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/module.h>
21 #include <linux/sched.h>
22
23 #include <asm/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;
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 siginfo_t info;
56 int fault;
57
58 tsk = current;
59
60 /*
61 * We fault-in kernel-space virtual memory on-demand. The
62 * 'reference' page table is init_mm.pgd.
63 *
64 * NOTE! We MUST NOT take any locks for this case. We may
65 * be in an interrupt or a critical region, and should
66 * only copy the information from the master page table,
67 * nothing more.
68 *
69 * NOTE2: This is done so that, when updating the vmalloc
70 * mappings we don't have to walk all processes pgdirs and
71 * add the high mappings all at once. Instead we do it as they
72 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
73 * bit set so sometimes the TLB can use a lingering entry.
74 *
75 * This verifies that the fault happens in kernel space
76 * and that the fault was not a protection error.
77 */
78
79 if (address >= VMALLOC_START &&
80 (vector != 0x300 && vector != 0x400) &&
81 !user_mode(regs))
82 goto vmalloc_fault;
83
84 /* If exceptions were enabled, we can reenable them here */
85 if (user_mode(regs)) {
86 /* Exception was in userspace: reenable interrupts */
87 local_irq_enable();
88 } else {
89 /* If exception was in a syscall, then IRQ's may have
90 * been enabled or disabled. If they were enabled,
91 * reenable them.
92 */
93 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
94 local_irq_enable();
95 }
96
97 mm = tsk->mm;
98 info.si_code = SEGV_MAPERR;
99
100 /*
101 * If we're in an interrupt or have no user
102 * context, we must not take the fault..
103 */
104
105 if (in_interrupt() || !mm)
106 goto no_context;
107
108 down_read(&mm->mmap_sem);
109 vma = find_vma(mm, address);
110
111 if (!vma)
112 goto bad_area;
113
114 if (vma->vm_start <= address)
115 goto good_area;
116
117 if (!(vma->vm_flags & VM_GROWSDOWN))
118 goto bad_area;
119
120 if (user_mode(regs)) {
121 /*
122 * accessing the stack below usp is always a bug.
123 * we get page-aligned addresses so we can only check
124 * if we're within a page from usp, but that might be
125 * enough to catch brutal errors at least.
126 */
127 if (address + PAGE_SIZE < regs->sp)
128 goto bad_area;
129 }
130 if (expand_stack(vma, address))
131 goto bad_area;
132
133 /*
134 * Ok, we have a good vm_area for this memory access, so
135 * we can handle it..
136 */
137
138 good_area:
139 info.si_code = SEGV_ACCERR;
140
141 /* first do some preliminary protection checks */
142
143 if (write_acc) {
144 if (!(vma->vm_flags & VM_WRITE))
145 goto bad_area;
146 } else {
147 /* not present */
148 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
149 goto bad_area;
150 }
151
152 /* are we trying to execute nonexecutable area */
153 if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
154 goto bad_area;
155
156 /*
157 * If for any reason at all we couldn't handle the fault,
158 * make sure we exit gracefully rather than endlessly redo
159 * the fault.
160 */
161
162 fault = handle_mm_fault(mm, vma, address, write_acc);
163 if (unlikely(fault & VM_FAULT_ERROR)) {
164 if (fault & VM_FAULT_OOM)
165 goto out_of_memory;
166 else if (fault & VM_FAULT_SIGBUS)
167 goto do_sigbus;
168 BUG();
169 }
170 /*RGD modeled on Cris */
171 if (fault & VM_FAULT_MAJOR)
172 tsk->maj_flt++;
173 else
174 tsk->min_flt++;
175
176 up_read(&mm->mmap_sem);
177 return;
178
179 /*
180 * Something tried to access memory that isn't in our memory map..
181 * Fix it, but check if it's kernel or user first..
182 */
183
184 bad_area:
185 up_read(&mm->mmap_sem);
186
187 bad_area_nosemaphore:
188
189 /* User mode accesses just cause a SIGSEGV */
190
191 if (user_mode(regs)) {
192 info.si_signo = SIGSEGV;
193 info.si_errno = 0;
194 /* info.si_code has been set above */
195 info.si_addr = (void *)address;
196 force_sig_info(SIGSEGV, &info, tsk);
197 return;
198 }
199
200 no_context:
201
202 /* Are we prepared to handle this kernel fault?
