x86: mm: Read cr2 before prefetching the mmap_lock
[linux-2.6] / arch / x86 / mm / hugetlbpage.c
1 /*
2  * IA-32 Huge TLB Page Support for Kernel.
3  *
4  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
5  */
6
7 #include <linux/init.h>
8 #include <linux/fs.h>
9 #include <linux/mm.h>
10 #include <linux/hugetlb.h>
11 #include <linux/pagemap.h>
12 #include <linux/slab.h>
13 #include <linux/err.h>
14 #include <linux/sysctl.h>
15 #include <asm/mman.h>
16 #include <asm/tlb.h>
17 #include <asm/tlbflush.h>
18 #include <asm/pgalloc.h>
19
20 static unsigned long page_table_shareable(struct vm_area_struct *svma,
21                                 struct vm_area_struct *vma,
22                                 unsigned long addr, pgoff_t idx)
23 {
24         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
25                                 svma->vm_start;
26         unsigned long sbase = saddr & PUD_MASK;
27         unsigned long s_end = sbase + PUD_SIZE;
28
29         /* Allow segments to share if only one is marked locked */
30         unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
31         unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
32
33         /*
34          * match the virtual addresses, permission and the alignment of the
35          * page table page.
36          */
37         if (pmd_index(addr) != pmd_index(saddr) ||
38             vm_flags != svm_flags ||
39             sbase < svma->vm_start || svma->vm_end < s_end)
40                 return 0;
41
42         return saddr;
43 }
44
45 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
46 {
47         unsigned long base = addr & PUD_MASK;
48         unsigned long end = base + PUD_SIZE;
49
50         /*
51          * check on proper vm_flags and page table alignment
52          */
53         if (vma->vm_flags & VM_MAYSHARE &&
54             vma->vm_start <= base && end <= vma->vm_end)
55                 return 1;
56         return 0;
57 }
58
59 /*
60  * search for a shareable pmd page for hugetlb.
61  */
62 static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
63 {
64         struct vm_area_struct *vma = find_vma(mm, addr);
65         struct address_space *mapping = vma->vm_file->f_mapping;
66         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
67                         vma->vm_pgoff;
68         struct prio_tree_iter iter;
69         struct vm_area_struct *svma;
70         unsigned long saddr;
71         pte_t *spte = NULL;
72
73         if (!vma_shareable(vma, addr))
74                 return;
75
76         spin_lock(&mapping->i_mmap_lock);
77         vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
78                 if (svma == vma)
79                         continue;
80
81                 saddr = page_table_shareable(svma, vma, addr, idx);
82                 if (saddr) {
83                         spte = huge_pte_offset(svma->vm_mm, saddr);
84                         if (spte) {
85                                 get_page(virt_to_page(spte));
86                                 break;
87                         }
88                 }
89         }
90
91         if (!spte)
92                 goto out;
93
94         spin_lock(&mm->page_table_lock);
95         if (pud_none(*pud))
96                 pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
97         else
98                 put_page(virt_to_page(spte));
99         spin_unlock(&mm->page_table_lock);
100 out:
101         spin_unlock(&mapping->i_mmap_lock);
102 }
103
104 /*
105  * unmap huge page backed by shared pte.
106  *
107  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
108  * indicated by page_count > 1, unmap is achieved by clearing pud and
109  * decrementing the ref count. If count == 1, the pte page is not shared.
110  *
111  * called with vma->vm_mm->page_table_lock held.
