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Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -08001/*
2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3 * Licensed under the GPL
4 */
5
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -08006#include "linux/kernel.h"
7#include "linux/sched.h"
8#include "linux/slab.h"
9#include "linux/types.h"
10#include "asm/uaccess.h"
11#include "asm/ptrace.h"
12#include "asm/segment.h"
13#include "asm/smp.h"
14#include "asm/desc.h"
15#include "choose-mode.h"
16#include "kern.h"
17#include "kern_util.h"
18#include "mode_kern.h"
19#include "os.h"
20#include "mode.h"
21
22#ifdef CONFIG_MODE_SKAS
23#include "skas.h"
24#endif
25
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -080026/* If needed we can detect when it's uninitialized. */
27static int host_supports_tls = -1;
28int host_gdt_entry_tls_min = -1;
29
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -080030#ifdef CONFIG_MODE_SKAS
31int do_set_thread_area_skas(struct user_desc *info)
32{
33 int ret;
34 u32 cpu;
35
36 cpu = get_cpu();
37 ret = os_set_thread_area(info, userspace_pid[cpu]);
38 put_cpu();
39 return ret;
40}
41
42int do_get_thread_area_skas(struct user_desc *info)
43{
44 int ret;
45 u32 cpu;
46
47 cpu = get_cpu();
48 ret = os_get_thread_area(info, userspace_pid[cpu]);
49 put_cpu();
50 return ret;
51}
52#endif
53
54/*
55 * sys_get_thread_area: get a yet unused TLS descriptor index.
56 * XXX: Consider leaving one free slot for glibc usage at first place. This must
57 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
58 *
59 * Also, this must be tested when compiling in SKAS mode with dinamic linking
60 * and running against NPTL.
61 */
62static int get_free_idx(struct task_struct* task)
63{
64 struct thread_struct *t = &task->thread;
65 int idx;
66
67 if (!t->arch.tls_array)
68 return GDT_ENTRY_TLS_MIN;
69
70 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
71 if (!t->arch.tls_array[idx].present)
72 return idx + GDT_ENTRY_TLS_MIN;
73 return -ESRCH;
74}
75
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -080076static inline void clear_user_desc(struct user_desc* info)
77{
78 /* Postcondition: LDT_empty(info) returns true. */
79 memset(info, 0, sizeof(*info));
80
81 /* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
82 * indeed an empty user_desc.
83 */
84 info->read_exec_only = 1;
85 info->seg_not_present = 1;
86}
87
Paolo 'Blaisorblade' Giarrusso54d8d3b2006-03-31 02:30:24 -080088#define O_FORCE 1
89
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -080090static int load_TLS(int flags, struct task_struct *to)
91{
92 int ret = 0;
93 int idx;
94
95 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
96 struct uml_tls_struct* curr = &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
97
98 /* Actually, now if it wasn't flushed it gets cleared and
99 * flushed to the host, which will clear it.*/
100 if (!curr->present) {
101 if (!curr->flushed) {
102 clear_user_desc(&curr->tls);
103 curr->tls.entry_number = idx;
104 } else {
105 WARN_ON(!LDT_empty(&curr->tls));
106 continue;
107 }
108 }
109
110 if (!(flags & O_FORCE) && curr->flushed)
111 continue;
112
113 ret = do_set_thread_area(&curr->tls);
114 if (ret)
115 goto out;
116
117 curr->flushed = 1;
118 }
119out:
120 return ret;
121}
122
123/* Verify if we need to do a flush for the new process, i.e. if there are any
124 * present desc's, only if they haven't been flushed.
125 */
126static inline int needs_TLS_update(struct task_struct *task)
127{
128 int i;
129 int ret = 0;
130
131 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
132 struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
133
134 /* Can't test curr->present, we may need to clear a descriptor
135 * which had a value. */
136 if (curr->flushed)
137 continue;
138 ret = 1;
139 break;
140 }
141 return ret;
142}
143
144/* On a newly forked process, the TLS descriptors haven't yet been flushed. So
145 * we mark them as such and the first switch_to will do the job.
146 */
147void clear_flushed_tls(struct task_struct *task)
148{
149 int i;
150
151 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
152 struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
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 if (!curr->present)
157 continue;
158
159 curr->flushed = 0;
160 }
161}
162
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800163/* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
164 * common host process. So this is needed in SKAS0 too.
165 *
166 * However, if each thread had a different host process (and this was discussed
167 * for SMP support) this won't be needed.
