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/systemcfg.h>
  38 #include <asm/vdso.h>
  39
  40 #undef DEBUG
  41
  42 #ifdef DEBUG
  43 #define DBG(fmt...) printk(fmt)
  44 #else
  45 #define DBG(fmt...)
  46 #endif
  47
  48
  49 /*
  50  * The vDSOs themselves are here
  51  */
  52 extern char vdso64_start, vdso64_end;
  53 extern char vdso32_start, vdso32_end;
  54
  55 static void *vdso64_kbase = &vdso64_start;
  56 static void *vdso32_kbase = &vdso32_start;
  57
  58 unsigned int vdso64_pages;
  59 unsigned int vdso32_pages;
  60
  61 /* Signal trampolines user addresses */
  62
  63 unsigned long vdso64_rt_sigtramp;
  64 unsigned long vdso32_sigtramp;
  65 unsigned long vdso32_rt_sigtramp;
  66
  67 /* Format of the patch table */
  68 struct vdso_patch_def
  69 {
  70         u32             pvr_mask, pvr_value;
  71         const char      *gen_name;
  72         const char      *fix_name;
  73 };
  74
  75 /* Table of functions to patch based on the CPU type/revision
  76  *
  77  * TODO: Improve by adding whole lists for each entry
  78  */
  79 static struct vdso_patch_def vdso_patches[] = {
  80         {
  81                 0xffff0000, 0x003a0000,         /* POWER5 */
  82                 "__kernel_sync_dicache", "__kernel_sync_dicache_p5"
  83         },
  84         {
  85                 0xffff0000, 0x003b0000,         /* POWER5 */
  86                 "__kernel_sync_dicache", "__kernel_sync_dicache_p5"
  87         },
  88 };
  89
  90 /*
  91  * Some infos carried around for each of them during parsing at
  92  * boot time.
  93  */
  94 struct lib32_elfinfo
  95 {
  96         Elf32_Ehdr      *hdr;           /* ptr to ELF */
  97         Elf32_Sym       *dynsym;        /* ptr to .dynsym section */
  98         unsigned long   dynsymsize;     /* size of .dynsym section */
  99         char            *dynstr;        /* ptr to .dynstr section */
 100         unsigned long   text;           /* offset of .text section in .so */
 101 };
 102
 103 struct lib64_elfinfo
 104 {
 105         Elf64_Ehdr      *hdr;
 106         Elf64_Sym       *dynsym;
 107         unsigned long   dynsymsize;
 108         char            *dynstr;
 109         unsigned long   text;
 110 };
 111
 112
 113 #ifdef __DEBUG
 114 static void dump_one_vdso_page(struct page *pg, struct page *upg)
 115 {
 116         printk("kpg: %p (c:%d,f:%08lx)", __va(page_to_pfn(pg) << PAGE_SHIFT),
 117                page_count(pg),
 118                pg->flags);
 119         if (upg/* && pg != upg*/) {
 120                 printk(" upg: %p (c:%d,f:%08lx)", __va(page_to_pfn(upg) << PAGE_SHIFT),
 121                        page_count(upg),
 122                        upg->flags);
 123         }
 124         printk("\n");
 125 }
 126
 127 static void dump_vdso_pages(struct vm_area_struct * vma)
 128 {
 129         int i;
 130
 131         if (!vma || test_thread_flag(TIF_32BIT)) {
 132                 printk("vDSO32 @ %016lx:\n", (unsigned long)vdso32_kbase);
 133                 for (i=0; i<vdso32_pages; i++) {
 134                         struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 135                         struct page *upg = (vma && vma->vm_mm) ?
 136                                 follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
 137                                 : NULL;
 138                         dump_one_vdso_page(pg, upg);
 139                 }
 140         }
 141         if (!vma || !test_thread_flag(TIF_32BIT)) {
 142                 printk("vDSO64 @ %016lx:\n", (unsigned long)vdso64_kbase);
 143                 for (i=0; i<vdso64_pages; i++) {
 144                         struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 145                         struct page *upg = (vma && vma->vm_mm) ?
