Commit | Line | Data |
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aa6758d4 PBG |
1 | /* |
2 | * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> | |
3 | * Licensed under the GPL | |
4 | */ | |
5 | ||
ba180fd4 | 6 | #include "linux/percpu.h" |
aa6758d4 | 7 | #include "linux/sched.h" |
aa6758d4 | 8 | #include "asm/uaccess.h" |
aa6758d4 | 9 | #include "os.h" |
aa6758d4 | 10 | #include "skas.h" |
ba180fd4 | 11 | #include "sysdep/tls.h" |
aa6758d4 | 12 | |
65a58ab0 JD |
13 | /* |
14 | * If needed we can detect when it's uninitialized. | |
15 | * | |
16 | * These are initialized in an initcall and unchanged thereafter. | |
17 | */ | |
3feb8856 | 18 | static int host_supports_tls = -1; |
65a58ab0 | 19 | int host_gdt_entry_tls_min; |
3feb8856 | 20 | |
6aa802ce | 21 | int do_set_thread_area(struct user_desc *info) |
aa6758d4 PBG |
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(); | |
b8bec829 JD |
29 | |
30 | if (ret) | |
31 | printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, " | |
32 | "index = %d\n", ret, info->entry_number); | |
33 | ||
aa6758d4 PBG |
34 | return ret; |
35 | } | |
36 | ||
6aa802ce | 37 | int do_get_thread_area(struct user_desc *info) |
aa6758d4 PBG |
38 | { |
39 | int ret; | |
40 | u32 cpu; | |
41 | ||
42 | cpu = get_cpu(); | |
43 | ret = os_get_thread_area(info, userspace_pid[cpu]); | |
44 | put_cpu(); | |
b8bec829 JD |
45 | |
46 | if (ret) | |
47 | printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, " | |
48 | "index = %d\n", ret, info->entry_number); | |
49 | ||
aa6758d4 PBG |
50 | return ret; |
51 | } | |
aa6758d4 PBG |
52 | |
53 | /* | |
54 | * sys_get_thread_area: get a yet unused TLS descriptor index. | |
55 | * XXX: Consider leaving one free slot for glibc usage at first place. This must | |
56 | * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else. | |
57 | * | |
b60745b9 | 58 | * Also, this must be tested when compiling in SKAS mode with dynamic linking |
aa6758d4 PBG |
59 | * and running against NPTL. |
60 | */ | |
61 | static int get_free_idx(struct task_struct* task) | |
62 | { | |
63 | struct thread_struct *t = &task->thread; | |
64 | int idx; | |
65 | ||
66 | if (!t->arch.tls_array) | |
67 | return GDT_ENTRY_TLS_MIN; | |
68 | ||
69 | for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++) | |
70 | if (!t->arch.tls_array[idx].present) | |
71 | return idx + GDT_ENTRY_TLS_MIN; | |
72 | return -ESRCH; | |
73 | } | |
74 | ||
aa6758d4 PBG |
75 | static inline void clear_user_desc(struct user_desc* info) |
76 | { | |
77 | /* Postcondition: LDT_empty(info) returns true. */ | |
78 | memset(info, 0, sizeof(*info)); | |
79 | ||
ba180fd4 JD |
80 | /* |
81 | * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain | |
aa6758d4 PBG |
82 | * indeed an empty user_desc. |
83 | */ | |
84 | info->read_exec_only = 1; | |
85 | info->seg_not_present = 1; | |
86 | } | |
87 | ||
54d8d3b5 PBG |
88 | #define O_FORCE 1 |
89 | ||
aa6758d4 PBG |
90 | static 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++) { | |
ba180fd4 JD |
96 | struct uml_tls_struct* curr = |
97 | &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN]; | |
aa6758d4 | 98 | |
ba180fd4 JD |
99 | /* |
100 | * Actually, now if it wasn't flushed it gets cleared and | |
101 | * flushed to the host, which will clear it. | |
