arch/i386/kernel/sysenter.c

   1 /*
   2  * linux/arch/i386/kernel/sysenter.c
   3  *
   4  * (C) Copyright 2002 Linus Torvalds
   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/mman.h>
  17
  18 #include <asm/cpufeature.h>
  19 #include <asm/msr.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/unistd.h>
  22
  23 extern asmlinkage void sysenter_entry(void);
  24
  25 void enable_sep_cpu(void *info)
  26 {
  27         int cpu = get_cpu();
  28         struct tss_struct *tss = &per_cpu(init_tss, cpu);
  29
  30         tss->ss1 = __KERNEL_CS;
  31         tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  32         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  33         wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
  34         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
  35         put_cpu();
  36 }
  37
  38 /*
  39  * These symbols are defined by vsyscall.o to mark the bounds
  40  * of the ELF DSO images included therein.
  41  */
  42 extern const char vsyscall_int80_start, vsyscall_int80_end;
  43 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
  44
  45 struct page *sysenter_page;
  46
  47 static int __init sysenter_setup(void)
  48 {
  49         void *page = (void *)get_zeroed_page(GFP_ATOMIC);
  50
  51         sysenter_page = virt_to_page(page);
  52
  53         if (1 || (!boot_cpu_has(X86_FEATURE_SEP))) {
  54                 memcpy(page,
  55                        &vsyscall_int80_start,
  56                        &vsyscall_int80_end - &vsyscall_int80_start);
  57                 return 0;
  58         }
  59
  60         memcpy(page,
  61                &vsyscall_sysenter_start,
  62                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  63
  64         on_each_cpu(enable_sep_cpu, NULL, 1, 1);
  65         return 0;
  66 }
  67
  68 __initcall(sysenter_setup);
  69
  70 extern void SYSENTER_RETURN_OFFSET;
  71
  72 unsigned int vdso_enabled = 1;
  73
  74 /*
  75  * This is called from binfmt_elf, we create the special vma for the
  76  * vDSO and insert it into the mm struct tree.
  77  */
  78 int arch_setup_additional_pages(struct linux_binprm *bprm,
  79                                 int executable_stack)
  80 {
  81         struct thread_info *ti = current_thread_info();
  82         unsigned long addr, len;
  83         int err;
  84
  85         current->mm->context.vdso = NULL;
  86         if (unlikely(!vdso_enabled) || unlikely(!sysenter_page))
  87                 return 0;
  88
  89         /*
  90          * Map the vDSO (it will be randomized):
  91          */
  92         down_write(&current->mm->mmap_sem);
  93         len = PAGE_SIZE > ELF_EXEC_PAGESIZE ? PAGE_SIZE : ELF_EXEC_PAGESIZE;
  94         addr = get_unmapped_area_prot(NULL, 0, len, 0,
  95                                       MAP_PRIVATE, PROT_READ | PROT_EXEC);
  96         if (unlikely(addr & ~PAGE_MASK)) {
  97                 up_write(&current->mm->mmap_sem);
  98                 return addr;
  99         }
 100         get_page(sysenter_page);
 101         err = install_special_mapping(current->mm, addr, len,
 102                                       VM_DONTEXPAND | VM_READ | VM_EXEC |
 103                                       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 104                                       PAGE_READONLY_EXEC,
 105                                       &sysenter_page, 1);
 106         if (likely(err == 0)) {
 107                 current->mm->context.vdso = (void *)addr;
 108                 ti->sysenter_return = &SYSENTER_RETURN_OFFSET + addr;
 109         }
 110         up_write(&current->mm->mmap_sem);
 111         return err;
 112 }
 113
 114 int in_gate_area_no_task(unsigned long addr)
 115 {
 116         return 0;
 117 }
 118
 119 int in_gate_area(struct task_struct *task, unsigned long addr)
 120 {
 121         return 0;
 122 }
 123
 124 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 125 {
 126         return NULL;
 127 }
 128
 129 static int __init vdso_setup(char *str)
 130 {
 131         vdso_enabled = simple_strtoul(str, NULL, 0);
 132         return 1;
 133 }
 134 __setup("vdso=", vdso_setup);
 135