Loading...
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 <linux/syscalls.h>
9#include <linux/uaccess.h>
10#include <asm/ptrace-abi.h>
11#include <os.h>
12#include <skas.h>
13#include <sysdep/tls.h>
14#include <asm/desc.h>
15
16/*
17 * If needed we can detect when it's uninitialized.
18 *
19 * These are initialized in an initcall and unchanged thereafter.
20 */
21static int host_supports_tls = -1;
22int host_gdt_entry_tls_min;
23
24static int do_set_thread_area(struct user_desc *info)
25{
26 int ret;
27 u32 cpu;
28
29 cpu = get_cpu();
30 ret = os_set_thread_area(info, userspace_pid[cpu]);
31 put_cpu();
32
33 if (ret)
34 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
35 "index = %d\n", ret, info->entry_number);
36
37 return ret;
38}
39
40/*
41 * sys_get_thread_area: get a yet unused TLS descriptor index.
42 * XXX: Consider leaving one free slot for glibc usage at first place. This must
43 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
44 *
45 * Also, this must be tested when compiling in SKAS mode with dynamic linking
46 * and running against NPTL.
47 */
48static int get_free_idx(struct task_struct* task)
49{
50 struct thread_struct *t = &task->thread;
51 int idx;
52
53 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
54 if (!t->arch.tls_array[idx].present)
55 return idx + GDT_ENTRY_TLS_MIN;
56 return -ESRCH;
57}
58
59static inline void clear_user_desc(struct user_desc* info)
60{
61 /* Postcondition: LDT_empty(info) returns true. */
62 memset(info, 0, sizeof(*info));
63
64 /*
65 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
66 * indeed an empty user_desc.
67 */
68 info->read_exec_only = 1;
69 info->seg_not_present = 1;
70}
71
72#define O_FORCE 1
73
74static int load_TLS(int flags, struct task_struct *to)
75{
76 int ret = 0;
77 int idx;
78
79 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
80 struct uml_tls_struct* curr =
81 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
82
83 /*
84 * Actually, now if it wasn't flushed it gets cleared and
85 * flushed to the host, which will clear it.
86 */
87 if (!curr->present) {
88 if (!curr->flushed) {
89 clear_user_desc(&curr->tls);
90 curr->tls.entry_number = idx;
91 } else {
92 WARN_ON(!LDT_empty(&curr->tls));
93 continue;
94 }
95 }
96
97 if (!(flags & O_FORCE) && curr->flushed)
98 continue;
99
100 ret = do_set_thread_area(&curr->tls);
101 if (ret)
102 goto out;
103
104 curr->flushed = 1;
105 }
106out:
107 return ret;
108}
109
110/*
111 * Verify if we need to do a flush for the new process, i.e. if there are any
112 * present desc's, only if they haven't been flushed.
113 */
114static inline int needs_TLS_update(struct task_struct *task)
115{
116 int i;
117 int ret = 0;
118
119 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
120 struct uml_tls_struct* curr =
121 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
122
123 /*
124 * Can't test curr->present, we may need to clear a descriptor
125 * which had a value.
126 */
127 if (curr->flushed)
128 continue;
129 ret = 1;
130 break;
131 }
132 return ret;
133}
134
135/*
136 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
137 * we mark them as such and the first switch_to will do the job.
138 */
139void clear_flushed_tls(struct task_struct *task)
140{
141 int i;
142
143 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
144 struct uml_tls_struct* curr =
145 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
146
147 /*
148 * Still correct to do this, if it wasn't present on the host it
149 * will remain as flushed as it was.
150 */
151 if (!curr->present)
152 continue;
153
154 curr->flushed = 0;
155 }
156}
157
158/*
159 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
160 * common host process. So this is needed in SKAS0 too.
161 *
162 * However, if each thread had a different host process (and this was discussed
163 * for SMP support) this won't be needed.
164 *
165 * And this will not need be used when (and if) we'll add support to the host
166 * SKAS patch.
167 */
168
169int arch_switch_tls(struct task_struct *to)
170{
171 if (!host_supports_tls)
172 return 0;
173
174 /*
175 * We have no need whatsoever to switch TLS for kernel threads; beyond
176 * that, that would also result in us calling os_set_thread_area with
177 * userspace_pid[cpu] == 0, which gives an error.
