aboutsummaryrefslogtreecommitdiff
path: root/arch/openrisc/mm/fault.c
blob: d2224ccca2941f4777c3f4aee06eb02db39f1e98 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * OpenRISC fault.c
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 */

#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/extable.h>
#include <linux/sched/signal.h>

#include <linux/uaccess.h>
#include <asm/siginfo.h>
#include <asm/signal.h>

#define NUM_TLB_ENTRIES 64
#define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))

unsigned long pte_misses;	/* updated by do_page_fault() */
unsigned long pte_errors;	/* updated by do_page_fault() */

/* __PHX__ :: - check the vmalloc_fault in do_page_fault()
 *            - also look into include/asm-or32/mmu_context.h
 */
volatile pgd_t *current_pgd[NR_CPUS];

extern void die(char *, struct pt_regs *, long);

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * If this routine detects a bad access, it returns 1, otherwise it
 * returns 0.
 */

asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
			      unsigned long vector, int write_acc)
{
	struct task_struct *tsk;
	struct mm_struct *mm;
	struct vm_area_struct *vma;
	int si_code;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_DEFAULT;

	tsk = current;

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * NOTE2: This is done so that, when updating the vmalloc
	 * mappings we don't have to walk all processes pgdirs and
	 * add the high mappings all at once. Instead we do it as they
	 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
	 * bit set so sometimes the TLB can use a lingering entry.
	 *
	 * This verifies that the fault happens in kernel space
	 * and that the fault was not a protection error.
	 */

	if (address >= VMALLOC_START &&
	    (vector != 0x300 && vector != 0x400) &&
	    !user_mode(regs))
		goto vmalloc_fault;

	/* If exceptions were enabled, we can reenable them here */
	if (user_mode(regs)) {
		/* Exception was in userspace: reenable interrupts */
		local_irq_enable();
		flags |= FAULT_FLAG_USER;
	} else {
		/* If exception was in a syscall, then IRQ's may have
		 * been enabled or disabled.  If they were enabled,
		 * reenable them.
		 */
		if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
			local_irq_enable();
	}

	mm = tsk->mm;
	si_code = SEGV_MAPERR;

	/*
	 * If we're in an interrupt or have no user
	 * context, we must not take the fault..
	 */

	if (in_interrupt() || !mm)
		goto no_context;

retry:
	mmap_read_lock(mm);
	vma = find_vma(mm, address);

	if (!vma)
		goto bad_area;

	if (vma->vm_start <= address)
		goto good_area;

	if (!(vma->vm_flags & VM_GROWSDOWN))
		goto bad_area;

	if (user_mode(regs)) {
		/*
		 * accessing the stack below usp is always a bug.
		 * we get page-aligned addresses so we can only check
		 * if we're within a page from usp, but that might be
		 * enough to catch brutal errors at least.
		 */
		if (address + PAGE_SIZE < regs->sp)
			goto bad_area;
	}
	if (expand_stack(vma, address))
		goto bad_area;

	/*
	 * Ok, we have a good vm_area for this memory access, so
	 * we can handle it..
	 */

good_area:
	si_code = SEGV_ACCERR;

	/* first do some preliminary protection checks */

	if (write_acc) {
		if (!(vma->vm_flags & VM_WRITE))
			goto bad_area;
		flags |= FAULT_FLAG_WRITE;
	} else {
		/* not present */
		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
			goto bad_area;
	}

	/* are we trying to execute nonexecutable area */
	if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
		goto bad_area;

	/*
	 * If for any reason at all we couldn't handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault.
	 */

	fault = handle_mm_fault(vma, address, flags);

	if (fault_signal_pending(fault, regs))
		return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
		if (fault & VM_FAULT_OOM)
			goto out_of_memory;
		else if (fault & VM_FAULT_SIGSEGV)
			goto bad_area;
		else if (fault & VM_FAULT_SIGBUS)
			goto do_sigbus;
		BUG();
	}

	if (flags & FAULT_FLAG_ALLOW_RETRY) {
		/*RGD modeled on Cris */
		if (fault & VM_FAULT_MAJOR)
			tsk->maj_flt++;
		else
			tsk->min_flt++;
		if (fault & VM_FAULT_RETRY) {
			flags |= FAULT_FLAG_TRIED;

			 /* No need to mmap_read_unlock(mm) as we would
			 * have already released it in __lock_page_or_retry
			 * in mm/filemap.c.
			 */

			goto retry;
		}
	}

	mmap_read_unlock(mm);
	return;

