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/a.out.h>
  19 #include <asm/cpufeature.h>
  20 #include <asm/msr.h>
  21 #include <asm/pgtable.h>
  22 #include <asm/unistd.h>
  23
  24 extern asmlinkage void sysenter_entry(void);
  25
  26 void enable_sep_cpu(void)
  27 {
  28         int cpu = get_cpu();
  29         struct tss_struct *tss = &per_cpu(init_tss, cpu);
  30
  31         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  32                 put_cpu();
  33                 return;
  34         }
  35
  36         tss->ss1 = __KERNEL_CS;
  37         tss->esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
  38         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
  39         wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp1, 0);
  40         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
  41         put_cpu();
  42 }
  43
  44 /*
  45  * These symbols are defined by vsyscall.o to mark the bounds
  46  * of the ELF DSO images included therein.
  47  */
  48 extern const char vsyscall_int80_start, vsyscall_int80_end;
  49 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
  50
  51 static struct page *sysenter_pages[2];
  52
  53 int __init sysenter_setup(void)
  54 {
  55         void *page = (void *)get_zeroed_page(GFP_ATOMIC);
  56
  57         sysenter_pages[0] = virt_to_page(page);
  58
  59         if (!boot_cpu_has(X86_FEATURE_SEP)) {
  60                 memcpy(page,
  61                        &vsyscall_int80_start,
  62                        &vsyscall_int80_end - &vsyscall_int80_start);
  63                 return 0;
  64         }
  65
  66         memcpy(page,
  67                &vsyscall_sysenter_start,
  68                &vsyscall_sysenter_end - &vsyscall_sysenter_start);
  69
  70         return 0;
  71 }
  72
  73 extern void SYSENTER_RETURN_OFFSET;
  74
  75 unsigned int vdso_enabled = 1;
  76
  77 /*
  78  * This is called from binfmt_elf, we create the special vma for the
  79  * vDSO and insert it into the mm struct tree.
  80  */
  81 int arch_setup_additional_pages(struct linux_binprm *bprm,
  82         int executable_stack, unsigned long start_code,
  83         unsigned long interp_map_address)
  84 {
  85         struct thread_info *ti = current_thread_info();
  86         unsigned long addr = 0, len;
  87         unsigned flags = MAP_PRIVATE;
  88         int err;
  89
  90         current->mm->context.vdso = NULL;
  91         if (unlikely(!vdso_enabled) || unlikely(!sysenter_pages[0]))
  92                 return 0;
  93
  94         /*
  95          * Map the vDSO (it will be randomized):
  96          */
  97         down_write(&current->mm->mmap_sem);
  98         len = PAGE_SIZE > ELF_EXEC_PAGESIZE ? PAGE_SIZE : ELF_EXEC_PAGESIZE;
  99         if (0==exec_shield) { /* off; %cs limit off */
 100                 addr = STACK_TOP;  /* minimal interference with anybody */
 101                 flags = MAP_PRIVATE | MAP_FIXED;
 102         }
 103         else if ((3<<2) & exec_shield) { /* vdso just below .text */
 104                 addr = (((2<<2) & exec_shield) && interp_map_address) ?
 105                         interp_map_address : start_code;
 106                 /* 1MB for vm86; 64K for vm86 himem */
 107                 if ((0x110000 + len) <= addr) {
 108                         addr = (PAGE_MASK & addr) - len;
 109                 }
 110                 else { /* start_code is too low */
 111                         addr = 0;
 112                 }
 113         }
 114         addr = get_unmapped_area_prot(NULL, addr, len, 0,
 115                                       flags, PROT_READ | PROT_EXEC);
 116         if (unlikely(addr & ~PAGE_MASK)) {
 117                 up_write(&current->mm->mmap_sem);
 118                 return addr;
 119         }
 120         err = install_special_mapping(current->mm, addr, len,
 121                                       VM_DONTEXPAND | VM_READ | VM_EXEC |
 122                                       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 123                                       PAGE_READONLY_EXEC,
 124                                       sysenter_pages);
 125         if (likely(err == 0)) {
 126                 current->mm->context.vdso = (void *)addr;
 127                 ti->sysenter_return = &SYSENTER_RETURN_OFFSET + addr;
 128         }
 129         up_write(&current->mm->mmap_sem);
 130         return err;
 131 }
 132
 133 int in_gate_area_no_task(unsigned long addr)
 134 {
 135         return 0;
 136 }
 137
 138 int in_gate_area(struct task_struct *task, unsigned long addr)
 139 {
 140         return 0;
 141 }
 142
 143 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 144 {
 145         return NULL;
 146 }