 146                                 follow_page(vma->vm_mm, vma->vm_start + i*PAGE_SIZE, 0)
 147                                 : NULL;
 148                         dump_one_vdso_page(pg, upg);
 149                 }
 150         }
 151 }
 152 #endif /* DEBUG */
 153
 154 /*
 155  * Keep a dummy vma_close for now, it will prevent VMA merging.
 156  */
 157 static void vdso_vma_close(struct vm_area_struct * vma)
 158 {
 159 }
 160
 161 /*
 162  * Our nopage() function, maps in the actual vDSO kernel pages, they will
 163  * be mapped read-only by do_no_page(), and eventually COW'ed, either
 164  * right away for an initial write access, or by do_wp_page().
 165  */
 166 static struct page * vdso_vma_nopage(struct vm_area_struct * vma,
 167                                      unsigned long address, int *type)
 168 {
 169         unsigned long offset = address - vma->vm_start;
 170         struct page *pg;
 171         void *vbase = test_thread_flag(TIF_32BIT) ? vdso32_kbase : vdso64_kbase;
 172
 173         DBG("vdso_vma_nopage(current: %s, address: %016lx, off: %lx)\n",
 174             current->comm, address, offset);
 175
 176         if (address < vma->vm_start || address > vma->vm_end)
 177                 return NOPAGE_SIGBUS;
 178
 179         /*
 180          * Last page is systemcfg.
 181          */
 182         if ((vma->vm_end - address) <= PAGE_SIZE)
 183                 pg = virt_to_page(_systemcfg);
 184         else
 185                 pg = virt_to_page(vbase + offset);
 186
 187         get_page(pg);
 188         DBG(" ->page count: %d\n", page_count(pg));
 189
 190         return pg;
 191 }
 192
 193 static struct vm_operations_struct vdso_vmops = {
 194         .close  = vdso_vma_close,
 195         .nopage = vdso_vma_nopage,
 196 };
 197
 198 /*
 199  * This is called from binfmt_elf, we create the special vma for the
 200  * vDSO and insert it into the mm struct tree
 201  */
 202 int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack)
 203 {
 204         struct mm_struct *mm = current->mm;
 205         struct vm_area_struct *vma;
 206         unsigned long vdso_pages;
 207         unsigned long vdso_base;
 208
 209         if (test_thread_flag(TIF_32BIT)) {
 210                 vdso_pages = vdso32_pages;
 211                 vdso_base = VDSO32_MBASE;
 212         } else {
 213                 vdso_pages = vdso64_pages;
 214                 vdso_base = VDSO64_MBASE;
 215         }
 216
 217         current->thread.vdso_base = 0;
 218
 219         /* vDSO has a problem and was disabled, just don't "enable" it for the
 220          * process
 221          */
 222         if (vdso_pages == 0)
 223                 return 0;
 224
 225         vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 226         if (vma == NULL)
 227                 return -ENOMEM;
 228
 229         memset(vma, 0, sizeof(*vma));
 230
 231         /*
 232          * pick a base address for the vDSO in process space. We try to put it
 233          * at vdso_base which is the "natural" base for it, but we might fail
 234          * and end up putting it elsewhere.