112  *
113  * returns: 1 successfully unmapped a shared pte page
114  *          0 the underlying pte page is not shared, or it is the last user
115  */
116 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
117 {
118         pgd_t *pgd = pgd_offset(mm, *addr);
119         pud_t *pud = pud_offset(pgd, *addr);
120
121         BUG_ON(page_count(virt_to_page(ptep)) == 0);
122         if (page_count(virt_to_page(ptep)) == 1)
123                 return 0;
124
125         pud_clear(pud);
126         put_page(virt_to_page(ptep));
127         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
128         return 1;
129 }
130
131 pte_t *huge_pte_alloc(struct mm_struct *mm,
132                         unsigned long addr, unsigned long sz)
133 {
134         pgd_t *pgd;
135         pud_t *pud;
136         pte_t *pte = NULL;
137
138         pgd = pgd_offset(mm, addr);
139         pud = pud_alloc(mm, pgd, addr);
140         if (pud) {
141                 if (sz == PUD_SIZE) {
142                         pte = (pte_t *)pud;
143                 } else {
144                         BUG_ON(sz != PMD_SIZE);
145                         if (pud_none(*pud))
146                                 huge_pmd_share(mm, addr, pud);
147                         pte = (pte_t *) pmd_alloc(mm, pud, addr);
148                 }
149         }
150         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
151
152         return pte;
153 }
154
155 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
156 {
157         pgd_t *pgd;
158         pud_t *pud;
159         pmd_t *pmd = NULL;
160
161         pgd = pgd_offset(mm, addr);
162         if (pgd_present(*pgd)) {
163                 pud = pud_offset(pgd, addr);
164                 if (pud_present(*pud)) {
165                         if (pud_large(*pud))
166                                 return (pte_t *)pud;
167                         pmd = pmd_offset(pud, addr);
168                 }
169         }
170         return (pte_t *) pmd;
171 }
172
173 #if 0   /* This is just for testing */
174 struct page *
175 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
176 {
177         unsigned long start = address;
178         int length = 1;
179         int nr;
180         struct page *page;
181         struct vm_area_struct *vma;
182
183         vma = find_vma(mm, addr);
184         if (!vma || !is_vm_hugetlb_page(vma))
185                 return ERR_PTR(-EINVAL);
186
187         pte = huge_pte_offset(mm, address);
188
189         /* hugetlb should be locked, and hence, prefaulted */
190         WARN_ON(!pte || pte_none(*pte));
191
192         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
193
194         WARN_ON(!PageHead(page));
195
196         return page;
197 }
198
199 int pmd_huge(pmd_t pmd)
200 {
201         return 0;
202 }
203
204 int pud_huge(pud_t pud)
205 {
206         return 0;
207 }
208
209 struct page *
210 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
211                 pmd_t *pmd, int write)
212 {
213         return NULL;
214 }
215
216 #else
217
218 struct page *
219 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
220 {
221         return ERR_PTR(-EINVAL);
222 }
223
224 int pmd_huge(pmd_t pmd)
225 {
226         return !!(pmd_val(pmd) & _PAGE_PSE);
227 }
228
229 int pud_huge(pud_t pud)
230 {
231         return !!(pud_val(pud) & _PAGE_PSE);
232 }
233
234 struct page *
235 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
236                 pmd_t *pmd, int write)
237 {
238         struct page *page;
239
240         page = pte_page(*(pte_t *)pmd);
241         if (page)
242                 page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
243         return page;
244 }
245
246 struct page *
247 follow_huge_pud(struct mm_struct *mm, unsigned long address,
248                 pud_t *pud, int write)
249 {
250         struct page *page;
251
252         page = pte_page(*(pte_t *)pud);
253         if (page)
254                 page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
255         return page;
256 }
257
258 #endif
259
260 /* x86_64 also uses this file */
261
262 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
263 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
264                 unsigned long addr, unsigned long len,
265                 unsigned long pgoff, unsigned long flags)
266 {
267         struct hstate *h = hstate_file(file);
268         struct mm_struct *mm = current->mm;
269         struct vm_area_struct *vma;
270         unsigned long start_addr;
271
272         if (len > mm->cached_hole_size) {
273                 start_addr = mm->free_area_cache;
274         } else {
275                 start_addr = TASK_UNMAPPED_BASE;
276                 mm->cached_hole_size = 0;
277         }
278
279 full_search:
280         addr = ALIGN(start_addr, huge_page_size(h));
281
282         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
283                 /* At this point:  (!vma || addr < vma->vm_end). */
284                 if (TASK_SIZE - len < addr) {
285                         /*
286                          * Start a new search - just in case we missed
287                          * some holes.
