diff options
Diffstat (limited to 'elf')
| -rw-r--r-- | elf/dl-runtime.c | 100 | ||||
| -rw-r--r-- | elf/dynamic-link.h | 4 |
2 files changed, 102 insertions, 2 deletions
diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c new file mode 100644 index 0000000..7e554bc --- /dev/null +++ b/elf/dl-runtime.c @@ -0,0 +1,100 @@ +/* On-demand PLT fixup for shared objects. +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. */ + +#include <link.h> +#include "dynamic-link.h" + +/* Figure out the right type, Rel or Rela. */ +#define elf_machine_rel 1 +#define elf_machine_rela 2 +#if elf_machine_relplt == elf_machine_rel +#define PLTREL Elf32_Rel +#elif elf_machine_relplt == elf_machine_rela +#define PLTREL Elf32_Rela +#else +#error "dl-machine.h bug: elf_machine_relplt not rel or rela" +#endif +#undef elf_machine_rel +#undef elf_machine_rela + +/* We need to define the function as a local symbol so that the reference + in the trampoline code will be a local PC-relative call. Tell the + compiler not to worry that the function appears not to be called. */ + +static Elf32_Addr fixup (struct link_map *l, Elf32_Word reloc_offset) + __attribute__ ((unused)); + +/* This function is called through a special trampoline from the PLT the + first time each PLT entry is called. We must perform the relocation + specified in the PLT of the given shared object, and return the resolved + function address to the trampoline, which will restart the original call + to that address. Future calls will bounce directly from the PLT to the + function. */ + +static Elf32_Addr +fixup (struct link_map *l, Elf32_Word reloc_offset) +{ + const Elf32_Sym *const symtab + = (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr); + const char *strtab = + (const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr); + + const PLTREL *const reloc + = (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr + + reloc_offset); + + const Elf32_Sym *definer; + Elf32_Addr loadbase; + struct link_map *scope, *real_next; + + /* Look up the symbol's run-time value. */ + + real_next = l->l_next; + if (l->l_info[DT_SYMBOLIC]) + { + l->l_next = _dl_loaded; + if (l->l_prev) + l->l_prev->l_next = real_next; + scope = l; + } + else + scope = _dl_loaded; + + definer = &symtab[ELF32_R_SYM (reloc->r_info)]; + loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, + scope, l->l_name, 0); + + /* Restore list frobnication done above for DT_SYMBOLIC. */ + l->l_next = real_next; + if (l->l_prev) + l->l_prev->l_next = l; + + /* Apply the relocation with that value. */ + elf_machine_relplt (l, reloc, loadbase, definer); + + return *(Elf32_Addr *) (l->l_addr + reloc->r_offset); +} + + +/* This macro is defined in dl-machine.h to define the entry point called + by the PLT. The `fixup' function above does the real work, but a little + more twiddling is needed to get the stack right and jump to the address + finally resolved. */ + +ELF_MACHINE_RUNTIME_TRAMPOLINE diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h index ed8d24c..38236ba 100644 --- a/elf/dynamic-link.h +++ b/elf/dynamic-link.h @@ -1,5 +1,5 @@ /* Inline functions for dynamic linking. -Copyright (C) 1995 Free Software Foundation, Inc. +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 @@ -43,7 +43,7 @@ elf_get_dynamic_info (Elf32_Dyn *dyn, Elf32_Dyn *info[DT_NUM + DT_PROCNUM]) dyn->d_tag < DT_LOPROC + DT_PROCNUM) info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn; else - assert (! "bad dynamic tag"); + assert (! "bad dynamic tag"); dyn++; } |