arch/ppc64/kernel/module.c

   1 /*  Kernel module help for PPC64.
   2     Copyright (C) 2001, 2003 Rusty Russell IBM Corporation.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18 #include <linux/module.h>
  19 #include <linux/elf.h>
  20 #include <linux/moduleloader.h>
  21 #include <linux/err.h>
  22 #include <linux/vmalloc.h>
  23 #include <asm/module.h>
  24 #include <asm/uaccess.h>
  25
  26 /* FIXME: We don't do .init separately.  To do this, we'd need to have
  27    a separate r2 value in the init and core section, and stub between
  28    them, too.
  29
  30    Using a magic allocator which places modules within 32MB solves
  31    this, and makes other things simpler.  Anton?
  32    --RR.  */
  33 #if 0
  34 #define DEBUGP printk
  35 #else
  36 #define DEBUGP(fmt , ...)
  37 #endif
  38
  39 /* There's actually a third entry here, but it's unused */
  40 struct ppc64_opd_entry
  41 {
  42         unsigned long funcaddr;
  43         unsigned long r2;
  44 };
  45
  46 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
  47    the kernel itself).  But on PPC64, these need to be used for every
  48    jump, actually, to reset r2 (TOC+0x8000). */
  49 struct ppc64_stub_entry
  50 {
  51         /* 28 byte jump instruction sequence (7 instructions) */
  52         unsigned char jump[28];
  53         unsigned char unused[4];
  54         /* Data for the above code */
  55         struct ppc64_opd_entry opd;
  56 };
  57
  58 /* We use a stub to fix up r2 (TOC ptr) and to jump to the (external)
  59    function which may be more than 24-bits away.  We could simply
  60    patch the new r2 value and function pointer into the stub, but it's
  61    significantly shorter to put these values at the end of the stub
  62    code, and patch the stub address (32-bits relative to the TOC ptr,
  63    r2) into the stub. */
  64 static struct ppc64_stub_entry ppc64_stub =
  65 { .jump = {
  66         0x3d, 0x82, 0x00, 0x00, /* addis   r12,r2, <high> */
  67         0x39, 0x8c, 0x00, 0x00, /* addi    r12,r12, <low> */
  68         /* Save current r2 value in magic place on the stack. */
  69         0xf8, 0x41, 0x00, 0x28, /* std     r2,40(r1) */
  70         0xe9, 0x6c, 0x00, 0x20, /* ld      r11,32(r12) */
  71         0xe8, 0x4c, 0x00, 0x28, /* ld      r2,40(r12) */
  72         0x7d, 0x69, 0x03, 0xa6, /* mtctr   r11 */
  73         0x4e, 0x80, 0x04, 0x20  /* bctr */
  74 } };
  75
  76 /* Count how many different 24-bit relocations (different symbol,
  77    different addend) */
  78 static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num)
  79 {
  80         unsigned int i, j, ret = 0;
  81
  82         /* FIXME: Only count external ones --RR */
  83         /* Sure, this is order(n^2), but it's usually short, and not
  84            time critical */
  85         for (i = 0; i < num; i++) {
  86                 /* Only count 24-bit relocs, others don't need stubs */
  87                 if (ELF64_R_TYPE(rela[i].r_info) != R_PPC_REL24)
  88                         continue;
  89                 for (j = 0; j < i; j++) {
  90                         /* If this addend appeared before, it's
  91                            already been counted */
  92                         if (rela[i].r_info == rela[j].r_info
  93                             && rela[i].r_addend == rela[j].r_addend)
  94                                 break;
  95                 }
  96                 if (j == i) ret++;
  97         }
  98         return ret;
  99 }
 100
 101 void *module_alloc(unsigned long size)
 102 {
 103         if (size == 0)
 104                 return NULL;
 105
 106         return vmalloc_exec(size);
 107 }
 108
 109 /* Free memory returned from module_alloc */
 110 void module_free(struct module *mod, void *module_region)
 111 {
 112         vfree(module_region);
 113         /* FIXME: If module_region == mod->init_region, trim exception
 114            table entries. */
 115 }
 116
 117 /* Get size of potential trampolines required. */
 118 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 119                                     const Elf64_Shdr *sechdrs)
 120 {
 121         /* One extra reloc so it's always 0-funcaddr terminated */
 122         unsigned long relocs = 1;
 123         unsigned i;
 124
 125         /* Every relocated section... */
 126         for (i = 1; i < hdr->e_shnum; i++) {
 127                 if (sechdrs[i].sh_type == SHT_RELA) {
