]>
Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
1da177e4 LT |
2 | * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds |
3 | * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> | |
4 | * Copyright (C) 2002 Andi Kleen | |
78aa1f66 | 5 | * |
1da177e4 | 6 | * This handles calls from both 32bit and 64bit mode. |
bf7ee649 PZ |
7 | * |
8 | * Lock order: | |
9 | * contex.ldt_usr_sem | |
10 | * mmap_sem | |
11 | * context.lock | |
1da177e4 LT |
12 | */ |
13 | ||
14 | #include <linux/errno.h> | |
5a0e3ad6 | 15 | #include <linux/gfp.h> |
1da177e4 LT |
16 | #include <linux/sched.h> |
17 | #include <linux/string.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/smp.h> | |
d865f635 | 20 | #include <linux/syscalls.h> |
37868fe1 | 21 | #include <linux/slab.h> |
1da177e4 | 22 | #include <linux/vmalloc.h> |
423a5405 | 23 | #include <linux/uaccess.h> |
1da177e4 | 24 | |
1da177e4 | 25 | #include <asm/ldt.h> |
c2506438 | 26 | #include <asm/tlb.h> |
1da177e4 | 27 | #include <asm/desc.h> |
70f5088d | 28 | #include <asm/mmu_context.h> |
bbc1f698 | 29 | #include <asm/syscalls.h> |
1da177e4 | 30 | |
295cb0b0 AL |
31 | static void refresh_ldt_segments(void) |
32 | { | |
33 | #ifdef CONFIG_X86_64 | |
34 | unsigned short sel; | |
35 | ||
36 | /* | |
37 | * Make sure that the cached DS and ES descriptors match the updated | |
38 | * LDT. | |
39 | */ | |
40 | savesegment(ds, sel); | |
41 | if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) | |
42 | loadsegment(ds, sel); | |
43 | ||
44 | savesegment(es, sel); | |
45 | if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) | |
46 | loadsegment(es, sel); | |
47 | #endif | |
48 | } | |
49 | ||
bf7ee649 | 50 | /* context.lock is held by the task which issued the smp function call */ |
3d28ebce | 51 | static void flush_ldt(void *__mm) |
1da177e4 | 52 | { |
3d28ebce | 53 | struct mm_struct *mm = __mm; |
37868fe1 | 54 | |
3d28ebce | 55 | if (this_cpu_read(cpu_tlbstate.loaded_mm) != mm) |
37868fe1 AL |
56 | return; |
57 | ||
c2506438 | 58 | load_mm_ldt(mm); |
295cb0b0 AL |
59 | |
60 | refresh_ldt_segments(); | |
1da177e4 | 61 | } |
1da177e4 | 62 | |
37868fe1 | 63 | /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */ |
bbf79d21 | 64 | static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) |
1da177e4 | 65 | { |
37868fe1 | 66 | struct ldt_struct *new_ldt; |
990e9dc3 | 67 | unsigned int alloc_size; |
37868fe1 | 68 | |
bbf79d21 | 69 | if (num_entries > LDT_ENTRIES) |
37868fe1 AL |
70 | return NULL; |
71 | ||
72 | new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL); | |
73 | if (!new_ldt) | |
74 | return NULL; | |
75 | ||
76 | BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct)); | |
bbf79d21 | 77 | alloc_size = num_entries * LDT_ENTRY_SIZE; |
37868fe1 AL |
78 | |
79 | /* | |
80 | * Xen is very picky: it requires a page-aligned LDT that has no | |
81 | * trailing nonzero bytes in any page that contains LDT descriptors. | |
82 | * Keep it simple: zero the whole allocation and never allocate less | |
83 | * than PAGE_SIZE. | |
84 | */ | |
85 | if (alloc_size > PAGE_SIZE) | |
86 | new_ldt->entries = vzalloc(alloc_size); | |
1da177e4 | 87 | else |
f454b478 | 88 | new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL); |
1da177e4 | 89 | |
37868fe1 AL |
90 | if (!new_ldt->entries) { |
91 | kfree(new_ldt); | |
92 | return NULL; | |
93 | } | |
77e463d1 | 94 | |
c2506438 AL |
95 | /* The new LDT isn't aliased for PTI yet. */ |
96 | new_ldt->slot = -1; | |