102 | */ | |
aa6758d4 PBG |
103 | if (!curr->present) { |
104 | if (!curr->flushed) { | |
105 | clear_user_desc(&curr->tls); | |
106 | curr->tls.entry_number = idx; | |
107 | } else { | |
108 | WARN_ON(!LDT_empty(&curr->tls)); | |
109 | continue; | |
110 | } | |
111 | } | |
112 | ||
113 | if (!(flags & O_FORCE) && curr->flushed) | |
114 | continue; | |
115 | ||
116 | ret = do_set_thread_area(&curr->tls); | |
117 | if (ret) | |
118 | goto out; | |
119 | ||
120 | curr->flushed = 1; | |
121 | } | |
122 | out: | |
123 | return ret; | |
124 | } | |
125 | ||
ba180fd4 JD |
126 | /* |
127 | * Verify if we need to do a flush for the new process, i.e. if there are any | |
aa6758d4 PBG |
128 | * present desc's, only if they haven't been flushed. |
129 | */ | |
130 | static inline int needs_TLS_update(struct task_struct *task) | |
131 | { | |
132 | int i; | |
133 | int ret = 0; | |
134 | ||
135 | for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { | |
ba180fd4 JD |
136 | struct uml_tls_struct* curr = |
137 | &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; | |
aa6758d4 | 138 | |
ba180fd4 JD |
139 | /* |
140 | * Can't test curr->present, we may need to clear a descriptor | |
141 | * which had a value. | |
142 | */ | |
aa6758d4 PBG |
143 | if (curr->flushed) |
144 | continue; | |
145 | ret = 1; | |
146 | break; | |
147 | } | |
148 | return ret; | |
149 | } | |
150 | ||
ba180fd4 JD |
151 | /* |
152 | * On a newly forked process, the TLS descriptors haven't yet been flushed. So | |
aa6758d4 PBG |
153 | * we mark them as such and the first switch_to will do the job. |
154 | */ | |
155 | void clear_flushed_tls(struct task_struct *task) | |
156 | { | |
157 | int i; | |
158 | ||
159 | for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { | |
ba180fd4 JD |
160 | struct uml_tls_struct* curr = |
161 | &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; | |
aa6758d4 | 162 | |
ba180fd4 JD |
163 | /* |
164 | * Still correct to do this, if it wasn't present on the host it | |
165 | * will remain as flushed as it was. | |
166 | */ | |
aa6758d4 PBG |
167 | if (!curr->present) |
168 | continue; | |
169 | ||
170 | curr->flushed = 0; | |
171 | } | |
172 | } | |
173 | ||
ba180fd4 JD |
174 | /* |
175 | * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a | |
3feb8856 PBG |
176 | * common host process. So this is needed in SKAS0 too. |
177 | * | |
178 | * However, if each thread had a different host process (and this was discussed | |
179 | * for SMP support) this won't be needed. | |
180 | * | |
181 | * And this will not need be used when (and if) we'll add support to the host | |
ba180fd4 JD |
182 | * SKAS patch. |
183 | */ | |
3feb8856 | 184 | |
291248fd | 185 | int arch_switch_tls(struct task_struct *to) |
aa6758d4 | 186 | { |
3feb8856 PBG |
187 | if (!host_supports_tls) |
188 | return 0; | |
189 | ||
ba180fd4 JD |
190 | /* |
191 | * We have no need whatsoever to switch TLS for kernel threads; beyond | |
54d8d3b5 | 192 | * that, that would also result in us calling os_set_thread_area with |
ba180fd4 JD |
193 | * userspace_pid[cpu] == 0, which gives an error. |
194 | */ | |
54d8d3b5 PBG |
195 | if (likely(to->mm)) |
196 | return load_TLS(O_FORCE, to); | |
197 | ||
198 | return 0; | |
aa6758d4 PBG |
199 | } |
200 | ||
aa6758d4 PBG |
