linux/arch/x86/kernel/tls.c
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   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/ldt.h>
  10#include <asm/processor.h>
  11#include <asm/proto.h>
  12#include <asm/syscalls.h>
  13
  14#include "tls.h"
  15
  16/*
  17 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
  18 */
  19static 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
  30static 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 */
  60int 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
  92asmlinkage 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        asmlinkage_protect(1, ret, u_info);
  96        return ret;
  97}
  98
  99
 100/*
 101 * Get the current Thread-Local Storage area:
 102 */
 103
 104static 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
 123int 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
 142asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
 143{
 144        int ret = do_get_thread_area(current, -1, u_info);
 145        asmlinkage_protect(1, ret, u_info);
 146        return ret;
 147}
 148
 149int 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
 159int 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
 193int 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}
 218