97 | ||
bbf79d21 | 98 | new_ldt->nr_entries = num_entries; |
37868fe1 AL |
99 | return new_ldt; |
100 | } | |
38ffbe66 | 101 | |
c2506438 AL |
102 | /* |
103 | * If PTI is enabled, this maps the LDT into the kernelmode and | |
104 | * usermode tables for the given mm. | |
105 | * | |
106 | * There is no corresponding unmap function. Even if the LDT is freed, we | |
107 | * leave the PTEs around until the slot is reused or the mm is destroyed. | |
108 | * This is harmless: the LDT is always in ordinary memory, and no one will | |
109 | * access the freed slot. | |
110 | * | |
111 | * If we wanted to unmap freed LDTs, we'd also need to do a flush to make | |
112 | * it useful, and the flush would slow down modify_ldt(). | |
113 | */ | |
114 | static int | |
115 | map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) | |
116 | { | |
117 | #ifdef CONFIG_PAGE_TABLE_ISOLATION | |
118 | bool is_vmalloc, had_top_level_entry; | |
119 | unsigned long va; | |
120 | spinlock_t *ptl; | |
121 | pgd_t *pgd; | |
122 | int i; | |
123 | ||
124 | if (!static_cpu_has(X86_FEATURE_PTI)) | |
125 | return 0; | |
126 | ||
127 | /* | |
128 | * Any given ldt_struct should have map_ldt_struct() called at most | |
129 | * once. | |
130 | */ | |
131 | WARN_ON(ldt->slot != -1); | |
132 | ||
133 | /* | |
134 | * Did we already have the top level entry allocated? We can't | |
135 | * use pgd_none() for this because it doens't do anything on | |
136 | * 4-level page table kernels. | |
137 | */ | |
138 | pgd = pgd_offset(mm, LDT_BASE_ADDR); | |
139 | had_top_level_entry = (pgd->pgd != 0); | |
140 | ||
141 | is_vmalloc = is_vmalloc_addr(ldt->entries); | |
142 | ||
143 | for (i = 0; i * PAGE_SIZE < ldt->nr_entries * LDT_ENTRY_SIZE; i++) { | |
144 | unsigned long offset = i << PAGE_SHIFT; | |
145 | const void *src = (char *)ldt->entries + offset; | |
146 | unsigned long pfn; | |
147 | pte_t pte, *ptep; | |
148 | ||
149 | va = (unsigned long)ldt_slot_va(slot) + offset; | |
150 | pfn = is_vmalloc ? vmalloc_to_pfn(src) : | |
151 | page_to_pfn(virt_to_page(src)); | |
152 | /* | |
153 | * Treat the PTI LDT range as a *userspace* range. | |
154 | * get_locked_pte() will allocate all needed pagetables | |
155 | * and account for them in this mm. | |
156 | */ | |
157 | ptep = get_locked_pte(mm, va, &ptl); | |
158 | if (!ptep) | |
159 | return -ENOMEM; | |
f4b13d6f TG |
160 | /* |
161 | * Map it RO so the easy to find address is not a primary | |
162 | * target via some kernel interface which misses a | |
163 | * permission check. | |
164 | */ | |
165 | pte = pfn_pte(pfn, __pgprot(__PAGE_KERNEL_RO & ~_PAGE_GLOBAL)); | |
c2506438 AL |
166 | set_pte_at(mm, va, ptep, pte); |
167 | pte_unmap_unlock(ptep, ptl); | |
168 | } | |
169 | ||
170 | if (mm->context.ldt) { | |
171 | /* | |
172 | * We already had an LDT. The top-level entry should already | |
173 | * have been allocated and synchronized with the usermode | |
174 | * tables. | |
175 | */ | |
176 | WARN_ON(!had_top_level_entry); | |
177 | if (static_cpu_has(X86_FEATURE_PTI)) | |
178 | WARN_ON(!kernel_to_user_pgdp(pgd)->pgd); | |
179 | } else { | |
180 | /* | |
181 | * This is the first time we're mapping an LDT for this process. | |
182 | * Sync the pgd to the usermode tables. | |
183 | */ | |
184 | WARN_ON(had_top_level_entry); | |
185 | if (static_cpu_has(X86_FEATURE_PTI)) { | |
186 | WARN_ON(kernel_to_user_pgdp(pgd)->pgd); | |
187 | set_pgd(kernel_to_user_pgdp(pgd), *pgd); | |
188 | } | |
