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