linux/arch/um/os-Linux/elf_aux.c
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   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
  16typedef Elf32_auxv_t elf_auxv_t;
  17
  18/* These are initialized very early in boot and never changed */
  19char * elf_aux_platform;
  20extern long elf_aux_hwcap;
  21unsigned long vsyscall_ehdr;
  22unsigned long vsyscall_end;
  23unsigned 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}
  74
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