libc/misc/internals/reloc_static_pie.c

   1 /* Support for relocating static PIE.
   2    Copyright (C) 2017-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18 #define IS_IN_rtld      // force inline function calls
  19 #include <link.h>
  20 #include <elf.h>
  21 #include <dl-elf.h>
  22
  23 #include <ldso.h>
  24 #ifdef __mips__
  25 #include <dl-startup.h>
  26 #endif
  27
  28 extern ElfW(Addr) _dl_load_base;
  29
  30 void
  31 reloc_static_pie (ElfW(Addr) load_addr);
  32
  33 void
  34 reloc_static_pie(ElfW(Addr) load_addr)
  35 {
  36     int indx;
  37     ElfW(Addr) got;
  38     ElfW(Dyn) *dpnt;
  39     struct elf_resolve tpnt_tmp;
  40         struct elf_resolve *tpnt = &tpnt_tmp;
  41
  42     DL_BOOT_COMPUTE_GOT(got);
  43     DL_BOOT_COMPUTE_DYN(dpnt, got, (DL_LOADADDR_TYPE)load_addr);
  44
  45     _dl_memset(tpnt, 0, sizeof(struct elf_resolve));
  46     tpnt->loadaddr = load_addr;
  47     tpnt->dynamic_addr = dpnt;
  48
  49     __dl_parse_dynamic_info(dpnt, tpnt->dynamic_info, NULL, load_addr);
  50
  51 #if defined(PERFORM_BOOTSTRAP_GOT)
  52         /* some arches (like MIPS) we have to tweak the GOT before relocations */
  53         PERFORM_BOOTSTRAP_GOT(tpnt);
  54 #endif
  55
  56
  57 #if defined(ELF_MACHINE_PLTREL_OVERLAP)
  58 # define INDX_MAX 1
  59 #else
  60 # define INDX_MAX 2
  61 #endif
  62
  63     for (indx = 0; indx < INDX_MAX; indx++) {
  64         unsigned long rel_addr, rel_size;
  65         ElfW(Word) relative_count = tpnt->dynamic_info[DT_RELCONT_IDX];
  66
  67         rel_addr = (indx ? tpnt->dynamic_info[DT_JMPREL] :
  68                            tpnt->dynamic_info[DT_RELOC_TABLE_ADDR]);
  69         rel_size = (indx ? tpnt->dynamic_info[DT_PLTRELSZ] :
  70                                        tpnt->dynamic_info[DT_RELOC_TABLE_SIZE]);
  71
  72         if (!rel_addr)
  73             continue;
  74
  75         if((0 == indx) && relative_count) {
  76                         rel_size -= relative_count * sizeof(ELF_RELOC);
  77             elf_machine_relative(load_addr, rel_addr, relative_count);
  78                         rel_addr += relative_count * sizeof(ELF_RELOC);
  79         }
  80
  81 #ifdef ARCH_NEEDS_BOOTSTRAP_RELOCS
  82                         {
  83                                 ELF_RELOC *rpnt;
  84                                 unsigned int i;
  85                                 ElfW(Sym) *sym;
  86                                 unsigned long symbol_addr;
  87                                 int symtab_index;
  88                                 unsigned long *reloc_addr;
  89
  90                                 /* Now parse the relocation information */
  91                                 rpnt = (ELF_RELOC *) rel_addr;
  92                                 for (i = 0; i < rel_size; i += sizeof(ELF_RELOC), rpnt++) {
  93                                         reloc_addr = (unsigned long *) DL_RELOC_ADDR(load_addr, (unsigned long)rpnt->r_offset);
  94                                         symtab_index = ELF_R_SYM(rpnt->r_info);
  95                                         symbol_addr = 0;
  96                                         sym = NULL;
  97                                         if (symtab_index) {
  98                                                 ElfW(Sym) *symtab;
  99                                                 symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB];
 100                                                 sym = &symtab[symtab_index];
 101                                                 symbol_addr = (unsigned long) DL_RELOC_ADDR(load_addr, sym->st_value);
 102                                         }
 103                                         /* Use this machine-specific macro to perform the actual relocation.  */
 104                                         PERFORM_BOOTSTRAP_RELOC(rpnt, reloc_addr, symbol_addr, load_addr, sym);
 105                                 }
 106                         }
 107 #endif
 108     }
 109     _dl_load_base = load_addr;
 110 }