edx # Get register content back.
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popl %ecx
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xchgl %eax, (%esp) # Get %eax contents end store function address.
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ret $8 # Jump to function address.
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.size _dl_runtime_profile, .-_dl_runtime_profile
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.previous
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");
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#else
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# define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
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.text
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.globl _dl_runtime_resolve
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.globl _dl_runtime_profile
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.type _dl_runtime_resolve, @function
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.type _dl_runtime_profile, @function
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.align 16
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_dl_runtime_resolve:
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_dl_runtime_profile:
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pushl %eax # Preserve registers otherwise clobbered.
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pushl %ecx
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pushl %edx
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movl 16(%esp), %edx # Push the arguments for `fixup'
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movl 12(%esp), %eax
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pushl %edx
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pushl %eax
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call fixup # Call resolver.
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popl %edx # Pop the parameters
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popl %ecx
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popl %edx # Get register content back.
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popl %ecx
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xchgl %eax, (%esp) # Get %eax contents end store function address.
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ret $8 # Jump to function address.
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.size _dl_runtime_resolve, .-_dl_runtime_resolve
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.size _dl_runtime_profile, .-_dl_runtime_profile
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.previous
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");
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#endif
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/* Mask identifying addresses reserved for the user program,
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where the dynamic linker should not map anything. */
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#define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL
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/* Initial entry point code for the dynamic linker.
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The C function `_dl_start' is the real entry point;
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its return value is the user program's entry point. */
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#define RTLD_START asm ("\
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.text\n\
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.align 16\n\
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0: movl (%esp), %ebx\n\
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ret\n\
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.align 16\n\
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.globl _start\n\
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.globl _dl_start_user\n\
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_start:\n\
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pushl %esp\n\
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call _dl_start\n\
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popl %ebx\n\
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_dl_start_user:\n\
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# Save the user entry point address in %edi.\n\
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movl %eax, %edi\n\
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# Point %ebx at the GOT.
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call 0b\n\
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addl $_GLOBAL_OFFSET_TABLE_, %ebx\n\
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# Store the highest stack address\n\
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movl __libc_stack_end@GOT(%ebx), %eax\n\
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movl %esp, (%eax)\n\
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# See if we were run as a command with the executable file\n\
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# name as an extra leading argument.\n\
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movl _dl_skip_args@GOT(%ebx), %eax\n\
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movl (%eax), %eax\n\
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# Pop the original argument count.\n\
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popl %edx\n\
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# Adjust the stack pointer to skip _dl_skip_args words.\n\
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leal (%esp,%eax,4), %esp\n\
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# Subtract _dl_skip_args from argc.\n\
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subl %eax, %edx\n\
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# Push argc back on the stack.\n\
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push %edx\n\
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# The special initializer gets called with the stack just\n\
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# as the application's entry point will see it; it can\n\
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# switch stacks if it moves these contents over.\n\
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" RTLD_START_SPECIAL_INIT "\n\
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# Load the parameters again.\n\
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# (eax, edx, ecx, *--esp) = (_dl_loaded, argc, argv, envp)\n\
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movl _dl_loaded@GOT(%ebx), %esi\n\
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leal 8(%esp,%edx,4), %eax\n\
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leal 4(%esp), %ecx\n\
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pushl %eax\n\
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movl (%esi), %eax\n\
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# Call the function to run the initializers.\n\
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call _dl_init@PLT\n\
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# Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
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movl _dl_fini@GOT(%ebx), %edx\n\
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# Jump to the user's entry point.\n\
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jmp *%edi\n\
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.previous\n\
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");
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#ifndef RTLD_START_SPECIAL_INIT
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#define RTLD_START_SPECIAL_INIT /* nothing */
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#endif
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/* Nonzero iff TYPE should not be allowed to resolve to one of
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the main executable's symbols, as for a COPY reloc. */
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#define elf_machine_lookup_noexec_p(type) ((type) == R_386_COPY)
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/* Nonzero iff TYPE describes relocation of a PLT entry, so
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PLT entries should not be allowed to define the value. */
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#define elf_machine_lookup_noplt_p(type) ((type) == R_386_JMP_SLOT)
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/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
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#define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT
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/* The i386 never uses Elf32_Rela relocations. */
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#define ELF_MACHINE_NO_RELA 1