 235          */
 236         vdso_base = get_unmapped_area(NULL, vdso_base,
 237                                       vdso_pages << PAGE_SHIFT, 0, 0);
 238         if (vdso_base & ~PAGE_MASK) {
 239                 kmem_cache_free(vm_area_cachep, vma);
 240                 return (int)vdso_base;
 241         }
 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 | VM_RESERVED;
 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         if (insert_vm_struct(mm, vma)) {
 270                 up_write(&mm->mmap_sem);
 271                 kmem_cache_free(vm_area_cachep, vma);
 272                 return -ENOMEM;
 273         }
 274         mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 275         up_write(&mm->mmap_sem);
 276
 277         return 0;
 278 }
 279
 280 static void * __init find_section32(Elf32_Ehdr *ehdr, const char *secname,
 281                                   unsigned long *size)
 282 {
 283         Elf32_Shdr *sechdrs;
 284         unsigned int i;
 285         char *secnames;
 286
 287         /* Grab section headers and strings so we can tell who is who */
 288         sechdrs = (void *)ehdr + ehdr->e_shoff;
 289         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 290
 291         /* Find the section they want */
 292         for (i = 1; i < ehdr->e_shnum; i++) {
 293                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 294                         if (size)
 295                                 *size = sechdrs[i].sh_size;
 296                         return (void *)ehdr + sechdrs[i].sh_offset;
 297                 }
 298         }
 299         *size = 0;
 300         return NULL;
 301 }
 302
 303 static void * __init find_section64(Elf64_Ehdr *ehdr, const char *secname,
 304                                   unsigned long *size)
 305 {
 306         Elf64_Shdr *sechdrs;
 307         unsigned int i;
 308         char *secnames;
 309
 310         /* Grab section headers and strings so we can tell who is who */
 311         sechdrs = (void *)ehdr + ehdr->e_shoff;
 312         secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
 313
 314         /* Find the section they want */
 315         for (i = 1; i < ehdr->e_shnum; i++) {
 316                 if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
 317                         if (size)
 318                                 *size = sechdrs[i].sh_size;
 319                         return (void *)ehdr + sechdrs[i].sh_offset;
 320                 }
 321         }
 322         if (size)
 323                 *size = 0;
 324         return NULL;
 325 }
 326
 327 static Elf32_Sym * __init find_symbol32(struct lib32_elfinfo *lib, const char *symname)
 328 {
 329         unsigned int i;
 330         char name[32], *c;
 331
 332         for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
 333                 if (lib->dynsym[i].st_name == 0)
 334                         continue;
 335                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 336                 c = strchr(name, '@');
 337                 if (c)
 338                         *c = 0;
 339                 if (strcmp(symname, name) == 0)
 340                         return &lib->dynsym[i];
 341         }
 342         return NULL;
 343 }
 344
 345 static Elf64_Sym * __init find_symbol64(struct lib64_elfinfo *lib, const char *symname)
 346 {
 347         unsigned int i;
 348         char name[32], *c;
 349
 350         for (i = 0; i < (lib->dynsymsize / sizeof(Elf64_Sym)); i++) {
 351                 if (lib->dynsym[i].st_name == 0)
 352                         continue;
 353                 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name, 32);
 354                 c = strchr(name, '@');
 355                 if (c)
 356                         *c = 0;
 357                 if (strcmp(symname, name) == 0)
 358                         return &lib->dynsym[i];
 359         }
 360         return NULL;
 361 }
 362
 363 /* Note that we assume the section is .text and the symbol is relative to
 364  * the library base
 365  */
 366 static unsigned long __init find_function32(struct lib32_elfinfo *lib, const char *symname)
 367 {
 368         Elf32_Sym *sym = find_symbol32(lib, symname);
 369
 370         if (sym == NULL) {
 371                 printk(KERN_WARNING "vDSO32: function %s not found !\n", symname);
 372                 return 0;
 373         }
 374         return sym->st_value - VDSO32_LBASE;
 375 }
 376
 377 /* Note that we assume the section is .text and the symbol is relative to
 378  * the library base
 379  */
