lightnvm: NVM should depend on HAS_DMA
[deliverable/linux.git] / arch / powerpc / mm / fault.c
1 /*
2 * PowerPC version
3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
4 *
5 * Derived from "arch/i386/mm/fault.c"
6 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
7 *
8 * Modified by Cort Dougan and Paul Mackerras.
9 *
10 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
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/signal.h>
19 #include <linux/sched.h>
20 #include <linux/kernel.h>
21 #include <linux/errno.h>
22 #include <linux/string.h>
23 #include <linux/types.h>
24 #include <linux/ptrace.h>
25 #include <linux/mman.h>
26 #include <linux/mm.h>
27 #include <linux/interrupt.h>
28 #include <linux/highmem.h>
29 #include <linux/module.h>
30 #include <linux/kprobes.h>
31 #include <linux/kdebug.h>
32 #include <linux/perf_event.h>
33 #include <linux/ratelimit.h>
34 #include <linux/context_tracking.h>
35 #include <linux/hugetlb.h>
36 #include <linux/uaccess.h>
37
38 #include <asm/firmware.h>
39 #include <asm/page.h>
40 #include <asm/pgtable.h>
41 #include <asm/mmu.h>
42 #include <asm/mmu_context.h>
43 #include <asm/tlbflush.h>
44 #include <asm/siginfo.h>
45 #include <asm/debug.h>
46
47 #include "icswx.h"
48
49 #ifdef CONFIG_KPROBES
50 static inline int notify_page_fault(struct pt_regs *regs)
51 {
52 int ret = 0;
53
54 /* kprobe_running() needs smp_processor_id() */
55 if (!user_mode(regs)) {
56 preempt_disable();
57 if (kprobe_running() && kprobe_fault_handler(regs, 11))
58 ret = 1;
59 preempt_enable();
60 }
61
62 return ret;
63 }
64 #else
65 static inline int notify_page_fault(struct pt_regs *regs)
66 {
67 return 0;
68 }
69 #endif
70
71 /*
72 * Check whether the instruction at regs->nip is a store using
73 * an update addressing form which will update r1.
74 */
75 static int store_updates_sp(struct pt_regs *regs)
76 {
77 unsigned int inst;
78
79 if (get_user(inst, (unsigned int __user *)regs->nip))
80 return 0;
81 /* check for 1 in the rA field */
82 if (((inst >> 16) & 0x1f) != 1)
83 return 0;
84 /* check major opcode */
85 switch (inst >> 26) {
86 case 37: /* stwu */
87 case 39: /* stbu */
88 case 45: /* sthu */
89 case 53: /* stfsu */
90 case 55: /* stfdu */
91 return 1;
92 case 62: /* std or stdu */
93 return (inst & 3) == 1;
94 case 31:
95 /* check minor opcode */
96 switch ((inst >> 1) & 0x3ff) {
97 case 181: /* stdux */
98 case 183: /* stwux */
99 case 247: /* stbux */
100 case 439: /* sthux */
101 case 695: /* stfsux */
102 case 759: /* stfdux */
103 return 1;
104 }
105 }
106 return 0;
107 }
108 /*
109 * do_page_fault error handling helpers
110 */
111
112 #define MM_FAULT_RETURN 0
113 #define MM_FAULT_CONTINUE -1
114 #define MM_FAULT_ERR(sig) (sig)
115
116 static int do_sigbus(struct pt_regs *regs, unsigned long address,
117 unsigned int fault)
118 {
119 siginfo_t info;
120 unsigned int lsb = 0;
121
122 up_read(&current->mm->mmap_sem);
123
124 if (!user_mode(regs))
125 return MM_FAULT_ERR(SIGBUS);
126
127 current->thread.trap_nr = BUS_ADRERR;
128 info.si_signo = SIGBUS;
129 info.si_errno = 0;
130 info.si_code = BUS_ADRERR;
131 info.si_addr = (void __user *)address;
132 #ifdef CONFIG_MEMORY_FAILURE
133 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
134 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
135 current->comm, current->pid, address);
136 info.si_code = BUS_MCEERR_AR;
137 }
138
139 if (fault & VM_FAULT_HWPOISON_LARGE)
140 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
141 if (fault & VM_FAULT_HWPOISON)
142 lsb = PAGE_SHIFT;
143 #endif
144 info.si_addr_lsb = lsb;
145 force_sig_info(SIGBUS, &info, current);
146 return MM_FAULT_RETURN;
147 }
148
149 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
150 {
151 /*
152 * Pagefault was interrupted by SIGKILL. We have no reason to
153 * continue the pagefault.
