1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * OpenRISC fault.c
4 *
5 * Linux architectural port borrowing liberally from similar works of
6 * others. All original copyrights apply as per the original source
7 * declaration.
8 *
9 * Modifications for the OpenRISC architecture:
10 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
11 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
12 */
13
14 #include <linux/mm.h>
15 #include <linux/interrupt.h>
16 #include <linux/extable.h>
17 #include <linux/sched/signal.h>
18
19 #include <linux/uaccess.h>
20 #include <asm/siginfo.h>
21 #include <asm/signal.h>
22
23 #define NUM_TLB_ENTRIES 64
24 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
25
26 unsigned long pte_misses; /* updated by do_page_fault() */
27 unsigned long pte_errors; /* updated by do_page_fault() */
28
29 /* __PHX__ :: - check the vmalloc_fault in do_page_fault()
30 * - also look into include/asm-or32/mmu_context.h
31 */
32 volatile pgd_t *current_pgd[NR_CPUS];
33
34 extern void die(char *, struct pt_regs *, long);
35
36 /*
37 * This routine handles page faults. It determines the address,
38 * and the problem, and then passes it off to one of the appropriate
39 * routines.
40 *
41 * If this routine detects a bad access, it returns 1, otherwise it
42 * returns 0.
43 */
44
45 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
46 unsigned long vector, int write_acc)
47 {
48 struct task_struct *tsk;
49 struct mm_struct *mm;
50 struct vm_area_struct *vma;
51 int si_code;
52 vm_fault_t fault;
53 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
54
55 tsk = current;
56
57 /*
58 * We fault-in kernel-space virtual memory on-demand. The
59 * 'reference' page table is init_mm.pgd.
60 *
61 * NOTE! We MUST NOT take any locks for this case. We may
62 * be in an interrupt or a critical region, and should
63 * only copy the information from the master page table,
64 * nothing more.
65 *
66 * NOTE2: This is done so that, when updating the vmalloc
67 * mappings we don't have to walk all processes pgdirs and
68 * add the high mappings all at once. Instead we do it as they
69 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
70 * bit set so sometimes the TLB can use a lingering entry.
71 *
72 * This verifies that the fault happens in kernel space
73 * and that the fault was not a protection error.
74 */
75
76 if (address >= VMALLOC_START &&
77 (vector != 0x300 && vector != 0x400) &&
78 !user_mode(regs))
79 goto vmalloc_fault;
80
81 /* If exceptions were enabled, we can reenable them here */
82 if (user_mode(regs)) {
83 /* Exception was in userspace: reenable interrupts */
84 local_irq_enable();
85 flags |= FAULT_FLAG_USER;
86 } else {
87 /* If exception was in a syscall, then IRQ's may have
88 * been enabled or disabled. If they were enabled,
89 * reenable them.
90 */
91 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
92 local_irq_enable();
93 }
94
95 mm = tsk->mm;
96 si_code = SEGV_MAPERR;
97
98 /*
99 * If we're in an interrupt or have no user
100 * context, we must not take the fault..
101 */
102
103 if (in_interrupt() || !mm)
104 goto no_context;
105
106 retry:
107 down_read(&mm->mmap_sem);
108 vma = find_vma(mm, address);
109
110 if (!vma)
111 goto bad_area;
112
113 if (vma->vm_start <= address)
114 goto good_area;
115
116 if (!(vma->vm_flags & VM_GROWSDOWN))
117 goto bad_area;
118
119 if (user_mode(regs)) {
120 /*
121 * accessing the stack below usp is always a bug.
122 * we get page-aligned addresses so we can only check
123 * if we're within a page from usp, but that might be
124 * enough to catch brutal errors at least.
125 */
126 if (address + PAGE_SIZE < regs->sp)
127 goto bad_area;
128 }
129 if (expand_stack(vma, address))
130 goto bad_area;
131
132 /*
133 * Ok, we have a good vm_area for this memory access, so
134 * we can handle it..
135 */
136
137 good_area:
138 si_code = SEGV_ACCERR;
139
140 /* first do some preliminary protection checks */
141
142 if (write_acc) {
143 if (!(vma->vm_flags & VM_WRITE))
144 goto bad_area;
145 flags |= FAULT_FLAG_WRITE;
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(vma, address, flags);
163
164 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
165 return;
166
167 if (unlikely(fault & VM_FAULT_ERROR)) {
168 if (fault & VM_FAULT_OOM)
169 goto out_of_memory;
170 else if (fault & VM_FAULT_SIGSEGV)
171 goto bad_area;
172 else if (fault & VM_FAULT_SIGBUS)
173 goto do_sigbus;
174 BUG();
175 }
176
177 if (flags & FAULT_FLAG_ALLOW_RETRY) {
178 /*RGD modeled on Cris */
179 if (fault & VM_FAULT_MAJOR)
180 tsk->maj_flt++;
181 else
182 tsk->min_flt++;
183 if (fault & VM_FAULT_RETRY) {
184 flags &= ~FAULT_FLAG_ALLOW_RETRY;
185 flags |= FAULT_FLAG_TRIED;
186
187 /* No need to up_read(&mm->mmap_sem) as we would
188 * have already released it in __lock_page_or_retry
189 * in mm/filemap.c.
