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         /* vDSO has a problem and was disabled, just don't "enable" it for the
 217          * process
 218          */
 219         if (vdso_pages == 0) {
 220                 current->thread.vdso_base = 0;
 221                 return 0;
 222         }
 223         vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 224         if (vma == NULL)
 225                 return -ENOMEM;
 226         if (security_vm_enough_memory(vdso_pages)) {
 227                 kmem_cache_free(vm_area_cachep, vma);
 228                 return -ENOMEM;
 229         }
 230         memset(vma, 0, sizeof(*vma));
 231
 232         /*
 233          * pick a base address for the vDSO in process space. We have a default
 234          * base of 1Mb on which we had a random offset up to 1Mb.
 235          * XXX: Add possibility for a program header to specify that location
 236          */
 237         current->thread.vdso_base = vdso_base;
 238         /*  + ((unsigned long)vma & 0x000ff000); */
 239
 240         vma->vm_mm = mm;
 241         vma->vm_start = current->thread.vdso_base;
 242
 243         /*
 244          * the VMA size is one page more than the vDSO since systemcfg
 245          * is mapped in the last one
 246          */
 247         vma->vm_end = vma->vm_start + ((vdso_pages + 1) << PAGE_SHIFT);
 248
 249         /*
 250          * our vma flags don't have VM_WRITE so by default, the process isn't allowed
 251          * to write those pages.
 252          * gdb can break that with ptrace interface, and thus trigger COW on those
 253          * pages but it's then your responsibility to never do that on the "data" page
 254          * of the vDSO or you'll stop getting kernel updates and your nice userland
 255          * gettimeofday will be totally dead. It's fine to use that for setting
 256          * breakpoints in the vDSO code pages though
 257          */
 258         vma->vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 259         vma->vm_flags |= mm->def_flags;
 260         vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
 261         vma->vm_ops = &vdso_vmops;
 262
 263         down_write(&mm->mmap_sem);
 264         insert_vm_struct(mm, vma);
 265         mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 266         up_write(&mm->mmap_sem);
 267
 268         return 0;
 269 }
 270
 271 static void * __init find_section32(Elf32_Ehdr *ehdr, const char *secname,
 272                                   unsigned long *size)
 273 {
 274         Elf32_Shdr *sechdrs;
 275         unsigned int i;
 276         char *secnames;
 277
 278         /* Grab section headers and strings so we can tell who is who */
 279         sechdrs = (void *)ehdr + ehdr->e_shoff;
 280         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 281
 282         /* Find the section they want */
 283         for (i = 1; i < ehdr->e_shnum; i++) {
 284                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 285                         if (size)
 286                                 *size = sechdrs[i].sh_size;
 287                         return (void *)ehdr + sechdrs[i].sh_offset;
 288                 }
 289         }
 290         *size = 0;
 291         return NULL;
 292 }
 293
 294 static void * __init find_section64(Elf64_Ehdr *ehdr, const char *secname,
 295                                   unsigned long *size)
 296 {
 297         Elf64_Shdr *sechdrs;
 298         unsigned int i;
 299         char *secnames;
 300
 301         /* Grab section headers and strings so we can tell who is who */
 302         sechdrs = (void *)ehdr + ehdr->e_shoff;
 303         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 304
 305         /* Find the section they want */
 306         for (i = 1; i < ehdr->e_shnum; i++) {
 307                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 308                         if (size)
 309                                 *size = sechdrs[i].sh_size;
 310                         return (void *)ehdr + sechdrs[i].sh_offset;
 311                 }
 312         }
 313         if (size)
 314                 *size = 0;
 315         return NULL;
 316 }
 317
 318 static Elf32_Sym * __init find_symbol32(struct lib32_elfinfo *lib, const char *symname)
 319 {
 320         unsigned int i;
 321         char name[32], *c;
 322
 323         for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
 324                 if (lib->dynsym[i].st_name == 0)
 325                         continue;
 326                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 327                 c = strchr(name, '@');
 328                 if (c)
 329                         *c = 0;
 330                 if (strcmp(symname, name) == 0)
 331                         return &lib->dynsym[i];
 332         }
 333         return NULL;
 334 }
 335
 336 static Elf64_Sym * __init find_symbol64(struct lib64_elfinfo *lib, const char *symname)
 337 {
 338         unsigned int i;
 339         char name[32], *c;
 340
 341         for (i = 0; i < (lib->dynsymsize / sizeof(Elf64_Sym)); i++) {
