arch/ppc64/kernel/vdso.c

   1 /*
   2  *  linux/arch/ppc64/kernel/vdso.c
   3  *
   4  *    Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
   5  *                       <benh@kernel.crashing.org>
   6  *
   7  *  This program is free software; you can redistribute it and/or
   8  *  modify it under the terms of the GNU General Public License
   9  *  as published by the Free Software Foundation; either version
  10  *  2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/config.h>
  14 #include <linux/module.h>
  15 #include <linux/errno.h>
  16 #include <linux/sched.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/smp.h>
  20 #include <linux/smp_lock.h>
  21 #include <linux/stddef.h>
  22 #include <linux/unistd.h>
  23 #include <linux/slab.h>
  24 #include <linux/user.h>
  25 #include <linux/elf.h>
  26 #include <linux/security.h>
  27 #include <linux/bootmem.h>
  28
  29 #include <asm/pgtable.h>
  30 #include <asm/system.h>
  31 #include <asm/processor.h>
  32 #include <asm/mmu.h>
  33 #include <asm/mmu_context.h>
  34 #include <asm/machdep.h>
  35 #include <asm/cputable.h>
  36 #include <asm/sections.h>
  37 #include <asm/vdso.h>
  38
  39 #undef DEBUG
  40
  41 #ifdef DEBUG
  42 #define DBG(fmt...) printk(fmt)
  43 #else
  44 #define DBG(fmt...)
  45 #endif
  46
  47
  48 /*
  49  * The vDSOs themselves are here
  50  */
  51 extern char vdso64_start, vdso64_end;
  52 extern char vdso32_start, vdso32_end;
  53
  54 static void *vdso64_kbase = &vdso64_start;
  55 static void *vdso32_kbase = &vdso32_start;
  56
  57 unsigned int vdso64_pages;
  58 unsigned int vdso32_pages;
  59
  60 /* Signal trampolines user addresses */
  61
  62 unsigned long vdso64_rt_sigtramp;
  63 unsigned long vdso32_sigtramp;
  64 unsigned long vdso32_rt_sigtramp;
  65
  66 /* Format of the patch table */
  67 struct vdso_patch_def
  68 {
  69         u32             pvr_mask, pvr_value;
  70         const char      *gen_name;
  71         const char      *fix_name;
  72 };
  73
  74 /* Table of functions to patch based on the CPU type/revision
  75  *
  76  * TODO: Improve by adding whole lists for each entry
  77  */
  78 static struct vdso_patch_def vdso_patches[] = {
  79         {
  80                 0xffff0000, 0x003a0000,         /* POWER5 */
  81                 "__kernel_sync_dicache", "__kernel_sync_dicache_p5"
  82         },
  83         {
  84                 0xffff0000, 0x003b0000,         /* POWER5 */
  85                 "__kernel_sync_dicache", "__kernel_sync_dicache_p5"
  86         },
  87 };
  88
  89 /*
  90  * Some infos carried around for each of them during parsing at
  91  * boot time.
  92  */
  93 struct lib32_elfinfo
  94 {
  95         Elf32_Ehdr      *hdr;           /* ptr to ELF */
  96         Elf32_Sym       *dynsym;        /* ptr to .dynsym section */
  97         unsigned long   dynsymsize;     /* size of .dynsym section */
  98         char            *dynstr;        /* ptr to .dynstr section */
  99         unsigned long   text;           /* offset of .text section in .so */
 100 };
 101
 102 struct lib64_elfinfo
 103 {
 104         Elf64_Ehdr      *hdr;
 105         Elf64_Sym       *dynsym;
 106         unsigned long   dynsymsize;
 107         char            *dynstr;
 108         unsigned long   text;
 109 };
 110
 111
 112 #ifdef __DEBUG
 113 static void dump_one_vdso_page(struct page *pg, struct page *upg)
 114 {
 115         printk("kpg: %p (c:%d,f:%08lx)", __va(page_to_pfn(pg) << PAGE_SHIFT),
 116                page_count(pg),
 117                pg->flags);
 118         if (upg/* && pg != upg*/) {
 119                 printk(" upg: %p (c:%d,f:%08lx)", __va(page_to_pfn(upg) << PAGE_SHIFT),
 120                        page_count(upg),
 121                        upg->flags);
 122         }
 123         printk("\n");
 124 }
 125
 126 static void dump_vdso_pages(struct vm_area_struct * vma)
 127 {
 128         int i;
 129
 130         if (!vma || test_thread_flag(TIF_32BIT)) {
 131                 printk("vDSO32 @ %016lx:\n", (unsigned long)vdso32_kbase);
 132                 for (i=0; i<vdso32_pages; i++) {
 133                         struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 134                         struct page *upg = (vma && vma->vm_mm) ?
