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
37 #include <asm/firmware.h>
38 #include <asm/page.h>
39 #include <asm/pgtable.h>
40 #include <asm/mmu.h>
41 #include <asm/mmu_context.h>
42 #include <asm/uaccess.h>
43 #include <asm/tlbflush.h>
44 #include <asm/siginfo.h>
45 #include <asm/debug.h>
46 #include <mm/mmu_decl.h>
47
48 #include "icswx.h"
49
50 #ifdef CONFIG_KPROBES
notify_page_fault(struct pt_regs * regs)51 static inline int notify_page_fault(struct pt_regs *regs)
52 {
53 int ret = 0;
54
55 /* kprobe_running() needs smp_processor_id() */
56 if (!user_mode(regs)) {
57 preempt_disable();
58 if (kprobe_running() && kprobe_fault_handler(regs, 11))
59 ret = 1;
60 preempt_enable();
61 }
62
63 return ret;
64 }
65 #else
notify_page_fault(struct pt_regs * regs)66 static inline int notify_page_fault(struct pt_regs *regs)
67 {
68 return 0;
69 }
70 #endif
71
72 /*
73 * Check whether the instruction at regs->nip is a store using
74 * an update addressing form which will update r1.
75 */
store_updates_sp(struct pt_regs * regs)76 static int store_updates_sp(struct pt_regs *regs)
77 {
78 unsigned int inst;
79
80 if (get_user(inst, (unsigned int __user *)regs->nip))
81 return 0;
82 /* check for 1 in the rA field */
83 if (((inst >> 16) & 0x1f) != 1)
84 return 0;
85 /* check major opcode */
86 switch (inst >> 26) {
87 case 37: /* stwu */
88 case 39: /* stbu */
89 case 45: /* sthu */
90 case 53: /* stfsu */
91 case 55: /* stfdu */
92 return 1;
93 case 62: /* std or stdu */
94 return (inst & 3) == 1;
95 case 31:
96 /* check minor opcode */
97 switch ((inst >> 1) & 0x3ff) {
98 case 181: /* stdux */
99 case 183: /* stwux */
100 case 247: /* stbux */
101 case 439: /* sthux */
102 case 695: /* stfsux */
103 case 759: /* stfdux */
104 return 1;
105 }
106 }
107 return 0;
108 }
109 /*
110 * do_page_fault error handling helpers
111 */
112
113 #define MM_FAULT_RETURN 0
114 #define MM_FAULT_CONTINUE -1
115 #define MM_FAULT_ERR(sig) (sig)
116
do_sigbus(struct pt_regs * regs,unsigned long address,unsigned int fault)117 static int do_sigbus(struct pt_regs *regs, unsigned long address,
118 unsigned int fault)
119 {
120 siginfo_t info;
121 unsigned int lsb = 0;
122
123 up_read(¤t->mm->mmap_sem);
124
125 if (!user_mode(regs))
126 return MM_FAULT_ERR(SIGBUS);
127
128 current->thread.trap_nr = BUS_ADRERR;
129 info.si_signo = SIGBUS;
130 info.si_errno = 0;
131 info.si_code = BUS_ADRERR;
132 info.si_addr = (void __user *)address;
133 #ifdef CONFIG_MEMORY_FAILURE
134 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
135 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
136 current->comm, current->pid, address);
137 info.si_code = BUS_MCEERR_AR;
138 }
139
140 if (fault & VM_FAULT_HWPOISON_LARGE)
141 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
142 if (fault & VM_FAULT_HWPOISON)
143 lsb = PAGE_SHIFT;
144 #endif
145 info.si_addr_lsb = lsb;
146 force_sig_info(SIGBUS, &info, current);
147 return MM_FAULT_RETURN;
148 }
149
mm_fault_error(struct pt_regs * regs,unsigned long addr,int fault)150 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
151 {
152 /*
153 * Pagefault was interrupted by SIGKILL. We have no reason to
154 * continue the pagefault.
155 */
156 if (fatal_signal_pending(current)) {
157 /*
158 * If we have retry set, the mmap semaphore will have
159 * alrady been released in __lock_page_or_retry(). Else
160 * we release it now.
161 */
162 if (!(fault & VM_FAULT_RETRY))
163 up_read(¤t->mm->mmap_sem);
164 /* Coming from kernel, we need to deal with uaccess fixups */
165 if (user_mode(regs))
166 return MM_FAULT_RETURN;
167 return MM_FAULT_ERR(SIGKILL);
168 }
169
170 /* No fault: be happy */
171 if (!(fault & VM_FAULT_ERROR))
172 return MM_FAULT_CONTINUE;
173
174 /* Out of memory */
175 if (fault & VM_FAULT_OOM) {
176 up_read(¤t->mm->mmap_sem);
177
178 /*
179 * We ran out of memory, or some other thing happened to us that
180 * made us unable to handle the page fault gracefully.