154 */
155 if (fatal_signal_pending(current)) {
156 /*
157 * If we have retry set, the mmap semaphore will have
158 * alrady been released in __lock_page_or_retry(). Else
159 * we release it now.
160 */
161 if (!(fault & VM_FAULT_RETRY))
162 up_read(&current->mm->mmap_sem);
163 /* Coming from kernel, we need to deal with uaccess fixups */
164 if (user_mode(regs))
165 return MM_FAULT_RETURN;
166 return MM_FAULT_ERR(SIGKILL);
167 }
168
169 /* No fault: be happy */
170 if (!(fault & VM_FAULT_ERROR))
171 return MM_FAULT_CONTINUE;
172
173 /* Out of memory */
174 if (fault & VM_FAULT_OOM) {
175 up_read(&current->mm->mmap_sem);
176
177 /*
178 * We ran out of memory, or some other thing happened to us that
179 * made us unable to handle the page fault gracefully.
180 */
181 if (!user_mode(regs))
182 return MM_FAULT_ERR(SIGKILL);
183 pagefault_out_of_memory();
184 return MM_FAULT_RETURN;
185 }
186
187 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
188 return do_sigbus(regs, addr, fault);
189
190 /* We don't understand the fault code, this is fatal */
191 BUG();
192 return MM_FAULT_CONTINUE;
193 }
194
195 /*
196 * For 600- and 800-family processors, the error_code parameter is DSISR
197 * for a data fault, SRR1 for an instruction fault. For 400-family processors
198 * the error_code parameter is ESR for a data fault, 0 for an instruction
199 * fault.
200 * For 64-bit processors, the error_code parameter is
201 * - DSISR for a non-SLB data access fault,
202 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
203 * - 0 any SLB fault.
204 *
205 * The return value is 0 if the fault was handled, or the signal
206 * number if this is a kernel fault that can't be handled here.
207 */
208 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
209 unsigned long error_code)
210 {
211 enum ctx_state prev_state = exception_enter();
212 struct vm_area_struct * vma;
213 struct mm_struct *mm = current->mm;
214 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
215 int code = SEGV_MAPERR;
216 int is_write = 0;
217 int trap = TRAP(regs);
218 int is_exec = trap == 0x400;
219 int fault;
220 int rc = 0, store_update_sp = 0;
221
222 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
223 /*
224 * Fortunately the bit assignments in SRR1 for an instruction
225 * fault and DSISR for a data fault are mostly the same for the
226 * bits we are interested in. But there are some bits which
227 * indicate errors in DSISR but can validly be set in SRR1.
228 */
229 if (trap == 0x400)
230 error_code &= 0x48200000;
231 else
232 is_write = error_code & DSISR_ISSTORE;
233 #else
234 is_write = error_code & ESR_DST;
235 #endif /* CONFIG_4xx || CONFIG_BOOKE */
236
237 #ifdef CONFIG_PPC_ICSWX
238 /*
239 * we need to do this early because this "data storage
240 * interrupt" does not update the DAR/DEAR so we don't want to
241 * look at it
242 */
243 if (error_code & ICSWX_DSI_UCT) {
244 rc = acop_handle_fault(regs, address, error_code);
245 if (rc)
246 goto bail;
247 }
248 #endif /* CONFIG_PPC_ICSWX */
249
250 if (notify_page_fault(regs))
251 goto bail;
252
253 if (unlikely(debugger_fault_handler(regs)))
254 goto bail;
255
256 /* On a kernel SLB miss we can only check for a valid exception entry */
257 if (!user_mode(regs) && (address >= TASK_SIZE)) {
258 rc = SIGSEGV;
259 goto bail;
260 }
261
262 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
263 defined(CONFIG_PPC_BOOK3S_64))
264 if (error_code & DSISR_DABRMATCH) {
265 /* breakpoint match */
266 do_break(regs, address, error_code);
267 goto bail;
268 }
269 #endif
270
271 /* We restore the interrupt state now */
272 if (!arch_irq_disabled_regs(regs))
273 local_irq_enable();
274
275 if (faulthandler_disabled() || mm == NULL) {
276 if (!user_mode(regs)) {
277 rc = SIGSEGV;
278 goto bail;
279 }
280 /* faulthandler_disabled() in user mode is really bad,
281 as is current->mm == NULL. */
282 printk(KERN_EMERG "Page fault in user mode with "
283 "faulthandler_disabled() = %d mm = %p\n",
284 faulthandler_disabled(), mm);
285 printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
286 regs->nip, regs->msr);
287 die("Weird page fault", regs, SIGSEGV);
288 }
289
290 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
291
292 /*
293 * We want to do this outside mmap_sem, because reading code around nip
294 * can result in fault, which will cause a deadlock when called with
295 * mmap_sem held
296 */
297 if (user_mode(regs))
298 store_update_sp = store_updates_sp(regs);
299
300 if (user_mode(regs))
301 flags |= FAULT_FLAG_USER;
302
303 /* When running in the kernel we expect faults to occur only to
304 * addresses in user space. All other faults represent errors in the
305 * kernel and should generate an OOPS. Unfortunately, in the case of an
306 * erroneous fault occurring in a code path which already holds mmap_sem
307 * we will deadlock attempting to validate the fault against the
308 * address space. Luckily the kernel only validly references user
309 * space from well defined areas of code, which are listed in the
310 * exceptions table.
