summaryrefslogtreecommitdiff
path: root/arch/ia64/mm/fault.c
blob: abf2808f9b4bafabf3eef9a398c2344d6c833a47 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * MMU fault handling support.
 *
 * Copyright (C) 1998-2002 Hewlett-Packard Co
 *	David Mosberger-Tang <davidm@hpl.hp.com>
 */
#include <linux/sched/signal.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/extable.h>
#include <linux/interrupt.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/prefetch.h>
#include <linux/uaccess.h>

#include <asm/processor.h>
#include <asm/exception.h>

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

/*
 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
 * (inside region 5, on ia64) and that page is present.
 */
static int
mapped_kernel_page_is_present (unsigned long address)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *ptep, pte;

	pgd = pgd_offset_k(address);
	if (pgd_none(*pgd) || pgd_bad(*pgd))
		return 0;

	p4d = p4d_offset(pgd, address);
	if (p4d_none(*p4d) || p4d_bad(*p4d))
		return 0;

	pud = pud_offset(p4d, address);
	if (pud_none(*pud) || pud_bad(*pud))
		return 0;

	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd) || pmd_bad(*pmd))
		return 0;

	ptep = pte_offset_kernel(pmd, address);
	if (!ptep)
		return 0;

	pte = *ptep;
	return pte_present(pte);
}

#	define VM_READ_BIT	0
#	define VM_WRITE_BIT	1
#	define VM_EXEC_BIT	2

void __kprobes
ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
{
	int signal = SIGSEGV, code = SEGV_MAPERR;
	struct vm_area_struct *vma, *prev_vma;
	struct mm_struct *mm = current->mm;
	unsigned long mask;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_DEFAULT;

	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));

	/* mmap_lock is performance critical.... */
	prefetchw(&mm->mmap_lock);

	/*
	 * If we're in an interrupt or have no user context, we must not take the fault..
	 */
	if (faulthandler_disabled() || !mm)
		goto no_context;

#ifdef CONFIG_VIRTUAL_MEM_MAP
	/*
	 * If fault is in region 5 and we are in the kernel, we may already
	 * have the mmap_lock (pfn_valid macro is called during mmap). There
	 * is no vma for region 5 addr's anyway, so skip getting the semaphore
	 * and go directly to the exception handling code.
	 */

	if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
		goto bad_area_no_up;
#endif

	/*
	 * This is to handle the kprobes on user space access instructions
	 */
	if (kprobe_page_fault(regs, TRAP_BRKPT))
		return;

	if (user_mode(regs))
		flags |= FAULT_FLAG_USER;
	if (mask & VM_WRITE)
		flags |= FAULT_FLAG_WRITE;
retry:
	mmap_read_lock(mm);

	vma = find_vma_prev(mm, address, &prev_vma);
	if (!vma && !prev_vma )
		goto bad_area;

        /*
         * find_vma_prev() returns vma such that address < vma->vm_end or NULL
         *
         * May find no vma, but could be that the last vm area is the
         * register backing store that needs to expand upwards, in
         * this case vma will be null, but prev_vma will ne non-null
         */
        if (( !vma && prev_vma ) || (address < vma->vm_start) )
		goto check_expansion;

  good_area:
	code = SEGV_ACCERR;

	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */

#	if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
	    || (1 << VM_EXEC_BIT) != VM_EXEC)
#		error File is out of sync with <linux/mm.h>.  Please update.
#	endif

	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
		goto bad_area;

	if ((vma->vm_flags & mask) != mask)
		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, NULL);

	if (fault_signal_pending(fault, regs))
		return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
		/*
		 * We ran out of memory, or some other thing happened
		 * to us that made us unable to handle the page fault
		 * gracefully.
		 */
		if (fault & VM_FAULT_OOM) {
			goto out_of_memory;
		} else if (fault & VM_FAULT_SIGSEGV) {
			goto bad_area;
		} else if (fault & VM_FAULT_SIGBUS) {
			signal = SIGBUS;
			goto bad_area;
		}
		BUG();
	}

	if (flags & FAULT_FLAG_ALLOW_RETRY) {
		if (fault & VM_FAULT_MAJOR)
			current->maj_flt++;
		else
			current->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;

  check_expansion:
	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
		if (!vma)
			goto bad_area;
		if (!(vma->vm_flags & VM_GROWSDOWN))
			goto bad_area;
		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
			goto bad_area;
		if (expand_stack(vma, address))
			goto bad_area;
	} else {
		vma = prev_vma;
		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
			goto bad_area;
		/*
		 * Since the register backing store is accessed sequentially,
		 * we disallow growing it by more than a page at a time.
		 */
		if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
			goto bad_area;
		if (expand_upwards(vma, address))
			goto bad_area;
	}
	goto good_area;

  bad_area:
	mmap_read_unlock(mm);
#ifdef CONFIG_VIRTUAL_MEM_MAP
  bad_area_no_up:
#endif
	if ((isr & IA64_ISR_SP)
	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
	{
		/*
		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
		 * bit in the psr to ensure forward progress.  (Target register will get a
		 * NaT for ld.s, lfetch will be canceled.)
		 */
		ia64_psr(regs)->ed = 1;
		return;
	}
	if (user_mode(regs)) {
		force_sig_fault(signal, code, (void __user *) address,
				0, __ISR_VALID, isr);
		return;
	}

  no_context:
	if ((isr & IA64_ISR_SP)
	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
	{
		/*
		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
		 * bit in the psr to ensure forward progress.  (Target register will get a
		 * NaT for ld.s, lfetch will be canceled.)
		 */
		ia64_psr(regs)->ed = 1;
		return;
	}

	/*
	 * Since we have no vma's for region 5, we might get here even if the address is
	 * valid, due to the VHPT walker inserting a non present translation that becomes
	 * stale. If that happens, the non present fault handler already purged the stale
	 * translation, which fixed the problem. So, we check to see if the translation is
	 * valid, and return if it is.
	 */
	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
		return;

	if (ia64_done_with_exception(regs))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to terminate things
	 * with extreme prejudice.
	 */
	bust_spinlocks(1);

	if (address < PAGE_SIZE)
		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
	else
		printk(KERN_ALERT "Unable to handle kernel paging request at "
		       "virtual address %016lx\n", address);
	if (die("Oops", regs, isr))
		regs = NULL;
	bust_spinlocks(0);
	if (regs)
		do_exit(SIGKILL);
	return;

  out_of_memory:
	mmap_read_unlock(mm);
	if (!user_mode(regs))
		goto no_context;
	pagefault_out_of_memory();
}