 342                 if (lib->dynsym[i].st_name == 0)
 343                         continue;
 344                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 345                 c = strchr(name, '@');
 346                 if (c)
 347                         *c = 0;
 348                 if (strcmp(symname, name) == 0)
 349                         return &lib->dynsym[i];
 350         }
 351         return NULL;
 352 }
 353
 354 /* Note that we assume the section is .text and the symbol is relative to
 355  * the library base
 356  */
 357 static unsigned long __init find_function32(struct lib32_elfinfo *lib, const char *symname)
 358 {
 359         Elf32_Sym *sym = find_symbol32(lib, symname);
 360
 361         if (sym == NULL) {
 362                 printk(KERN_WARNING "vDSO32: function %s not found !\n", symname);
 363                 return 0;
 364         }
 365         return sym->st_value - VDSO32_LBASE;
 366 }
 367
 368 /* Note that we assume the section is .text and the symbol is relative to
 369  * the library base
 370  */
 371 static unsigned long __init find_function64(struct lib64_elfinfo *lib, const char *symname)
 372 {
 373         Elf64_Sym *sym = find_symbol64(lib, symname);
 374
 375         if (sym == NULL) {
 376                 printk(KERN_WARNING "vDSO64: function %s not found !\n", symname);
 377                 return 0;
 378         }
 379 #ifdef VDS64_HAS_DESCRIPTORS
 380         return *((u64 *)(vdso64_kbase + sym->st_value - VDSO64_LBASE)) - VDSO64_LBASE;
 381 #else
 382         return sym->st_value - VDSO64_LBASE;
 383 #endif
 384 }
 385
 386
 387 static __init int vdso_do_find_sections(struct lib32_elfinfo *v32,
 388                                         struct lib64_elfinfo *v64)
 389 {
 390         void *sect;
 391
 392         /*
 393          * Locate symbol tables & text section
 394          */
 395
 396         v32->dynsym = find_section32(v32->hdr, ".dynsym", &v32->dynsymsize);
 397         v32->dynstr = find_section32(v32->hdr, ".dynstr", NULL);
 398         if (v32->dynsym == NULL || v32->dynstr == NULL) {
 399                 printk(KERN_ERR "vDSO32: a required symbol section was not found\n");
 400                 return -1;
 401         }
 402         sect = find_section32(v32->hdr, ".text", NULL);
 403         if (sect == NULL) {
 404                 printk(KERN_ERR "vDSO32: the .text section was not found\n");
 405                 return -1;
 406         }
 407         v32->text = sect - vdso32_kbase;
 408
 409         v64->dynsym = find_section64(v64->hdr, ".dynsym", &v64->dynsymsize);
 410         v64->dynstr = find_section64(v64->hdr, ".dynstr", NULL);
 411         if (v64->dynsym == NULL || v64->dynstr == NULL) {
 412                 printk(KERN_ERR "vDSO64: a required symbol section was not found\n");
 413                 return -1;
 414         }
 415         sect = find_section64(v64->hdr, ".text", NULL);
 416         if (sect == NULL) {
 417                 printk(KERN_ERR "vDSO64: the .text section was not found\n");
 418                 return -1;
 419         }
 420         v64->text = sect - vdso64_kbase;
 421
 422         return 0;
 423 }
 424
 425 static __init void vdso_setup_trampolines(struct lib32_elfinfo *v32,
 426                                           struct lib64_elfinfo *v64)
 427 {
 428         /*
 429          * Find signal trampolines
 430          */
 431
 432         vdso64_rt_sigtramp      = find_function64(v64, "__kernel_sigtramp_rt64");
 433         vdso32_sigtramp         = find_function32(v32, "__kernel_sigtramp32");
 434         vdso32_rt_sigtramp      = find_function32(v32, "__kernel_sigtramp_rt32");
 435 }
 436
 437 static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
 438                                        struct lib64_elfinfo *v64)
 439 {
 440         Elf32_Sym *sym32;
 441         Elf64_Sym *sym64;
 442
 443         sym32 = find_symbol32(v32, "__kernel_datapage_offset");
 444         if (sym32 == NULL) {
 445                 printk(KERN_ERR "vDSO32: Can't find symbol __kernel_datapage_offset !\n");
 446                 return -1;
 447         }
 448         *((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
 449                 (vdso32_pages << PAGE_SHIFT) - (sym32->st_value - VDSO32_LBASE);
 450
 451         sym64 = find_symbol64(v64, "__kernel_datapage_offset");
 452         if (sym64 == NULL) {
 453                 printk(KERN_ERR "vDSO64: Can't find symbol __kernel_datapage_offset !\n");
 454                 return -1;
 455         }
 456         *((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
 457                 (vdso64_pages << PAGE_SHIFT) - (sym64->st_value - VDSO64_LBASE);
 458
 459         return 0;
 460 }
 461
 462 static int vdso_do_func_patch32(struct lib32_elfinfo *v32,
 463                                 struct lib64_elfinfo *v64,
 464                                 const char *orig, const char *fix)
 465 {
 466         Elf32_Sym *sym32_gen, *sym32_fix;
 467
 468         sym32_gen = find_symbol32(v32, orig);
 469         if (sym32_gen == NULL) {
 470                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", orig);
