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 <linux/uaccess.h>
10#include <asm/ptrace-abi.h>
11#include <os.h>
12#include <skas.h>
13#include <sysdep/tls.h>
14
15/*
16 * If needed we can detect when it's uninitialized.
17 *
18 * These are initialized in an initcall and unchanged thereafter.
19 */
20static int host_supports_tls = -1;
21int host_gdt_entry_tls_min;
22
23int do_set_thread_area(struct user_desc *info)
24{
25 int ret;
26 u32 cpu;
27
28 cpu = get_cpu();
29 ret = os_set_thread_area(info, userspace_pid[cpu]);
30 put_cpu();
31
32 if (ret)
33 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
34 "index = %d\n", ret, info->entry_number);
35
36 return ret;
37}
38
39int do_get_thread_area(struct user_desc *info)
40{
41 int ret;
42 u32 cpu;
43
44 cpu = get_cpu();
45 ret = os_get_thread_area(info, userspace_pid[cpu]);
46 put_cpu();
47
48 if (ret)
49 printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, "
50 "index = %d\n", ret, info->entry_number);
51
52 return ret;
53}
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 dynamic linking
61 * and running against NPTL.
62 */
63static int get_free_idx(struct task_struct* task)
64{
65 struct thread_struct *t = &task->thread;
66 int idx;
67
68 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
69 if (!t->arch.tls_array[idx].present)
70 return idx + GDT_ENTRY_TLS_MIN;
71 return -ESRCH;
72}
73
74static inline void clear_user_desc(struct user_desc* info)
75{
76 /* Postcondition: LDT_empty(info) returns true. */
77 memset(info, 0, sizeof(*info));
78
79 /*
80 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
81 * indeed an empty user_desc.
82 */
83 info->read_exec_only = 1;
84 info->seg_not_present = 1;
85}
86
87#define O_FORCE 1
88
89static int load_TLS(int flags, struct task_struct *to)
90{
91 int ret = 0;
92 int idx;
93
94 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
95 struct uml_tls_struct* curr =
96 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
97
98 /*
99 * Actually, now if it wasn't flushed it gets cleared and
100 * flushed to the host, which will clear it.
101 */
102 if (!curr->present) {
103 if (!curr->flushed) {
104 clear_user_desc(&curr->tls);
105 curr->tls.entry_number = idx;
106 } else {
107 WARN_ON(!LDT_empty(&curr->tls));
108 continue;
109 }
110 }
111
112 if (!(flags & O_FORCE) && curr->flushed)
113 continue;
114
115 ret = do_set_thread_area(&curr->tls);
116 if (ret)
117 goto out;
118
119 curr->flushed = 1;
120 }
121out:
122 return ret;
123}
124
125/*
126 * Verify if we need to do a flush for the new process, i.e. if there are any
127 * present desc's, only if they haven't been flushed.
128 */
129static inline int needs_TLS_update(struct task_struct *task)
130{
131 int i;
132 int ret = 0;
133
134 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
135 struct uml_tls_struct* curr =
136 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
137
138 /*
139 * Can't test curr->present, we may need to clear a descriptor
140 * which had a value.
141 */
142 if (curr->flushed)
143 continue;
144 ret = 1;
145 break;
146 }
147 return ret;
148}
149
150/*
151 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
152 * we mark them as such and the first switch_to will do the job.
153 */
154void clear_flushed_tls(struct task_struct *task)
155{
156 int i;
157
158 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
159 struct uml_tls_struct* curr =
160 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
161
162 /*
163 * Still correct to do this, if it wasn't present on the host it
164 * will remain as flushed as it was.
165 */
166 if (!curr->present)
167 continue;
168
169 curr->flushed = 0;
170 }
171}
172
173/*
174 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
175 * common host process. So this is needed in SKAS0 too.
176 *
177 * However, if each thread had a different host process (and this was discussed
178 * for SMP support) this won't be needed.
179 *
180 * And this will not need be used when (and if) we'll add support to the host
181 * SKAS patch.
182 */
183
184int arch_switch_tls(struct task_struct *to)
185{
186 if (!host_supports_tls)
187 return 0;
188
189 /*
190 * We have no need whatsoever to switch TLS for kernel threads; beyond
191 * that, that would also result in us calling os_set_thread_area with
192 * userspace_pid[cpu] == 0, which gives an error.
