The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/compat/linux/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: releng/11.2/sys/compat/linux/linux_vdso.c 315953 2017-03-25 14:25:20Z dchagin $");
   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 
   69 void
   70 __elfN(linux_vdso_sym_init)(struct linux_vdso_sym *s)
   71 {
   72 
   73         SLIST_INSERT_HEAD(&__elfN(linux_vdso_syms), s, sym);
   74 }
   75 
   76 vm_object_t
   77 __elfN(linux_shared_page_init)(char **mapping)
   78 {
   79         vm_page_t m;
   80         vm_object_t obj;
   81         vm_offset_t addr;
   82 
   83         obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
   84             VM_PROT_DEFAULT, 0, NULL);
   85         VM_OBJECT_WLOCK(obj);
   86         m = vm_page_grab(obj, 0, VM_ALLOC_NOBUSY | VM_ALLOC_ZERO);
   87         m->valid = VM_PAGE_BITS_ALL;
   88         VM_OBJECT_WUNLOCK(obj);
   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)
   97 {
   98 
   99         vm_object_deallocate(obj);
  100 }
  101 
  102 void
  103 __elfN(linux_vdso_fixup)(struct sysentvec *sv)
  104 {
  105         Elf_Ehdr *ehdr;
  106         Elf_Shdr *shdr;
  107         int i;
  108 
  109         ehdr = (Elf_Ehdr *) sv->sv_sigcode;
  110 
  111         if (!IS_ELF(*ehdr) ||
  112             ehdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
  113             ehdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
  114             ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
  115             ehdr->e_shoff == 0 ||
  116             ehdr->e_shentsize != sizeof(Elf_Shdr))
  117                 panic("Linux invalid vdso header.\n");
  118 
  119         if (ehdr->e_type != ET_DYN)
  120                 panic("Linux invalid vdso header.\n");
  121 
  122         shdr = (Elf_Shdr *) ((caddr_t)ehdr + ehdr->e_shoff);
  123 
  124         __elfN(symtabindex) = -1;
  125         __elfN(symstrindex) = -1;
  126         for (i = 0; i < ehdr->e_shnum; i++) {
  127                 if (shdr[i].sh_size == 0)
  128                         continue;
  129                 if (shdr[i].sh_type == SHT_DYNSYM) {
  130                         __elfN(symtabindex) = i;
  131                         __elfN(symstrindex) = shdr[i].sh_link;
  132                 }
  133         }
  134 
  135         if (__elfN(symtabindex) == -1 || __elfN(symstrindex) == -1)
  136                 panic("Linux invalid vdso header.\n");
  137 
  138         ehdr->e_ident[EI_OSABI] = ELFOSABI_LINUX;
  139 }
  140 
  141 void
  142 __elfN(linux_vdso_reloc)(struct sysentvec *sv, long vdso_adjust)
  143 {
  144         struct linux_vdso_sym *lsym;
  145         Elf_Ehdr *ehdr;
  146         Elf_Phdr *phdr;
  147         Elf_Shdr *shdr;
  148         Elf_Dyn *dyn;
  149         Elf_Sym *sym;
  150         int i, j, symcnt;
  151 
  152         ehdr = (Elf_Ehdr *) sv->sv_sigcode;
  153 
  154         /* Adjust our so relative to the sigcode_base */
  155         if (vdso_adjust != 0) {
  156                 ehdr->e_entry += vdso_adjust;
  157                 phdr = (Elf_Phdr *)((caddr_t)ehdr + ehdr->e_phoff);
  158 
  159                 /* phdrs */
  160                 for (i = 0; i < ehdr->e_phnum; i++) {
  161                         phdr[i].p_vaddr += vdso_adjust;
  162                         if (phdr[i].p_type != PT_DYNAMIC)
  163                                 continue;
  164                         dyn = (Elf_Dyn *)((caddr_t)ehdr + phdr[i].p_offset);
  165                         for(; dyn->d_tag != DT_NULL; dyn++) {
  166                                 switch (dyn->d_tag) {
  167                                 case DT_PLTGOT:
  168                                 case DT_HASH:
  169                                 case DT_STRTAB:
  170                                 case DT_SYMTAB:
  171                                 case DT_RELA:
  172                                 case DT_INIT:
  173                                 case DT_FINI:
  174                                 case DT_REL:
  175                                 case DT_DEBUG:
  176                                 case DT_JMPREL:
  177                                 case DT_VERSYM:
  178                                 case DT_VERDEF:
  179                                 case DT_VERNEED:
  180                                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
  181                                         dyn->d_un.d_ptr += vdso_adjust;
  182                                         break;
  183                                 case DT_ENCODING ... DT_LOOS-1:
  184                                 case DT_LOOS ... DT_HIOS:
  185                                         if (dyn->d_tag >= DT_ENCODING &&
  186                                             (dyn->d_tag & 1) == 0)
  187                                                 dyn->d_un.d_ptr += vdso_adjust;
  188                                         break;
  189                                 default:
  190                                         break;
  191                                 }
  192                         }
  193                 }
  194 
  195                 /* sections */
  196                 shdr = (Elf_Shdr *)((caddr_t)ehdr + ehdr->e_shoff);
  197                 for(i = 0; i < ehdr->e_shnum; i++) {
  198                         if (!(shdr[i].sh_flags & SHF_ALLOC))
  199                                 continue;
  200                         shdr[i].sh_addr += vdso_adjust;
  201                         if (shdr[i].sh_type != SHT_SYMTAB &&
  202                             shdr[i].sh_type != SHT_DYNSYM)
  203                                 continue;
  204 
  205                         sym = (Elf_Sym *)((caddr_t)ehdr + shdr[i].sh_offset);
  206                         symcnt = shdr[i].sh_size / sizeof(*sym);
  207 
  208                         for(j = 0; j < symcnt; j++, sym++) {
  209                                 if (sym->st_shndx == SHN_UNDEF ||
  210                                     sym->st_shndx == SHN_ABS)
  211                                         continue;
  212                                 sym->st_value += vdso_adjust;
  213                         }
  214                 }
  215         }
  216 
  217         SLIST_FOREACH(lsym, &__elfN(linux_vdso_syms), sym)
  218                 __elfN(linux_vdso_lookup)(ehdr, lsym);
  219 }
  220 
  221 static void
  222 __elfN(linux_vdso_lookup)(Elf_Ehdr *ehdr, struct linux_vdso_sym *vsym)
  223 {
  224         vm_offset_t strtab, symname;
  225         uint32_t symcnt;
  226         Elf_Shdr *shdr;
  227         int i;
  228 
  229         shdr = (Elf_Shdr *) ((caddr_t)ehdr + ehdr->e_shoff);
  230 
  231         strtab = (vm_offset_t)((caddr_t)ehdr +
  232             shdr[__elfN(symstrindex)].sh_offset);
  233         Elf_Sym *sym = (Elf_Sym *)((caddr_t)ehdr +
  234             shdr[__elfN(symtabindex)].sh_offset);
  235         symcnt = shdr[__elfN(symtabindex)].sh_size / sizeof(*sym);
  236 
  237         for (i = 0; i < symcnt; ++i, ++sym) {
  238                 symname = strtab + sym->st_name;
  239                 if (strncmp(vsym->symname, (char *)symname, vsym->size) == 0) {
  240                         *vsym->ptr = (uintptr_t)sym->st_value;
  241                         break;
  242                 }
  243         }
  244 }

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