 128                         DEBUGP("Found relocations in section %u\n", i);
 129                         DEBUGP("Ptr: %p.  Number: %lu\n",
 130                                (void *)sechdrs[i].sh_addr,
 131                                sechdrs[i].sh_size / sizeof(Elf64_Rela));
 132                         relocs += count_relocs((void *)sechdrs[i].sh_addr,
 133                                                sechdrs[i].sh_size
 134                                                / sizeof(Elf64_Rela));
 135                 }
 136         }
 137
 138         DEBUGP("Looks like a total of %lu stubs, max\n", relocs);
 139         return relocs * sizeof(struct ppc64_stub_entry);
 140 }
 141
 142 static void dedotify_versions(struct modversion_info *vers,
 143                               unsigned long size)
 144 {
 145         struct modversion_info *end;
 146
 147         for (end = (void *)vers + size; vers < end; vers++)
 148                 if (vers->name[0] == '.')
 149                         memmove(vers->name, vers->name+1, strlen(vers->name));
 150 }
 151
 152 /* Undefined symbols which refer to .funcname, hack to funcname */
 153 static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
 154 {
 155         unsigned int i;
 156
 157         for (i = 1; i < numsyms; i++) {
 158                 if (syms[i].st_shndx == SHN_UNDEF) {
 159                         char *name = strtab + syms[i].st_name;
 160                         if (name[0] == '.')
 161                                 memmove(name, name+1, strlen(name));
 162                 }
 163         }
 164 }
 165
 166 int module_frob_arch_sections(Elf64_Ehdr *hdr,
 167                               Elf64_Shdr *sechdrs,
 168                               char *secstrings,
 169                               struct module *me)
 170 {
 171         unsigned int i;
 172
 173         /* Find .toc and .stubs sections, symtab and strtab */
 174         for (i = 1; i < hdr->e_shnum; i++) {
 175                 char *p;
 176                 if (strcmp(secstrings + sechdrs[i].sh_name, ".stubs") == 0)
 177                         me->arch.stubs_section = i;
 178                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".toc") == 0)
 179                         me->arch.toc_section = i;
 180                 else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")==0)
 181                         dedotify_versions((void *)hdr + sechdrs[i].sh_offset,
 182                                           sechdrs[i].sh_size);
 183
 184                 /* We don't handle .init for the moment: rename to _init */
 185                 while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))
 186                         p[0] = '_';
 187
 188                 if (sechdrs[i].sh_type == SHT_SYMTAB)
 189                         dedotify((void *)hdr + sechdrs[i].sh_offset,
 190                                  sechdrs[i].sh_size / sizeof(Elf64_Sym),
 191                                  (void *)hdr
 192                                  + sechdrs[sechdrs[i].sh_link].sh_offset);
 193         }
 194         if (!me->arch.stubs_section || !me->arch.toc_section) {
 195                 printk("%s: doesn't contain .toc or .stubs.\n", me->name);
 196                 return -ENOEXEC;
 197         }
 198
 199         /* Override the stubs size */
 200         sechdrs[me->arch.stubs_section].sh_size = get_stubs_size(hdr, sechdrs);
 201         return 0;
 202 }
 203
 204 int apply_relocate(Elf64_Shdr *sechdrs,
 205                    const char *strtab,
 206                    unsigned int symindex,
 207                    unsigned int relsec,
 208                    struct module *me)
 209 {
 210         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n", me->name);
 211         return -ENOEXEC;
 212 }
 213
 214 /* r2 is the TOC pointer: it actually points 0x8000 into the TOC (this
 215    gives the value maximum span in an instruction which uses a signed
 216    offset) */
 217 static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me)
 218 {
 219         return sechdrs[me->arch.toc_section].sh_addr + 0x8000;
 220 }
 221
 222 /* Both low and high 16 bits are added as SIGNED additions, so if low
 223    16 bits has high bit set, high 16 bits must be adjusted.  These
 224    macros do that (stolen from binutils). */
 225 #define PPC_LO(v) ((v) & 0xffff)
 226 #define PPC_HI(v) (((v) >> 16) & 0xffff)
 227 #define PPC_HA(v) PPC_HI ((v) + 0x8000)
 228
 229 /* Patch stub to reference function and correct r2 value. */
