1 // 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 *
9 * Copyright (C) 2001 - 2010 Tensilica Inc.
10 *
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/extable.h>
17 #include <linux/hardirq.h>
18 #include <linux/perf_event.h>
19 #include <linux/uaccess.h>
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/hardirq.h>
23 #include <asm/pgalloc.h>
24
25 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
26 void bad_page_fault(struct pt_regs*, unsigned long, int);
27
28 /*
29 * This routine handles page faults. It determines the address,
30 * and the problem, and then passes it off to one of the appropriate
31 * routines.
32 *
33 * Note: does not handle Miss and MultiHit.
34 */
35
do_page_fault(struct pt_regs * regs)36 void do_page_fault(struct pt_regs *regs)
37 {
38 struct vm_area_struct * vma;
39 struct mm_struct *mm = current->mm;
40 unsigned int exccause = regs->exccause;
41 unsigned int address = regs->excvaddr;
42 int code;
43
44 int is_write, is_exec;
45 vm_fault_t fault;
46 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
47
48 code = SEGV_MAPERR;
49
50 /* We fault-in kernel-space virtual memory on-demand. The
51 * 'reference' page table is init_mm.pgd.
52 */
53 if (address >= TASK_SIZE && !user_mode(regs))
54 goto vmalloc_fault;
55
56 /* If we're in an interrupt or have no user
57 * context, we must not take the fault..
58 */
59 if (faulthandler_disabled() || !mm) {
60 bad_page_fault(regs, address, SIGSEGV);
61 return;
62 }
63
64 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
65 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
66 exccause == EXCCAUSE_ITLB_MISS ||
67 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
68
69 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
70 current->comm, current->pid,
71 address, exccause, regs->pc,
72 is_write ? "w" : "", is_exec ? "x" : "");
73
74 if (user_mode(regs))
75 flags |= FAULT_FLAG_USER;
76 retry:
77 down_read(&mm->mmap_sem);
78 vma = find_vma(mm, address);
79
80 if (!vma)
81 goto bad_area;
82 if (vma->vm_start <= address)
83 goto good_area;
84 if (!(vma->vm_flags & VM_GROWSDOWN))
85 goto bad_area;
86 if (expand_stack(vma, address))
87 goto bad_area;
88
89 /* Ok, we have a good vm_area for this memory access, so
90 * we can handle it..
91 */
92
93 good_area:
94 code = SEGV_ACCERR;
95
96 if (is_write) {
97 if (!(vma->vm_flags & VM_WRITE))
98 goto bad_area;
99 flags |= FAULT_FLAG_WRITE;
100 } else if (is_exec) {
101 if (!(vma->vm_flags & VM_EXEC))
102 goto bad_area;
103 } else /* Allow read even from write-only pages. */
104 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
105 goto bad_area;
106
107 /* If for any reason at all we couldn't handle the fault,
108 * make sure we exit gracefully rather than endlessly redo
109 * the fault.
110 */
111 fault = handle_mm_fault(vma, address, flags);
112
113 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
114 return;
115
116 if (unlikely(fault & VM_FAULT_ERROR)) {
117 if (fault & VM_FAULT_OOM)
118 goto out_of_memory;
119 else if (fault & VM_FAULT_SIGSEGV)
120 goto bad_area;
121 else if (fault & VM_FAULT_SIGBUS)
122 goto do_sigbus;
123 BUG();
124 }
125 if (flags & FAULT_FLAG_ALLOW_RETRY) {
126 if (fault & VM_FAULT_MAJOR)
127 current->maj_flt++;
128 else
129 current->min_flt++;
130 if (fault & VM_FAULT_RETRY) {
131 flags &= ~FAULT_FLAG_ALLOW_RETRY;
132 flags |= FAULT_FLAG_TRIED;
133
134 /* No need to up_read(&mm->mmap_sem) as we would
135 * have already released it in __lock_page_or_retry
136 * in mm/filemap.c.
137 */
138
139 goto retry;
140 }
141 }
142
143 up_read(&mm->mmap_sem);
144 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
145 if (flags & VM_FAULT_MAJOR)
146 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
147 else
148 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
149
150 return;
151
152 /* Something tried to access memory that isn't in our memory map..
153 * Fix it, but check if it's kernel or user first..
154 */
155 bad_area:
156 up_read(&mm->mmap_sem);
157 if (user_mode(regs)) {
158 current->thread.bad_vaddr = address;
159 current->thread.error_code = is_write;
160 force_sig_fault(SIGSEGV, code, (void *) address);
161 return;
162 }
163 bad_page_fault(regs, address, SIGSEGV);
164 return;
165
166
167 /* We ran out of memory, or some other thing happened to us that made
168 * us unable to handle the page fault gracefully.
169 */
170 out_of_memory:
171 up_read(&mm->mmap_sem);
172 if (!user_mode(regs))
173 bad_page_fault(regs, address, SIGKILL);
174 else
175 pagefault_out_of_memory();
176 return;
177
178 do_sigbus:
179 up_read(&mm->mmap_sem);
180
181 /* Send a sigbus, regardless of whether we were in kernel
182 * or user mode.
183 */
184 current->thread.bad_vaddr = address;
185 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
186
187 /* Kernel mode? Handle exceptions or die */
188 if (!user_mode(regs))
189 bad_page_fault(regs, address, SIGBUS);
190 return;
191
192 vmalloc_fault:
193 {
194 /* Synchronize this task's top level page-table
195 * with the 'reference' page table.
196 */
197 struct mm_struct *act_mm = current->active_mm;
198 int index = pgd_index(address);
199 pgd_t *pgd, *pgd_k;
200 pmd_t *pmd, *pmd_k;
201 pte_t *pte_k;
202
203 if (act_mm == NULL)
204 goto bad_page_fault;
205
206 pgd = act_mm->pgd + index;
207 pgd_k = init_mm.pgd + index;
208
209 if (!pgd_present(*pgd_k))
210 goto bad_page_fault;
211
212 pgd_val(*pgd) = pgd_val(*pgd_k);
213
214 pmd = pmd_offset(pgd, address);
215 pmd_k = pmd_offset(pgd_k, address);
216 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
217 goto bad_page_fault;
218
219 pmd_val(*pmd) = pmd_val(*pmd_k);
220 pte_k = pte_offset_kernel(pmd_k, address);
221
222 if (!pte_present(*pte_k))
223 goto bad_page_fault;
224 return;
225 }
226 bad_page_fault:
227 bad_page_fault(regs, address, SIGKILL);
228 return;
229 }
230
231
232 void
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)233 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
234 {
235 extern void die(const char*, struct pt_regs*, long);
236 const struct exception_table_entry *entry;
237
238 /* Are we prepared to handle this kernel fault? */
239 if ((entry = search_exception_tables(regs->pc)) != NULL) {
240 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
241 current->comm, regs->pc, entry->fixup);
242 current->thread.bad_uaddr = address;
243 regs->pc = entry->fixup;
244 return;
245 }
246
247 /* Oops. The kernel tried to access some bad page. We'll have to
248 * terminate things with extreme prejudice.
249 */
250 pr_alert("Unable to handle kernel paging request at virtual "
251 "address %08lx\n pc = %08lx, ra = %08lx\n",
252 address, regs->pc, regs->areg[0]);
253 die("Oops", regs, sig);
254 do_exit(sig);
255 }
256