189 | } | |
190 | ||
191 | va = (unsigned long)ldt_slot_va(slot); | |
192 | flush_tlb_mm_range(mm, va, va + LDT_SLOT_STRIDE, 0); | |
193 | ||
194 | ldt->slot = slot; | |
195 | #endif | |
196 | return 0; | |
197 | } | |
198 | ||
199 | static void free_ldt_pgtables(struct mm_struct *mm) | |
200 | { | |
201 | #ifdef CONFIG_PAGE_TABLE_ISOLATION | |
202 | struct mmu_gather tlb; | |
203 | unsigned long start = LDT_BASE_ADDR; | |
204 | unsigned long end = start + (1UL << PGDIR_SHIFT); | |
205 | ||
206 | if (!static_cpu_has(X86_FEATURE_PTI)) | |
207 | return; | |
208 | ||
209 | tlb_gather_mmu(&tlb, mm, start, end); | |
210 | free_pgd_range(&tlb, start, end, start, end); | |
211 | tlb_finish_mmu(&tlb, start, end); | |
212 | #endif | |
213 | } | |
214 | ||
37868fe1 AL |
215 | /* After calling this, the LDT is immutable. */ |
216 | static void finalize_ldt_struct(struct ldt_struct *ldt) | |
217 | { | |
bbf79d21 | 218 | paravirt_alloc_ldt(ldt->entries, ldt->nr_entries); |
1da177e4 LT |
219 | } |
220 | ||
bf7ee649 | 221 | static void install_ldt(struct mm_struct *mm, struct ldt_struct *ldt) |
1da177e4 | 222 | { |
bf7ee649 PZ |
223 | mutex_lock(&mm->context.lock); |
224 | ||
7252704b | 225 | /* Synchronizes with READ_ONCE in load_mm_ldt. */ |
bf7ee649 | 226 | smp_store_release(&mm->context.ldt, ldt); |
37868fe1 | 227 | |
bf7ee649 PZ |
228 | /* Activate the LDT for all CPUs using currents mm. */ |
229 | on_each_cpu_mask(mm_cpumask(mm), flush_ldt, mm, true); | |
230 | ||
231 | mutex_unlock(&mm->context.lock); | |
37868fe1 | 232 | } |
78aa1f66 | 233 | |
37868fe1 AL |
234 | static void free_ldt_struct(struct ldt_struct *ldt) |
235 | { | |
236 | if (likely(!ldt)) | |
237 | return; | |
38ffbe66 | 238 | |
bbf79d21 BP |
239 | paravirt_free_ldt(ldt->entries, ldt->nr_entries); |
240 | if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE) | |
8d5341a6 | 241 | vfree_atomic(ldt->entries); |
37868fe1 | 242 | else |
f454b478 | 243 | free_page((unsigned long)ldt->entries); |
37868fe1 | 244 | kfree(ldt); |
1da177e4 LT |
245 | } |
246 | ||
247 | /* | |
f90d2542 TG |
248 | * Called on fork from arch_dup_mmap(). Just copy the current LDT state, |
249 | * the new task is not running, so nothing can be installed. | |
1da177e4 | 250 | */ |
f90d2542 | 251 | int ldt_dup_context(struct mm_struct *old_mm, struct mm_struct *mm) |
1da177e4 | 252 | { |
37868fe1 | 253 | struct ldt_struct *new_ldt; |
1da177e4 LT |
254 | int retval = 0; |
255 | ||
f90d2542 | 256 | if (!old_mm) |
37868fe1 | 257 | return 0; |
37868fe1 AL |
258 | |
259 | mutex_lock(&old_mm->context.lock); | |
f90d2542 | 260 | if (!old_mm->context.ldt) |
37868fe1 | 261 | goto out_unlock; |
37868fe1 | 262 | |
bbf79d21 | 263 | new_ldt = alloc_ldt_struct(old_mm->context.ldt->nr_entries); |
37868fe1 AL |
264 | if (!new_ldt) { |
265 | retval = -ENOMEM; | |
266 | goto out_unlock; | |
267 | } | |
268 | ||
269 | memcpy(new_ldt->entries, old_mm->context.ldt->entries, | |
bbf79d21 | 270 | new_ldt->nr_entries * LDT_ENTRY_SIZE); |
37868fe1 AL |
271 | finalize_ldt_struct(new_ldt); |
272 | ||
c2506438 AL |
273 | retval = map_ldt_struct(mm, new_ldt, 0); |
274 | if (retval) { | |
275 | free_ldt_pgtables(mm); | |
276 | free_ldt_struct(new_ldt); | |
277 | goto out_unlock; | |
278 | } | |
37868fe1 AL |
279 | mm->context.ldt = new_ldt; |
280 | ||
281 | out_unlock: | |
282 | mutex_unlock(&old_mm->context.lock); | |
1da177e4 LT |
283 | return retval; |
284 | } | |
285 | ||
286 | /* | |
77e463d1 TG |