 230 static inline int create_stub(Elf64_Shdr *sechdrs,
 231                               struct ppc64_stub_entry *entry,
 232                               struct ppc64_opd_entry *opd,
 233                               struct module *me)
 234 {
 235         Elf64_Half *loc1, *loc2;
 236         long reladdr;
 237
 238         *entry = ppc64_stub;
 239
 240         loc1 = (Elf64_Half *)&entry->jump[2];
 241         loc2 = (Elf64_Half *)&entry->jump[6];
 242
 243         /* Stub uses address relative to r2. */
 244         reladdr = (unsigned long)entry - my_r2(sechdrs, me);
 245         if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
 246                 printk("%s: Address %p of stub out of range of %p.\n",
 247                        me->name, (void *)reladdr, (void *)my_r2);
 248                 return 0;
 249         }
 250         DEBUGP("Stub %p get data from reladdr %li\n", entry, reladdr);
 251
 252         *loc1 = PPC_HA(reladdr);
 253         *loc2 = PPC_LO(reladdr);
 254         entry->opd.funcaddr = opd->funcaddr;
 255         entry->opd.r2 = opd->r2;
 256         return 1;
 257 }
 258
 259 /* Create stub to jump to function described in this OPD: we need the
 260    stub to set up the TOC ptr (r2) for the function. */
 261 static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,
 262                                    unsigned long opdaddr,
 263                                    struct module *me)
 264 {
 265         struct ppc64_stub_entry *stubs;
 266         struct ppc64_opd_entry *opd = (void *)opdaddr;
 267         unsigned int i, num_stubs;
 268
 269         num_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*stubs);
 270
 271         /* Find this stub, or if that fails, the next avail. entry */
 272         stubs = (void *)sechdrs[me->arch.stubs_section].sh_addr;
 273         for (i = 0; stubs[i].opd.funcaddr; i++) {
 274                 BUG_ON(i >= num_stubs);
 275
 276                 if (stubs[i].opd.funcaddr == opd->funcaddr)
 277                         return (unsigned long)&stubs[i];
 278         }
 279
 280         if (!create_stub(sechdrs, &stubs[i], opd, me))
 281                 return 0;
 282
 283         return (unsigned long)&stubs[i];
 284 }
 285
 286 /* We expect a noop next: if it is, replace it with instruction to
 287    restore r2. */
 288 static int restore_r2(u32 *instruction, struct module *me)
 289 {
 290         if (*instruction != 0x60000000) {
 291                 printk("%s: Expect noop after relocate, got %08x\n",
 292                        me->name, *instruction);
 293                 return 0;
 294         }
 295         *instruction = 0xe8410028;      /* ld r2,40(r1) */
 296         return 1;
 297 }
 298
 299 int apply_relocate_add(Elf64_Shdr *sechdrs,
 300                        const char *strtab,
 301                        unsigned int symindex,
 302                        unsigned int relsec,
 303                        struct module *me)
 304 {
 305         unsigned int i;
 306         Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 307         Elf64_Sym *sym;
 308         unsigned long *location;
 309         unsigned long value;
 310
 311         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 312                sechdrs[relsec].sh_info);
 313         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 314                 /* This is where to make the change */
 315                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 316                         + rela[i].r_offset;
 317                 /* This is the symbol it is referring to */
 318                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 319                         + ELF64_R_SYM(rela[i].r_info);
 320
 321                 DEBUGP("RELOC at %p: %li-type as %s (%lu) + %li\n",
 322                        location, (long)ELF64_R_TYPE(rela[i].r_info),
 323                        strtab + sym->st_name, (unsigned long)sym->st_value,
 324                        (long)rela[i].r_addend);
 325
 326                 /* `Everything is relative'. */
 327                 value = sym->st_value + rela[i].r_addend;
 328
 329                 switch (ELF64_R_TYPE(rela[i].r_info)) {
 330                 case R_PPC64_ADDR32:
 331                         /* Simply set it */
 332                         *(u32 *)location = value;
 333                         break;
 334
 335                 case R_PPC64_ADDR64:
 336                         /* Simply set it */