178 */
179 if (likely(to->mm))
180 return load_TLS(O_FORCE, to);
181
182 return 0;
183}
184
185static int set_tls_entry(struct task_struct* task, struct user_desc *info,
186 int idx, int flushed)
187{
188 struct thread_struct *t = &task->thread;
189
190 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
191 return -EINVAL;
192
193 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
194 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
195 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
196
197 return 0;
198}
199
200int arch_set_tls(struct task_struct *new, unsigned long tls)
201{
202 struct user_desc info;
203 int idx, ret = -EFAULT;
204
205 if (copy_from_user(&info, (void __user *) tls, sizeof(info)))
206 goto out;
207
208 ret = -EINVAL;
209 if (LDT_empty(&info))
210 goto out;
211
212 idx = info.entry_number;
213
214 ret = set_tls_entry(new, &info, idx, 0);
215out:
216 return ret;
217}
218
219static int get_tls_entry(struct task_struct *task, struct user_desc *info,
220 int idx)
221{
222 struct thread_struct *t = &task->thread;
223
224 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
225 return -EINVAL;
226
227 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
228 goto clear;
229
230 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
231
232out:
233 /*
234 * Temporary debugging check, to make sure that things have been
235 * flushed. This could be triggered if load_TLS() failed.
236 */
237 if (unlikely(task == current &&
238 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
239 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
240 "without flushed TLS.", current->pid);
241 }
242
243 return 0;
244clear:
245 /*
246 * When the TLS entry has not been set, the values read to user in the
247 * tls_array are 0 (because it's cleared at boot, see
248 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
249 */
250 clear_user_desc(info);
251 info->entry_number = idx;
252 goto out;
253}
254
255SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
256{
257 struct user_desc info;
258 int idx, ret;
259
260 if (!host_supports_tls)
261 return -ENOSYS;
262
263 if (copy_from_user(&info, user_desc, sizeof(info)))
264 return -EFAULT;
265
266 idx = info.entry_number;
267
268 if (idx == -1) {
269 idx = get_free_idx(current);
270 if (idx < 0)
271 return idx;
272 info.entry_number = idx;
273 /* Tell the user which slot we chose for him.*/
274 if (put_user(idx, &user_desc->entry_number))
275 return -EFAULT;
276 }
277
278 ret = do_set_thread_area(&info);
279 if (ret)
280 return ret;
281 return set_tls_entry(current, &info, idx, 1);
282}
283
284/*
285 * Perform set_thread_area on behalf of the traced child.
286 * Note: error handling is not done on the deferred load, and this differ from
287 * i386. However the only possible error are caused by bugs.
288 */
289int ptrace_set_thread_area(struct task_struct *child, int idx,
290 struct user_desc __user *user_desc)
291{
292 struct user_desc info;
293
294 if (!host_supports_tls)
295 return -EIO;
296
297 if (copy_from_user(&info, user_desc, sizeof(info)))
298 return -EFAULT;
299
300 return set_tls_entry(child, &info, idx, 0);
301}
302
303SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
304{
305 struct user_desc info;
306 int idx, ret;
307
308 if (!host_supports_tls)
309 return -ENOSYS;
310
311 if (get_user(idx, &user_desc->entry_number))
312 return -EFAULT;
313
314 ret = get_tls_entry(current, &info, idx);
315 if (ret < 0)
316 goto out;
317
318 if (copy_to_user(user_desc, &info, sizeof(info)))
319 ret = -EFAULT;
320
321out:
322 return ret;
323}
324
325/*
326 * Perform get_thread_area on behalf of the traced child.
327 */
328int ptrace_get_thread_area(struct task_struct *child, int idx,
329 struct user_desc __user *user_desc)
330{
331 struct user_desc info;
332 int ret;
333
334 if (!host_supports_tls)
335 return -EIO;
336
337 ret = get_tls_entry(child, &info, idx);
338 if (ret < 0)
339 goto out;
340
341 if (copy_to_user(user_desc, &info, sizeof(info)))
342 ret = -EFAULT;
343out:
344 return ret;
345}
346
347/*
348 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
349 * if a 32-bit UML is running on a 64-bit host.
