arch/um/os-Linux/elf_aux.c

   1 /*
   2  *  arch/um/kernel/elf_aux.c
   3  *
   4  *  Scan the Elf auxiliary vector provided by the host to extract
   5  *  information about vsyscall-page, etc.
   6  *
   7  *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH
   8  *  Author: Bodo Stroesser (bodo.stroesser@fujitsu-siemens.com)
   9  */
  10 #include <elf.h>
  11 #include <stddef.h>
  12 #include "init.h"
  13 #include "elf_user.h"
  14 #include "mem_user.h"
  15 #include <kern_constants.h>
  16
  17 /* Use the one from the kernel - the host may miss it, if having old headers. */
  18 #if UM_ELF_CLASS == UM_ELFCLASS32
  19 typedef Elf32_auxv_t elf_auxv_t;
  20 #else
  21 typedef Elf64_auxv_t elf_auxv_t;
  22 #endif
  23
  24 /* These are initialized very early in boot and never changed */
  25 char * elf_aux_platform;
  26 long elf_aux_hwcap;
  27 unsigned long vsyscall_ehdr;
  28 unsigned long vsyscall_end;
  29 unsigned long __kernel_vsyscall;
  30
  31 __init void scan_elf_aux( char **envp)
  32 {
  33         long page_size = 0;
  34         elf_auxv_t * auxv;
  35
  36         while ( *envp++ != NULL) ;
  37
  38         for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
  39                 switch ( auxv->a_type ) {
  40                         case AT_SYSINFO:
  41                                 __kernel_vsyscall = auxv->a_un.a_val;
  42                                 break;
  43                         case AT_SYSINFO_EHDR:
  44                                 vsyscall_ehdr = auxv->a_un.a_val;
  45                                 /* See if the page is under TASK_SIZE */
  46                                 if (vsyscall_ehdr < (unsigned long) envp)
  47                                         vsyscall_ehdr = 0;
  48                                 break;
  49                         case AT_HWCAP:
  50                                 elf_aux_hwcap = auxv->a_un.a_val;
  51                                 break;
  52                         case AT_PLATFORM:
  53                                 /* elf.h removed the pointer elements from
  54                                  * a_un, so we have to use a_val, which is
  55                                  * all that's left.
  56                                  */
  57                                 elf_aux_platform =
  58                                         (char *) (long) auxv->a_un.a_val;
  59                                 break;
  60                         case AT_PAGESZ:
  61                                 page_size = auxv->a_un.a_val;
  62                                 break;
  63                 }
  64         }
  65         if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
  66              ! elf_aux_hwcap || ! elf_aux_platform ||
  67              ! page_size || (vsyscall_ehdr % page_size) ) {
  68                 __kernel_vsyscall = 0;
  69                 vsyscall_ehdr = 0;
  70                 elf_aux_hwcap = 0;
  71                 elf_aux_platform = "i586";
  72         }
  73         else {
  74                 vsyscall_end = vsyscall_ehdr + page_size;
  75         }
  76 }