arch/x86/entry/vdso/vdso32-setup.c

   1 /*
   2  * (C) Copyright 2002 Linus Torvalds
   3  * Portions based on the vdso-randomization code from exec-shield:
   4  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
   5  *
   6  * This file contains the needed initializations to support sysenter.
   7  */
   8
   9 #include <linux/init.h>
  10 #include <linux/smp.h>
  11 #include <linux/kernel.h>
  12 #include <linux/mm_types.h>
  13
  14 #include <asm/cpufeature.h>
  15 #include <asm/processor.h>
  16 #include <asm/vdso.h>
  17
  18 #ifdef CONFIG_COMPAT_VDSO
  19 #define VDSO_DEFAULT    0
  20 #else
  21 #define VDSO_DEFAULT    1
  22 #endif
  23
  24 /*
  25  * Should the kernel map a VDSO page into processes and pass its
  26  * address down to glibc upon exec()?
  27  */
  28 unsigned int __read_mostly vdso32_enabled = VDSO_DEFAULT;
  29
  30 static int __init vdso32_setup(char *s)
  31 {
  32         vdso32_enabled = simple_strtoul(s, NULL, 0);
  33
  34         if (vdso32_enabled > 1)
  35                 pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
  36
  37         return 1;
  38 }
  39
  40 /*
  41  * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
  42  * behavior on both 64-bit and 32-bit kernels.
  43  * On 32-bit kernels, vdso=[012] means the same thing.
  44  */
  45 __setup("vdso32=", vdso32_setup);
  46
  47 #ifdef CONFIG_X86_32
  48 __setup_param("vdso=", vdso_setup, vdso32_setup, 0);
  49 #endif
  50
  51 #ifdef CONFIG_X86_64
  52
  53 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SYSENTER32))
  54 #define vdso32_syscall()        (boot_cpu_has(X86_FEATURE_SYSCALL32))
  55
  56 #else  /* CONFIG_X86_32 */
  57
  58 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
  59 #define vdso32_syscall()        (0)
  60
  61 #endif  /* CONFIG_X86_64 */
  62
  63 #if defined(CONFIG_X86_32) || defined(CONFIG_COMPAT)
  64 const struct vdso_image *selected_vdso32;
  65 #endif
  66
  67 int __init sysenter_setup(void)
  68 {
  69 #ifdef CONFIG_COMPAT
  70         if (vdso32_syscall())
  71                 selected_vdso32 = &vdso_image_32_syscall;
  72         else
  73 #endif
  74         if (vdso32_sysenter())
  75                 selected_vdso32 = &vdso_image_32_sysenter;
  76         else
  77                 selected_vdso32 = &vdso_image_32_int80;
  78
  79         init_vdso_image(selected_vdso32);
  80
  81         return 0;
  82 }
  83
  84 #ifdef CONFIG_X86_64
  85
  86 subsys_initcall(sysenter_setup);
  87
  88 #ifdef CONFIG_SYSCTL
  89 /* Register vsyscall32 into the ABI table */
  90 #include <linux/sysctl.h>
  91
  92 static struct ctl_table abi_table2[] = {
  93         {
  94                 .procname       = "vsyscall32",
  95                 .data           = &vdso32_enabled,
  96                 .maxlen         = sizeof(int),
  97                 .mode           = 0644,
  98                 .proc_handler   = proc_dointvec
  99         },
 100         {}
 101 };
 102
 103 static struct ctl_table abi_root_table2[] = {
 104         {
 105                 .procname = "abi",
 106                 .mode = 0555,
 107                 .child = abi_table2
 108         },
 109         {}
 110 };
 111
 112 static __init int ia32_binfmt_init(void)
 113 {
 114         register_sysctl_table(abi_root_table2);
 115         return 0;
 116 }
 117 __initcall(ia32_binfmt_init);
 118 #endif /* CONFIG_SYSCTL */
 119
 120 #endif  /* CONFIG_X86_64 */