 471                 return -1;
 472         }
 473         sym32_fix = find_symbol32(v32, fix);
 474         if (sym32_fix == NULL) {
 475                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", fix);
 476                 return -1;
 477         }
 478         sym32_gen->st_value = sym32_fix->st_value;
 479         sym32_gen->st_size = sym32_fix->st_size;
 480         sym32_gen->st_info = sym32_fix->st_info;
 481         sym32_gen->st_other = sym32_fix->st_other;
 482         sym32_gen->st_shndx = sym32_fix->st_shndx;
 483
 484         return 0;
 485 }
 486
 487 static int vdso_do_func_patch64(struct lib32_elfinfo *v32,
 488                                 struct lib64_elfinfo *v64,
 489                                 const char *orig, const char *fix)
 490 {
 491         Elf64_Sym *sym64_gen, *sym64_fix;
 492
 493         sym64_gen = find_symbol64(v64, orig);
 494         if (sym64_gen == NULL) {
 495                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", orig);
 496                 return -1;
 497         }
 498         sym64_fix = find_symbol64(v64, fix);
 499         if (sym64_fix == NULL) {
 500                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", fix);
 501                 return -1;
 502         }
 503         sym64_gen->st_value = sym64_fix->st_value;
 504         sym64_gen->st_size = sym64_fix->st_size;
 505         sym64_gen->st_info = sym64_fix->st_info;
 506         sym64_gen->st_other = sym64_fix->st_other;
 507         sym64_gen->st_shndx = sym64_fix->st_shndx;
 508
 509         return 0;
 510 }
 511
 512 static __init int vdso_fixup_alt_funcs(struct lib32_elfinfo *v32,
 513                                        struct lib64_elfinfo *v64)
 514 {
 515         u32 pvr;
 516         int i;
 517
 518         pvr = mfspr(SPRN_PVR);
 519         for (i = 0; i < ARRAY_SIZE(vdso_patches); i++) {
 520                 struct vdso_patch_def *patch = &vdso_patches[i];
 521                 int match = (pvr & patch->pvr_mask) == patch->pvr_value;
 522
 523                 DBG("patch %d (mask: %x, pvr: %x) : %s\n",
 524                     i, patch->pvr_mask, patch->pvr_value, match ? "match" : "skip");
 525
 526                 if (!match)
 527                         continue;
 528
 529                 DBG("replacing %s with %s...\n", patch->gen_name, patch->fix_name);
 530
 531                 /*
 532                  * Patch the 32 bits and 64 bits symbols. Note that we do not patch
 533                  * the "." symbol on 64 bits. It would be easy to do, but doesn't
 534                  * seem to be necessary, patching the OPD symbol is enough.
 535                  */
 536                 vdso_do_func_patch32(v32, v64, patch->gen_name, patch->fix_name);
 537                 vdso_do_func_patch64(v32, v64, patch->gen_name, patch->fix_name);
 538         }
 539
 540         return 0;
 541 }
 542
 543
 544 static __init int vdso_setup(void)
 545 {
 546         struct lib32_elfinfo    v32;
 547         struct lib64_elfinfo    v64;
 548
 549         v32.hdr = vdso32_kbase;
 550         v64.hdr = vdso64_kbase;
 551
 552         if (vdso_do_find_sections(&v32, &v64))
 553                 return -1;
 554
 555         if (vdso_fixup_datapage(&v32, &v64))
 556                 return -1;
 557
 558         if (vdso_fixup_alt_funcs(&v32, &v64))
 559                 return -1;
 560
 561         vdso_setup_trampolines(&v32, &v64);
 562
 563         return 0;
 564 }
 565
 566 void __init vdso_init(void)
 567 {
 568         int i;
 569
 570         vdso64_pages = (&vdso64_end - &vdso64_start) >> PAGE_SHIFT;
 571         vdso32_pages = (&vdso32_end - &vdso32_start) >> PAGE_SHIFT;
 572
 573         DBG("vdso64_kbase: %p, 0x%x pages, vdso32_kbase: %p, 0x%x pages\n",
 574                vdso64_kbase, vdso64_pages, vdso32_kbase, vdso32_pages);
 575
 576         /*
 577          * Initialize the vDSO images in memory, that is do necessary
 578          * fixups of vDSO symbols, locate trampolines, etc...
 579          */
 580         if (vdso_setup()) {
 581                 printk(KERN_ERR "vDSO setup failure, not enabled !\n");
 582                 /* XXX should free pages here ? */
 583                 vdso64_pages = vdso32_pages = 0;
 584                 return;
 585         }
 586
 587         /* Make sure pages are in the correct state */
 588         for (i = 0; i < vdso64_pages; i++) {
 589                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 590                 ClearPageReserved(pg);
 591                 get_page(pg);
 592         }
 593         for (i = 0; i < vdso32_pages; i++) {
 594                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 595                 ClearPageReserved(pg);
 596                 get_page(pg);
 597         }
 598 }
 599
 600 int in_gate_area_no_task(unsigned long addr)
 601 {
 602         return 0;
 603 }
 604
 605 int in_gate_area(struct task_struct *task, unsigned long addr)
 606 {
 607         return 0;
 608 }
 609
 610 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 611 {
 612         return NULL;
 613 }
 614