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
  15 #if ELF_CLASS == ELFCLASS32
  16 typedef Elf32_auxv_t elf_auxv_t;
  17 #else
  18 typedef Elf64_auxv_t elf_auxv_t;
  19 #endif
  20
  21 char * elf_aux_platform;
  22 long elf_aux_hwcap;
  23
  24 unsigned long vsyscall_ehdr;
  25 unsigned long vsyscall_end;
  26
  27 unsigned long __kernel_vsyscall;
  28
  29 __init void scan_elf_aux( char **envp)
  30 {
  31         long page_size = 0;
  32         elf_auxv_t * auxv;
  33
  34         while ( *envp++ != NULL) ;
  35
  36         for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
  37                 switch ( auxv->a_type ) {
  38                         case AT_SYSINFO:
  39                                 __kernel_vsyscall = auxv->a_un.a_val;
  40                                 break;
  41                         case AT_SYSINFO_EHDR:
  42                                 vsyscall_ehdr = auxv->a_un.a_val;
  43                                 break;
  44                         case AT_HWCAP:
  45                                 elf_aux_hwcap = auxv->a_un.a_val;
  46                                 break;
  47                         case AT_PLATFORM:
  48                                 /* elf.h removed the pointer elements from
  49                                  * a_un, so we have to use a_val, which is
  50                                  * all that's left.
  51                                  */
  52                                 elf_aux_platform = (char *) auxv->a_un.a_val;
  53                                 break;
  54                         case AT_PAGESZ:
  55                                 page_size = auxv->a_un.a_val;
  56                                 break;
  57                 }
  58         }
  59         if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
  60              ! elf_aux_hwcap || ! elf_aux_platform ||
  61              ! page_size || (vsyscall_ehdr % page_size) ) {
  62                 __kernel_vsyscall = 0;
  63                 vsyscall_ehdr = 0;
  64                 elf_aux_hwcap = 0;
  65                 elf_aux_platform = "i586";
  66         }
  67         else {
  68                 vsyscall_end = vsyscall_ehdr + page_size;
  69         }
  70 }