[PATCH] uml: remove unneeded time definitions
[linux-2.6] / arch / um / sys-i386 / tls.c
1 /*
2  * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3  * Licensed under the GPL
4  */
5
6 #include "linux/config.h"
7 #include "linux/kernel.h"
8 #include "linux/sched.h"
9 #include "linux/slab.h"
10 #include "linux/types.h"
11 #include "asm/uaccess.h"
12 #include "asm/ptrace.h"
13 #include "asm/segment.h"
14 #include "asm/smp.h"
15 #include "asm/desc.h"
16 #include "choose-mode.h"
17 #include "kern.h"
18 #include "kern_util.h"
19 #include "mode_kern.h"
20 #include "os.h"
21 #include "mode.h"
22
23 #ifdef CONFIG_MODE_SKAS
24 #include "skas.h"
25 #endif
26
27 /* If needed we can detect when it's uninitialized. */
28 static int host_supports_tls = -1;
29 int host_gdt_entry_tls_min = -1;
30
31 #ifdef CONFIG_MODE_SKAS
32 int do_set_thread_area_skas(struct user_desc *info)
33 {
34         int ret;
35         u32 cpu;
36
37         cpu = get_cpu();
38         ret = os_set_thread_area(info, userspace_pid[cpu]);
39         put_cpu();
40         return ret;
41 }
42
43 int do_get_thread_area_skas(struct user_desc *info)
44 {
45         int ret;
46         u32 cpu;
47
48         cpu = get_cpu();
49         ret = os_get_thread_area(info, userspace_pid[cpu]);
50         put_cpu();
51         return ret;
52 }
53 #endif
54
55 /*
56  * sys_get_thread_area: get a yet unused TLS descriptor index.
57  * XXX: Consider leaving one free slot for glibc usage at first place. This must
58  * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
59  *
60  * Also, this must be tested when compiling in SKAS mode with dinamic linking
61  * and running against NPTL.
62  */
63 static int get_free_idx(struct task_struct* task)
64 {
65         struct thread_struct *t = &task->thread;
66         int idx;
67
68         if (!t->arch.tls_array)
69                 return GDT_ENTRY_TLS_MIN;
70
71         for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
72                 if (!t->arch.tls_array[idx].present)
73                         return idx + GDT_ENTRY_TLS_MIN;
74         return -ESRCH;
75 }
76
77 static inline void clear_user_desc(struct user_desc* info)
78 {
79         /* Postcondition: LDT_empty(info) returns true. */
80         memset(info, 0, sizeof(*info));
81
82         /* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
83          * indeed an empty user_desc.
84          */
85         info->read_exec_only = 1;
86         info->seg_not_present = 1;
87 }
88
89 #define O_FORCE 1
90
91 static int load_TLS(int flags, struct task_struct *to)
92 {
93         int ret = 0;
94         int idx;
95
96         for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
97                 struct uml_tls_struct* curr = &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
98
99                 /* Actually, now if it wasn't flushed it gets cleared and
100                  * flushed to the host, which will clear it.*/
101                 if (!curr->present) {
102                         if (!curr->flushed) {
103                                 clear_user_desc(&curr->tls);
104                                 curr->tls.entry_number = idx;
105                         } else {
106                                 WARN_ON(!LDT_empty(&curr->tls));
107                                 continue;
108                         }
109                 }
110
111                 if (!(flags & O_FORCE) && curr->flushed)
112                         continue;
113
114                 ret = do_set_thread_area(&curr->tls);
115                 if (ret)
116                         goto out;
117
118                 curr->flushed = 1;
119         }
120 out:
121         return ret;
122 }
123
124 /* Verify if we need to do a flush for the new process, i.e. if there are any
125  * present desc's, only if they haven't been flushed.
126  */
127 static inline int needs_TLS_update(struct task_struct *task)
128 {
129         int i;
130         int ret = 0;
131
132         for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
133                 struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
134
135                 /* Can't test curr->present, we may need to clear a descriptor
136                  * which had a value. */
137                 if (curr->flushed)
138                         continue;
139                 ret = 1;
140                 break;
141         }
142         return ret;
143 }
144
145 /* On a newly forked process, the TLS descriptors haven't yet been flushed. So
146  * we mark them as such and the first switch_to will do the job.
147  */
148 void clear_flushed_tls(struct task_struct *task)
149 {
150         int i;
151
152         for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
153                 struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
154
155                 /* Still correct to do this, if it wasn't present on the host it
156                  * will remain as flushed as it was. */
157                 if (!curr->present)
158                         continue;
159
160                 curr->flushed = 0;
161         }
162 }
163
164 /* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
165  * common host process. So this is needed in SKAS0 too.
166  *
167  * However, if each thread had a different host process (and this was discussed
168  * for SMP support) this won't be needed.