 135                                 follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
 136                                 : NULL;
 137                         dump_one_vdso_page(pg, upg);
 138                 }
 139         }
 140         if (!vma || !test_thread_flag(TIF_32BIT)) {
 141                 printk("vDSO64 @ %016lx:\n", (unsigned long)vdso64_kbase);
 142                 for (i=0; i<vdso64_pages; i++) {
 143                         struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 144                         struct page *upg = (vma && vma->vm_mm) ?
 145                                 follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
 146                                 : NULL;
 147                         dump_one_vdso_page(pg, upg);
 148                 }
 149         }
 150 }
 151 #endif /* DEBUG */
 152
 153 /*
 154  * Keep a dummy vma_close for now, it will prevent VMA merging.
 155  */
 156 static void vdso_vma_close(struct vm_area_struct * vma)
 157 {
 158 }
 159
 160 /*
 161  * Our nopage() function, maps in the actual vDSO kernel pages, they will
 162  * be mapped read-only by do_no_page(), and eventually COW'ed, either
 163  * right away for an initial write access, or by do_wp_page().
 164  */
 165 static struct page * vdso_vma_nopage(struct vm_area_struct * vma,
 166                                      unsigned long address, int *type)
 167 {
 168         unsigned long offset = address - vma->vm_start;
 169         struct page *pg;
 170         void *vbase = test_thread_flag(TIF_32BIT) ? vdso32_kbase : vdso64_kbase;
 171
 172         DBG("vdso_vma_nopage(current: %s, address: %016lx, off: %lx)\n",
 173             current->comm, address, offset);
 174
 175         if (address < vma->vm_start || address > vma->vm_end)
 176                 return NOPAGE_SIGBUS;
 177
 178         /*
 179          * Last page is systemcfg, special handling here, no get_page() a
 180          * this is a reserved page
 181          */
 182         if ((vma->vm_end - address) <= PAGE_SIZE)
 183                 return virt_to_page(systemcfg);
 184
 185         pg = virt_to_page(vbase + offset);
 186         get_page(pg);
 187         DBG(" ->page count: %d\n", page_count(pg));
 188
 189         return pg;
 190 }
 191
 192 static struct vm_operations_struct vdso_vmops = {
 193         .close  = vdso_vma_close,
 194         .nopage = vdso_vma_nopage,
 195 };
 196
 197 /*
 198  * This is called from binfmt_elf, we create the special vma for the
 199  * vDSO and insert it into the mm struct tree
 200  */
 201 int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack)
 202 {
 203         struct mm_struct *mm = current->mm;
 204         struct vm_area_struct *vma;
 205         unsigned long vdso_pages;
 206         unsigned long vdso_base;
 207
 208         if (test_thread_flag(TIF_32BIT)) {
 209                 vdso_pages = vdso32_pages;
 210                 vdso_base = VDSO32_MBASE;
 211         } else {
 212                 vdso_pages = vdso64_pages;
 213                 vdso_base = VDSO64_MBASE;
 214         }
 215
 216         current->thread.vdso_base = 0;
 217
 218         /* vDSO has a problem and was disabled, just don't "enable" it for the
 219          * process
 220          */
 221         if (vdso_pages == 0)
 222                 return 0;
 223
 224         vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 225         if (vma == NULL)
 226                 return -ENOMEM;
 227         if (security_vm_enough_memory(vdso_pages)) {
 228                 kmem_cache_free(vm_area_cachep, vma);
 229                 return -ENOMEM;
 230         }
 231         memset(vma, 0, sizeof(*vma));
 232
 233         /*
 234          * pick a base address for the vDSO in process space. We try to put it
 235          * at vdso_base which is the "natural" base for it, but we might fail
 236          * and end up putting it elsewhere.
 237          */
 238         vdso_base = get_unmapped_area(NULL, vdso_base,
 239                                       vdso_pages << PAGE_SHIFT, 0, 0);
 240         if (vdso_base & ~PAGE_MASK)
 241                 return (int)vdso_base;
 242
 243         current->thread.vdso_base = vdso_base;
 244
 245         vma->vm_mm = mm;
 246         vma->vm_start = current->thread.vdso_base;
 247
 248         /*
 249          * the VMA size is one page more than the vDSO since systemcfg
 250          * is mapped in the last one
 251          */
 252         vma->vm_end = vma->vm_start + ((vdso_pages + 1) << PAGE_SHIFT);
 253
 254         /*
 255          * our vma flags don't have VM_WRITE so by default, the process isn't allowed
 256          * to write those pages.
