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Linux/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 }
214 

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