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 #include <linux/highmem.h>
  23
  24 extern asmlinkage void sysenter_entry(void);
  25
  26 void enable_sep_cpu(void *info)
  27 {
  28         int cpu = get_cpu();
  29 #ifdef CONFIG_X86_HIGH_ENTRY
  30         struct tss_struct *tss = (struct tss_struct *) __fix_to_virt(FIX_TSS_0) + cpu;
  31 #else
  32         struct tss_struct *tss = init_tss + cpu;
  33 #endif
  34
  35         tss->ss1 = __KERNEL_CS;
  36         tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  37         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  38         wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
  39         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
  40         put_cpu();
  41 }
  42
  43 /*
  44  * These symbols are defined by vsyscall.o to mark the bounds
  45  * of the ELF DSO images included therein.
  46  */
  47 extern const char vsyscall_int80_start, vsyscall_int80_end;
  48 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
  49
  50 struct page *sysenter_page;
  51
  52 static int __init sysenter_setup(void)
  53 {
  54         unsigned long page = get_zeroed_page(GFP_ATOMIC);
  55
  56         __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_KERNEL_RO);
  57         sysenter_page = virt_to_page(page);
  58
  59         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  60                 memcpy((void *) page,
  61                        &vsyscall_int80_start,
  62                        &vsyscall_int80_end - &vsyscall_int80_start);
  63                 return 0;
  64         }
  65
  66         memcpy((void *) page,
  67                &vsyscall_sysenter_start,
  68                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  69
  70         on_each_cpu(enable_sep_cpu, NULL, 1, 1);
  71
  72         return 0;
  73 }
  74
  75 __initcall(sysenter_setup);
  76
  77 extern void SYSENTER_RETURN_OFFSET;
  78
  79 unsigned int vdso_enabled = 1;
  80
  81 void map_vsyscall(void)
  82 {
  83         struct thread_info *ti = current_thread_info();
  84         struct vm_area_struct *vma;
  85         unsigned long addr;
  86
  87         if (unlikely(!vdso_enabled)) {
  88                 current->mm->context.vdso = NULL;
  89                 return;
  90         }
  91
  92         /*
  93          * Map the vDSO (it will be randomized):
  94          */
  95         down_write(&current->mm->mmap_sem);
  96         addr = do_mmap(NULL, 0, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, 0);
  97         current->mm->context.vdso = (void *)addr;
  98         ti->sysenter_return = (void *)addr + (long)&SYSENTER_RETURN_OFFSET;
  99         if (addr != -1) {
 100                 vma = find_vma(current->mm, addr);
 101                 if (vma) {
 102                         pgprot_val(vma->vm_page_prot) &= ~_PAGE_RW;
 103                         get_page(sysenter_page);
 104                         install_page(current->mm, vma, addr,
 105                                         sysenter_page, vma->vm_page_prot);
 106
 107                 }
 108         }
 109         up_write(&current->mm->mmap_sem);
 110 }
 111
 112 static int __init vdso_setup(char *str)
 113 {
 114         vdso_enabled = simple_strtoul(str, NULL, 0);
 115         return 1;
 116 }
 117 __setup("vdso=", vdso_setup);
 118