 380 static unsigned long __init find_function64(struct lib64_elfinfo *lib, const char *symname)
 381 {
 382         Elf64_Sym *sym = find_symbol64(lib, symname);
 383
 384         if (sym == NULL) {
 385                 printk(KERN_WARNING "vDSO64: function %s not found !\n", symname);
 386                 return 0;
 387         }
 388 #ifdef VDS64_HAS_DESCRIPTORS
 389         return *((u64 *)(vdso64_kbase + sym->st_value - VDSO64_LBASE)) - VDSO64_LBASE;
 390 #else
 391         return sym->st_value - VDSO64_LBASE;
 392 #endif
 393 }
 394
 395
 396 static __init int vdso_do_find_sections(struct lib32_elfinfo *v32,
 397                                         struct lib64_elfinfo *v64)
 398 {
 399         void *sect;
 400
 401         /*
 402          * Locate symbol tables & text section
 403          */
 404
 405         v32->dynsym = find_section32(v32->hdr, ".dynsym", &v32->dynsymsize);
 406         v32->dynstr = find_section32(v32->hdr, ".dynstr", NULL);
 407         if (v32->dynsym == NULL || v32->dynstr == NULL) {
 408                 printk(KERN_ERR "vDSO32: a required symbol section was not found\n");
 409                 return -1;
 410         }
 411         sect = find_section32(v32->hdr, ".text", NULL);
 412         if (sect == NULL) {
 413                 printk(KERN_ERR "vDSO32: the .text section was not found\n");
 414                 return -1;
 415         }
 416         v32->text = sect - vdso32_kbase;
 417
 418         v64->dynsym = find_section64(v64->hdr, ".dynsym", &v64->dynsymsize);
 419         v64->dynstr = find_section64(v64->hdr, ".dynstr", NULL);
 420         if (v64->dynsym == NULL || v64->dynstr == NULL) {
 421                 printk(KERN_ERR "vDSO64: a required symbol section was not found\n");
 422                 return -1;
 423         }
 424         sect = find_section64(v64->hdr, ".text", NULL);
 425         if (sect == NULL) {
 426                 printk(KERN_ERR "vDSO64: the .text section was not found\n");
 427                 return -1;
 428         }
 429         v64->text = sect - vdso64_kbase;
 430
 431         return 0;
 432 }
 433
 434 static __init void vdso_setup_trampolines(struct lib32_elfinfo *v32,
 435                                           struct lib64_elfinfo *v64)
 436 {
 437         /*
 438          * Find signal trampolines
 439          */
 440
 441         vdso64_rt_sigtramp      = find_function64(v64, "__kernel_sigtramp_rt64");
 442         vdso32_sigtramp         = find_function32(v32, "__kernel_sigtramp32");
 443         vdso32_rt_sigtramp      = find_function32(v32, "__kernel_sigtramp_rt32");
 444 }
 445
 446 static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
 447                                        struct lib64_elfinfo *v64)
 448 {
 449         Elf32_Sym *sym32;
 450         Elf64_Sym *sym64;
 451
 452         sym32 = find_symbol32(v32, "__kernel_datapage_offset");
 453         if (sym32 == NULL) {
 454                 printk(KERN_ERR "vDSO32: Can't find symbol __kernel_datapage_offset !\n");
 455                 return -1;
 456         }
 457         *((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
 458                 (vdso32_pages << PAGE_SHIFT) - (sym32->st_value - VDSO32_LBASE);
 459
 460         sym64 = find_symbol64(v64, "__kernel_datapage_offset");
 461         if (sym64 == NULL) {
 462                 printk(KERN_ERR "vDSO64: Can't find symbol __kernel_datapage_offset !\n");
 463                 return -1;
 464         }
 465         *((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
 466                 (vdso64_pages << PAGE_SHIFT) - (sym64->st_value - VDSO64_LBASE);
 467
 468         return 0;
 469 }
 470
 471 static int vdso_do_func_patch32(struct lib32_elfinfo *v32,
 472                                 struct lib64_elfinfo *v64,
 473                                 const char *orig, const char *fix)
 474 {
 475         Elf32_Sym *sym32_gen, *sym32_fix;
 476
 477         sym32_gen = find_symbol32(v32, orig);
 478         if (sym32_gen == NULL) {
 479                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", orig);
 480                 return -1;
 481         }
 482         sym32_fix = find_symbol32(v32, fix);
 483         if (sym32_fix == NULL) {
 484                 printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", fix);
 485                 return -1;
 486         }
 487         sym32_gen->st_value = sym32_fix->st_value;
 488         sym32_gen->st_size = sym32_fix->st_size;
 489         sym32_gen->st_info = sym32_fix->st_info;
 490         sym32_gen->st_other = sym32_fix->st_other;
 491         sym32_gen->st_shndx = sym32_fix->st_shndx;
 492