288                          */
289                         if (start_addr != TASK_UNMAPPED_BASE) {
290                                 start_addr = TASK_UNMAPPED_BASE;
291                                 mm->cached_hole_size = 0;
292                                 goto full_search;
293                         }
294                         return -ENOMEM;
295                 }
296                 if (!vma || addr + len <= vma->vm_start) {
297                         mm->free_area_cache = addr + len;
298                         return addr;
299                 }
300                 if (addr + mm->cached_hole_size < vma->vm_start)
301                         mm->cached_hole_size = vma->vm_start - addr;
302                 addr = ALIGN(vma->vm_end, huge_page_size(h));
303         }
304 }
305
306 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
307                 unsigned long addr0, unsigned long len,
308                 unsigned long pgoff, unsigned long flags)
309 {
310         struct hstate *h = hstate_file(file);
311         struct mm_struct *mm = current->mm;
312         struct vm_area_struct *vma, *prev_vma;
313         unsigned long base = mm->mmap_base, addr = addr0;
314         unsigned long largest_hole = mm->cached_hole_size;
315         int first_time = 1;
316
317         /* don't allow allocations above current base */
318         if (mm->free_area_cache > base)
319                 mm->free_area_cache = base;
320
321         if (len <= largest_hole) {
322                 largest_hole = 0;
323                 mm->free_area_cache  = base;
324         }
325 try_again:
326         /* make sure it can fit in the remaining address space */
327         if (mm->free_area_cache < len)
328                 goto fail;
329
330         /* either no address requested or cant fit in requested address hole */
331         addr = (mm->free_area_cache - len) & huge_page_mask(h);
332         do {
333                 /*
334                  * Lookup failure means no vma is above this address,
335                  * i.e. return with success:
336                  */
337                 if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
338                         return addr;
339
340                 /*
341                  * new region fits between prev_vma->vm_end and
342                  * vma->vm_start, use it:
343                  */
344                 if (addr + len <= vma->vm_start &&
345                             (!prev_vma || (addr >= prev_vma->vm_end))) {
346                         /* remember the address as a hint for next time */
347                         mm->cached_hole_size = largest_hole;
348                         return (mm->free_area_cache = addr);
349                 } else {
350                         /* pull free_area_cache down to the first hole */
351                         if (mm->free_area_cache == vma->vm_end) {
352                                 mm->free_area_cache = vma->vm_start;
353                                 mm->cached_hole_size = largest_hole;
354                         }
355                 }
356
357                 /* remember the largest hole we saw so far */
358                 if (addr + largest_hole < vma->vm_start)
359                         largest_hole = vma->vm_start - addr;
360
361                 /* try just below the current vma->vm_start */
362                 addr = (vma->vm_start - len) & huge_page_mask(h);
363         } while (len <= vma->vm_start);
364
365 fail:
366         /*
367          * if hint left us with no space for the requested
368          * mapping then try again:
369          */
370         if (first_time) {
371                 mm->free_area_cache = base;
372                 largest_hole = 0;
373                 first_time = 0;
374                 goto try_again;
375         }
376         /*
377          * A failed mmap() very likely causes application failure,
378          * so fall back to the bottom-up function here. This scenario
379          * can happen with large stack limits and large mmap()
380          * allocations.
381          */
382         mm->free_area_cache = TASK_UNMAPPED_BASE;
383         mm->cached_hole_size = ~0UL;
384         addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
385                         len, pgoff, flags);
386
387         /*
388          * Restore the topdown base:
389          */
390         mm->free_area_cache = base;
391         mm->cached_hole_size = ~0UL;
392
393         return addr;
394 }
395
396 unsigned long
397 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
398                 unsigned long len, unsigned long pgoff, unsigned long flags)
399 {
400         struct hstate *h = hstate_file(file);
401         struct mm_struct *mm = current->mm;
402         struct vm_area_struct *vma;
403
404         if (len & ~huge_page_mask(h))
405                 return -EINVAL;
406         if (len > TASK_SIZE)
407                 return -ENOMEM;
408
409         if (flags & MAP_FIXED) {
410                 if (prepare_hugepage_range(file, addr, len))
411                         return -EINVAL;
412                 return addr;
413         }
414
415         if (addr) {
416                 addr = ALIGN(addr, huge_page_size(h));
417                 vma = find_vma(mm, addr);
418                 if (TASK_SIZE - len >= addr &&
419                     (!vma || addr + len <= vma->vm_start))
420                         return addr;
421         }
422         if (mm->get_unmapped_area == arch_get_unmapped_area)
423                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
424                                 pgoff, flags);
425         else
426                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
427                                 pgoff, flags);
428 }
429
430 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
431
432 #ifdef CONFIG_X86_64
433 static __init int setup_hugepagesz(char *opt)
434 {
435         unsigned long ps = memparse(opt, &opt);
436         if (ps == PMD_SIZE) {
437                 hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
438         } else if (ps == PUD_SIZE && cpu_has_gbpages) {
439                 hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
440         } else {
441                 printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
442                         ps >> 20);
443                 return 0;
444         }
445         return 1;
446 }
447 __setup("hugepagesz=", setup_hugepagesz);
448 #endif