arch/x86/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/thread_info.h>
  12 #include <linux/sched.h>
  13 #include <linux/gfp.h>
  14 #include <linux/string.h>
  15 #include <linux/elf.h>
  16 #include <linux/mm.h>
  17 #include <linux/err.h>
  18 #include <linux/module.h>
  19
  20 #include <asm/cpufeature.h>
  21 #include <asm/msr.h>
  22 #include <asm/pgtable.h>
  23 #include <asm/unistd.h>
  24 #include <asm/elf.h>
  25 #include <asm/tlbflush.h>
  26 #include <asm/vdso.h>
  27 #include <asm/proto.h>
  28
  29 #ifdef CONFIG_COMPAT_VDSO
  30 #define VDSO_DEFAULT    0
  31 #else
  32 #define VDSO_DEFAULT    1
  33 #endif
  34
  35 #ifdef CONFIG_X86_64
  36 #define vdso_enabled                    sysctl_vsyscall32
  37 #define arch_setup_additional_pages     syscall32_setup_pages
  38 #endif
  39
  40 /*
  41  * Should the kernel map a VDSO page into processes and pass its
  42  * address down to glibc upon exec()?
  43  */
  44 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
  45
  46 static int __init vdso_setup(char *s)
  47 {
  48         vdso_enabled = simple_strtoul(s, NULL, 0);
  49
  50         if (vdso_enabled > 1)
  51                 pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
  52
  53         return 1;
  54 }
  55
  56 /*
  57  * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
  58  * behavior on both 64-bit and 32-bit kernels.
  59  * On 32-bit kernels, vdso=[012] means the same thing.
  60  */
  61 __setup("vdso32=", vdso_setup);
  62
  63 #ifdef CONFIG_X86_32
  64 __setup_param("vdso=", vdso32_setup, vdso_setup, 0);
  65
  66 EXPORT_SYMBOL_GPL(vdso_enabled);
  67 #endif
  68
  69 static struct page *vdso32_pages[1];
  70
  71 #ifdef CONFIG_X86_64
  72
  73 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SYSENTER32))
  74 #define vdso32_syscall()        (boot_cpu_has(X86_FEATURE_SYSCALL32))
  75
  76 /* May not be __init: called during resume */
  77 void syscall32_cpu_init(void)
  78 {
  79         /* Load these always in case some future AMD CPU supports
  80            SYSENTER from compat mode too. */
  81         wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
  82         wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
  83         wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
  84
  85         wrmsrl(MSR_CSTAR, ia32_cstar_target);
  86 }
  87
  88 #else  /* CONFIG_X86_32 */
  89
  90 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
  91 #define vdso32_syscall()        (0)
  92
  93 void enable_sep_cpu(void)
  94 {
  95         int cpu = get_cpu();
  96         struct tss_struct *tss = &per_cpu(init_tss, cpu);
  97
  98         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  99                 put_cpu();
 100                 return;
 101         }
 102
 103         tss->x86_tss.ss1 = __KERNEL_CS;
 104         tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
 105         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
 106         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
 107         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
 108         put_cpu();
 109 }
 110
 111 #endif  /* CONFIG_X86_64 */
 112
 113 int __init sysenter_setup(void)
 114 {
 115         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 116         const void *vsyscall;
 117         size_t vsyscall_len;
 118
 119         vdso32_pages[0] = virt_to_page(syscall_page);
 120
 121         if (vdso32_syscall()) {
 122                 vsyscall = &vdso32_syscall_start;
 123                 vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
 124         } else if (vdso32_sysenter()){
 125                 vsyscall = &vdso32_sysenter_start;
 126                 vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
 127         } else {
 128                 vsyscall = &vdso32_int80_start;
 129                 vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
 130         }
 131
 132         memcpy(syscall_page, vsyscall, vsyscall_len);
 133
 134         return 0;
 135 }
 136
 137 /* Setup a VMA at program startup for the vsyscall page */
 138 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 139 {
 140         struct mm_struct *mm = current->mm;
 141         unsigned long addr;
 142         int ret = 0;
 143
 144 #ifdef CONFIG_X86_X32_ABI
 145         if (test_thread_flag(TIF_X32))
 146                 return x32_setup_additional_pages(bprm, uses_interp);
 147 #endif
 148
 149         if (vdso_enabled != 1)  /* Other values all mean "disabled" */
 150                 return 0;
 151
 152         down_write(&mm->mmap_sem);
 153
 154         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 155         if (IS_ERR_VALUE(addr)) {
 156                 ret = addr;
 157                 goto up_fail;
 158         }
 159
 160         current->mm->context.vdso = (void *)addr;
 161
 162         /*
 163          * MAYWRITE to allow gdb to COW and set breakpoints
 164          */
 165         ret = install_special_mapping(mm, addr, PAGE_SIZE,
 166                                       VM_READ|VM_EXEC|
 167                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 168                                       vdso32_pages);
 169
 170         if (ret)
 171                 goto up_fail;
 172
 173         current_thread_info()->sysenter_return =
 174                 VDSO32_SYMBOL(addr, SYSENTER_RETURN);
 175
 176   up_fail:
 177         if (ret)
 178                 current->mm->context.vdso = NULL;
 179
 180         up_write(&mm->mmap_sem);
 181
 182         return ret;
 183 }
 184
 185 #ifdef CONFIG_X86_64
 186
 187 subsys_initcall(sysenter_setup);
 188
 189 #ifdef CONFIG_SYSCTL
 190 /* Register vsyscall32 into the ABI table */
 191 #include <linux/sysctl.h>
 192
 193 static struct ctl_table abi_table2[] = {
 194         {
 195                 .procname       = "vsyscall32",
 196                 .data           = &sysctl_vsyscall32,
 197                 .maxlen         = sizeof(int),
 198                 .mode           = 0644,
 199                 .proc_handler   = proc_dointvec
 200         },
 201         {}
 202 };
 203
 204 static struct ctl_table abi_root_table2[] = {
 205         {
 206                 .procname = "abi",
 207                 .mode = 0555,
 208                 .child = abi_table2
 209         },
 210         {}
 211 };
 212
 213 static __init int ia32_binfmt_init(void)
 214 {
 215         register_sysctl_table(abi_root_table2);
 216         return 0;
 217 }
 218 __initcall(ia32_binfmt_init);
 219 #endif
 220
 221 #else  /* CONFIG_X86_32 */
 222
 223 const char *arch_vma_name(struct vm_area_struct *vma)
 224 {
 225         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 226                 return "[vdso]";
 227         return NULL;
 228 }
 229
 230 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
 231 {
 232         return NULL;
 233 }
 234
 235 int in_gate_area(struct mm_struct *mm, unsigned long addr)
 236 {
 237         return 0;
 238 }
 239
 240 int in_gate_area_no_mm(unsigned long addr)
 241 {
 242         return 0;
 243 }
 244
 245 #endif  /* CONFIG_X86_64 */