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   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 *info)
  25 {
  26         int cpu = get_cpu();
  27         struct tss_struct *tss = &per_cpu(init_tss, cpu);
  28
  29         tss->ss1 = __KERNEL_CS;
  30         tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  31         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  32         wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
  33         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
  34         put_cpu();
  35 }
  36
  37 /*
  38  * These symbols are defined by vsyscall.o to mark the bounds
  39  * of the ELF DSO images included therein.
  40  */
  41 extern const char vsyscall_int80_start, vsyscall_int80_end;
  42 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
  43
  44 static int __init sysenter_setup(void)
  45 {
  46         void *page = (void *)get_zeroed_page(GFP_ATOMIC);
  47
  48         __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_READONLY_EXEC);
  49
  50         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  51                 memcpy(page,
  52                        &vsyscall_int80_start,
  53                        &vsyscall_int80_end - &vsyscall_int80_start);
  54                 return 0;
  55         }
  56
  57         memcpy(page,
  58                &vsyscall_sysenter_start,
  59                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  60
  61         on_each_cpu(enable_sep_cpu, NULL, 1, 1);
  62         return 0;
  63 }
  64
  65 __initcall(sysenter_setup);