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Chris Zankel3f65ce42005-06-23 22:01:24 -07001// TODO VM_EXEC flag work-around, cache aliasing
2/*
3 * arch/xtensa/mm/fault.c
4 *
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License. See the file "COPYING" in the main directory of this archive
7 * for more details.
8 *
Marc Gauthier1bbedc32012-10-15 03:55:36 +04009 * Copyright (C) 2001 - 2010 Tensilica Inc.
Chris Zankel3f65ce42005-06-23 22:01:24 -070010 *
11 * Chris Zankel <chris@zankel.net>
12 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
13 */
14
15#include <linux/mm.h>
16#include <linux/module.h>
Alexey Dobriyan5a891ed2009-03-10 12:55:49 -070017#include <linux/hardirq.h>
David Hildenbrand70ffdb92015-05-11 17:52:11 +020018#include <linux/uaccess.h>
Chris Zankel3f65ce42005-06-23 22:01:24 -070019#include <asm/mmu_context.h>
20#include <asm/cacheflush.h>
21#include <asm/hardirq.h>
Chris Zankel3f65ce42005-06-23 22:01:24 -070022#include <asm/pgalloc.h>
23
Max Filippovf6151362013-10-17 02:42:26 +040024DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
Chris Zankel3f65ce42005-06-23 22:01:24 -070025void bad_page_fault(struct pt_regs*, unsigned long, int);
26
Chris Zankel66569202007-08-22 10:14:51 -070027#undef DEBUG_PAGE_FAULT
28
Chris Zankel3f65ce42005-06-23 22:01:24 -070029/*
30 * This routine handles page faults. It determines the address,
31 * and the problem, and then passes it off to one of the appropriate
32 * routines.
33 *
34 * Note: does not handle Miss and MultiHit.
35 */
36
37void do_page_fault(struct pt_regs *regs)
38{
39 struct vm_area_struct * vma;
40 struct mm_struct *mm = current->mm;
41 unsigned int exccause = regs->exccause;
42 unsigned int address = regs->excvaddr;
43 siginfo_t info;
44
45 int is_write, is_exec;
Nick Piggin83c54072007-07-19 01:47:05 -070046 int fault;
Kautuk Consulf1077012012-07-30 14:39:21 -070047 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
Chris Zankel3f65ce42005-06-23 22:01:24 -070048
49 info.si_code = SEGV_MAPERR;
50
51 /* We fault-in kernel-space virtual memory on-demand. The
52 * 'reference' page table is init_mm.pgd.
53 */
54 if (address >= TASK_SIZE && !user_mode(regs))
55 goto vmalloc_fault;
56
57 /* If we're in an interrupt or have no user
58 * context, we must not take the fault..
59 */
David Hildenbrand70ffdb92015-05-11 17:52:11 +020060 if (faulthandler_disabled() || !mm) {
Chris Zankel3f65ce42005-06-23 22:01:24 -070061 bad_page_fault(regs, address, SIGSEGV);
62 return;
63 }
64
Chris Zankel173d66812006-12-10 02:18:48 -080065 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
66 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
67 exccause == EXCCAUSE_ITLB_MISS ||
68 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
Chris Zankel3f65ce42005-06-23 22:01:24 -070069
Chris Zankel66569202007-08-22 10:14:51 -070070#ifdef DEBUG_PAGE_FAULT
Chris Zankel3f65ce42005-06-23 22:01:24 -070071 printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
72 address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
73#endif
74
Johannes Weiner759496b2013-09-12 15:13:39 -070075 if (user_mode(regs))
76 flags |= FAULT_FLAG_USER;
Kautuk Consulf1077012012-07-30 14:39:21 -070077retry:
Chris Zankel3f65ce42005-06-23 22:01:24 -070078 down_read(&mm->mmap_sem);
79 vma = find_vma(mm, address);
80
81 if (!vma)
82 goto bad_area;
83 if (vma->vm_start <= address)
84 goto good_area;
85 if (!(vma->vm_flags & VM_GROWSDOWN))
86 goto bad_area;
87 if (expand_stack(vma, address))
88 goto bad_area;
89
90 /* Ok, we have a good vm_area for this memory access, so
91 * we can handle it..
92 */
93
94good_area:
95 info.si_code = SEGV_ACCERR;
96
97 if (is_write) {
98 if (!(vma->vm_flags & VM_WRITE))
99 goto bad_area;
Kautuk Consulf1077012012-07-30 14:39:21 -0700100 flags |= FAULT_FLAG_WRITE;
Chris Zankel3f65ce42005-06-23 22:01:24 -0700101 } else if (is_exec) {
102 if (!(vma->vm_flags & VM_EXEC))
103 goto bad_area;
104 } else /* Allow read even from write-only pages. */
105 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
106 goto bad_area;
107
108 /* If for any reason at all we couldn't handle the fault,
109 * make sure we exit gracefully rather than endlessly redo
110 * the fault.
