/* 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 #include #include /* 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\ ");