arch/x86/kernel/tls.c

   1 #include <linux/kernel.h>
   2 #include <linux/errno.h>
   3 #include <linux/sched.h>
   4 #include <linux/user.h>
   5 #include <linux/regset.h>
   6
   7 #include <asm/uaccess.h>
   8 #include <asm/desc.h>
   9 #include <asm/system.h>
  10 #include <asm/ldt.h>
  11 #include <asm/processor.h>
  12 #include <asm/proto.h>
  13
  14 #include "tls.h"
  15
  16 /*
  17  * sys_alloc_thread_area: get a yet unused TLS descriptor index.
  18  */
  19 static int get_free_idx(void)
  20 {
  21         struct thread_struct *t = &current->thread;
  22         int idx;
  23
  24         for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
  25                 if (desc_empty(&t->tls_array[idx]))
  26                         return idx + GDT_ENTRY_TLS_MIN;
  27         return -ESRCH;
  28 }
  29
  30 static void set_tls_desc(struct task_struct *p, int idx,
  31                          const struct user_desc *info, int n)
  32 {
  33         struct thread_struct *t = &p->thread;
  34         struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
  35         int cpu;
  36
  37         /*
  38          * We must not get preempted while modifying the TLS.
  39          */
  40         cpu = get_cpu();
  41
  42         while (n-- > 0) {
  43                 if (LDT_empty(info))
  44                         desc->a = desc->b = 0;
  45                 else
  46                         fill_ldt(desc, info);
  47                 ++info;
  48                 ++desc;
  49         }
  50
  51         if (t == &current->thread)
  52                 load_TLS(t, cpu);
  53
  54         put_cpu();
  55 }
  56
  57 /*
  58  * Set a given TLS descriptor:
  59  */
  60 int do_set_thread_area(struct task_struct *p, int idx,
  61                        struct user_desc __user *u_info,
  62                        int can_allocate)
  63 {
  64         struct user_desc info;
  65
  66         if (copy_from_user(&info, u_info, sizeof(info)))
  67                 return -EFAULT;
  68
  69         if (idx == -1)
  70                 idx = info.entry_number;
  71
  72         /*
  73          * index -1 means the kernel should try to find and
  74          * allocate an empty descriptor:
  75          */
  76         if (idx == -1 && can_allocate) {
  77                 idx = get_free_idx();
  78                 if (idx < 0)
  79                         return idx;
  80                 if (put_user(idx, &u_info->entry_number))
  81                         return -EFAULT;
  82         }
  83
  84         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
  85                 return -EINVAL;
  86
  87         set_tls_desc(p, idx, &info, 1);
  88
  89         return 0;
  90 }
  91
  92 asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
  93 {
  94         int ret = do_set_thread_area(current, -1, u_info, 1);
  95         prevent_tail_call(ret);
  96         return ret;
  97 }
  98
  99
 100 /*
 101  * Get the current Thread-Local Storage area:
 102  */
 103
 104 static void fill_user_desc(struct user_desc *info, int idx,
 105                            const struct desc_struct *desc)
 106
 107 {
 108         memset(info, 0, sizeof(*info));
 109         info->entry_number = idx;
 110         info->base_addr = get_desc_base(desc);
 111         info->limit = get_desc_limit(desc);
 112         info->seg_32bit = desc->d;
 113         info->contents = desc->type >> 2;
 114         info->read_exec_only = !(desc->type & 2);
 115         info->limit_in_pages = desc->g;
 116         info->seg_not_present = !desc->p;
 117         info->useable = desc->avl;
 118 #ifdef CONFIG_X86_64
 119         info->lm = desc->l;
 120 #endif
 121 }
 122
 123 int do_get_thread_area(struct task_struct *p, int idx,
 124                        struct user_desc __user *u_info)
 125 {
 126         struct user_desc info;
 127
 128         if (idx == -1 && get_user(idx, &u_info->entry_number))
 129                 return -EFAULT;
 130
 131         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 132                 return -EINVAL;
 133
 134         fill_user_desc(&info, idx,
 135                        &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);
 136
 137         if (copy_to_user(u_info, &info, sizeof(info)))
 138                 return -EFAULT;
 139         return 0;
 140 }
 141
 142 asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
 143 {
 144         int ret = do_get_thread_area(current, -1, u_info);
 145         prevent_tail_call(ret);
 146         return ret;
 147 }
 148
 149 int regset_tls_active(struct task_struct *target,
 150                       const struct user_regset *regset)
 151 {
 152         struct thread_struct *t = &target->thread;
 153         int n = GDT_ENTRY_TLS_ENTRIES;
 154         while (n > 0 && desc_empty(&t->tls_array[n - 1]))
 155                 --n;
 156         return n;
 157 }
 158
 159 int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
 160                    unsigned int pos, unsigned int count,
 161                    void *kbuf, void __user *ubuf)
 162 {
 163         const struct desc_struct *tls;
 164
 165         if (pos > GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 166             (pos % sizeof(struct user_desc)) != 0 ||
 167             (count % sizeof(struct user_desc)) != 0)
 168                 return -EINVAL;
 169
 170         pos /= sizeof(struct user_desc);
 171         count /= sizeof(struct user_desc);
 172
 173         tls = &target->thread.tls_array[pos];
 174
 175         if (kbuf) {
 176                 struct user_desc *info = kbuf;
 177                 while (count-- > 0)
 178                         fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
 179                                        tls++);
 180         } else {
 181                 struct user_desc __user *u_info = ubuf;
 182                 while (count-- > 0) {
 183                         struct user_desc info;
 184                         fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
 185                         if (__copy_to_user(u_info++, &info, sizeof(info)))
 186                                 return -EFAULT;
 187                 }
 188         }
 189
 190         return 0;
 191 }
 192
 193 int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
 194                    unsigned int pos, unsigned int count,
 195                    const void *kbuf, const void __user *ubuf)
 196 {
 197         struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
 198         const struct user_desc *info;
 199
 200         if (pos > GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 201             (pos % sizeof(struct user_desc)) != 0 ||
 202             (count % sizeof(struct user_desc)) != 0)
 203                 return -EINVAL;
 204
 205         if (kbuf)
 206                 info = kbuf;
 207         else if (__copy_from_user(infobuf, ubuf, count))
 208                 return -EFAULT;
 209         else
 210                 info = infobuf;
 211
 212         set_tls_desc(target,
 213                      GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
 214                      info, count / sizeof(struct user_desc));
 215
 216         return 0;
 217 }