201 | static int set_tls_entry(struct task_struct* task, struct user_desc *info, |
202 | int idx, int flushed) | |
203 | { | |
204 | struct thread_struct *t = &task->thread; | |
205 | ||
206 | if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) | |
207 | return -EINVAL; | |
208 | ||
209 | t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info; | |
210 | t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1; | |
211 | t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed; | |
212 | ||
213 | return 0; | |
214 | } | |
215 | ||
216 | int arch_copy_tls(struct task_struct *new) | |
217 | { | |
218 | struct user_desc info; | |
219 | int idx, ret = -EFAULT; | |
220 | ||
221 | if (copy_from_user(&info, | |
222 | (void __user *) UPT_ESI(&new->thread.regs.regs), | |
223 | sizeof(info))) | |
224 | goto out; | |
225 | ||
226 | ret = -EINVAL; | |
227 | if (LDT_empty(&info)) | |
228 | goto out; | |
229 | ||
230 | idx = info.entry_number; | |
231 | ||
232 | ret = set_tls_entry(new, &info, idx, 0); | |
233 | out: | |
234 | return ret; | |
235 | } | |
236 | ||
237 | /* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */ | |
b2cf7707 JD |
238 | static int get_tls_entry(struct task_struct *task, struct user_desc *info, |
239 | int idx) | |
aa6758d4 PBG |
240 | { |
241 | struct thread_struct *t = &task->thread; | |
242 | ||
243 | if (!t->arch.tls_array) | |
244 | goto clear; | |
245 | ||
246 | if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) | |
247 | return -EINVAL; | |
248 | ||
249 | if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present) | |
250 | goto clear; | |
251 | ||
252 | *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls; | |
253 | ||
254 | out: | |
ba180fd4 JD |
255 | /* |
256 | * Temporary debugging check, to make sure that things have been | |
aa6758d4 PBG |
257 | * flushed. This could be triggered if load_TLS() failed. |
258 | */ | |
ba180fd4 JD |
259 | if (unlikely(task == current && |
260 | !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) { | |
aa6758d4 PBG |
261 | printk(KERN_ERR "get_tls_entry: task with pid %d got here " |
262 | "without flushed TLS.", current->pid); | |
263 | } | |
264 | ||
265 | return 0; | |
266 | clear: | |
ba180fd4 JD |
267 | /* |
268 | * When the TLS entry has not been set, the values read to user in the | |
aa6758d4 PBG |
269 | * tls_array are 0 (because it's cleared at boot, see |
270 | * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that. | |
271 | */ | |
272 | clear_user_desc(info); | |
273 | info->entry_number = idx; | |
274 | goto out; | |
275 | } | |
276 | ||
b2cf7707 | 277 | int sys_set_thread_area(struct user_desc __user *user_desc) |
aa6758d4 PBG |
278 | { |
279 | struct user_desc info; | |
280 | int idx, ret; | |
281 | ||
3feb8856 PBG |
282 | if (!host_supports_tls) |
283 | return -ENOSYS; | |
284 | ||
aa6758d4 PBG |
285 | if (copy_from_user(&info, user_desc, sizeof(info))) |
286 | return -EFAULT; | |
287 | ||
288 | idx = info.entry_number; | |
289 | ||
290 | if (idx == -1) { | |
291 | idx = get_free_idx(current); | |
292 | if (idx < 0) | |
293 | return idx; | |
294 | info.entry_number = idx; | |
295 | /* Tell the user which slot we chose for him.*/ | |
296 | if (put_user(idx, &user_desc->entry_number)) | |
297 | return -EFAULT; | |
298 | } | |
299 | ||
6aa802ce | 300 | ret = do_set_thread_area(&info); |