181 */
182 if (!user_mode(regs))
183 return MM_FAULT_ERR(SIGKILL);
184 pagefault_out_of_memory();
185 return MM_FAULT_RETURN;
186 }
187
188 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
189 return do_sigbus(regs, addr, fault);
190
191 /* We don't understand the fault code, this is fatal */
192 BUG();
193 return MM_FAULT_CONTINUE;
194 }
195
196 /*
197 * For 600- and 800-family processors, the error_code parameter is DSISR
198 * for a data fault, SRR1 for an instruction fault. For 400-family processors
199 * the error_code parameter is ESR for a data fault, 0 for an instruction
200 * fault.
201 * For 64-bit processors, the error_code parameter is
202 * - DSISR for a non-SLB data access fault,
203 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
204 * - 0 any SLB fault.
205 *
206 * The return value is 0 if the fault was handled, or the signal
207 * number if this is a kernel fault that can't be handled here.
208 */
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned long error_code)209 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
210 unsigned long error_code)
211 {
212 enum ctx_state prev_state = exception_enter();
213 struct vm_area_struct * vma;
214 struct mm_struct *mm = current->mm;
215 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
216 int code = SEGV_MAPERR;
217 int is_write = 0;
218 int trap = TRAP(regs);
219 int is_exec = trap == 0x400;
220 int fault;
221 int rc = 0, store_update_sp = 0;
222
223 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
224 /*
225 * Fortunately the bit assignments in SRR1 for an instruction
226 * fault and DSISR for a data fault are mostly the same for the
227 * bits we are interested in. But there are some bits which
228 * indicate errors in DSISR but can validly be set in SRR1.
229 */
230 if (trap == 0x400)
231 error_code &= 0x48200000;
232 else
233 is_write = error_code & DSISR_ISSTORE;
234 #else
235 is_write = error_code & ESR_DST;
236 #endif /* CONFIG_4xx || CONFIG_BOOKE */
237
238 #ifdef CONFIG_PPC_ICSWX
239 /*
240 * we need to do this early because this "data storage
241 * interrupt" does not update the DAR/DEAR so we don't want to
242 * look at it
243 */
244 if (error_code & ICSWX_DSI_UCT) {
245 rc = acop_handle_fault(regs, address, error_code);
246 if (rc)
247 goto bail;
248 }
249 #endif /* CONFIG_PPC_ICSWX */
250
251 if (notify_page_fault(regs))
252 goto bail;
253
254 if (unlikely(debugger_fault_handler(regs)))
255 goto bail;
256
257 /* On a kernel SLB miss we can only check for a valid exception entry */
258 if (!user_mode(regs) && (address >= TASK_SIZE)) {
259 rc = SIGSEGV;
260 goto bail;
261 }
262
263 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
264 defined(CONFIG_PPC_BOOK3S_64))
265 if (error_code & DSISR_DABRMATCH) {
266 /* breakpoint match */
267 do_break(regs, address, error_code);
268 goto bail;
269 }
270 #endif
271
272 /* We restore the interrupt state now */
273 if (!arch_irq_disabled_regs(regs))
274 local_irq_enable();
275
276 if (in_atomic() || mm == NULL) {
277 if (!user_mode(regs)) {
278 rc = SIGSEGV;
279 goto bail;
280 }
281 /* in_atomic() in user mode is really bad,
282 as is current->mm == NULL. */
283 printk(KERN_EMERG "Page fault in user mode with "
284 "in_atomic() = %d mm = %p\n", in_atomic(), 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 /* 8xx sometimes need to load a invalid/non-present TLBs.
384 * These must be invalidated separately as linux mm don't.
385 */
386 if (error_code & 0x40000000) /* no translation? */
387 _tlbil_va(address, 0, 0, 0);
388
389 /* The MPC8xx seems to always set 0x80000000, which is
390 * "undefined". Of those that can be set, this is the only
391 * one which seems bad.
392 */
393 if (error_code & 0x10000000)
394 /* Guarded storage error. */
395 goto bad_area;
396 #endif /* CONFIG_8xx */
397
398 if (is_exec) {
399 #ifdef CONFIG_PPC_STD_MMU
400 /* Protection fault on exec go straight to failure on
401 * Hash based MMUs as they either don't support per-page
402 * execute permission, or if they do, it's handled already
403 * at the hash level. This test would probably have to
404 * be removed if we change the way this works to make hash
405 * processors use the same I/D cache coherency mechanism
406 * as embedded.
