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 ([email protected])
   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 typedef Elf32_auxv_t elf_auxv_t;
  17
  18 /* These are initialized very early in boot and never changed */
  19 char * elf_aux_platform;
  20 extern long elf_aux_hwcap;
  21 unsigned long vsyscall_ehdr;
  22 unsigned long vsyscall_end;
  23 unsigned long __kernel_vsyscall;
  24
  25 __init void scan_elf_aux( char **envp)
  26 {
  27         long page_size = 0;
  28         elf_auxv_t * auxv;
  29
  30         while ( *envp++ != NULL) ;
  31
  32         for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
  33                 switch ( auxv->a_type ) {
  34                         case AT_SYSINFO:
  35                                 __kernel_vsyscall = auxv->a_un.a_val;
  36                                 /* See if the page is under TASK_SIZE */
  37                                 if (__kernel_vsyscall < (unsigned long) envp)
  38                                         __kernel_vsyscall = 0;
  39                                 break;
  40                         case AT_SYSINFO_EHDR:
  41                                 vsyscall_ehdr = auxv->a_un.a_val;
  42                                 /* See if the page is under TASK_SIZE */
  43                                 if (vsyscall_ehdr < (unsigned long) envp)
  44                                         vsyscall_ehdr = 0;
  45                                 break;
  46                         case AT_HWCAP:
  47                                 elf_aux_hwcap = auxv->a_un.a_val;
  48                                 break;
  49                         case AT_PLATFORM:
  50                                 /* elf.h removed the pointer elements from
  51                                  * a_un, so we have to use a_val, which is
  52                                  * all that's left.
  53                                  */
  54                                 elf_aux_platform =
  55                                         (char *) (long) auxv->a_un.a_val;
  56                                 break;
  57                         case AT_PAGESZ:
  58                                 page_size = auxv->a_un.a_val;
  59                                 break;
  60                 }
  61         }
  62         if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
  63              ! elf_aux_hwcap || ! elf_aux_platform ||
  64              ! page_size || (vsyscall_ehdr % page_size) ) {
  65                 __kernel_vsyscall = 0;
  66                 vsyscall_ehdr = 0;
  67                 elf_aux_hwcap = 0;
  68                 elf_aux_platform = "i586";
  69         }
  70         else {
  71                 vsyscall_end = vsyscall_ehdr + page_size;
  72         }
  73 }