 257          * gdb can break that with ptrace interface, and thus trigger COW on those
 258          * pages but it's then your responsibility to never do that on the "data" page
 259          * of the vDSO or you'll stop getting kernel updates and your nice userland
 260          * gettimeofday will be totally dead. It's fine to use that for setting
 261          * breakpoints in the vDSO code pages though
 262          */
 263         vma->vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 264         vma->vm_flags |= mm->def_flags;
 265         vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
 266         vma->vm_ops = &vdso_vmops;
 267
 268         down_write(&mm->mmap_sem);
 269         insert_vm_struct(mm, vma);
 270         mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 271         up_write(&mm->mmap_sem);
 272
 273         return 0;
 274 }
 275
 276 static void * __init find_section32(Elf32_Ehdr *ehdr, const char *secname,
 277                                   unsigned long *size)
 278 {
 279         Elf32_Shdr *sechdrs;
 280         unsigned int i;
 281         char *secnames;
 282
 283         /* Grab section headers and strings so we can tell who is who */
 284         sechdrs = (void *)ehdr + ehdr->e_shoff;
 285         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 286
 287         /* Find the section they want */
 288         for (i = 1; i < ehdr->e_shnum; i++) {
 289                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 290                         if (size)
 291                                 *size = sechdrs[i].sh_size;
 292                         return (void *)ehdr + sechdrs[i].sh_offset;
 293                 }
 294         }
 295         *size = 0;
 296         return NULL;
 297 }
 298
 299 static void * __init find_section64(Elf64_Ehdr *ehdr, const char *secname,
 300                                   unsigned long *size)
 301 {
 302         Elf64_Shdr *sechdrs;
 303         unsigned int i;
 304         char *secnames;
 305
 306         /* Grab section headers and strings so we can tell who is who */
 307         sechdrs = (void *)ehdr + ehdr->e_shoff;
 308         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 309
 310         /* Find the section they want */
 311         for (i = 1; i < ehdr->e_shnum; i++) {
 312                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 313                         if (size)
 314                                 *size = sechdrs[i].sh_size;
 315                         return (void *)ehdr + sechdrs[i].sh_offset;
 316                 }
 317         }
 318         if (size)
 319                 *size = 0;
 320         return NULL;
 321 }
 322
 323 static Elf32_Sym * __init find_symbol32(struct lib32_elfinfo *lib, const char *symname)
 324 {
 325         unsigned int i;
 326         char name[32], *c;
 327
 328         for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
 329                 if (lib->dynsym[i].st_name == 0)
 330                         continue;
 331                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 332                 c = strchr(name, '@');
 333                 if (c)
 334                         *c = 0;
 335                 if (strcmp(symname, name) == 0)
 336                         return &lib->dynsym[i];
 337         }
 338         return NULL;
 339 }
 340
 341 static Elf64_Sym * __init find_symbol64(struct lib64_elfinfo *lib, const char *symname)
 342 {
 343         unsigned int i;
 344         char name[32], *c;
 345
 346         for (i = 0; i < (lib->dynsymsize / sizeof(Elf64_Sym)); i++) {
 347                 if (lib->dynsym[i].st_name == 0)
 348                         continue;
 349                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 350                 c = strchr(name, '@');
 351                 if (c)
 352                         *c = 0;
 353                 if (strcmp(symname, name) == 0)
 354                         return &lib->dynsym[i];
 355         }
 356         return NULL;
 357 }
 358
 359 /* Note that we assume the section is .text and the symbol is relative to
 360  * the library base
 361  */
 362 static unsigned long __init find_function32(struct lib32_elfinfo *lib, const char *symname)
 363 {
 364         Elf32_Sym *sym = find_symbol32(lib, symname);
 365
 366         if (sym == NULL) {
 367                 printk(KERN_WARNING "vDSO32: function %s not found !\n", symname);
 368                 return 0;
 369         }
 370         return sym->st_value - VDSO32_LBASE;
 371 }
 372
 373 /* Note that we assume the section is .text and the symbol is relative to