193 */
194 if (likely(to->mm))
195 return load_TLS(O_FORCE, to);
196
197 return 0;
198}
199
200static int set_tls_entry(struct task_struct* task, struct user_desc *info,
201 int idx, int flushed)
202{
203 struct thread_struct *t = &task->thread;
204
205 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
206 return -EINVAL;
207
208 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
209 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
210 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
211
212 return 0;
213}
214
215int arch_set_tls(struct task_struct *new, unsigned long tls)
216{
217 struct user_desc info;
218 int idx, ret = -EFAULT;
219
220 if (copy_from_user(&info, (void __user *) tls, 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);
230out:
231 return ret;
232}
233
234/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
235static int get_tls_entry(struct task_struct *task, struct user_desc *info,
236 int idx)
237{
238 struct thread_struct *t = &task->thread;
239
240 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
241 return -EINVAL;
242
243 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
244 goto clear;
245
246 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
247
248out:
249 /*
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 &&
254 !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;
260clear:
261 /*
262 * When the TLS entry has not been set, the values read to user in the
263 * tls_array are 0 (because it's cleared at boot, see
264 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
265 */
266 clear_user_desc(info);
267 info->entry_number = idx;
268 goto out;
269}
270
271SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
272{
273 struct user_desc info;
274 int idx, ret;
275
276 if (!host_supports_tls)
277 return -ENOSYS;
278
279 if (copy_from_user(&info, user_desc, sizeof(info)))
280 return -EFAULT;
281
282 idx = info.entry_number;
283
284 if (idx == -1) {
285 idx = get_free_idx(current);
286 if (idx < 0)
287 return idx;
288 info.entry_number = idx;
289 /* Tell the user which slot we chose for him.*/
290 if (put_user(idx, &user_desc->entry_number))
291 return -EFAULT;
292 }
293
294 ret = do_set_thread_area(&info);
295 if (ret)
296 return ret;
297 return set_tls_entry(current, &info, idx, 1);
298}
299
300/*
301 * Perform set_thread_area on behalf of the traced child.
302 * Note: error handling is not done on the deferred load, and this differ from
303 * i386. However the only possible error are caused by bugs.
304 */
305int ptrace_set_thread_area(struct task_struct *child, int idx,
306 struct user_desc __user *user_desc)
307{
308 struct user_desc info;
309
310 if (!host_supports_tls)
311 return -EIO;
312
313 if (copy_from_user(&info, user_desc, sizeof(info)))
314 return -EFAULT;
315
316 return set_tls_entry(child, &info, idx, 0);
317}
318
319SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
320{
321 struct user_desc info;
322 int idx, ret;
323
324 if (!host_supports_tls)
325 return -ENOSYS;
326
327 if (get_user(idx, &user_desc->entry_number))
328 return -EFAULT;
329
330 ret = get_tls_entry(current, &info, idx);
331 if (ret < 0)
332 goto out;
333
334 if (copy_to_user(user_desc, &info, sizeof(info)))
335 ret = -EFAULT;
336
337out:
338 return ret;
339}
340
341/*
342 * Perform get_thread_area on behalf of the traced child.
343 */
344int ptrace_get_thread_area(struct task_struct *child, int idx,
345 struct user_desc __user *user_desc)
346{
347 struct user_desc info;
348 int ret;
349
350 if (!host_supports_tls)
351 return -EIO;
352
353 ret = get_tls_entry(child, &info, idx);
354 if (ret < 0)
355 goto out;
356
357 if (copy_to_user(user_desc, &info, sizeof(info)))
358 ret = -EFAULT;
359out:
360 return ret;
361}
362
363/*
364 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
365 * if a 32-bit UML is running on a 64-bit host.
366 */
367static int __init __setup_host_supports_tls(void)
368{
369 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
370 if (host_supports_tls) {
371 printk(KERN_INFO "Host TLS support detected\n");
372 printk(KERN_INFO "Detected host type: ");
373 switch (host_gdt_entry_tls_min) {
374 case GDT_ENTRY_TLS_MIN_I386:
375 printk(KERN_CONT "i386");
376 break;
377 case GDT_ENTRY_TLS_MIN_X86_64:
378 printk(KERN_CONT "x86_64");
379 break;
380 }
381 printk(KERN_CONT " (GDT indexes %d to %d)\n",
382 host_gdt_entry_tls_min,
383 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
384 } else
385 printk(KERN_ERR " Host TLS support NOT detected! "
386 "TLS support inside UML will not work\n");
387 return 0;
388}
389
390__initcall(__setup_host_supports_tls);