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1/*
2 * MMU fault handling support.
3 *
4 * Copyright (C) 1998-2002 Hewlett-Packard Co
5 * David Mosberger-Tang <davidm@hpl.hp.com>
6 */
7#include <linux/sched.h>
8#include <linux/kernel.h>
9#include <linux/mm.h>
10#include <linux/interrupt.h>
11#include <linux/kprobes.h>
12#include <linux/kdebug.h>
13#include <linux/prefetch.h>
14#include <linux/uaccess.h>
15
16#include <asm/pgtable.h>
17#include <asm/processor.h>
18
19extern int die(char *, struct pt_regs *, long);
20
21#ifdef CONFIG_KPROBES
22static inline int notify_page_fault(struct pt_regs *regs, int trap)
23{
24 int ret = 0;
25
26 if (!user_mode(regs)) {
27 /* kprobe_running() needs smp_processor_id() */
28 preempt_disable();
29 if (kprobe_running() && kprobe_fault_handler(regs, trap))
30 ret = 1;
31 preempt_enable();
32 }
33
34 return ret;
35}
36#else
37static inline int notify_page_fault(struct pt_regs *regs, int trap)
38{
39 return 0;
40}
41#endif
42
43/*
44 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
45 * (inside region 5, on ia64) and that page is present.
46 */
47static int
48mapped_kernel_page_is_present (unsigned long address)
49{
50 pgd_t *pgd;
51 pud_t *pud;
52 pmd_t *pmd;
53 pte_t *ptep, pte;
54
55 pgd = pgd_offset_k(address);
56 if (pgd_none(*pgd) || pgd_bad(*pgd))
57 return 0;
58
59 pud = pud_offset(pgd, address);
60 if (pud_none(*pud) || pud_bad(*pud))
61 return 0;
62
63 pmd = pmd_offset(pud, address);
64 if (pmd_none(*pmd) || pmd_bad(*pmd))
65 return 0;
66
67 ptep = pte_offset_kernel(pmd, address);
68 if (!ptep)
69 return 0;
70
71 pte = *ptep;
72 return pte_present(pte);
73}
74
75# define VM_READ_BIT 0
76# define VM_WRITE_BIT 1
77# define VM_EXEC_BIT 2
78
79void __kprobes
80ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
81{
82 int signal = SIGSEGV, code = SEGV_MAPERR;
83 struct vm_area_struct *vma, *prev_vma;
84 struct mm_struct *mm = current->mm;
85 struct siginfo si;
86 unsigned long mask;
87 int fault;
88 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
89
90 mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
91 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
92
93 /* mmap_sem is performance critical.... */
94 prefetchw(&mm->mmap_sem);
95
96 /*
97 * If we're in an interrupt or have no user context, we must not take the fault..
98 */
99 if (faulthandler_disabled() || !mm)
100 goto no_context;
101
102#ifdef CONFIG_VIRTUAL_MEM_MAP
103 /*
104 * If fault is in region 5 and we are in the kernel, we may already
105 * have the mmap_sem (pfn_valid macro is called during mmap). There
106 * is no vma for region 5 addr's anyway, so skip getting the semaphore
107 * and go directly to the exception handling code.
108 */
109
110 if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
111 goto bad_area_no_up;
112#endif
113
114 /*
115 * This is to handle the kprobes on user space access instructions
116 */
117 if (notify_page_fault(regs, TRAP_BRKPT))
118 return;
119
120 if (user_mode(regs))
121 flags |= FAULT_FLAG_USER;
122 if (mask & VM_WRITE)
123 flags |= FAULT_FLAG_WRITE;
124retry:
125 down_read(&mm->mmap_sem);
126
127 vma = find_vma_prev(mm, address, &prev_vma);
128 if (!vma && !prev_vma )
129 goto bad_area;
130
131 /*
132 * find_vma_prev() returns vma such that address < vma->vm_end or NULL
133 *
134 * May find no vma, but could be that the last vm area is the
135 * register backing store that needs to expand upwards, in
136 * this case vma will be null, but prev_vma will ne non-null
137 */
138 if (( !vma && prev_vma ) || (address < vma->vm_start) )
139 goto check_expansion;
140
141 good_area:
142 code = SEGV_ACCERR;
143
144 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */
145
146# if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
147 || (1 << VM_EXEC_BIT) != VM_EXEC)
148# error File is out of sync with <linux/mm.h>. Please update.