407 */
408 if (error_code & DSISR_PROTFAULT)
409 goto bad_area;
410 #endif /* CONFIG_PPC_STD_MMU */
411
412 /*
413 * Allow execution from readable areas if the MMU does not
414 * provide separate controls over reading and executing.
415 *
416 * Note: That code used to not be enabled for 4xx/BookE.
417 * It is now as I/D cache coherency for these is done at
418 * set_pte_at() time and I see no reason why the test
419 * below wouldn't be valid on those processors. This -may-
420 * break programs compiled with a really old ABI though.
421 */
422 if (!(vma->vm_flags & VM_EXEC) &&
423 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
424 !(vma->vm_flags & (VM_READ | VM_WRITE))))
425 goto bad_area;
426 /* a write */
427 } else if (is_write) {
428 if (!(vma->vm_flags & VM_WRITE))
429 goto bad_area;
430 flags |= FAULT_FLAG_WRITE;
431 /* a read */
432 } else {
433 /* protection fault */
434 if (error_code & 0x08000000)
435 goto bad_area;
436 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
437 goto bad_area;
438 }
439
440 /*
441 * If for any reason at all we couldn't handle the fault,
442 * make sure we exit gracefully rather than endlessly redo
443 * the fault.
444 */
445 fault = handle_mm_fault(mm, vma, address, flags);
446 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
447 if (fault & VM_FAULT_SIGSEGV)
448 goto bad_area;
449 rc = mm_fault_error(regs, address, fault);
450 if (rc >= MM_FAULT_RETURN)
451 goto bail;
452 else
453 rc = 0;
454 }
455
456 /*
457 * Major/minor page fault accounting is only done on the
458 * initial attempt. If we go through a retry, it is extremely
459 * likely that the page will be found in page cache at that point.
460 */
461 if (flags & FAULT_FLAG_ALLOW_RETRY) {
462 if (fault & VM_FAULT_MAJOR) {
463 current->maj_flt++;
464 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
465 regs, address);
466 #ifdef CONFIG_PPC_SMLPAR
467 if (firmware_has_feature(FW_FEATURE_CMO)) {
468 u32 page_ins;
469
470 preempt_disable();
471 page_ins = be32_to_cpu(get_lppaca()->page_ins);
472 page_ins += 1 << PAGE_FACTOR;
473 get_lppaca()->page_ins = cpu_to_be32(page_ins);
474 preempt_enable();
475 }
476 #endif /* CONFIG_PPC_SMLPAR */
477 } else {
478 current->min_flt++;
479 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
480 regs, address);
481 }
482 if (fault & VM_FAULT_RETRY) {
483 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
484 * of starvation. */
485 flags &= ~FAULT_FLAG_ALLOW_RETRY;
486 flags |= FAULT_FLAG_TRIED;
487 goto retry;
488 }
489 }
490
491 up_read(&mm->mmap_sem);
492 goto bail;
493
494 bad_area:
495 up_read(&mm->mmap_sem);
496
497 bad_area_nosemaphore:
498 /* User mode accesses cause a SIGSEGV */
499 if (user_mode(regs)) {
500 _exception(SIGSEGV, regs, code, address);
501 goto bail;
502 }
503
504 if (is_exec && (error_code & DSISR_PROTFAULT))
505 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
506 " page (%lx) - exploit attempt? (uid: %d)\n",
507 address, from_kuid(&init_user_ns, current_uid()));
508
509 rc = SIGSEGV;
510
511 bail:
512 exception_exit(prev_state);
513 return rc;
514
515 }
516
517 /*
518 * bad_page_fault is called when we have a bad access from the kernel.
519 * It is called from the DSI and ISI handlers in head.S and from some
520 * of the procedures in traps.c.
521 */
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)522 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
523 {
524 const struct exception_table_entry *entry;
525
526 /* Are we prepared to handle this fault? */
527 if ((entry = search_exception_tables(regs->nip)) != NULL) {
528 regs->nip = entry->fixup;
529 return;
530 }
531
532 /* kernel has accessed a bad area */
533
534 switch (regs->trap) {
535 case 0x300:
536 case 0x380:
537 printk(KERN_ALERT "Unable to handle kernel paging request for "
538 "data at address 0x%08lx\n", regs->dar);
539 break;
540 case 0x400:
541 case 0x480:
542 printk(KERN_ALERT "Unable to handle kernel paging request for "
543 "instruction fetch\n");
544 break;
545 default:
546 printk(KERN_ALERT "Unable to handle kernel paging request for "
547 "unknown fault\n");
548 break;
549 }
550 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
551 regs->nip);
552
553 if (task_stack_end_corrupted(current))
554 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
555
556 die("Kernel access of bad area", regs, sig);
557 }
558