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