 493         return 0;
 494 }
 495
 496 static int vdso_do_func_patch64(struct lib32_elfinfo *v32,
 497                                 struct lib64_elfinfo *v64,
 498                                 const char *orig, const char *fix)
 499 {
 500         Elf64_Sym *sym64_gen, *sym64_fix;
 501
 502         sym64_gen = find_symbol64(v64, orig);
 503         if (sym64_gen == NULL) {
 504                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", orig);
 505                 return -1;
 506         }
 507         sym64_fix = find_symbol64(v64, fix);
 508         if (sym64_fix == NULL) {
 509                 printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", fix);
 510                 return -1;
 511         }
 512         sym64_gen->st_value = sym64_fix->st_value;
 513         sym64_gen->st_size = sym64_fix->st_size;
 514         sym64_gen->st_info = sym64_fix->st_info;
 515         sym64_gen->st_other = sym64_fix->st_other;
 516         sym64_gen->st_shndx = sym64_fix->st_shndx;
 517
 518         return 0;
 519 }
 520
 521 static __init int vdso_fixup_alt_funcs(struct lib32_elfinfo *v32,
 522                                        struct lib64_elfinfo *v64)
 523 {
 524         u32 pvr;
 525         int i;
 526
 527         pvr = mfspr(SPRN_PVR);
 528         for (i = 0; i < ARRAY_SIZE(vdso_patches); i++) {
 529                 struct vdso_patch_def *patch = &vdso_patches[i];
 530                 int match = (pvr & patch->pvr_mask) == patch->pvr_value;
 531
 532                 DBG("patch %d (mask: %x, pvr: %x) : %s\n",
 533                     i, patch->pvr_mask, patch->pvr_value, match ? "match" : "skip");
 534
 535                 if (!match)
 536                         continue;
 537
 538                 DBG("replacing %s with %s...\n", patch->gen_name, patch->fix_name);
 539
 540                 /*
 541                  * Patch the 32 bits and 64 bits symbols. Note that we do not patch
 542                  * the "." symbol on 64 bits. It would be easy to do, but doesn't
 543                  * seem to be necessary, patching the OPD symbol is enough.
 544                  */
 545                 vdso_do_func_patch32(v32, v64, patch->gen_name, patch->fix_name);
 546                 vdso_do_func_patch64(v32, v64, patch->gen_name, patch->fix_name);
 547         }
 548
 549         return 0;
 550 }
 551
 552
 553 static __init int vdso_setup(void)
 554 {
 555         struct lib32_elfinfo    v32;
 556         struct lib64_elfinfo    v64;
 557
 558         v32.hdr = vdso32_kbase;
 559         v64.hdr = vdso64_kbase;
 560
 561         if (vdso_do_find_sections(&v32, &v64))
 562                 return -1;
 563
 564         if (vdso_fixup_datapage(&v32, &v64))
 565                 return -1;
 566
 567         if (vdso_fixup_alt_funcs(&v32, &v64))
 568                 return -1;
 569
 570         vdso_setup_trampolines(&v32, &v64);
 571
 572         return 0;
 573 }
 574
 575 void __init vdso_init(void)
 576 {
 577         int i;
 578
 579         vdso64_pages = (&vdso64_end - &vdso64_start) >> PAGE_SHIFT;
 580         vdso32_pages = (&vdso32_end - &vdso32_start) >> PAGE_SHIFT;
 581
 582         DBG("vdso64_kbase: %p, 0x%x pages, vdso32_kbase: %p, 0x%x pages\n",
 583                vdso64_kbase, vdso64_pages, vdso32_kbase, vdso32_pages);
 584
 585         /*
 586          * Initialize the vDSO images in memory, that is do necessary
 587          * fixups of vDSO symbols, locate trampolines, etc...
 588          */
 589         if (vdso_setup()) {
 590                 printk(KERN_ERR "vDSO setup failure, not enabled !\n");
 591                 /* XXX should free pages here ? */
 592                 vdso64_pages = vdso32_pages = 0;
 593                 return;
 594         }
 595
 596         /* Make sure pages are in the correct state */
 597         for (i = 0; i < vdso64_pages; i++) {
 598                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 599                 ClearPageReserved(pg);
 600                 get_page(pg);
 601         }
 602         for (i = 0; i < vdso32_pages; i++) {
 603                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 604                 ClearPageReserved(pg);
 605                 get_page(pg);
 606         }
 607
 608         get_page(virt_to_page(_systemcfg));
 609 }
 610
 611 int in_gate_area_no_task(unsigned long addr)
 612 {
 613         return 0;
 614 }
 615
 616 int in_gate_area(struct task_struct *task, unsigned long addr)
 617 {
 618         return 0;
 619 }
 620
 621 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 622 {
 623         return NULL;
 624 }
 625