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
  17 #include <asm/cpufeature.h>
  18 #include <asm/msr.h>
  19 #include <asm/pgtable.h>
  20 #include <asm/unistd.h>
  21
  22 extern asmlinkage void sysenter_entry(void);
  23
  24 void enable_sep_cpu(void)
  25 {
  26         int cpu = get_cpu();
  27         struct tss_struct *tss = &per_cpu(init_tss, cpu);
  28
  29         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  30                 put_cpu();
  31                 return;
  32         }
  33
  34         tss->ss1 = __KERNEL_CS;
  35         tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  36         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  37         wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
  38         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
  39         put_cpu();
  40 }
  41
  42 /*
  43  * These symbols are defined by vsyscall.o to mark the bounds
  44  * of the ELF DSO images included therein.
  45  */
  46 extern const char vsyscall_int80_start, vsyscall_int80_end;
  47 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
  48
  49 int __init sysenter_setup(void)
  50 {
  51         void *page = (void *)get_zeroed_page(GFP_ATOMIC);
  52
  53         __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_READONLY_EXEC);
  54
  55         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  56                 memcpy(page,
  57                        &vsyscall_int80_start,
  58                        &vsyscall_int80_end - &vsyscall_int80_start);
  59                 return 0;
  60         }
  61
  62         memcpy(page,
  63                &vsyscall_sysenter_start,
  64                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  65
  66         return 0;
  67 }