arch/um/os-Linux/elf_aux.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  arch/um/kernel/elf_aux.c
   4  *
   5  *  Scan the ELF auxiliary vector provided by the host to extract
   6  *  information about vsyscall-page, etc.
   7  *
   8  *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH
   9  *  Author: Bodo Stroesser (bodo.stroesser@fujitsu-siemens.com)
  10  */
  11 #include <elf.h>
  12 #include <stddef.h>
  13 #include <init.h>
  14 #include <elf_user.h>
  15 #include <mem_user.h>
  16 #include "internal.h"
  17
  18 typedef Elf32_auxv_t elf_auxv_t;
  19
  20 /* These are initialized very early in boot and never changed */
  21 char * elf_aux_platform;
  22 extern long elf_aux_hwcap;
  23 unsigned long vsyscall_ehdr;
  24 unsigned long vsyscall_end;
  25 unsigned long __kernel_vsyscall;
  26
  27 __init void scan_elf_aux( char **envp)
  28 {
  29         long page_size = 0;
  30         elf_auxv_t * auxv;
  31
  32         while ( *envp++ != NULL) ;
  33
  34         for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
  35                 switch ( auxv->a_type ) {
  36                         case AT_SYSINFO:
  37                                 __kernel_vsyscall = auxv->a_un.a_val;
  38                                 /* See if the page is under TASK_SIZE */
  39                                 if (__kernel_vsyscall < (unsigned long) envp)
  40                                         __kernel_vsyscall = 0;
  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 =
  57                                         (char *) (long) auxv->a_un.a_val;
  58                                 break;
  59                         case AT_PAGESZ:
  60                                 page_size = auxv->a_un.a_val;
  61                                 break;
  62                 }
  63         }
  64         if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
  65              ! elf_aux_hwcap || ! elf_aux_platform ||
  66              ! page_size || (vsyscall_ehdr % page_size) ) {
  67                 __kernel_vsyscall = 0;
  68                 vsyscall_ehdr = 0;
  69                 elf_aux_hwcap = 0;
  70                 elf_aux_platform = "i586";
  71         }
  72         else {
  73                 vsyscall_end = vsyscall_ehdr + page_size;
  74         }
  75 }