linux_vdso.c

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    1 /*-
    2  * Copyright (c) 2013 Dmitry Chagin
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer
   10  *    in this position and unchanged.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 #include "opt_compat.h"
   31 
   32 #if defined(__i386__) || (defined(__amd64__) && defined(COMPAT_LINUX32))
   33 #define __ELF_WORD_SIZE 32
   34 #else
   35 #define __ELF_WORD_SIZE 64
   36 #endif
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/elf.h>
   41 #include <sys/kernel.h>
   42 #include <sys/lock.h>
   43 #include <sys/rwlock.h>
   44 #include <sys/queue.h>
   45 #include <sys/sysent.h>
   46 
   47 #include <vm/vm.h>
   48 #include <vm/vm_param.h>
   49 #include <vm/pmap.h>
   50 #include <vm/vm_extern.h>
   51 #include <vm/vm_kern.h>
   52 #include <vm/vm_map.h>
   53 #include <vm/vm_object.h>
   54 #include <vm/vm_page.h>
   55 #include <vm/vm_pager.h>
   56 
   57 #include <compat/linux/linux_vdso.h>
   58 
   59 SLIST_HEAD(, linux_vdso_sym) __elfN(linux_vdso_syms) =
   60     SLIST_HEAD_INITIALIZER(__elfN(linux_vdso_syms));
   61 
   62 static int __elfN(symtabindex);
   63 static int __elfN(symstrindex);
   64 
   65 static void
   66 __elfN(linux_vdso_lookup)(Elf_Ehdr *, struct linux_vdso_sym *);
   67 
   68 void
   69 __elfN(linux_vdso_sym_init)(struct linux_vdso_sym *s)
   70 {
   71 
   72         SLIST_INSERT_HEAD(&__elfN(linux_vdso_syms), s, sym);
   73 }
   74 
   75 vm_object_t
   76 __elfN(linux_shared_page_init)(char **mapping)
   77 {
   78         vm_page_t m;
   79         vm_object_t obj;
   80         vm_offset_t addr;
   81 
   82         obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
   83             VM_PROT_DEFAULT, 0, NULL);
   84         VM_OBJECT_WLOCK(obj);
   85         m = vm_page_grab(obj, 0, VM_ALLOC_ZERO);
   86         VM_OBJECT_WUNLOCK(obj);
   87         vm_page_valid(m);
   88         vm_page_xunbusy(m);
   89         addr = kva_alloc(PAGE_SIZE);
   90         pmap_qenter(addr, &m, 1);
   91         *mapping = (char *)addr;
   92         return (obj);
   93 }
   94 
   95 void
   96 __elfN(linux_shared_page_fini)(vm_object_t obj, void *mapping)
   97 {
   98         vm_offset_t va;
   99 
  100         va = (vm_offset_t)mapping;
  101         pmap_qremove(va, 1);
  102         kva_free(va, PAGE_SIZE);
  103         vm_object_deallocate(obj);
  104 }
  105 
  106 void
  107 __elfN(linux_vdso_fixup)(struct sysentvec *sv)
  108 {
  109         Elf_Ehdr *ehdr;
  110         Elf_Shdr *shdr;
  111         int i;
  112 
  113         ehdr = (Elf_Ehdr *) sv->sv_sigcode;
  114 
  115         if (!IS_ELF(*ehdr) ||
  116             ehdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
  117             ehdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
  118             ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
  119             ehdr->e_shoff == 0 ||
  120             ehdr->e_shentsize != sizeof(Elf_Shdr))
  121                 panic("Linux invalid vdso header.\n");
  122 
  123         if (ehdr->e_type != ET_DYN)
  124                 panic("Linux invalid vdso header.\n");
  125 
  126         shdr = (Elf_Shdr *) ((caddr_t)ehdr + ehdr->e_shoff);
  127 
  128         __elfN(symtabindex) = -1;
  129         __elfN(symstrindex) = -1;
  130         for (i = 0; i < ehdr->e_shnum; i++) {
  131                 if (shdr[i].sh_size == 0)
  132                         continue;
  133                 if (shdr[i].sh_type == SHT_DYNSYM) {
  134                         __elfN(symtabindex) = i;
  135                         __elfN(symstrindex) = shdr[i].sh_link;
  136                 }
  137         }
  138 
  139         if (__elfN(symtabindex) == -1 || __elfN(symstrindex) == -1)
  140                 panic("Linux invalid vdso header.\n");
  141 
  142         ehdr->e_ident[EI_OSABI] = ELFOSABI_LINUX;
  143 }
  144 
  145 void
  146 __elfN(linux_vdso_reloc)(struct sysentvec *sv)
  147 {
  148         struct linux_vdso_sym *lsym;
  149         Elf_Ehdr *ehdr;
  150         Elf_Phdr *phdr;
  151         Elf_Shdr *shdr;
  152         Elf_Dyn *dyn;
  153         Elf_Sym *sym;
  154         int i, j, symcnt;
  155 
  156         ehdr = (Elf_Ehdr *) sv->sv_sigcode;
  157 
  158         /* Adjust our so relative to the sigcode_base */
  159         if (sv->sv_shared_page_base != 0) {
  160                 ehdr->e_entry += sv->sv_shared_page_base;
  161                 phdr = (Elf_Phdr *)((caddr_t)ehdr + ehdr->e_phoff);