311 *
312 * As the vast majority of faults will be valid we will only perform
313 * the source reference check when there is a possibility of a deadlock.
314 * Attempt to lock the address space, if we cannot we then validate the
315 * source. If this is invalid we can skip the address space check,
316 * thus avoiding the deadlock.
317 */
318 if (!down_read_trylock(&mm->mmap_sem)) {
319 if (!user_mode(regs) && !search_exception_tables(regs->nip))
320 goto bad_area_nosemaphore;
321
322 retry:
323 down_read(&mm->mmap_sem);
324 } else {
325 /*
326 * The above down_read_trylock() might have succeeded in
327 * which case we'll have missed the might_sleep() from
328 * down_read():
329 */
330 might_sleep();
331 }
332
333 vma = find_vma(mm, address);
334 if (!vma)
335 goto bad_area;
336 if (vma->vm_start <= address)
337 goto good_area;
338 if (!(vma->vm_flags & VM_GROWSDOWN))
339 goto bad_area;
340
341 /*
342 * N.B. The POWER/Open ABI allows programs to access up to
343 * 288 bytes below the stack pointer.
344 * The kernel signal delivery code writes up to about 1.5kB
345 * below the stack pointer (r1) before decrementing it.
346 * The exec code can write slightly over 640kB to the stack
347 * before setting the user r1. Thus we allow the stack to
348 * expand to 1MB without further checks.
349 */
350 if (address + 0x100000 < vma->vm_end) {
351 /* get user regs even if this fault is in kernel mode */
352 struct pt_regs *uregs = current->thread.regs;
353 if (uregs == NULL)
354 goto bad_area;
355
356 /*
357 * A user-mode access to an address a long way below
358 * the stack pointer is only valid if the instruction
359 * is one which would update the stack pointer to the
360 * address accessed if the instruction completed,
361 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
362 * (or the byte, halfword, float or double forms).
363 *
364 * If we don't check this then any write to the area
365 * between the last mapped region and the stack will
366 * expand the stack rather than segfaulting.
367 */
368 if (address + 2048 < uregs->gpr[1] && !store_update_sp)
369 goto bad_area;
370 }
371 if (expand_stack(vma, address))
372 goto bad_area;
373
374 good_area:
375 code = SEGV_ACCERR;
376 #if defined(CONFIG_6xx)
377 if (error_code & 0x95700000)
378 /* an error such as lwarx to I/O controller space,
379 address matching DABR, eciwx, etc. */
380 goto bad_area;
381 #endif /* CONFIG_6xx */
382 #if defined(CONFIG_8xx)
383 /* The MPC8xx seems to always set 0x80000000, which is
384 * "undefined". Of those that can be set, this is the only
385 * one which seems bad.
386 */
387 if (error_code & 0x10000000)
388 /* Guarded storage error. */
389 goto bad_area;
390 #endif /* CONFIG_8xx */
391
392 if (is_exec) {
393 /*
394 * Allow execution from readable areas if the MMU does not
395 * provide separate controls over reading and executing.
396 *
397 * Note: That code used to not be enabled for 4xx/BookE.
398 * It is now as I/D cache coherency for these is done at
399 * set_pte_at() time and I see no reason why the test
400 * below wouldn't be valid on those processors. This -may-
401 * break programs compiled with a really old ABI though.