111 */
Kautuk Consulf1077012012-07-30 14:39:21 -0700112 fault = handle_mm_fault(mm, vma, address, flags);
113
114 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
115 return;
116
Nick Piggin83c54072007-07-19 01:47:05 -0700117 if (unlikely(fault & VM_FAULT_ERROR)) {
118 if (fault & VM_FAULT_OOM)
119 goto out_of_memory;
Linus Torvalds33692f22015-01-29 10:51:32 -0800120 else if (fault & VM_FAULT_SIGSEGV)
121 goto bad_area;
Nick Piggin83c54072007-07-19 01:47:05 -0700122 else if (fault & VM_FAULT_SIGBUS)
123 goto do_sigbus;
Chris Zankel3f65ce42005-06-23 22:01:24 -0700124 BUG();
125 }
Kautuk Consulf1077012012-07-30 14:39:21 -0700126 if (flags & FAULT_FLAG_ALLOW_RETRY) {
127 if (fault & VM_FAULT_MAJOR)
128 current->maj_flt++;
129 else
130 current->min_flt++;
131 if (fault & VM_FAULT_RETRY) {
132 flags &= ~FAULT_FLAG_ALLOW_RETRY;
Shaohua Li45cac652012-10-08 16:32:19 -0700133 flags |= FAULT_FLAG_TRIED;
Kautuk Consulf1077012012-07-30 14:39:21 -0700134
135 /* No need to up_read(&mm->mmap_sem) as we would
136 * have already released it in __lock_page_or_retry
137 * in mm/filemap.c.
138 */
139
140 goto retry;
141 }
142 }
Chris Zankel3f65ce42005-06-23 22:01:24 -0700143
144 up_read(&mm->mmap_sem);
145 return;
146
147 /* Something tried to access memory that isn't in our memory map..
148 * Fix it, but check if it's kernel or user first..
149 */
150bad_area:
151 up_read(&mm->mmap_sem);
152 if (user_mode(regs)) {
153 current->thread.bad_vaddr = address;
154 current->thread.error_code = is_write;
155 info.si_signo = SIGSEGV;
156 info.si_errno = 0;
157 /* info.si_code has been set above */
158 info.si_addr = (void *) address;
159 force_sig_info(SIGSEGV, &info, current);
160 return;
161 }
162 bad_page_fault(regs, address, SIGSEGV);
163 return;
164
165
166 /* We ran out of memory, or some other thing happened to us that made
167 * us unable to handle the page fault gracefully.
168 */
169out_of_memory:
170 up_read(&mm->mmap_sem);
Nick Pigginf76f5d72010-06-04 14:14:51 -0700171 if (!user_mode(regs))
172 bad_page_fault(regs, address, SIGKILL);
173 else
174 pagefault_out_of_memory();
Chris Zankel3f65ce42005-06-23 22:01:24 -0700175 return;
176
177do_sigbus:
178 up_read(&mm->mmap_sem);
179
180 /* Send a sigbus, regardless of whether we were in kernel
181 * or user mode.
182 */
183 current->thread.bad_vaddr = address;
184 info.si_code = SIGBUS;
185 info.si_errno = 0;
186 info.si_code = BUS_ADRERR;
187 info.si_addr = (void *) address;
188 force_sig_info(SIGBUS, &info, current);
189
190 /* Kernel mode? Handle exceptions or die */
191 if (!user_mode(regs))
192 bad_page_fault(regs, address, SIGBUS);
Marc Gauthier1bbedc32012-10-15 03:55:36 +0400193 return;
Chris Zankel3f65ce42005-06-23 22:01:24 -0700194
195vmalloc_fault:
196 {
197 /* Synchronize this task's top level page-table
198 * with the 'reference' page table.
199 */
200 struct mm_struct *act_mm = current->active_mm;
201 int index = pgd_index(address);
202 pgd_t *pgd, *pgd_k;
203 pmd_t *pmd, *pmd_k;
204 pte_t *pte_k;
205
206 if (act_mm == NULL)
207 goto bad_page_fault;
208
209 pgd = act_mm->pgd + index;
210 pgd_k = init_mm.pgd + index;
211
212 if (!pgd_present(*pgd_k))
213 goto bad_page_fault;
214
215 pgd_val(*pgd) = pgd_val(*pgd_k);
216
217 pmd = pmd_offset(pgd, address);
218 pmd_k = pmd_offset(pgd_k, address);
219 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
220 goto bad_page_fault;
221
222 pmd_val(*pmd) = pmd_val(*pmd_k);
223 pte_k = pte_offset_kernel(pmd_k, address);
224
225 if (!pte_present(*pte_k))
226 goto bad_page_fault;
227 return;
228 }
229bad_page_fault:
230 bad_page_fault(regs, address, SIGKILL);
231 return;
232}
233
234
235void
236bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
237{
238 extern void die(const char*, struct pt_regs*, long);
239 const struct exception_table_entry *entry;
240
241 /* Are we prepared to handle this kernel fault? */
242 if ((entry = search_exception_tables(regs->pc)) != NULL) {
Chris Zankel66569202007-08-22 10:14:51 -0700243#ifdef DEBUG_PAGE_FAULT
Chris Zankel3f65ce42005-06-23 22:01:24 -0700244 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
245 current->comm, regs->pc, entry->fixup);
246#endif
247 current->thread.bad_uaddr = address;
248 regs->pc = entry->fixup;
249 return;
250 }
251
252 /* Oops. The kernel tried to access some bad page. We'll have to
253 * terminate things with extreme prejudice.
254 */
255 printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
256 "address %08lx\n pc = %08lx, ra = %08lx\n",
257 address, regs->pc, regs->areg[0]);
258 die("Oops", regs, sig);
259 do_exit(sig);
260}