287 | * No need to lock the MM as we are the last user |
288 | * | |
289 | * 64bit: Don't touch the LDT register - we're already in the next thread. | |
1da177e4 | 290 | */ |
39a0526f | 291 | void destroy_context_ldt(struct mm_struct *mm) |
1da177e4 | 292 | { |
37868fe1 AL |
293 | free_ldt_struct(mm->context.ldt); |
294 | mm->context.ldt = NULL; | |
1da177e4 LT |
295 | } |
296 | ||
c2506438 AL |
297 | void ldt_arch_exit_mmap(struct mm_struct *mm) |
298 | { | |
299 | free_ldt_pgtables(mm); | |
300 | } | |
301 | ||
78aa1f66 | 302 | static int read_ldt(void __user *ptr, unsigned long bytecount) |
1da177e4 | 303 | { |
78aa1f66 | 304 | struct mm_struct *mm = current->mm; |
bbf79d21 BP |
305 | unsigned long entries_size; |
306 | int retval; | |
1da177e4 | 307 | |
bf7ee649 | 308 | down_read(&mm->context.ldt_usr_sem); |
37868fe1 AL |
309 | |
310 | if (!mm->context.ldt) { | |
311 | retval = 0; | |
312 | goto out_unlock; | |
313 | } | |
314 | ||
78aa1f66 TG |
315 | if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES) |
316 | bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES; | |
1da177e4 | 317 | |
bbf79d21 BP |
318 | entries_size = mm->context.ldt->nr_entries * LDT_ENTRY_SIZE; |
319 | if (entries_size > bytecount) | |
320 | entries_size = bytecount; | |
1da177e4 | 321 | |
bbf79d21 | 322 | if (copy_to_user(ptr, mm->context.ldt->entries, entries_size)) { |
37868fe1 AL |
323 | retval = -EFAULT; |
324 | goto out_unlock; | |
325 | } | |
326 | ||
bbf79d21 | 327 | if (entries_size != bytecount) { |
37868fe1 | 328 | /* Zero-fill the rest and pretend we read bytecount bytes. */ |
bbf79d21 | 329 | if (clear_user(ptr + entries_size, bytecount - entries_size)) { |
37868fe1 AL |
330 | retval = -EFAULT; |
331 | goto out_unlock; | |
1da177e4 LT |
332 | } |
333 | } | |
37868fe1 AL |
334 | retval = bytecount; |
335 | ||
336 | out_unlock: | |
bf7ee649 | 337 | up_read(&mm->context.ldt_usr_sem); |
37868fe1 | 338 | return retval; |
1da177e4 LT |
339 | } |
340 | ||
78aa1f66 | 341 | static int read_default_ldt(void __user *ptr, unsigned long bytecount) |
1da177e4 | 342 | { |
77e463d1 TG |
343 | /* CHECKME: Can we use _one_ random number ? */ |
344 | #ifdef CONFIG_X86_32 | |
345 | unsigned long size = 5 * sizeof(struct desc_struct); | |
346 | #else | |
347 | unsigned long size = 128; | |
348 | #endif | |
349 | if (bytecount > size) | |
350 | bytecount = size; | |
1da177e4 LT |
351 | if (clear_user(ptr, bytecount)) |
352 | return -EFAULT; | |
78aa1f66 | 353 | return bytecount; |
1da177e4 LT |
354 | } |
355 | ||
78aa1f66 | 356 | static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) |
1da177e4 | 357 | { |
70f5088d | 358 | struct mm_struct *mm = current->mm; |
990e9dc3 | 359 | struct ldt_struct *new_ldt, *old_ldt; |
bbf79d21 | 360 | unsigned int old_nr_entries, new_nr_entries; |
990e9dc3 | 361 | struct user_desc ldt_info; |
5af72502 | 362 | struct desc_struct ldt; |
1da177e4 | 363 | int error; |
1da177e4 LT |
364 | |
365 | error = -EINVAL; | |
1da177e4 LT |
366 | if (bytecount != sizeof(ldt_info)) |
367 | goto out; | |
78aa1f66 | 368 | error = -EFAULT; |
70f5088d | 369 | if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info))) |
1da177e4 LT |
370 | goto out; |
371 | ||
372 | error = -EINVAL; | |
373 | if (ldt_info.entry_number >= LDT_ENTRIES) | |
374 | goto out; | |
375 | if (ldt_info.contents == 3) { | |
376 | if (oldmode) | |
377 | goto out; | |
378 | if (ldt_info.seg_not_present == 0) | |
379 | goto out; | |