350 */
351static int __init __setup_host_supports_tls(void)
352{
353 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
354 if (host_supports_tls) {
355 printk(KERN_INFO "Host TLS support detected\n");
356 printk(KERN_INFO "Detected host type: ");
357 switch (host_gdt_entry_tls_min) {
358 case GDT_ENTRY_TLS_MIN_I386:
359 printk(KERN_CONT "i386");
360 break;
361 case GDT_ENTRY_TLS_MIN_X86_64:
362 printk(KERN_CONT "x86_64");
363 break;
364 }
365 printk(KERN_CONT " (GDT indexes %d to %d)\n",
366 host_gdt_entry_tls_min,
367 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
368 } else
369 printk(KERN_ERR " Host TLS support NOT detected! "
370 "TLS support inside UML will not work\n");
371 return 0;
372}
373
374__initcall(__setup_host_supports_tls);
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 <linux/syscalls.h>
9#include <asm/uaccess.h>
10#include <os.h>
11#include <skas.h>
12#include <sysdep/tls.h>
13
14/*
15 * If needed we can detect when it's uninitialized.
16 *
17 * These are initialized in an initcall and unchanged thereafter.
18 */
19static int host_supports_tls = -1;
20int host_gdt_entry_tls_min;
21
22int do_set_thread_area(struct user_desc *info)
23{
24 int ret;
25 u32 cpu;
26
27 cpu = get_cpu();
28 ret = os_set_thread_area(info, userspace_pid[cpu]);
29 put_cpu();
30
31 if (ret)
32 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
33 "index = %d\n", ret, info->entry_number);
34
35 return ret;
36}
37
38int do_get_thread_area(struct user_desc *info)
39{
40 int ret;
41 u32 cpu;
42
43 cpu = get_cpu();
44 ret = os_get_thread_area(info, userspace_pid[cpu]);
45 put_cpu();
46
47 if (ret)
48 printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, "
49 "index = %d\n", ret, info->entry_number);
50
51 return ret;
52}
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 dynamic 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
76static 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 /*
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
91static 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 =
98 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
99
100 /*
101 * Actually, now if it wasn't flushed it gets cleared and
102 * flushed to the host, which will clear it.
103 */
104 if (!curr->present) {
105 if (!curr->flushed) {
106 clear_user_desc(&curr->tls);
107 curr->tls.entry_number = idx;
108 } else {
109 WARN_ON(!LDT_empty(&curr->tls));
110 continue;
111 }
112 }
113
114 if (!(flags & O_FORCE) && curr->flushed)
115 continue;
116
117 ret = do_set_thread_area(&curr->tls);
118 if (ret)
119 goto out;
120
121 curr->flushed = 1;
122 }
123out:
124 return ret;
125}
126
127/*
128 * Verify if we need to do a flush for the new process, i.e. if there are any
129 * present desc's, only if they haven't been flushed.
130 */
131static inline int needs_TLS_update(struct task_struct *task)
132{
133 int i;
134 int ret = 0;
135
136 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
137 struct uml_tls_struct* curr =
138 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
139
140 /*
141 * Can't test curr->present, we may need to clear a descriptor
142 * which had a value.
143 */
144 if (curr->flushed)
145 continue;
146 ret = 1;
147 break;
148 }
149 return ret;
150}
151
152/*
153 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
154 * we mark them as such and the first switch_to will do the job.
155 */
156void clear_flushed_tls(struct task_struct *task)
157{
158 int i;
159
160 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
161 struct uml_tls_struct* curr =
162 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
163
164 /*
165 * Still correct to do this, if it wasn't present on the host it
166 * will remain as flushed as it was.
167 */
168 if (!curr->present)
169 continue;
170
171 curr->flushed = 0;
172 }
173}
174
175/*
176 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
177 * common host process. So this is needed in SKAS0 too.
178 *
179 * However, if each thread had a different host process (and this was discussed
180 * for SMP support) this won't be needed.
181 *
182 * And this will not need be used when (and if) we'll add support to the host
183 * SKAS patch.
184 */
185
186int arch_switch_tls(struct task_struct *to)
187{
188 if (!host_supports_tls)
189 return 0;
190
191 /*
192 * We have no need whatsoever to switch TLS for kernel threads; beyond
193 * that, that would also result in us calling os_set_thread_area with
194 * userspace_pid[cpu] == 0, which gives an error.
