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 #include <asm/syscalls.h>
  14
  15 #include "tls.h"
  16
  17 /*
  18  * sys_alloc_thread_area: get a yet unused TLS descriptor index.
  19  */
  20 static int get_free_idx(void)
  21 {
  22         struct thread_struct *t = &current->thread;
  23         int idx;
  24
  25         for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
  26                 if (desc_empty(&t->tls_array[idx]))
  27                         return idx + GDT_ENTRY_TLS_MIN;
  28         return -ESRCH;
  29 }
  30
  31 static bool tls_desc_okay(const struct user_desc *info)
  32 {
  33         if (LDT_empty(info))
  34                 return true;
  35
  36         /*
  37          * espfix is required for 16-bit data segments, but espfix
  38          * only works for LDT segments.
  39          */
  40         if (!info->seg_32bit)
  41                 return false;
  42
  43         return true;
  44 }
  45
  46 static void set_tls_desc(struct task_struct *p, int idx,
  47                          const struct user_desc *info, int n)
  48 {
  49         struct thread_struct *t = &p->thread;
  50         struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
  51         int cpu;
  52
  53         /*
  54          * We must not get preempted while modifying the TLS.
  55          */
  56         cpu = get_cpu();
  57
  58         while (n-- > 0) {
  59                 if (LDT_empty(info))
  60                         desc->a = desc->b = 0;
  61                 else
  62                         fill_ldt(desc, info);
  63                 ++info;
  64                 ++desc;
  65         }
  66
  67         if (t == &current->thread)
  68                 load_TLS(t, cpu);
  69
  70         put_cpu();
  71 }
  72
  73 /*
  74  * Set a given TLS descriptor:
  75  */
  76 int do_set_thread_area(struct task_struct *p, int idx,
  77                        struct user_desc __user *u_info,
  78                        int can_allocate)
  79 {
  80         struct user_desc info;
  81
  82         if (copy_from_user(&info, u_info, sizeof(info)))
  83                 return -EFAULT;
  84
  85         if (!tls_desc_okay(&info))
  86                 return -EINVAL;
  87
  88         if (idx == -1)
  89                 idx = info.entry_number;
  90
  91         /*
  92          * index -1 means the kernel should try to find and
  93          * allocate an empty descriptor:
  94          */
  95         if (idx == -1 && can_allocate) {
  96                 idx = get_free_idx();
  97                 if (idx < 0)
  98                         return idx;
  99                 if (put_user(idx, &u_info->entry_number))
 100                         return -EFAULT;
 101         }
 102
 103         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 104                 return -EINVAL;
 105
 106         set_tls_desc(p, idx, &info, 1);
 107
 108         return 0;
 109 }
 110
 111 asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
 112 {
 113         int ret = do_set_thread_area(current, -1, u_info, 1);
 114         asmlinkage_protect(1, ret, u_info);
 115         return ret;
 116 }
 117
 118
 119 /*
 120  * Get the current Thread-Local Storage area:
 121  */
 122
 123 static void fill_user_desc(struct user_desc *info, int idx,
 124                            const struct desc_struct *desc)
 125
 126 {
 127         memset(info, 0, sizeof(*info));
 128         info->entry_number = idx;
 129         info->base_addr = get_desc_base(desc);
 130         info->limit = get_desc_limit(desc);
 131         info->seg_32bit = desc->d;
 132         info->contents = desc->type >> 2;
 133         info->read_exec_only = !(desc->type & 2);
 134         info->limit_in_pages = desc->g;
 135         info->seg_not_present = !desc->p;
 136         info->useable = desc->avl;
 137 #ifdef CONFIG_X86_64
 138         info->lm = desc->l;
 139 #endif
 140 }
 141
 142 int do_get_thread_area(struct task_struct *p, int idx,
 143                        struct user_desc __user *u_info)
 144 {
 145         struct user_desc info;
 146
 147         if (idx == -1 && get_user(idx, &u_info->entry_number))
 148                 return -EFAULT;
 149
 150         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 151                 return -EINVAL;
 152
 153         fill_user_desc(&info, idx,
 154                        &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);
 155
 156         if (copy_to_user(u_info, &info, sizeof(info)))
 157                 return -EFAULT;
 158         return 0;
 159 }
 160
 161 asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
 162 {
 163         int ret = do_get_thread_area(current, -1, u_info);
 164         asmlinkage_protect(1, ret, u_info);
 165         return ret;
 166 }
 167
 168 int regset_tls_active(struct task_struct *target,
 169                       const struct user_regset *regset)
 170 {
 171         struct thread_struct *t = &target->thread;
 172         int n = GDT_ENTRY_TLS_ENTRIES;
 173         while (n > 0 && desc_empty(&t->tls_array[n - 1]))
 174                 --n;
 175         return n;
 176 }
 177
 178 int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
 179                    unsigned int pos, unsigned int count,
 180                    void *kbuf, void __user *ubuf)
 181 {
 182         const struct desc_struct *tls;
 183
 184         if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 185             (pos % sizeof(struct user_desc)) != 0 ||
 186             (count % sizeof(struct user_desc)) != 0)
 187                 return -EINVAL;
 188
 189         pos /= sizeof(struct user_desc);
 190         count /= sizeof(struct user_desc);
 191
 192         tls = &target->thread.tls_array[pos];
 193
 194         if (kbuf) {
 195                 struct user_desc *info = kbuf;
 196                 while (count-- > 0)
 197                         fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
 198                                        tls++);
 199         } else {
 200                 struct user_desc __user *u_info = ubuf;
 201                 while (count-- > 0) {
 202                         struct user_desc info;
 203                         fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
 204                         if (__copy_to_user(u_info++, &info, sizeof(info)))
 205                                 return -EFAULT;
 206                 }
 207         }
 208
 209         return 0;
 210 }
 211
 212 int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
 213                    unsigned int pos, unsigned int count,
 214                    const void *kbuf, const void __user *ubuf)
 215 {
 216         struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
 217         const struct user_desc *info;
 218         int i;
 219
 220         if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 221             (pos % sizeof(struct user_desc)) != 0 ||
 222             (count % sizeof(struct user_desc)) != 0)
 223                 return -EINVAL;
 224
 225         if (kbuf)
 226                 info = kbuf;
 227         else if (__copy_from_user(infobuf, ubuf, count))
 228                 return -EFAULT;
 229         else
 230                 info = infobuf;
 231
 232         for (i = 0; i < count / sizeof(struct user_desc); i++)
 233                 if (!tls_desc_okay(info + i))
 234                         return -EINVAL;
 235
 236         set_tls_desc(target,
 237                      GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
 238                      info, count / sizeof(struct user_desc));
 239
 240         return 0;
 241 }