169  *
170  * And this will not need be used when (and if) we'll add support to the host
171  * SKAS patch. */
172
173 int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
174 {
175         if (!host_supports_tls)
176                 return 0;
177
178         /* We have no need whatsoever to switch TLS for kernel threads; beyond
179          * that, that would also result in us calling os_set_thread_area with
180          * userspace_pid[cpu] == 0, which gives an error. */
181         if (likely(to->mm))
182                 return load_TLS(O_FORCE, to);
183
184         return 0;
185 }
186
187 int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
188 {
189         if (!host_supports_tls)
190                 return 0;
191
192         if (needs_TLS_update(to))
193                 return load_TLS(0, to);
194
195         return 0;
196 }
197
198 static int set_tls_entry(struct task_struct* task, struct user_desc *info,
199                          int idx, int flushed)
200 {
201         struct thread_struct *t = &task->thread;
202
203         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
204                 return -EINVAL;
205
206         t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
207         t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
208         t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
209
210         return 0;
211 }
212
213 int arch_copy_tls(struct task_struct *new)
214 {
215         struct user_desc info;
216         int idx, ret = -EFAULT;
217
218         if (copy_from_user(&info,
219                            (void __user *) UPT_ESI(&new->thread.regs.regs),
220                            sizeof(info)))
221                 goto out;
222
223         ret = -EINVAL;
224         if (LDT_empty(&info))
225                 goto out;
226
227         idx = info.entry_number;
228
229         ret = set_tls_entry(new, &info, idx, 0);
230 out:
231         return ret;
232 }
233
234 /* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
235 static int get_tls_entry(struct task_struct* task, struct user_desc *info, int idx)
236 {
237         struct thread_struct *t = &task->thread;
238
239         if (!t->arch.tls_array)
240                 goto clear;
241
242         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
243                 return -EINVAL;
244
245         if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
246                 goto clear;
247
248         *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
249
250 out:
251         /* Temporary debugging check, to make sure that things have been
252          * flushed. This could be triggered if load_TLS() failed.
253          */
254         if (unlikely(task == current && !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
255                 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
256                                 "without flushed TLS.", current->pid);
257         }
258
259         return 0;
260 clear:
261         /* When the TLS entry has not been set, the values read to user in the
262          * tls_array are 0 (because it's cleared at boot, see
263          * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
264          */
265         clear_user_desc(info);
266         info->entry_number = idx;
267         goto out;
268 }
269
270 asmlinkage int sys_set_thread_area(struct user_desc __user *user_desc)
271 {
272         struct user_desc info;
273         int idx, ret;
274
275         if (!host_supports_tls)
276                 return -ENOSYS;
277
278         if (copy_from_user(&info, user_desc, sizeof(info)))
279                 return -EFAULT;
280
281         idx = info.entry_number;
282
283         if (idx == -1) {
284                 idx = get_free_idx(current);
285                 if (idx < 0)
286                         return idx;
287                 info.entry_number = idx;
288                 /* Tell the user which slot we chose for him.*/
289                 if (put_user(idx, &user_desc->entry_number))
290                         return -EFAULT;
291         }
292
293         ret = CHOOSE_MODE_PROC(do_set_thread_area_tt, do_set_thread_area_skas, &info);
294         if (ret)
295                 return ret;
296         return set_tls_entry(current, &info, idx, 1);
297 }
298
299 /*
300  * Perform set_thread_area on behalf of the traced child.
301  * Note: error handling is not done on the deferred load, and this differ from
302  * i386. However the only possible error are caused by bugs.
303  */
304 int ptrace_set_thread_area(struct task_struct *child, int idx,
305                 struct user_desc __user *user_desc)
306 {
307         struct user_desc info;
308
309         if (!host_supports_tls)
310                 return -EIO;
311
312         if (copy_from_user(&info, user_desc, sizeof(info)))
313                 return -EFAULT;
314
315         return set_tls_entry(child, &info, idx, 0);
316 }
317
318 asmlinkage int sys_get_thread_area(struct user_desc __user *user_desc)
319 {
320         struct user_desc info;
321         int idx, ret;
322
323         if (!host_supports_tls)
324                 return -ENOSYS;
325
326         if (get_user(idx, &user_desc->entry_number))
327                 return -EFAULT;
328
329         ret = get_tls_entry(current, &info, idx);
330         if (ret < 0)
331                 goto out;
332
333         if (copy_to_user(user_desc, &info, sizeof(info)))
334                 ret = -EFAULT;
335
336 out:
337         return ret;
338 }
339
340 /*
341  * Perform get_thread_area on behalf of the traced child.
342  */
343 int ptrace_get_thread_area(struct task_struct *child, int idx,
344                 struct user_desc __user *user_desc)
345 {
346         struct user_desc info;
347         int ret;
348
349         if (!host_supports_tls)
350                 return -EIO;
351
352         ret = get_tls_entry(child, &info, idx);
353         if (ret < 0)
354                 goto out;
355
356         if (copy_to_user(user_desc, &info, sizeof(info)))
357                 ret = -EFAULT;
358 out:
359         return ret;
360 }
361
362
363 /* XXX: This part is probably common to i386 and x86-64. Don't create a common
364  * file for now, do that when implementing x86-64 support.*/
365 static int __init __setup_host_supports_tls(void) {
366         check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
367         if (host_supports_tls) {
368                 printk(KERN_INFO "Host TLS support detected\n");
369                 printk(KERN_INFO "Detected host type: ");
370                 switch (host_gdt_entry_tls_min) {
371                         case GDT_ENTRY_TLS_MIN_I386:
372                                 printk("i386\n");
373                                 break;
374                         case GDT_ENTRY_TLS_MIN_X86_64:
375                                 printk("x86_64\n");
376                                 break;
377                 }
378         } else
379                 printk(KERN_ERR "  Host TLS support NOT detected! "
380                                 "TLS support inside UML will not work\n");
381         return 0;
382 }
383
384 __initcall(__setup_host_supports_tls);