arch/mips/kernel/module-elf32.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify
   3  *  it under the terms of the GNU General Public License as published by
   4  *  the Free Software Foundation; either version 2 of the License, or
   5  *  (at your option) any later version.
   6  *
   7  *  This program is distributed in the hope that it will be useful,
   8  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *  GNU General Public License for more details.
  11  *
  12  *  You should have received a copy of the GNU General Public License
  13  *  along with this program; if not, write to the Free Software
  14  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  15  *
  16  *  Copyright (C) 2001 Rusty Russell.
  17  *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
  18  */
  19
  20 #undef DEBUG
  21
  22 #include <linux/moduleloader.h>
  23 #include <linux/elf.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/slab.h>
  26 #include <linux/fs.h>
  27 #include <linux/string.h>
  28 #include <linux/kernel.h>
  29
  30 struct mips_hi16 {
  31         struct mips_hi16 *next;
  32         Elf32_Addr *addr;
  33         Elf32_Addr value;
  34 };
  35
  36 static struct mips_hi16 *mips_hi16_list;
  37
  38 void *module_alloc(unsigned long size)
  39 {
  40         if (size == 0)
  41                 return NULL;
  42         return vmalloc(size);
  43 }
  44
  45
  46 /* Free memory returned from module_alloc */
  47 void module_free(struct module *mod, void *module_region)
  48 {
  49         vfree(module_region);
  50         /* FIXME: If module_region == mod->init_region, trim exception
  51            table entries. */
  52 }
  53
  54 int module_frob_arch_sections(Elf_Ehdr *hdr,
  55                               Elf_Shdr *sechdrs,
  56                               char *secstrings,
  57                               struct module *mod)
  58 {
  59         return 0;
  60 }
  61
  62 static int apply_r_mips_none(struct module *me, uint32_t *location,
  63         Elf32_Addr v)
  64 {
  65         return 0;
  66 }
  67
  68 static int apply_r_mips_32(struct module *me, uint32_t *location,
  69         Elf32_Addr v)
  70 {
  71         *location += v;
  72
  73         return 0;
  74 }
  75
  76 static int apply_r_mips_26(struct module *me, uint32_t *location,
  77         Elf32_Addr v)
  78 {
  79         if (v % 4) {
  80                 printk(KERN_ERR "module %s: dangerous relocation\n", me->name);
  81                 return -ENOEXEC;
  82         }
  83
  84         if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
  85                 printk(KERN_ERR
  86                        "module %s: relocation overflow\n",
  87                        me->name);
  88                 return -ENOEXEC;
  89         }
  90
  91         *location = (*location & ~0x03ffffff) |
  92                     ((*location + (v >> 2)) & 0x03ffffff);
  93
  94         return 0;
  95 }
  96
  97 static int apply_r_mips_hi16(struct module *me, uint32_t *location,
  98         Elf32_Addr v)
  99 {
 100         struct mips_hi16 *n;
 101
 102         /*
 103          * We cannot relocate this one now because we don't know the value of
 104          * the carry we need to add.  Save the information, and let LO16 do the
 105          * actual relocation.
 106          */
 107         n = kmalloc(sizeof *n, GFP_KERNEL);
 108         if (!n)
 109                 return -ENOMEM;
 110
 111         n->addr = location;
 112         n->value = v;
 113         n->next = mips_hi16_list;
 114         mips_hi16_list = n;
 115
 116         return 0;
 117 }
 118
 119 static int apply_r_mips_lo16(struct module *me, uint32_t *location,
 120         Elf32_Addr v)
 121 {
 122         unsigned long insnlo = *location;
 123         Elf32_Addr val, vallo;
 124
 125         /* Sign extend the addend we extract from the lo insn.  */
 126         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
 127
 128         if (mips_hi16_list != NULL) {
 129                 struct mips_hi16 *l;
 130
 131                 l = mips_hi16_list;
 132                 while (l != NULL) {
 133                         struct mips_hi16 *next;
 134                         unsigned long insn;
 135
 136                         /*
 137                          * The value for the HI16 had best be the same.
 138                          */
 139                         if (v != l->value)
 140                                 goto out_danger;
 141
 142                         /*
 143                          * Do the HI16 relocation.  Note that we actually don't
 144                          * need to know anything about the LO16 itself, except
 145                          * where to find the low 16 bits of the addend needed
 146                          * by the LO16.
 147                          */
 148                         insn = *l->addr;
 149                         val = ((insn & 0xffff) << 16) + vallo;
 150                         val += v;
 151
 152                         /*
 153                          * Account for the sign extension that will happen in
 154                          * the low bits.
 155                          */
 156                         val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
 157
 158                         insn = (insn & ~0xffff) | val;
 159                         *l->addr = insn;
 160
 161                         next = l->next;
 162                         kfree(l);
 163                         l = next;
 164                 }
 165
 166                 mips_hi16_list = NULL;
 167         }
 168
 169         /*
 170          * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
 171          */
 172         val = v + vallo;
 173         insnlo = (insnlo & ~0xffff) | (val & 0xffff);
 174         *location = insnlo;
 175
 176         return 0;
 177
 178 out_danger:
 179         printk(KERN_ERR "module %s: dangerous " "relocation\n", me->name);
 180
 181         return -ENOEXEC;
 182 }
 183
 184 static int (*reloc_handlers[]) (struct module *me, uint32_t *location,
 185         Elf32_Addr v) = {
 186         [R_MIPS_NONE]   = apply_r_mips_none,
 187         [R_MIPS_32]     = apply_r_mips_32,
 188         [R_MIPS_26]     = apply_r_mips_26,
 189         [R_MIPS_HI16]   = apply_r_mips_hi16,
 190         [R_MIPS_LO16]   = apply_r_mips_lo16
 191 };
 192
 193 int apply_relocate(Elf32_Shdr *sechdrs,
 194                    const char *strtab,
 195                    unsigned int symindex,
 196                    unsigned int relsec,
 197                    struct module *me)
 198 {
 199         Elf32_Rel *rel = (void *) sechdrs[relsec].sh_addr;
 200         Elf32_Sym *sym;
 201         uint32_t *location;
 202         unsigned int i;
 203         Elf32_Addr v;
 204         int res;
 205
 206         pr_debug("Applying relocate section %u to %u\n", relsec,
 207                sechdrs[relsec].sh_info);
 208
 209         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 210                 Elf32_Word r_info = rel[i].r_info;
 211
 212                 /* This is where to make the change */
 213                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 214                         + rel[i].r_offset;
 215                 /* This is the symbol it is referring to */
 216                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 217                         + ELF32_R_SYM(r_info);
 218                 if (!sym->st_value) {
 219                         printk(KERN_WARNING "%s: Unknown symbol %s\n",
 220                                me->name, strtab + sym->st_name);
 221                         return -ENOENT;
 222                 }
 223
 224                 v = sym->st_value;
 225
 226                 res = reloc_handlers[ELF32_R_TYPE(r_info)](me, location, v);
 227                 if (res)
 228                         return res;
 229         }
 230
 231         return 0;
 232 }
 233
 234 int apply_relocate_add(Elf32_Shdr *sechdrs,
 235                        const char *strtab,
 236                        unsigned int symindex,
 237                        unsigned int relsec,
 238                        struct module *me)
 239 {
 240         /*
 241          * Current binutils always generate .rela relocations.  Keep smiling
 242          * if it's empty, abort otherwise.
 243          */
 244         if (!sechdrs[relsec].sh_size)
 245                 return 0;
 246
 247         printk(KERN_ERR "module %s: ADD RELOCATION unsupported\n",
 248                me->name);
 249         return -ENOEXEC;
 250 }