 374  * the library base
 375  */
 376 static unsigned long __init find_function64(struct lib64_elfinfo *lib, const char *symname)
 377 {
 378         Elf64_Sym *sym = find_symbol64(lib, symname);
 379
 380         if (sym == NULL) {
 381                 printk(KERN_WARNING "vDSO64: function %s not found !\n", symname);
 382                 return 0;
 383         }
 384 #ifdef VDS64_HAS_DESCRIPTORS
 385         return *((u64 *)(vdso64_kbase + sym->st_value - VDSO64_LBASE)) - VDSO64_LBASE;
 386 #else
 387         return sym->st_value - VDSO64_LBASE;
 388 #endif
 389 }
 390
 391
 392 static __init int vdso_do_find_sections(struct lib32_elfinfo *v32,
 393                                         struct lib64_elfinfo *v64)
 394 {
 395         void *sect;
 396
 397         /*
 398          * Locate symbol tables & text section
 399          */
 400
 401         v32->dynsym = find_section32(v32->hdr, ".dynsym", &v32->dynsymsize);
 402         v32->dynstr = find_section32(v32->hdr, ".dynstr", NULL);
 403         if (v32->dynsym == NULL || v32->dynstr == NULL) {
 404                 printk(KERN_ERR "vDSO32: a required symbol section was not found\n");
 405                 return -1;
 406         }
 407         sect = find_section32(v32->hdr, ".text", NULL);
 408         if (sect == NULL) {
 409                 printk(KERN_ERR "vDSO32: the .text section was not found\n");
 410                 return -1;
 411         }
 412         v32->text = sect - vdso32_kbase;
 413
 414         v64->dynsym = find_section64(v64->hdr, ".dynsym", &v64->dynsymsize);
 415         v64->dynstr = find_section64(v64->hdr, ".dynstr", NULL);
 416         if (v64->dynsym == NULL || v64->dynstr == NULL) {
 417                 printk(KERN_ERR "vDSO64: a required symbol section was not found\n");
 418                 return -1;
 419         }
 420         sect = find_section64(v64->hdr, ".text", NULL);
 421         if (sect == NULL) {
 422                 printk(KERN_ERR "vDSO64: the .text section was not found\n");
 423                 return -1;
 424         }
 425         v64->text = sect - vdso64_kbase;
 426
 427         return 0;
 428 }
 429
 430 static __init void vdso_setup_trampolines(struct lib32_elfinfo *v32,
 431                                           struct lib64_elfinfo *v64)
 432 {
 433         /*
 434          * Find signal trampolines
 435          */
 436
 437         vdso64_rt_sigtramp      = find_function64(v64, "__kernel_sigtramp_rt64");
 438         vdso32_sigtramp         = find_function32(v32, "__kernel_sigtramp32");
 439         vdso32_rt_sigtramp      = find_function32(v32, "__kernel_sigtramp_rt32");
 440 }
 441
 442 static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
 443                                        struct lib64_elfinfo *v64)
 444 {
 445         Elf32_Sym *sym32;
 446         Elf64_Sym *sym64;
 447
 448         sym32 = find_symbol32(v32, "__kernel_datapage_offset");
 449         if (sym32 == NULL) {
 450                 printk(KERN_ERR "vDSO32: Can't find symbol __kernel_datapage_offset !\n");
 451                 return -1;
 452         }
 453         *((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
 454                 (vdso32_pages << PAGE_SHIFT) - (sym32->st_value - VDSO32_LBASE);
 455
 456         sym64 = find_symbol64(v64, "__kernel_datapage_offset");
 457         if (sym64 == NULL) {
 458                 printk(KERN_ERR "vDSO64: Can't find symbol __kernel_datapage_offset !\n");
 459                 return -1;
 460         }
 461         *((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
 462                 (vdso64_pages << PAGE_SHIFT) - (sym64->st_value - VDSO64_LBASE);
 463
 464         return 0;
 465 }
 466
 467 static int vdso_do_func_patch32(struct lib32_elfinfo *v32,
 468                                 struct lib64_elfinfo *v64,
 469                                 const char *orig, const char *fix)
 470 {
 471         Elf32_Sym *sym32_gen, *sym32_fix;
 472
 473         sym32_gen = find_symbol32(v32, orig);
 474         if (sym32_gen == NULL) {
 475                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", orig);
 476                 return -1;
 477         }
 478         sym32_fix = find_symbol32(v32, fix);
 479         if (sym32_fix == NULL) {
 480                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", fix);
 481                 return -1;
 482         }
 483         sym32_gen->st_value = sym32_fix->st_value;
 484         sym32_gen->st_size = sym32_fix->st_size;
 485         sym32_gen->st_info = sym32_fix->st_info;
 486         sym32_gen->st_other = sym32_fix->st_other;