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/* We define an initialization functions. This is called very early in
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_dl_sysdep_start. */
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#define DL_PLATFORM_INIT dl_platform_init ()
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extern const char *_dl_platform;
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static inline void __attribute__ ((unused))
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dl_platform_init (void)
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{
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if (_dl_platform != NULL && *_dl_platform == '\0')
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/* Avoid an empty string which would disturb us. */
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_dl_platform = NULL;
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}
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static inline Elf32_Addr
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elf_machine_fixup_plt (struct link_map *map, lookup_t t,
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const Elf32_Rel *reloc,
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Elf32_Addr *reloc_addr, Elf32_Addr value)
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{
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return *reloc_addr = value;
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}
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/* Return the final value of a plt relocation. */
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static inline Elf32_Addr
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elf_machine_plt_value (struct link_map *map, const Elf32_Rel *reloc,
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Elf32_Addr value)
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{
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return value;
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}
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#endif /* !dl_machine_h */
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#ifdef RESOLVE
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/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
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MAP is the object containing the reloc. */
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static inline void
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elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
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const Elf32_Sym *sym, const struct r_found_version *version,
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Elf32_Addr *const reloc_addr)
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{
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if (ELF32_R_TYPE (reloc->r_info) == R_386_RELATIVE)
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{
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#ifndef RTLD_BOOTSTRAP
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/* This is defined in rtld.c, but nowhere in the static libc.a;
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make the reference weak so static programs can still link.
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This declaration cannot be done when compiling rtld.c
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(i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
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common defn for _dl_rtld_map, which is incompatible with a
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weak decl in the same file. */
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weak_extern (_dl_rtld_map);
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if (map != &_dl_rtld_map) /* Already done in rtld itself. */
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#endif
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*reloc_addr += map->l_addr;
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}
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else if (ELF32_R_TYPE (reloc->r_info) != R_386_NONE)
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{
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const Elf32_Sym *const refsym = sym;
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Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
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if (sym)
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value += sym->st_value;
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switch (ELF32_R_TYPE (reloc->r_info))
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{
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case R_386_GLOB_DAT:
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case R_386_JMP_SLOT:
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*reloc_addr = value;
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break;
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#ifndef RTLD_BOOTSTRAP
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case R_386_32:
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*reloc_addr += value;
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break;
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case R_386_PC32:
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*reloc_addr += (value - (Elf32_Addr) reloc_addr);
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break;
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case R_386_COPY:
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if (sym == NULL)
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/* This can happen in trace mode if an object could not be
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found. */
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break;
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if (__builtin_expect (sym->st_size > refsym->st_size, 0)
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|| (__builtin_expect (sym->st_size < refsym->st_size, 0)
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&& __builtin_expect (_dl_verbose, 0)))
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{
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const char *strtab;
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strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
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_dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
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": Symbol `", strtab + refsym->st_name,
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"' has different size in shared object, "
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"consider re-linking\n", NULL);
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}
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memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
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refsym->st_size));
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break;
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#endif
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#if !defined RTLD_BOOTSTRAP || defined _NDEBUG
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default:
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/* We add these checks in the version to relocate ld.so only
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if we are still debugging. */
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_dl_reloc_bad_type (map, ELFW(R_TYPE) (reloc->r_info), 0);
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break;
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#endif
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}
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}
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}
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static inline void
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elf_machine_lazy_rel (struct link_map *map,
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Elf32_Addr l_addr, const Elf32_Rel *reloc)
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{
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Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
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/* Check for unexpected PLT reloc type. */
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if (__builtin_expect (ELF32_R_TYPE (reloc->r_info), R_386_JMP_SLOT)
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== R_386_JMP_SLOT)
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*reloc_addr += l_addr;
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else
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_dl_reloc_bad_type (map, ELFW(R_TYPE) (reloc->r_info), 1);
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}
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#endif /* RESOLVE */
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