aa6758d4 PBG |
301 | if (ret) |
302 | return ret; | |
303 | return set_tls_entry(current, &info, idx, 1); | |
304 | } | |
305 | ||
306 | /* | |
307 | * Perform set_thread_area on behalf of the traced child. | |
308 | * Note: error handling is not done on the deferred load, and this differ from | |
309 | * i386. However the only possible error are caused by bugs. | |
310 | */ | |
311 | int ptrace_set_thread_area(struct task_struct *child, int idx, | |
b2cf7707 | 312 | struct user_desc __user *user_desc) |
aa6758d4 PBG |
313 | { |
314 | struct user_desc info; | |
315 | ||
3feb8856 PBG |
316 | if (!host_supports_tls) |
317 | return -EIO; | |
318 | ||
aa6758d4 PBG |
319 | if (copy_from_user(&info, user_desc, sizeof(info))) |
320 | return -EFAULT; | |
321 | ||
322 | return set_tls_entry(child, &info, idx, 0); | |
323 | } | |
324 | ||
b2cf7707 | 325 | int sys_get_thread_area(struct user_desc __user *user_desc) |
aa6758d4 PBG |
326 | { |
327 | struct user_desc info; | |
328 | int idx, ret; | |
329 | ||
3feb8856 PBG |
330 | if (!host_supports_tls) |
331 | return -ENOSYS; | |
332 | ||
aa6758d4 PBG |
333 | if (get_user(idx, &user_desc->entry_number)) |
334 | return -EFAULT; | |
335 | ||
336 | ret = get_tls_entry(current, &info, idx); | |
337 | if (ret < 0) | |
338 | goto out; | |
339 | ||
340 | if (copy_to_user(user_desc, &info, sizeof(info))) | |
341 | ret = -EFAULT; | |
342 | ||
343 | out: | |
344 | return ret; | |
345 | } | |
346 | ||
347 | /* | |
348 | * Perform get_thread_area on behalf of the traced child. | |
349 | */ | |
350 | int ptrace_get_thread_area(struct task_struct *child, int idx, | |
351 | struct user_desc __user *user_desc) | |
352 | { | |
353 | struct user_desc info; | |
354 | int ret; | |
355 | ||
3feb8856 PBG |
356 | if (!host_supports_tls) |
357 | return -EIO; | |
358 | ||
aa6758d4 PBG |
359 | ret = get_tls_entry(child, &info, idx); |
360 | if (ret < 0) | |
361 | goto out; | |
362 | ||
363 | if (copy_to_user(user_desc, &info, sizeof(info))) | |
364 | ret = -EFAULT; | |
365 | out: | |
366 | return ret; | |
367 | } | |
54d8d3b5 | 368 | |
ba180fd4 | 369 | /* |
b8bec829 JD |
370 | * This code is really i386-only, but it detects and logs x86_64 GDT indexes |
371 | * if a 32-bit UML is running on a 64-bit host. | |
ba180fd4 | 372 | */ |
65a58ab0 JD |
373 | static int __init __setup_host_supports_tls(void) |
374 | { | |
3feb8856 PBG |
375 | check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min); |
376 | if (host_supports_tls) { | |
377 | printk(KERN_INFO "Host TLS support detected\n"); | |
378 | printk(KERN_INFO "Detected host type: "); | |
379 | switch (host_gdt_entry_tls_min) { | |
b8bec829 JD |
380 | case GDT_ENTRY_TLS_MIN_I386: |
381 | printk(KERN_CONT "i386"); | |
382 | break; | |
383 | case GDT_ENTRY_TLS_MIN_X86_64: | |
384 | printk(KERN_CONT "x86_64"); | |
385 | break; | |
3feb8856 | 386 | } |
b8bec829 JD |
387 | printk(KERN_CONT " (GDT indexes %d to %d)\n", |
388 | host_gdt_entry_tls_min, | |
389 | host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES); | |
3feb8856 PBG |
390 | } else |
391 | printk(KERN_ERR " Host TLS support NOT detected! " | |
392 | "TLS support inside UML will not work\n"); | |
a5d2f46a | 393 | return 0; |
3feb8856 PBG |
394 | } |
395 | ||
396 | __initcall(__setup_host_supports_tls); |