	/*
	 * Something tried to access memory that isn't in our memory map..
	 * Fix it, but check if it's kernel or user first..
	 */

bad_area:
	mmap_read_unlock(mm);

bad_area_nosemaphore:

	/* User mode accesses just cause a SIGSEGV */

	if (user_mode(regs)) {
		force_sig_fault(SIGSEGV, si_code, (void __user *)address);
		return;
	}

no_context:

	/* Are we prepared to handle this kernel fault?
	 *
	 * (The kernel has valid exception-points in the source
	 *  when it acesses user-memory. When it fails in one
	 *  of those points, we find it in a table and do a jump
	 *  to some fixup code that loads an appropriate error
	 *  code)
	 */

	{
		const struct exception_table_entry *entry;

		__asm__ __volatile__("l.nop 42");

		if ((entry = search_exception_tables(regs->pc)) != NULL) {
			/* Adjust the instruction pointer in the stackframe */
			regs->pc = entry->fixup;
			return;
		}
	}

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
	 * terminate things with extreme prejudice.
	 */

	if ((unsigned long)(address) < PAGE_SIZE)
		printk(KERN_ALERT
		       "Unable to handle kernel NULL pointer dereference");
	else
		printk(KERN_ALERT "Unable to handle kernel access");
	printk(" at virtual address 0x%08lx\n", address);

	die("Oops", regs, write_acc);

	do_exit(SIGKILL);

	/*
	 * We ran out of memory, or some other thing happened to us that made
	 * us unable to handle the page fault gracefully.
	 */

out_of_memory:
	__asm__ __volatile__("l.nop 42");
	__asm__ __volatile__("l.nop 1");

	mmap_read_unlock(mm);
	if (!user_mode(regs))
		goto no_context;
	pagefault_out_of_memory();
	return;

do_sigbus:
	mmap_read_unlock(mm);

	/*
	 * Send a sigbus, regardless of whether we were in kernel
	 * or user mode.
	 */
	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);

	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs))
		goto no_context;
	return;

vmalloc_fault:
	{
		/*
		 * Synchronize this task's top level page-table
		 * with the 'reference' page table.
		 *
		 * Use current_pgd instead of tsk->active_mm->pgd
		 * since the latter might be unavailable if this
		 * code is executed in a misfortunately run irq
		 * (like inside schedule() between switch_mm and
		 *  switch_to...).
		 */

		int offset = pgd_index(address);
		pgd_t *pgd, *pgd_k;
		p4d_t *p4d, *p4d_k;
		pud_t *pud, *pud_k;
		pmd_t *pmd, *pmd_k;
		pte_t *pte_k;

/*
		phx_warn("do_page_fault(): vmalloc_fault will not work, "
			 "since current_pgd assign a proper value somewhere\n"
			 "anyhow we don't need this at the moment\n");

		phx_mmu("vmalloc_fault");
*/
		pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
		pgd_k = init_mm.pgd + offset;

		/* Since we're two-level, we don't need to do both
		 * set_pgd and set_pmd (they do the same thing). If
		 * we go three-level at some point, do the right thing
		 * with pgd_present and set_pgd here.
		 *
		 * Also, since the vmalloc area is global, we don't
		 * need to copy individual PTE's, it is enough to
		 * copy the pgd pointer into the pte page of the
		 * root task. If that is there, we'll find our pte if
		 * it exists.
		 */

		p4d = p4d_offset(pgd, address);
		p4d_k = p4d_offset(pgd_k, address);
		if (!p4d_present(*p4d_k))
			goto no_context;

		pud = pud_offset(p4d, address);
		pud_k = pud_offset(p4d_k, address);
		if (!pud_present(*pud_k))
			goto no_context;

		pmd = pmd_offset(pud, address);
		pmd_k = pmd_offset(pud_k, address);

		if (!pmd_present(*pmd_k))
			goto bad_area_nosemaphore;

		set_pmd(pmd, *pmd_k);

		/* Make sure the actual PTE exists as well to
		 * catch kernel vmalloc-area accesses to non-mapped
		 * addresses. If we don't do this, this will just
		 * silently loop forever.
		 */

		pte_k = pte_offset_kernel(pmd_k, address);
		if (!pte_present(*pte_k))
			goto no_context;

		return;
	}
}