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         __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_KERNEL_RO);
  52         sysenter_page = virt_to_page(page);
  53
  54         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  55                 memcpy(page,
  56                        &vsyscall_int80_start,
  57                        &vsyscall_int80_end - &vsyscall_int80_start);
  58                 return 0;
  59         }
  60
  61         memcpy(page,
  62                &vsyscall_sysenter_start,
  63                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  64
  65         on_each_cpu(enable_sep_cpu, NULL, 1, 1);
  66
  67         return 0;
  68 }
  69
  70 __initcall(sysenter_setup);
  71
  72 extern void SYSENTER_RETURN_OFFSET;
  73
  74 unsigned int vdso_enabled = 0;
  75
  76 void map_vsyscall(void)
  77 {
  78         struct thread_info *ti = current_thread_info();
  79         struct vm_area_struct *vma;
  80         unsigned long addr;
  81
  82         if (unlikely(!vdso_enabled)) {
  83                 current->mm->context.vdso = NULL;
  84                 return;
  85         }
  86
  87         /*
  88          * Map the vDSO (it will be randomized):
  89          */
  90         down_write(&current->mm->mmap_sem);
  91         addr = do_mmap(NULL, 0, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, 0);
  92         current->mm->context.vdso = (void *)addr;
  93         ti->sysenter_return = (void *)addr + (long)&SYSENTER_RETURN_OFFSET;
  94         if (addr != -1) {
  95                 vma = find_vma(current->mm, addr);
  96                 if (vma) {
  97                         pgprot_val(vma->vm_page_prot) &= ~_PAGE_RW;
  98                         get_page(sysenter_page);
  99                         install_page(current->mm, vma, addr,
 100                                         sysenter_page, vma->vm_page_prot);
 101
 102                 }
 103         }
 104         up_write(&current->mm->mmap_sem);
 105 }
 106
 107 static int __init vdso_setup(char *str)
 108 {
 109         vdso_enabled = simple_strtoul(str, NULL, 0);
 110         return 1;
 111 }
 112 __setup("vdso=", vdso_setup);
 113