149# endif
150
151 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
152 goto bad_area;
153
154 if ((vma->vm_flags & mask) != mask)
155 goto bad_area;
156
157 /*
158 * If for any reason at all we couldn't handle the fault, make
159 * sure we exit gracefully rather than endlessly redo the
160 * fault.
161 */
162 fault = handle_mm_fault(mm, 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 /*
169 * We ran out of memory, or some other thing happened
170 * to us that made us unable to handle the page fault
171 * gracefully.
172 */
173 if (fault & VM_FAULT_OOM) {
174 goto out_of_memory;
175 } else if (fault & VM_FAULT_SIGSEGV) {
176 goto bad_area;
177 } else if (fault & VM_FAULT_SIGBUS) {
178 signal = SIGBUS;
179 goto bad_area;
180 }
181 BUG();
182 }
183
184 if (flags & FAULT_FLAG_ALLOW_RETRY) {
185 if (fault & VM_FAULT_MAJOR)
186 current->maj_flt++;
187 else
188 current->min_flt++;
189 if (fault & VM_FAULT_RETRY) {
190 flags &= ~FAULT_FLAG_ALLOW_RETRY;
191 flags |= FAULT_FLAG_TRIED;
192
193 /* No need to up_read(&mm->mmap_sem) as we would
194 * have already released it in __lock_page_or_retry
195 * in mm/filemap.c.
196 */
197
198 goto retry;
199 }
200 }
201
202 up_read(&mm->mmap_sem);
203 return;
204
205 check_expansion:
206 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
207 if (!vma)
208 goto bad_area;
209 if (!(vma->vm_flags & VM_GROWSDOWN))
210 goto bad_area;
211 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
212 || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
213 goto bad_area;
214 if (expand_stack(vma, address))
215 goto bad_area;
216 } else {
217 vma = prev_vma;
218 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
219 || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
220 goto bad_area;
221 /*
222 * Since the register backing store is accessed sequentially,
223 * we disallow growing it by more than a page at a time.
224 */
225 if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
226 goto bad_area;
227 if (expand_upwards(vma, address))
228 goto bad_area;
229 }
230 goto good_area;
231
232 bad_area:
233 up_read(&mm->mmap_sem);
234#ifdef CONFIG_VIRTUAL_MEM_MAP
235 bad_area_no_up:
236#endif
237 if ((isr & IA64_ISR_SP)
238 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
239 {
240 /*
241 * This fault was due to a speculative load or lfetch.fault, set the "ed"
242 * bit in the psr to ensure forward progress. (Target register will get a
243 * NaT for ld.s, lfetch will be canceled.)
244 */
245 ia64_psr(regs)->ed = 1;
246 return;
247 }
248 if (user_mode(regs)) {
249 si.si_signo = signal;
250 si.si_errno = 0;
251 si.si_code = code;
252 si.si_addr = (void __user *) address;
253 si.si_isr = isr;
254 si.si_flags = __ISR_VALID;
255 force_sig_info(signal, &si, current);
256 return;
257 }
258
259 no_context:
260 if ((isr & IA64_ISR_SP)
261 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
262 {
263 /*
264 * This fault was due to a speculative load or lfetch.fault, set the "ed"
265 * bit in the psr to ensure forward progress. (Target register will get a
266 * NaT for ld.s, lfetch will be canceled.)
267 */
268 ia64_psr(regs)->ed = 1;
269 return;
270 }
271
272 /*
273 * Since we have no vma's for region 5, we might get here even if the address is
274 * valid, due to the VHPT walker inserting a non present translation that becomes
275 * stale. If that happens, the non present fault handler already purged the stale
276 * translation, which fixed the problem. So, we check to see if the translation is
277 * valid, and return if it is.
278 */
279 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
280 return;
281
282 if (ia64_done_with_exception(regs))
283 return;
284
285 /*
286 * Oops. The kernel tried to access some bad page. We'll have to terminate things
287 * with extreme prejudice.
288 */
289 bust_spinlocks(1);
290
291 if (address < PAGE_SIZE)
292 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
293 else
294 printk(KERN_ALERT "Unable to handle kernel paging request at "
295 "virtual address %016lx\n", address);
296 if (die("Oops", regs, isr))
297 regs = NULL;
298 bust_spinlocks(0);
299 if (regs)
300 do_exit(SIGKILL);
301 return;
302
303 out_of_memory:
304 up_read(&mm->mmap_sem);
305 if (!user_mode(regs))
306 goto no_context;
307 pagefault_out_of_memory();
308}