  162 
  163                 /* phdrs */
  164                 for (i = 0; i < ehdr->e_phnum; i++) {
  165                         phdr[i].p_vaddr += sv->sv_shared_page_base;
  166                         if (phdr[i].p_type != PT_DYNAMIC)
  167                                 continue;
  168                         dyn = (Elf_Dyn *)((caddr_t)ehdr + phdr[i].p_offset);
  169                         for(; dyn->d_tag != DT_NULL; dyn++) {
  170                                 switch (dyn->d_tag) {
  171                                 case DT_PLTGOT:
  172                                 case DT_HASH:
  173                                 case DT_STRTAB:
  174                                 case DT_SYMTAB:
  175                                 case DT_RELA:
  176                                 case DT_INIT:
  177                                 case DT_FINI:
  178                                 case DT_REL:
  179                                 case DT_DEBUG:
  180                                 case DT_JMPREL:
  181                                 case DT_VERSYM:
  182                                 case DT_VERDEF:
  183                                 case DT_VERNEED:
  184                                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
  185                                         dyn->d_un.d_ptr += sv->sv_shared_page_base;
  186                                         break;
  187                                 case DT_ENCODING ... DT_LOOS-1:
  188                                 case DT_LOOS ... DT_HIOS:
  189                                         if (dyn->d_tag >= DT_ENCODING &&
  190                                             (dyn->d_tag & 1) == 0)
  191                                                 dyn->d_un.d_ptr += sv->sv_shared_page_base;
  192                                         break;
  193                                 default:
  194                                         break;
  195                                 }
  196                         }
  197                 }
  198 
  199                 /* sections */
  200                 shdr = (Elf_Shdr *)((caddr_t)ehdr + ehdr->e_shoff);
  201                 for(i = 0; i < ehdr->e_shnum; i++) {
  202                         if (!(shdr[i].sh_flags & SHF_ALLOC))
  203                                 continue;
  204                         shdr[i].sh_addr += sv->sv_shared_page_base;
  205                         if (shdr[i].sh_type != SHT_SYMTAB &&
  206                             shdr[i].sh_type != SHT_DYNSYM)
  207                                 continue;
  208 
  209                         sym = (Elf_Sym *)((caddr_t)ehdr + shdr[i].sh_offset);
  210                         symcnt = shdr[i].sh_size / sizeof(*sym);
  211 
  212                         for(j = 0; j < symcnt; j++, sym++) {
  213                                 if (sym->st_shndx == SHN_UNDEF ||
  214                                     sym->st_shndx == SHN_ABS)
  215                                         continue;
  216                                 sym->st_value += sv->sv_shared_page_base;
  217                         }
  218                 }
  219         }
  220 
  221         SLIST_FOREACH(lsym, &__elfN(linux_vdso_syms), sym)
  222                 __elfN(linux_vdso_lookup)(ehdr, lsym);
  223 }
  224 
  225 static void
  226 __elfN(linux_vdso_lookup)(Elf_Ehdr *ehdr, struct linux_vdso_sym *vsym)
  227 {
  228         vm_offset_t strtab, symname;
  229         uint32_t symcnt;
  230         Elf_Shdr *shdr;
  231         int i;
  232 
  233         shdr = (Elf_Shdr *) ((caddr_t)ehdr + ehdr->e_shoff);
  234 
  235         strtab = (vm_offset_t)((caddr_t)ehdr +
  236             shdr[__elfN(symstrindex)].sh_offset);
  237         Elf_Sym *sym = (Elf_Sym *)((caddr_t)ehdr +
  238             shdr[__elfN(symtabindex)].sh_offset);
  239         symcnt = shdr[__elfN(symtabindex)].sh_size / sizeof(*sym);
  240 
  241         for (i = 0; i < symcnt; ++i, ++sym) {
  242                 symname = strtab + sym->st_name;
  243                 if (strncmp(vsym->symname, (char *)symname, vsym->size) == 0) {
  244                         *vsym->ptr = (uintptr_t)sym->st_value;
  245                         break;
  246                 }
  247         }
  248 }

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FreeBSD/Linux Kernel Cross Reference sys/compat/linux/linux_vdso.c

FreeBSD/Linux Kernel Cross Reference
sys/compat/linux/linux_vdso.c