1 /*
2 * OpenRISC fault.c
3 *
4 * Linux architectural port borrowing liberally from similar works of
5 * others. All original copyrights apply as per the original source
6 * declaration.
7 *
8 * Modifications for the OpenRISC architecture:
9 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
10 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version
15 * 2 of the License, or (at your option) any later version.
16 */
17
18 #include <linux/mm.h>
19 #include <linux/interrupt.h>
20 #include <linux/extable.h>
21 #include <linux/sched/signal.h>
22
23 #include <linux/uaccess.h>
24 #include <asm/siginfo.h>
25 #include <asm/signal.h>
26
27 #define NUM_TLB_ENTRIES 64
28 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
29
30 unsigned long pte_misses; /* updated by do_page_fault() */
31 unsigned long pte_errors; /* updated by do_page_fault() */
32
33 /* __PHX__ :: - check the vmalloc_fault in do_page_fault()
34 * - also look into include/asm-or32/mmu_context.h
35 */
36 volatile pgd_t *current_pgd[NR_CPUS];
37
38 extern void die(char *, struct pt_regs *, long);
39
40 /*
41 * This routine handles page faults. It determines the address,
42 * and the problem, and then passes it off to one of the appropriate
43 * routines.
44 *
45 * If this routine detects a bad access, it returns 1, otherwise it
46 * returns 0.
47 */
48
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned long vector,int write_acc)49 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
50 unsigned long vector, int write_acc)
51 {
52 struct task_struct *tsk;
53 struct mm_struct *mm;
54 struct vm_area_struct *vma;
55 int si_code;
56 vm_fault_t fault;
57 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
58
59 tsk = current;
60
61 /*
62 * We fault-in kernel-space virtual memory on-demand. The
63 * 'reference' page table is init_mm.pgd.
64 *
65 * NOTE! We MUST NOT take any locks for this case. We may
66 * be in an interrupt or a critical region, and should
67 * only copy the information from the master page table,
68 * nothing more.
69 *
70 * NOTE2: This is done so that, when updating the vmalloc
71 * mappings we don't have to walk all processes pgdirs and
72 * add the high mappings all at once. Instead we do it as they
73 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
74 * bit set so sometimes the TLB can use a lingering entry.
75 *
76 * This verifies that the fault happens in kernel space
77 * and that the fault was not a protection error.
78 */
79
80 if (address >= VMALLOC_START &&
81 (vector != 0x300 && vector != 0x400) &&
82 !user_mode(regs))
83 goto vmalloc_fault;
84
85 /* If exceptions were enabled, we can reenable them here */
86 if (user_mode(regs)) {
87 /* Exception was in userspace: reenable interrupts */
88 local_irq_enable();
89 flags |= FAULT_FLAG_USER;
90 } else {
91 /* If exception was in a syscall, then IRQ's may have
92 * been enabled or disabled. If they were enabled,
93 * reenable them.
94 */
95 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
96 local_irq_enable();
97 }
98
99 mm = tsk->mm;
100 si_code = SEGV_MAPERR;
101
102 /*
103 * If we're in an interrupt or have no user
104 * context, we must not take the fault..
105 */
106
107 if (in_interrupt() || !mm)
108 goto no_context;
109
110 retry:
111 down_read(&mm->mmap_sem);
112 vma = find_vma(mm, address);
113
114 if (!vma)
115 goto bad_area;
116
117 if (vma->vm_start <= address)
118 goto good_area;
119
120 if (!(vma->vm_flags & VM_GROWSDOWN))
121 goto bad_area;
122
123 if (user_mode(regs)) {
124 /*
125 * accessing the stack below usp is always a bug.
126 * we get page-aligned addresses so we can only check
127 * if we're within a page from usp, but that might be
128 * enough to catch brutal errors at least.
129 */
130 if (address + PAGE_SIZE < regs->sp)
131 goto bad_area;
132 }
133 if (expand_stack(vma, address))
134 goto bad_area;
135
136 /*
137 * Ok, we have a good vm_area for this memory access, so
138 * we can handle it..
139 */
140
141 good_area:
142 si_code = SEGV_ACCERR;
143
144 /* first do some preliminary protection checks */
145
146 if (write_acc) {
147 if (!(vma->vm_flags & VM_WRITE))
148 goto bad_area;
149 flags |= FAULT_FLAG_WRITE;
150 } else {
151 /* not present */
152 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
153 goto bad_area;
154 }
155
156 /* are we trying to execute nonexecutable area */
157 if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
158 goto bad_area;
159
160 /*
161 * If for any reason at all we couldn't handle the fault,
162 * make sure we exit gracefully rather than endlessly redo
163 * the fault.
