265 lines
8.5 KiB
C
265 lines
8.5 KiB
C
/* Machine-dependent ELF dynamic relocation inline functions. i386 version.
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Copyright (C) 1995, 1996 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
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, 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 <assert.h>
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/* Return nonzero iff E_MACHINE is compatible with the running host. */
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static inline int __attribute__ ((unused))
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elf_machine_matches_host (Elf32_Half e_machine)
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{
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switch (e_machine)
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{
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case EM_386:
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case EM_486:
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return 1;
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default:
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return 0;
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}
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}
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/* Return the run-time address of the _GLOBAL_OFFSET_TABLE_.
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Must be inlined in a function which uses global data. */
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static inline Elf32_Addr * __attribute__ ((unused))
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elf_machine_got (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 (" call here\n"
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"here: popl %0\n"
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" subl $here, %0"
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: "=r" (addr));
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return addr;
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}
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/* The `subl' insn above will contain an R_386_32 relocation entry
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intended to insert the run-time address of the label `here'.
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This will be the first relocation in the text of the dynamic linker;
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we skip it to avoid trying to modify read-only text in this early stage. */
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#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
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++(const Elf32_Rel *) (dynamic_info)[DT_REL]->d_un.d_ptr; \
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(dynamic_info)[DT_RELSZ]->d_un.d_val -= sizeof (Elf32_Rel);
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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 void __attribute__ ((unused))
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elf_machine_runtime_setup (struct link_map *l, int lazy)
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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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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 *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
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got[1] = (Elf32_Addr) l; /* Identify this shared object. */
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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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/* 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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#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
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.globl _dl_runtime_resolve
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.type _dl_runtime_resolve, @function
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_dl_runtime_resolve:
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call fixup # Args pushed by PLT.
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addl $8, %esp # Pop args.
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jmp *%eax # Jump to function address.
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");
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/* The PLT uses Elf32_Rel relocs. */
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#define elf_machine_relplt elf_machine_rel
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}
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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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.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 0f\n\
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0: popl %ebx\n\
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addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx\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 %ecx\n\
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# Subtract _dl_skip_args from it.\n\
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subl %eax, %ecx\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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# Push back the modified argument count.\n\
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pushl %ecx\n\
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# Push _dl_default_scope[2] as argument in _dl_init_next call below.\n\
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movl _dl_default_scope@GOT(%ebx), %eax\n\
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movl 8(%eax), %esi\n\
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0: pushl %esi\n\
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# Call _dl_init_next to return the address of an initializer\n\
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# function to run.\n\
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call _dl_init_next@PLT\n\
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addl $4, %esp # Pop argument.\n\
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# Check for zero return, when out of initializers.\n\
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testl %eax,%eax\n\
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jz 1f\n\
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# Call the shared object initializer function.\n\
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# NOTE: We depend only on the registers (%ebx, %esi and %edi)\n\
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# and the return address pushed by this call;\n\
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# the initializer is called with the stack just\n\
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# as it appears on entry, and it is free to move\n\
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# the stack around, as long as it winds up jumping to\n\
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# the return address on the top of the stack.\n\
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call *%eax\n\
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# Loop to call _dl_init_next for the next initializer.\n\
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jmp 0b\n\
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1: # 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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");
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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_pltrel_p(type) ((type) == 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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#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,
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const Elf32_Rel *reloc, const Elf32_Sym *sym)
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{
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Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
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Elf32_Addr loadbase;
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switch (ELF32_R_TYPE (reloc->r_info))
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{
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case R_386_COPY:
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loadbase = RESOLVE (&sym, DL_LOOKUP_NOEXEC);
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memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
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break;
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case R_386_GLOB_DAT:
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loadbase = RESOLVE (&sym, 0);
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*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
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break;
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case R_386_JMP_SLOT:
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loadbase = RESOLVE (&sym, DL_LOOKUP_NOPLT);
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*reloc_addr = sym ? (loadbase + sym->st_value) : 0;
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break;
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case R_386_32:
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{
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Elf32_Addr undo = 0;
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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. This
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declaration cannot be done when compiling rtld.c (i.e. #ifdef
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RTLD_BOOTSTRAP) because rtld.c contains the common defn for
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_dl_rtld_map, which is incompatible with a weak decl in the same
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file. */
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weak_extern (_dl_rtld_map);
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if (map == &_dl_rtld_map)
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/* Undo the relocation done here during bootstrapping. Now we will
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relocate it anew, possibly using a binding found in the user
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program or a loaded library rather than the dynamic linker's
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built-in definitions used while loading those libraries. */
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undo = map->l_addr + sym->st_value;
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#endif
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loadbase = RESOLVE (&sym, 0);
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*reloc_addr += (sym ? (loadbase + sym->st_value) : 0) - undo;
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break;
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}
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case R_386_RELATIVE:
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#ifndef RTLD_BOOTSTRAP
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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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break;
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case R_386_PC32:
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loadbase = RESOLVE (&sym, 0);
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*reloc_addr += ((sym ? (loadbase + sym->st_value) : 0) -
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(Elf32_Addr) reloc_addr);
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break;
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case R_386_NONE: /* Alright, Wilbur. */
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break;
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default:
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assert (! "unexpected dynamic reloc type");
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break;
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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, const Elf32_Rel *reloc)
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{
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Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
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switch (ELF32_R_TYPE (reloc->r_info))
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{
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case R_386_JMP_SLOT:
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*reloc_addr += map->l_addr;
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break;
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default:
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assert (! "unexpected PLT reloc type");
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break;
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}
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}
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#endif /* RESOLVE */
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