 487         sym32_gen->st_shndx = sym32_fix->st_shndx;
 488
 489         return 0;
 490 }
 491
 492 static int vdso_do_func_patch64(struct lib32_elfinfo *v32,
 493                                 struct lib64_elfinfo *v64,
 494                                 const char *orig, const char *fix)
 495 {
 496         Elf64_Sym *sym64_gen, *sym64_fix;
 497
 498         sym64_gen = find_symbol64(v64, orig);
 499         if (sym64_gen == NULL) {
 500                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", orig);
 501                 return -1;
 502         }
 503         sym64_fix = find_symbol64(v64, fix);
 504         if (sym64_fix == NULL) {
 505                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", fix);
 506                 return -1;
 507         }
 508         sym64_gen->st_value = sym64_fix->st_value;
 509         sym64_gen->st_size = sym64_fix->st_size;
 510         sym64_gen->st_info = sym64_fix->st_info;
 511         sym64_gen->st_other = sym64_fix->st_other;
 512         sym64_gen->st_shndx = sym64_fix->st_shndx;
 513
 514         return 0;
 515 }
 516
 517 static __init int vdso_fixup_alt_funcs(struct lib32_elfinfo *v32,
 518                                        struct lib64_elfinfo *v64)
 519 {
 520         u32 pvr;
 521         int i;
 522
 523         pvr = mfspr(SPRN_PVR);
 524         for (i = 0; i < ARRAY_SIZE(vdso_patches); i++) {
 525                 struct vdso_patch_def *patch = &vdso_patches[i];
 526                 int match = (pvr & patch->pvr_mask) == patch->pvr_value;
 527
 528                 DBG("patch %d (mask: %x, pvr: %x) : %s\n",
 529                     i, patch->pvr_mask, patch->pvr_value, match ? "match" : "skip");
 530
 531                 if (!match)
 532                         continue;
 533
 534                 DBG("replacing %s with %s...\n", patch->gen_name, patch->fix_name);
 535
 536                 /*
 537                  * Patch the 32 bits and 64 bits symbols. Note that we do not patch
 538                  * the "." symbol on 64 bits. It would be easy to do, but doesn't
 539                  * seem to be necessary, patching the OPD symbol is enough.
 540                  */
 541                 vdso_do_func_patch32(v32, v64, patch->gen_name, patch->fix_name);
 542                 vdso_do_func_patch64(v32, v64, patch->gen_name, patch->fix_name);
 543         }
 544
 545         return 0;
 546 }
 547
 548
 549 static __init int vdso_setup(void)
 550 {
 551         struct lib32_elfinfo    v32;
 552         struct lib64_elfinfo    v64;
 553
 554         v32.hdr = vdso32_kbase;
 555         v64.hdr = vdso64_kbase;
 556
 557         if (vdso_do_find_sections(&v32, &v64))
 558                 return -1;
 559
 560         if (vdso_fixup_datapage(&v32, &v64))
 561                 return -1;
 562
 563         if (vdso_fixup_alt_funcs(&v32, &v64))
 564                 return -1;
 565
 566         vdso_setup_trampolines(&v32, &v64);
 567
 568         return 0;
 569 }
 570
 571 void __init vdso_init(void)
 572 {
 573         int i;
 574
 575         vdso64_pages = (&vdso64_end - &vdso64_start) >> PAGE_SHIFT;
 576         vdso32_pages = (&vdso32_end - &vdso32_start) >> PAGE_SHIFT;
 577
 578         DBG("vdso64_kbase: %p, 0x%x pages, vdso32_kbase: %p, 0x%x pages\n",
 579                vdso64_kbase, vdso64_pages, vdso32_kbase, vdso32_pages);
 580
 581         /*
 582          * Initialize the vDSO images in memory, that is do necessary
 583          * fixups of vDSO symbols, locate trampolines, etc...
 584          */
 585         if (vdso_setup()) {
 586                 printk(KERN_ERR "vDSO setup failure, not enabled !\n");
 587                 /* XXX should free pages here ? */
 588                 vdso64_pages = vdso32_pages = 0;
 589                 return;
 590         }
 591
 592         /* Make sure pages are in the correct state */
 593         for (i = 0; i < vdso64_pages; i++) {
 594                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 595                 ClearPageReserved(pg);
 596                 get_page(pg);
 597         }
 598         for (i = 0; i < vdso32_pages; i++) {
 599                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 600                 ClearPageReserved(pg);
 601                 get_page(pg);
 602         }
 603 }
 604
 605 int in_gate_area_no_task(unsigned long addr)
 606 {
 607         return 0;
 608 }
 609
 610 int in_gate_area(struct task_struct *task, unsigned long addr)
 611 {
 612         return 0;
 613 }
 614
 615 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 616 {
 617         return NULL;
 618 }
 619