203 *
204 * (The kernel has valid exception-points in the source
205 * when it acesses user-memory. When it fails in one
206 * of those points, we find it in a table and do a jump
207 * to some fixup code that loads an appropriate error
208 * code)
209 */
210
211 {
212 const struct exception_table_entry *entry;
213
214 __asm__ __volatile__("l.nop 42");
215
216 if ((entry = search_exception_tables(regs->pc)) != NULL) {
217 /* Adjust the instruction pointer in the stackframe */
218 regs->pc = entry->fixup;
219 return;
220 }
221 }
222
223 /*
224 * Oops. The kernel tried to access some bad page. We'll have to
225 * terminate things with extreme prejudice.
226 */
227
228 if ((unsigned long)(address) < PAGE_SIZE)
229 printk(KERN_ALERT
230 "Unable to handle kernel NULL pointer dereference");
231 else
232 printk(KERN_ALERT "Unable to handle kernel access");
233 printk(" at virtual address 0x%08lx\n", address);
234
235 die("Oops", regs, write_acc);
236
237 do_exit(SIGKILL);
238
239 /*
240 * We ran out of memory, or some other thing happened to us that made
241 * us unable to handle the page fault gracefully.
242 */
243
244 out_of_memory:
245 __asm__ __volatile__("l.nop 42");
246 __asm__ __volatile__("l.nop 1");
247
248 up_read(&mm->mmap_sem);
249 printk("VM: killing process %s\n", tsk->comm);
250 if (user_mode(regs))
251 do_exit(SIGKILL);
252 goto no_context;
253
254 do_sigbus:
255 up_read(&mm->mmap_sem);
256
257 /*
258 * Send a sigbus, regardless of whether we were in kernel
259 * or user mode.
260 */
261 info.si_signo = SIGBUS;
262 info.si_errno = 0;
263 info.si_code = BUS_ADRERR;
264 info.si_addr = (void *)address;
265 force_sig_info(SIGBUS, &info, tsk);
266
267 /* Kernel mode? Handle exceptions or die */
268 if (!user_mode(regs))
269 goto no_context;
270 return;
271
272 vmalloc_fault:
273 {
274 /*
275 * Synchronize this task's top level page-table
276 * with the 'reference' page table.
277 *
278 * Use current_pgd instead of tsk->active_mm->pgd
279 * since the latter might be unavailable if this
280 * code is executed in a misfortunately run irq
281 * (like inside schedule() between switch_mm and
282 * switch_to...).
283 */
284
285 int offset = pgd_index(address);
286 pgd_t *pgd, *pgd_k;
287 pud_t *pud, *pud_k;
288 pmd_t *pmd, *pmd_k;
289 pte_t *pte_k;
290
291 /*
292 phx_warn("do_page_fault(): vmalloc_fault will not work, "
293 "since current_pgd assign a proper value somewhere\n"
294 "anyhow we don't need this at the moment\n");
295
296 phx_mmu("vmalloc_fault");
297 */
298 pgd = (pgd_t *)current_pgd + offset;
299 pgd_k = init_mm.pgd + offset;
300
301 /* Since we're two-level, we don't need to do both
302 * set_pgd and set_pmd (they do the same thing). If
303 * we go three-level at some point, do the right thing
304 * with pgd_present and set_pgd here.
305 *
306 * Also, since the vmalloc area is global, we don't
307 * need to copy individual PTE's, it is enough to
308 * copy the pgd pointer into the pte page of the
309 * root task. If that is there, we'll find our pte if
310 * it exists.
311 */
312
313 pud = pud_offset(pgd, address);
314 pud_k = pud_offset(pgd_k, address);
315 if (!pud_present(*pud_k))
316 goto no_context;
317
318 pmd = pmd_offset(pud, address);
319 pmd_k = pmd_offset(pud_k, address);
320
321 if (!pmd_present(*pmd_k))
322 goto bad_area_nosemaphore;
323
324 set_pmd(pmd, *pmd_k);
325
326 /* Make sure the actual PTE exists as well to
327 * catch kernel vmalloc-area accesses to non-mapped
328 * addresses. If we don't do this, this will just
329 * silently loop forever.
330 */
331
332 pte_k = pte_offset_kernel(pmd_k, address);
333 if (!pte_present(*pte_k))
334 goto no_context;
335
336 return;
337 }
338 }
339