402 */
403 if (!(vma->vm_flags & VM_EXEC) &&
404 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
405 !(vma->vm_flags & (VM_READ | VM_WRITE))))
406 goto bad_area;
407 #ifdef CONFIG_PPC_STD_MMU
408 /*
409 * protfault should only happen due to us
410 * mapping a region readonly temporarily. PROT_NONE
411 * is also covered by the VMA check above.
412 */
413 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
414 #endif /* CONFIG_PPC_STD_MMU */
415 /* a write */
416 } else if (is_write) {
417 if (!(vma->vm_flags & VM_WRITE))
418 goto bad_area;
419 flags |= FAULT_FLAG_WRITE;
420 /* a read */
421 } else {
422 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
423 goto bad_area;
424 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
425 }
426
427 /*
428 * If for any reason at all we couldn't handle the fault,
429 * make sure we exit gracefully rather than endlessly redo
430 * the fault.
431 */
432 fault = handle_mm_fault(vma, address, flags);
433 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
434 if (fault & VM_FAULT_SIGSEGV)
435 goto bad_area;
436 rc = mm_fault_error(regs, address, fault);
437 if (rc >= MM_FAULT_RETURN)
438 goto bail;
439 else
440 rc = 0;
441 }
442
443 /*
444 * Major/minor page fault accounting is only done on the
445 * initial attempt. If we go through a retry, it is extremely
446 * likely that the page will be found in page cache at that point.
447 */
448 if (flags & FAULT_FLAG_ALLOW_RETRY) {
449 if (fault & VM_FAULT_MAJOR) {
450 current->maj_flt++;
451 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
452 regs, address);
453 #ifdef CONFIG_PPC_SMLPAR
454 if (firmware_has_feature(FW_FEATURE_CMO)) {
455 u32 page_ins;
456
457 preempt_disable();
458 page_ins = be32_to_cpu(get_lppaca()->page_ins);
459 page_ins += 1 << PAGE_FACTOR;
460 get_lppaca()->page_ins = cpu_to_be32(page_ins);
461 preempt_enable();
462 }
463 #endif /* CONFIG_PPC_SMLPAR */
464 } else {
465 current->min_flt++;
466 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
467 regs, address);
468 }
469 if (fault & VM_FAULT_RETRY) {
470 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
471 * of starvation. */
472 flags &= ~FAULT_FLAG_ALLOW_RETRY;
473 flags |= FAULT_FLAG_TRIED;
474 goto retry;
475 }
476 }
477
478 up_read(&mm->mmap_sem);
479 goto bail;
480
481 bad_area:
482 up_read(&mm->mmap_sem);
483
484 bad_area_nosemaphore:
485 /* User mode accesses cause a SIGSEGV */
486 if (user_mode(regs)) {
487 _exception(SIGSEGV, regs, code, address);
488 goto bail;
489 }
490
491 if (is_exec && (error_code & DSISR_PROTFAULT))
492 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
493 " page (%lx) - exploit attempt? (uid: %d)\n",
494 address, from_kuid(&init_user_ns, current_uid()));
495
496 rc = SIGSEGV;
497
498 bail:
499 exception_exit(prev_state);
500 return rc;
501
502 }
503
504 /*
505 * bad_page_fault is called when we have a bad access from the kernel.
506 * It is called from the DSI and ISI handlers in head.S and from some
507 * of the procedures in traps.c.
508 */
509 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
510 {
511 const struct exception_table_entry *entry;
512
513 /* Are we prepared to handle this fault? */
514 if ((entry = search_exception_tables(regs->nip)) != NULL) {
515 regs->nip = entry->fixup;
516 return;
517 }
518
519 /* kernel has accessed a bad area */
520
521 switch (regs->trap) {
522 case 0x300:
523 case 0x380:
524 printk(KERN_ALERT "Unable to handle kernel paging request for "
525 "data at address 0x%08lx\n", regs->dar);
526 break;
527 case 0x400:
528 case 0x480:
529 printk(KERN_ALERT "Unable to handle kernel paging request for "
530 "instruction fetch\n");
531 break;
532 case 0x600:
533 printk(KERN_ALERT "Unable to handle kernel paging request for "
534 "unaligned access at address 0x%08lx\n", regs->dar);
535 break;
536 default:
537 printk(KERN_ALERT "Unable to handle kernel paging request for "
538 "unknown fault\n");
539 break;
540 }
541 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
542 regs->nip);
543
544 if (task_stack_end_corrupted(current))
545 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
546
547 die("Kernel access of bad area", regs, sig);
548 }
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