 337                         *(unsigned long *)location = value;
 338                         break;
 339
 340                 case R_PPC64_TOC:
 341                         *(unsigned long *)location = my_r2(sechdrs, me);
 342                         break;
 343
 344                 case R_PPC64_TOC16_DS:
 345                         /* Subtact TOC pointer */
 346                         value -= my_r2(sechdrs, me);
 347                         if ((value & 3) != 0 || value + 0x8000 > 0xffff) {
 348                                 printk("%s: bad TOC16_DS relocation (%lu)\n",
 349                                        me->name, value);
 350                                 return -ENOEXEC;
 351                         }
 352                         *((uint16_t *) location)
 353                                 = (*((uint16_t *) location) & ~0xfffc)
 354                                 | (value & 0xfffc);
 355                         break;
 356
 357                 case R_PPC_REL24:
 358                         /* FIXME: Handle weak symbols here --RR */
 359                         if (sym->st_shndx == SHN_UNDEF) {
 360                                 /* External: go via stub */
 361                                 value = stub_for_addr(sechdrs, value, me);
 362                                 if (!value)
 363                                         return -ENOENT;
 364                                 if (!restore_r2((u32 *)location + 1, me))
 365                                         return -ENOEXEC;
 366                         }
 367
 368                         /* Convert value to relative */
 369                         value -= (unsigned long)location;
 370                         if (value + 0x2000000 > 0x3ffffff || (value & 3) != 0){
 371                                 printk("%s: REL24 %li out of range!\n",
 372                                        me->name, (long int)value);
 373                                 return -ENOEXEC;
 374                         }
 375
 376                         /* Only replace bits 2 through 26 */
 377                         *(uint32_t *)location
 378                                 = (*(uint32_t *)location & ~0x03fffffc)
 379                                 | (value & 0x03fffffc);
 380                         break;
 381
 382                 default:
 383                         printk("%s: Unknown ADD relocation: %lu\n",
 384                                me->name,
 385                                (unsigned long)ELF64_R_TYPE(rela[i].r_info));
 386                         return -ENOEXEC;
 387                 }
 388         }
 389
 390         return 0;
 391 }
 392
 393 LIST_HEAD(module_bug_list);
 394
 395 int module_finalize(const Elf_Ehdr *hdr,
 396                 const Elf_Shdr *sechdrs, struct module *me)
 397 {
 398         char *secstrings;
 399         unsigned int i;
 400
 401         me->arch.bug_table = NULL;
 402         me->arch.num_bugs = 0;
 403
 404         /* Find the __bug_table section, if present */
 405         secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 406         for (i = 1; i < hdr->e_shnum; i++) {
 407                 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
 408                         continue;
 409                 me->arch.bug_table = (void *) sechdrs[i].sh_addr;
 410                 me->arch.num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
 411                 break;
 412         }
 413
 414         /*
 415          * Strictly speaking this should have a spinlock to protect against
 416          * traversals, but since we only traverse on BUG()s, a spinlock
 417          * could potentially lead to deadlock and thus be counter-productive.
 418          */
 419         list_add(&me->arch.bug_list, &module_bug_list);
 420
 421         return 0;
 422 }
 423
 424 void module_arch_cleanup(struct module *mod)
 425 {
 426         list_del(&mod->arch.bug_list);
 427 }
 428
 429 struct bug_entry *module_find_bug(unsigned long bugaddr)
 430 {
 431         struct mod_arch_specific *mod;
 432         unsigned int i;
 433         struct bug_entry *bug;
 434
 435         list_for_each_entry(mod, &module_bug_list, bug_list) {
 436                 bug = mod->bug_table;
 437                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
 438                         if (bugaddr == bug->bug_addr)
 439                                 return bug;
 440         }
 441         return NULL;
 442 }