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 #include <linux/syscalls.h>
   7
   8 #include <asm/uaccess.h>
   9 #include <asm/desc.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 SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, u_info)
  93 {
  94         return do_set_thread_area(current, -1, u_info, 1);
  95 }
  96
  97
  98 /*
  99  * Get the current Thread-Local Storage area:
 100  */
 101
 102 static void fill_user_desc(struct user_desc *info, int idx,
 103                            const struct desc_struct *desc)
 104
 105 {
 106         memset(info, 0, sizeof(*info));
 107         info->entry_number = idx;
 108         info->base_addr = get_desc_base(desc);
 109         info->limit = get_desc_limit(desc);
 110         info->seg_32bit = desc->d;
 111         info->contents = desc->type >> 2;
 112         info->read_exec_only = !(desc->type & 2);
 113         info->limit_in_pages = desc->g;
 114         info->seg_not_present = !desc->p;
 115         info->useable = desc->avl;
 116 #ifdef CONFIG_X86_64
 117         info->lm = desc->l;
 118 #endif
 119 }
 120
 121 int do_get_thread_area(struct task_struct *p, int idx,
 122                        struct user_desc __user *u_info)
 123 {
 124         struct user_desc info;
 125
 126         if (idx == -1 && get_user(idx, &u_info->entry_number))
 127                 return -EFAULT;
 128
 129         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 130                 return -EINVAL;
 131
 132         fill_user_desc(&info, idx,
 133                        &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);
 134
 135         if (copy_to_user(u_info, &info, sizeof(info)))
 136                 return -EFAULT;
 137         return 0;
 138 }
 139
 140 SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, u_info)
 141 {
 142         return do_get_thread_area(current, -1, u_info);
 143 }
 144
 145 int regset_tls_active(struct task_struct *target,
 146                       const struct user_regset *regset)
 147 {
 148         struct thread_struct *t = &target->thread;
 149         int n = GDT_ENTRY_TLS_ENTRIES;
 150         while (n > 0 && desc_empty(&t->tls_array[n - 1]))
 151                 --n;
 152         return n;
 153 }
 154
 155 int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
 156                    unsigned int pos, unsigned int count,
 157                    void *kbuf, void __user *ubuf)
 158 {
 159         const struct desc_struct *tls;
 160
 161         if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 162             (pos % sizeof(struct user_desc)) != 0 ||
 163             (count % sizeof(struct user_desc)) != 0)
 164                 return -EINVAL;
 165
 166         pos /= sizeof(struct user_desc);
 167         count /= sizeof(struct user_desc);
 168
 169         tls = &target->thread.tls_array[pos];
 170
 171         if (kbuf) {
 172                 struct user_desc *info = kbuf;
 173                 while (count-- > 0)
 174                         fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
 175                                        tls++);
 176         } else {
 177                 struct user_desc __user *u_info = ubuf;
 178                 while (count-- > 0) {
 179                         struct user_desc info;
 180                         fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
 181                         if (__copy_to_user(u_info++, &info, sizeof(info)))
 182                                 return -EFAULT;
 183                 }
 184         }
 185
 186         return 0;
 187 }
 188
 189 int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
 190                    unsigned int pos, unsigned int count,
 191                    const void *kbuf, const void __user *ubuf)
 192 {
 193         struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
 194         const struct user_desc *info;
 195
 196         if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
 197             (pos % sizeof(struct user_desc)) != 0 ||
 198             (count % sizeof(struct user_desc)) != 0)
 199                 return -EINVAL;
 200
 201         if (kbuf)
 202                 info = kbuf;
 203         else if (__copy_from_user(infobuf, ubuf, count))
 204                 return -EFAULT;
 205         else
 206                 info = infobuf;
 207
 208         set_tls_desc(target,
 209                      GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
 210                      info, count / sizeof(struct user_desc));
 211
 212         return 0;
 213 }