164 */
165
166 fault = handle_mm_fault(vma, address, flags);
167
168 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
169 return;
170
171 if (unlikely(fault & VM_FAULT_ERROR)) {
172 if (fault & VM_FAULT_OOM)
173 goto out_of_memory;
174 else if (fault & VM_FAULT_SIGSEGV)
175 goto bad_area;
176 else if (fault & VM_FAULT_SIGBUS)
177 goto do_sigbus;
178 BUG();
179 }
180
181 if (flags & FAULT_FLAG_ALLOW_RETRY) {
182 /*RGD modeled on Cris */
183 if (fault & VM_FAULT_MAJOR)
184 tsk->maj_flt++;
185 else
186 tsk->min_flt++;
187 if (fault & VM_FAULT_RETRY) {
188 flags &= ~FAULT_FLAG_ALLOW_RETRY;
189 flags |= FAULT_FLAG_TRIED;
190
191 /* No need to up_read(&mm->mmap_sem) as we would
192 * have already released it in __lock_page_or_retry
193 * in mm/filemap.c.
194 */
195
196 goto retry;
197 }
198 }
199
200 up_read(&mm->mmap_sem);
201 return;
202
203 /*
204 * Something tried to access memory that isn't in our memory map..
205 * Fix it, but check if it's kernel or user first..
206 */
207
208 bad_area:
209 up_read(&mm->mmap_sem);
210
211 bad_area_nosemaphore:
212
213 /* User mode accesses just cause a SIGSEGV */
214
215 if (user_mode(regs)) {
216 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk);
217 return;
218 }
219
220 no_context:
221
222 /* Are we prepared to handle this kernel fault?
223 *
224 * (The kernel has valid exception-points in the source
225 * when it acesses user-memory. When it fails in one
226 * of those points, we find it in a table and do a jump
227 * to some fixup code that loads an appropriate error
228 * code)
229 */
230
231 {
232 const struct exception_table_entry *entry;
233
234 __asm__ __volatile__("l.nop 42");
235
236 if ((entry = search_exception_tables(regs->pc)) != NULL) {
237 /* Adjust the instruction pointer in the stackframe */
238 regs->pc = entry->fixup;
239 return;
240 }
241 }
242
243 /*
244 * Oops. The kernel tried to access some bad page. We'll have to
245 * terminate things with extreme prejudice.
246 */
247
248 if ((unsigned long)(address) < PAGE_SIZE)
249 printk(KERN_ALERT
250 "Unable to handle kernel NULL pointer dereference");
251 else
252 printk(KERN_ALERT "Unable to handle kernel access");
253 printk(" at virtual address 0x%08lx\n", address);
254
255 die("Oops", regs, write_acc);
256
257 do_exit(SIGKILL);
258
259 /*
260 * We ran out of memory, or some other thing happened to us that made
261 * us unable to handle the page fault gracefully.
262 */
263
264 out_of_memory:
265 __asm__ __volatile__("l.nop 42");
266 __asm__ __volatile__("l.nop 1");
267
268 up_read(&mm->mmap_sem);
269 if (!user_mode(regs))
270 goto no_context;
271 pagefault_out_of_memory();
272 return;
273
274 do_sigbus:
275 up_read(&mm->mmap_sem);
276
277 /*
278 * Send a sigbus, regardless of whether we were in kernel
279 * or user mode.
280 */
281 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk);
282
283 /* Kernel mode? Handle exceptions or die */
284 if (!user_mode(regs))
285 goto no_context;
286 return;
287
288 vmalloc_fault:
289 {
290 /*
291 * Synchronize this task's top level page-table
292 * with the 'reference' page table.
293 *
294 * Use current_pgd instead of tsk->active_mm->pgd
295 * since the latter might be unavailable if this
296 * code is executed in a misfortunately run irq
297 * (like inside schedule() between switch_mm and
298 * switch_to...).
299 */
300
301 int offset = pgd_index(address);
302 pgd_t *pgd, *pgd_k;
303 pud_t *pud, *pud_k;
304 pmd_t *pmd, *pmd_k;
305 pte_t *pte_k;
306
307 /*
308 phx_warn("do_page_fault(): vmalloc_fault will not work, "
309 "since current_pgd assign a proper value somewhere\n"
310 "anyhow we don't need this at the moment\n");
311
312 phx_mmu("vmalloc_fault");
313 */
314 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
315 pgd_k = init_mm.pgd + offset;
316
317 /* Since we're two-level, we don't need to do both
318 * set_pgd and set_pmd (they do the same thing). If
319 * we go three-level at some point, do the right thing
320 * with pgd_present and set_pgd here.
321 *
322 * Also, since the vmalloc area is global, we don't
323 * need to copy individual PTE's, it is enough to
324 * copy the pgd pointer into the pte page of the
325 * root task. If that is there, we'll find our pte if
326 * it exists.
327 */
328
329 pud = pud_offset(pgd, address);
330 pud_k = pud_offset(pgd_k, address);
331 if (!pud_present(*pud_k))
332 goto no_context;
333
334 pmd = pmd_offset(pud, address);
335 pmd_k = pmd_offset(pud_k, address);
336
337 if (!pmd_present(*pmd_k))
338 goto bad_area_nosemaphore;
339
340 set_pmd(pmd, *pmd_k);
341
342 /* Make sure the actual PTE exists as well to
343 * catch kernel vmalloc-area accesses to non-mapped
344 * addresses. If we don't do this, this will just
345 * silently loop forever.
346 */
347
348 pte_k = pte_offset_kernel(pmd_k, address);
349 if (!pte_present(*pte_k))
350 goto no_context;
351
352 return;
353 }
354 }
355