380 | } | |
381 | ||
37868fe1 AL |
382 | if ((oldmode && !ldt_info.base_addr && !ldt_info.limit) || |
383 | LDT_empty(&ldt_info)) { | |
384 | /* The user wants to clear the entry. */ | |
385 | memset(&ldt, 0, sizeof(ldt)); | |
386 | } else { | |
387 | if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) { | |
388 | error = -EINVAL; | |
389 | goto out; | |
1da177e4 | 390 | } |
37868fe1 AL |
391 | |
392 | fill_ldt(&ldt, &ldt_info); | |
393 | if (oldmode) | |
394 | ldt.avl = 0; | |
1da177e4 LT |
395 | } |
396 | ||
bf7ee649 PZ |
397 | if (down_write_killable(&mm->context.ldt_usr_sem)) |
398 | return -EINTR; | |
37868fe1 | 399 | |
bbf79d21 BP |
400 | old_ldt = mm->context.ldt; |
401 | old_nr_entries = old_ldt ? old_ldt->nr_entries : 0; | |
402 | new_nr_entries = max(ldt_info.entry_number + 1, old_nr_entries); | |
37868fe1 AL |
403 | |
404 | error = -ENOMEM; | |
bbf79d21 | 405 | new_ldt = alloc_ldt_struct(new_nr_entries); |
37868fe1 | 406 | if (!new_ldt) |
34273f41 | 407 | goto out_unlock; |
34273f41 | 408 | |
37868fe1 | 409 | if (old_ldt) |
bbf79d21 BP |
410 | memcpy(new_ldt->entries, old_ldt->entries, old_nr_entries * LDT_ENTRY_SIZE); |
411 | ||
37868fe1 AL |
412 | new_ldt->entries[ldt_info.entry_number] = ldt; |
413 | finalize_ldt_struct(new_ldt); | |
1da177e4 | 414 | |
c2506438 AL |
415 | /* |
416 | * If we are using PTI, map the new LDT into the userspace pagetables. | |
417 | * If there is already an LDT, use the other slot so that other CPUs | |
418 | * will continue to use the old LDT until install_ldt() switches | |
419 | * them over to the new LDT. | |
420 | */ | |
421 | error = map_ldt_struct(mm, new_ldt, old_ldt ? !old_ldt->slot : 0); | |
422 | if (error) { | |
03d02494 TG |
423 | /* |
424 | * This only can fail for the first LDT setup. If an LDT is | |
425 | * already installed then the PTE page is already | |
426 | * populated. Mop up a half populated page table. | |
427 | */ | |
4e23d9d8 TG |
428 | if (!WARN_ON_ONCE(old_ldt)) |
429 | free_ldt_pgtables(mm); | |
03d02494 | 430 | free_ldt_struct(new_ldt); |
c2506438 AL |
431 | goto out_unlock; |
432 | } | |
433 | ||
37868fe1 AL |
434 | install_ldt(mm, new_ldt); |
435 | free_ldt_struct(old_ldt); | |
1da177e4 LT |
436 | error = 0; |
437 | ||
438 | out_unlock: | |
bf7ee649 | 439 | up_write(&mm->context.ldt_usr_sem); |
1da177e4 LT |
440 | out: |
441 | return error; | |
442 | } | |
443 | ||
d865f635 DH |
444 | SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr , |
445 | unsigned long , bytecount) | |
1da177e4 LT |
446 | { |
447 | int ret = -ENOSYS; | |
448 | ||
449 | switch (func) { | |
450 | case 0: | |
451 | ret = read_ldt(ptr, bytecount); | |
452 | break; | |
453 | case 1: | |
454 | ret = write_ldt(ptr, bytecount, 1); | |
455 | break; | |
456 | case 2: | |
457 | ret = read_default_ldt(ptr, bytecount); | |
458 | break; | |
459 | case 0x11: | |
460 | ret = write_ldt(ptr, bytecount, 0); | |
461 | break; | |
462 | } | |
d865f635 DH |
463 | /* |
464 | * The SYSCALL_DEFINE() macros give us an 'unsigned long' | |
465 | * return type, but tht ABI for sys_modify_ldt() expects | |
466 | * 'int'. This cast gives us an int-sized value in %rax | |
467 | * for the return code. The 'unsigned' is necessary so | |
468 | * the compiler does not try to sign-extend the negative | |
469 | * return codes into the high half of the register when | |
470 | * taking the value from int->long. | |
471 | */ | |
472 | return (unsigned int)ret; | |
1da177e4 | 473 | } |