168 *
169 * And this will not need be used when (and if) we'll add support to the host
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800170 * SKAS patch. */
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800171
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800172int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
173{
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800174 if (!host_supports_tls)
175 return 0;
176
Paolo 'Blaisorblade' Giarrusso54d8d3b2006-03-31 02:30:24 -0800177 /* We have no need whatsoever to switch TLS for kernel threads; beyond
178 * that, that would also result in us calling os_set_thread_area with
179 * userspace_pid[cpu] == 0, which gives an error. */
180 if (likely(to->mm))
181 return load_TLS(O_FORCE, to);
182
183 return 0;
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800184}
185
186int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
187{
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800188 if (!host_supports_tls)
189 return 0;
190
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800191 if (needs_TLS_update(to))
192 return load_TLS(0, to);
193
194 return 0;
195}
196
197static int set_tls_entry(struct task_struct* task, struct user_desc *info,
198 int idx, int flushed)
199{
200 struct thread_struct *t = &task->thread;
201
202 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
203 return -EINVAL;
204
205 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
206 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
207 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
208
209 return 0;
210}
211
212int arch_copy_tls(struct task_struct *new)
213{
214 struct user_desc info;
215 int idx, ret = -EFAULT;
216
217 if (copy_from_user(&info,
218 (void __user *) UPT_ESI(&new->thread.regs.regs),
219 sizeof(info)))
220 goto out;
221
222 ret = -EINVAL;
223 if (LDT_empty(&info))
224 goto out;
225
226 idx = info.entry_number;
227
228 ret = set_tls_entry(new, &info, idx, 0);
229out:
230 return ret;
231}
232
233/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
234static int get_tls_entry(struct task_struct* task, struct user_desc *info, int idx)
235{
236 struct thread_struct *t = &task->thread;
237
238 if (!t->arch.tls_array)
239 goto clear;
240
241 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
242 return -EINVAL;
243
244 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
245 goto clear;
246
247 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
248
249out:
250 /* Temporary debugging check, to make sure that things have been
251 * flushed. This could be triggered if load_TLS() failed.
252 */
253 if (unlikely(task == current && !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
254 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
255 "without flushed TLS.", current->pid);
256 }
257
258 return 0;
259clear:
260 /* When the TLS entry has not been set, the values read to user in the
261 * tls_array are 0 (because it's cleared at boot, see
262 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
263 */
264 clear_user_desc(info);
265 info->entry_number = idx;
266 goto out;
267}
268
269asmlinkage int sys_set_thread_area(struct user_desc __user *user_desc)
270{
271 struct user_desc info;
272 int idx, ret;
273
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800274 if (!host_supports_tls)
275 return -ENOSYS;
276
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800277 if (copy_from_user(&info, user_desc, sizeof(info)))
278 return -EFAULT;
279
280 idx = info.entry_number;
281
282 if (idx == -1) {
283 idx = get_free_idx(current);
284 if (idx < 0)
285 return idx;
286 info.entry_number = idx;
287 /* Tell the user which slot we chose for him.*/
288 if (put_user(idx, &user_desc->entry_number))
289 return -EFAULT;
290 }
291
292 ret = CHOOSE_MODE_PROC(do_set_thread_area_tt, do_set_thread_area_skas, &info);
293 if (ret)
294 return ret;
295 return set_tls_entry(current, &info, idx, 1);
296}
297
298/*
299 * Perform set_thread_area on behalf of the traced child.
300 * Note: error handling is not done on the deferred load, and this differ from
301 * i386. However the only possible error are caused by bugs.
302 */
303int ptrace_set_thread_area(struct task_struct *child, int idx,
304 struct user_desc __user *user_desc)
305{
306 struct user_desc info;
307
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800308 if (!host_supports_tls)
309 return -EIO;
310
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800311 if (copy_from_user(&info, user_desc, sizeof(info)))
312 return -EFAULT;
313
314 return set_tls_entry(child, &info, idx, 0);
315}
316
317asmlinkage int sys_get_thread_area(struct user_desc __user *user_desc)
318{
319 struct user_desc info;
320 int idx, ret;
321
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800322 if (!host_supports_tls)
323 return -ENOSYS;
324
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800325 if (get_user(idx, &user_desc->entry_number))
326 return -EFAULT;
327
328 ret = get_tls_entry(current, &info, idx);
329 if (ret < 0)
330 goto out;
331
332 if (copy_to_user(user_desc, &info, sizeof(info)))
333 ret = -EFAULT;
334
335out:
336 return ret;
337}
338
339/*
340 * Perform get_thread_area on behalf of the traced child.
341 */
342int ptrace_get_thread_area(struct task_struct *child, int idx,
343 struct user_desc __user *user_desc)
344{
345 struct user_desc info;
346 int ret;
347
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800348 if (!host_supports_tls)
349 return -EIO;
350
Paolo 'Blaisorblade' Giarrussoaa6758d2006-03-31 02:30:22 -0800351 ret = get_tls_entry(child, &info, idx);
352 if (ret < 0)
353 goto out;
354
355 if (copy_to_user(user_desc, &info, sizeof(info)))
356 ret = -EFAULT;
357out:
358 return ret;
359}
Paolo 'Blaisorblade' Giarrusso54d8d3b2006-03-31 02:30:24 -0800360
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800361
362/* XXX: This part is probably common to i386 and x86-64. Don't create a common
363 * file for now, do that when implementing x86-64 support.*/
364static int __init __setup_host_supports_tls(void) {
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");
Jeff Dikea5d2f462006-04-10 22:53:26 -0700380 return 0;
Paolo 'Blaisorblade' Giarrusso3feb8852006-03-31 02:30:25 -0800381}
382
383__initcall(__setup_host_supports_tls);