195 */
196 if (likely(to->mm))
197 return load_TLS(O_FORCE, to);
198
199 return 0;
200}
201
202static int set_tls_entry(struct task_struct* task, struct user_desc *info,
203 int idx, int flushed)
204{
205 struct thread_struct *t = &task->thread;
206
207 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
208 return -EINVAL;
209
210 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
211 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
212 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
213
214 return 0;
215}
216
217int arch_copy_tls(struct task_struct *new)
218{
219 struct user_desc info;
220 int idx, ret = -EFAULT;
221
222 if (copy_from_user(&info,
223 (void __user *) UPT_SI(&new->thread.regs.regs),
224 sizeof(info)))
225 goto out;
226
227 ret = -EINVAL;
228 if (LDT_empty(&info))
229 goto out;
230
231 idx = info.entry_number;
232
233 ret = set_tls_entry(new, &info, idx, 0);
234out:
235 return ret;
236}
237
238/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
239static int get_tls_entry(struct task_struct *task, struct user_desc *info,
240 int idx)
241{
242 struct thread_struct *t = &task->thread;
243
244 if (!t->arch.tls_array)
245 goto clear;
246
247 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
248 return -EINVAL;
249
250 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
251 goto clear;
252
253 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
254
255out:
256 /*
257 * Temporary debugging check, to make sure that things have been
258 * flushed. This could be triggered if load_TLS() failed.
259 */
260 if (unlikely(task == current &&
261 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
262 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
263 "without flushed TLS.", current->pid);
264 }
265
266 return 0;
267clear:
268 /*
269 * When the TLS entry has not been set, the values read to user in the
270 * tls_array are 0 (because it's cleared at boot, see
271 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
272 */
273 clear_user_desc(info);
274 info->entry_number = idx;
275 goto out;
276}
277
278SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
279{
280 struct user_desc info;
281 int idx, ret;
282
283 if (!host_supports_tls)
284 return -ENOSYS;
285
286 if (copy_from_user(&info, user_desc, sizeof(info)))
287 return -EFAULT;
288
289 idx = info.entry_number;
290
291 if (idx == -1) {
292 idx = get_free_idx(current);
293 if (idx < 0)
294 return idx;
295 info.entry_number = idx;
296 /* Tell the user which slot we chose for him.*/
297 if (put_user(idx, &user_desc->entry_number))
298 return -EFAULT;
299 }
300
301 ret = do_set_thread_area(&info);
302 if (ret)
303 return ret;
304 return set_tls_entry(current, &info, idx, 1);
305}
306
307/*
308 * Perform set_thread_area on behalf of the traced child.
309 * Note: error handling is not done on the deferred load, and this differ from
310 * i386. However the only possible error are caused by bugs.
311 */
312int ptrace_set_thread_area(struct task_struct *child, int idx,
313 struct user_desc __user *user_desc)
314{
315 struct user_desc info;
316
317 if (!host_supports_tls)
318 return -EIO;
319
320 if (copy_from_user(&info, user_desc, sizeof(info)))
321 return -EFAULT;
322
323 return set_tls_entry(child, &info, idx, 0);
324}
325
326SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
327{
328 struct user_desc info;
329 int idx, ret;
330
331 if (!host_supports_tls)
332 return -ENOSYS;
333
334 if (get_user(idx, &user_desc->entry_number))
335 return -EFAULT;
336
337 ret = get_tls_entry(current, &info, idx);
338 if (ret < 0)
339 goto out;
340
341 if (copy_to_user(user_desc, &info, sizeof(info)))
342 ret = -EFAULT;
343
344out:
345 return ret;
346}
347
348/*
349 * Perform get_thread_area on behalf of the traced child.
350 */
351int ptrace_get_thread_area(struct task_struct *child, int idx,
352 struct user_desc __user *user_desc)
353{
354 struct user_desc info;
355 int ret;
356
357 if (!host_supports_tls)
358 return -EIO;
359
360 ret = get_tls_entry(child, &info, idx);
361 if (ret < 0)
362 goto out;
363
364 if (copy_to_user(user_desc, &info, sizeof(info)))
365 ret = -EFAULT;
366out:
367 return ret;
368}
369
370/*
371 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
372 * if a 32-bit UML is running on a 64-bit host.
373 */
374static int __init __setup_host_supports_tls(void)
375{
376 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
377 if (host_supports_tls) {
378 printk(KERN_INFO "Host TLS support detected\n");
379 printk(KERN_INFO "Detected host type: ");
380 switch (host_gdt_entry_tls_min) {
381 case GDT_ENTRY_TLS_MIN_I386:
382 printk(KERN_CONT "i386");
383 break;
384 case GDT_ENTRY_TLS_MIN_X86_64:
385 printk(KERN_CONT "x86_64");
386 break;
387 }
388 printk(KERN_CONT " (GDT indexes %d to %d)\n",
389 host_gdt_entry_tls_min,
390 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
391 } else
392 printk(KERN_ERR " Host TLS support NOT detected! "
393 "TLS support inside UML will not work\n");
394 return 0;
395}
396
397__initcall(__setup_host_supports_tls);