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