190 */
191
192 goto retry;
193 }
194 }
195
196 up_read(&mm->mmap_sem);
197 return;
198
199 /*
200 * Something tried to access memory that isn't in our memory map..
201 * Fix it, but check if it's kernel or user first..
202 */
203
204 bad_area:
205 up_read(&mm->mmap_sem);
206
207 bad_area_nosemaphore:
208
209 /* User mode accesses just cause a SIGSEGV */
210
211 if (user_mode(regs)) {
212 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
213 return;
214 }
215
216 no_context:
217
218 /* Are we prepared to handle this kernel fault?
219 *
220 * (The kernel has valid exception-points in the source
221 * when it acesses user-memory. When it fails in one
222 * of those points, we find it in a table and do a jump
223 * to some fixup code that loads an appropriate error
224 * code)
225 */
226
227 {
228 const struct exception_table_entry *entry;
229
230 __asm__ __volatile__("l.nop 42");
231
232 if ((entry = search_exception_tables(regs->pc)) != NULL) {
233 /* Adjust the instruction pointer in the stackframe */
234 regs->pc = entry->fixup;
235 return;
236 }
237 }
238
239 /*
240 * Oops. The kernel tried to access some bad page. We'll have to
241 * terminate things with extreme prejudice.
242 */
243
244 if ((unsigned long)(address) < PAGE_SIZE)
245 printk(KERN_ALERT
246 "Unable to handle kernel NULL pointer dereference");
247 else
248 printk(KERN_ALERT "Unable to handle kernel access");
249 printk(" at virtual address 0x%08lx\n", address);
250
251 die("Oops", regs, write_acc);
252
253 do_exit(SIGKILL);
254
255 /*
256 * We ran out of memory, or some other thing happened to us that made
257 * us unable to handle the page fault gracefully.
258 */
259
260 out_of_memory:
261 __asm__ __volatile__("l.nop 42");
262 __asm__ __volatile__("l.nop 1");
263
264 up_read(&mm->mmap_sem);
265 if (!user_mode(regs))
266 goto no_context;
267 pagefault_out_of_memory();
268 return;
269
270 do_sigbus:
271 up_read(&mm->mmap_sem);
272
273 /*
274 * Send a sigbus, regardless of whether we were in kernel
275 * or user mode.
276 */
277 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
278
279 /* Kernel mode? Handle exceptions or die */
280 if (!user_mode(regs))
281 goto no_context;
282 return;
283
284 vmalloc_fault:
285 {
286 /*
287 * Synchronize this task's top level page-table
288 * with the 'reference' page table.
289 *
290 * Use current_pgd instead of tsk->active_mm->pgd
291 * since the latter might be unavailable if this
292 * code is executed in a misfortunately run irq
293 * (like inside schedule() between switch_mm and
294 * switch_to...).
295 */
296
297 int offset = pgd_index(address);
298 pgd_t *pgd, *pgd_k;
299 pud_t *pud, *pud_k;
300 pmd_t *pmd, *pmd_k;
301 pte_t *pte_k;
302
303 /*
304 phx_warn("do_page_fault(): vmalloc_fault will not work, "
305 "since current_pgd assign a proper value somewhere\n"
306 "anyhow we don't need this at the moment\n");
307
308 phx_mmu("vmalloc_fault");
309 */
310 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
311 pgd_k = init_mm.pgd + offset;
312
313 /* Since we're two-level, we don't need to do both
314 * set_pgd and set_pmd (they do the same thing). If
315 * we go three-level at some point, do the right thing
316 * with pgd_present and set_pgd here.
317 *
318 * Also, since the vmalloc area is global, we don't
319 * need to copy individual PTE's, it is enough to
320 * copy the pgd pointer into the pte page of the
321 * root task. If that is there, we'll find our pte if
322 * it exists.
323 */
324
325 pud = pud_offset(pgd, address);
326 pud_k = pud_offset(pgd_k, address);
327 if (!pud_present(*pud_k))
328 goto no_context;
329
330 pmd = pmd_offset(pud, address);
331 pmd_k = pmd_offset(pud_k, address);
332
333 if (!pmd_present(*pmd_k))
334 goto bad_area_nosemaphore;
335
336 set_pmd(pmd, *pmd_k);
337
338 /* Make sure the actual PTE exists as well to
339 * catch kernel vmalloc-area accesses to non-mapped
340 * addresses. If we don't do this, this will just
341 * silently loop forever.
342 */
343
344 pte_k = pte_offset_kernel(pmd_k, address);
345 if (!pte_present(*pte_k))
346 goto no_context;
347
348 return;
349 }
350 }