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
  16 #if ELF_CLASS == ELFCLASS32
  17 typedef Elf32_auxv_t elf_auxv_t;
  18 #else
  19 typedef Elf64_auxv_t elf_auxv_t;
  20 #endif
  21
  22 char * elf_aux_platform;
  23 long elf_aux_hwcap;
  24
  25 unsigned long vsyscall_ehdr;
  26 unsigned long vsyscall_end;
  27
  28 unsigned long __kernel_vsyscall;
  29
  30 __init void scan_elf_aux( char **envp)
  31 {
  32         long page_size = 0;
  33         elf_auxv_t * auxv;
  34
  35         while ( *envp++ != NULL) ;
  36
  37         for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
  38                 switch ( auxv->a_type ) {
  39                         case AT_SYSINFO:
  40                                 __kernel_vsyscall = auxv->a_un.a_val;
  41                                 break;
  42                         case AT_SYSINFO_EHDR:
  43                                 vsyscall_ehdr = auxv->a_un.a_val;
  44                                 /* See if the page is under TASK_SIZE */
  45                                 if (vsyscall_ehdr < (unsigned long) envp)
  46                                         vsyscall_ehdr = 0;
  47                                 break;
  48                         case AT_HWCAP:
  49                                 elf_aux_hwcap = auxv->a_un.a_val;
  50                                 break;
  51                         case AT_PLATFORM:
  52                                 /* elf.h removed the pointer elements from
  53                                  * a_un, so we have to use a_val, which is
  54                                  * all that's left.
  55                                  */
  56                                 elf_aux_platform = (char *) auxv->a_un.a_val;
  57                                 break;
  58                         case AT_PAGESZ:
  59                                 page_size = auxv->a_un.a_val;
  60                                 break;
  61                 }
  62         }
  63         if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
  64              ! elf_aux_hwcap || ! elf_aux_platform ||
  65              ! page_size || (vsyscall_ehdr % page_size) ) {
  66                 __kernel_vsyscall = 0;
  67                 vsyscall_ehdr = 0;
  68                 elf_aux_hwcap = 0;
  69                 elf_aux_platform = "i586";
  70         }
  71         else {
  72                 vsyscall_end = vsyscall_ehdr + page_size;
  73         }
  74 }