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/magic.h>
34 #include <linux/ratelimit.h>
35
36 #include <asm/firmware.h>
37 #include <asm/page.h>
38 #include <asm/pgtable.h>
39 #include <asm/mmu.h>
40 #include <asm/mmu_context.h>
41 #include <asm/uaccess.h>
42 #include <asm/tlbflush.h>
43 #include <asm/siginfo.h>
44 #include <asm/debug.h>
45 #include <mm/mmu_decl.h>
46
47 #include "icswx.h"
48
49 #ifdef CONFIG_KPROBES
notify_page_fault(struct pt_regs * regs)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
notify_page_fault(struct pt_regs * regs)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 */
store_updates_sp(struct pt_regs * regs)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
out_of_memory(struct pt_regs * regs)116 static int out_of_memory(struct pt_regs *regs)
117 {
118 /*
119 * We ran out of memory, or some other thing happened to us that made
120 * us unable to handle the page fault gracefully.
121 */
122 up_read(¤t->mm->mmap_sem);
123 if (!user_mode(regs))
124 return MM_FAULT_ERR(SIGKILL);
125 pagefault_out_of_memory();
126 return MM_FAULT_RETURN;
127 }
128
do_sigbus(struct pt_regs * regs,unsigned long address)129 static int do_sigbus(struct pt_regs *regs, unsigned long address)
130 {
131 siginfo_t info;
132
133 up_read(¤t->mm->mmap_sem);
134
135 if (user_mode(regs)) {
136 info.si_signo = SIGBUS;
137 info.si_errno = 0;
138 info.si_code = BUS_ADRERR;
139 info.si_addr = (void __user *)address;
140 force_sig_info(SIGBUS, &info, current);
141 return MM_FAULT_RETURN;
142 }
143 return MM_FAULT_ERR(SIGBUS);
144 }
145
mm_fault_error(struct pt_regs * regs,unsigned long addr,int fault)146 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
147 {
148 /*
149 * Pagefault was interrupted by SIGKILL. We have no reason to
150 * continue the pagefault.
151 */
152 if (fatal_signal_pending(current)) {
153 /*
154 * If we have retry set, the mmap semaphore will have
155 * alrady been released in __lock_page_or_retry(). Else
156 * we release it now.
157 */
158 if (!(fault & VM_FAULT_RETRY))
159 up_read(¤t->mm->mmap_sem);
160 /* Coming from kernel, we need to deal with uaccess fixups */
161 if (user_mode(regs))
162 return MM_FAULT_RETURN;
163 return MM_FAULT_ERR(SIGKILL);
164 }
165
166 /* No fault: be happy */
167 if (!(fault & VM_FAULT_ERROR))
168 return MM_FAULT_CONTINUE;
169
170 /* Out of memory */
171 if (fault & VM_FAULT_OOM)
172 return out_of_memory(regs);
173
174 /* Bus error. x86 handles HWPOISON here, we'll add this if/when
175 * we support the feature in HW
176 */
177 if (fault & VM_FAULT_SIGBUS)
178 return do_sigbus(regs, addr);
179
180 /* We don't understand the fault code, this is fatal */
181 BUG();
182 return MM_FAULT_CONTINUE;
183 }
184
185 /*
186 * For 600- and 800-family processors, the error_code parameter is DSISR
187 * for a data fault, SRR1 for an instruction fault. For 400-family processors
188 * the error_code parameter is ESR for a data fault, 0 for an instruction
189 * fault.
190 * For 64-bit processors, the error_code parameter is
191 * - DSISR for a non-SLB data access fault,
192 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
193 * - 0 any SLB fault.
194 *
195 * The return value is 0 if the fault was handled, or the signal
196 * number if this is a kernel fault that can't be handled here.
197 */
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned long error_code)198 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
199 unsigned long error_code)
200 {
201 struct vm_area_struct * vma;
202 struct mm_struct *mm = current->mm;
203 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
204 int code = SEGV_MAPERR;
205 int is_write = 0;
206 int trap = TRAP(regs);
207 int is_exec = trap == 0x400;
208 int fault;
209
210 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
211 /*
212 * Fortunately the bit assignments in SRR1 for an instruction
213 * fault and DSISR for a data fault are mostly the same for the
214 * bits we are interested in. But there are some bits which
215 * indicate errors in DSISR but can validly be set in SRR1.
216 */
217 if (trap == 0x400)
218 error_code &= 0x48200000;
219 else
220 is_write = error_code & DSISR_ISSTORE;
221 #else
222 is_write = error_code & ESR_DST;
223 #endif /* CONFIG_4xx || CONFIG_BOOKE */
224
225 if (is_write)
226 flags |= FAULT_FLAG_WRITE;
227
228 #ifdef CONFIG_PPC_ICSWX
229 /*
230 * we need to do this early because this "data storage
231 * interrupt" does not update the DAR/DEAR so we don't want to
232 * look at it
233 */
234 if (error_code & ICSWX_DSI_UCT) {
235 int rc = acop_handle_fault(regs, address, error_code);
236 if (rc)
237 return rc;
238 }
239 #endif /* CONFIG_PPC_ICSWX */
240
241 if (notify_page_fault(regs))
242 return 0;
243
244 if (unlikely(debugger_fault_handler(regs)))
245 return 0;
246
247 /* On a kernel SLB miss we can only check for a valid exception entry */
248 if (!user_mode(regs) && (address >= TASK_SIZE))
249 return SIGSEGV;
250
251 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
252 defined(CONFIG_PPC_BOOK3S_64))
253 if (error_code & DSISR_DABRMATCH) {
254 /* DABR match */
255 do_dabr(regs, address, error_code);
256 return 0;
257 }
258 #endif
259
260 /* We restore the interrupt state now */
261 if (!arch_irq_disabled_regs(regs))
262 local_irq_enable();
263
264 if (in_atomic() || mm == NULL) {
265 if (!user_mode(regs))
266 return SIGSEGV;
267 /* in_atomic() in user mode is really bad,
268 as is current->mm == NULL. */
269 printk(KERN_EMERG "Page fault in user mode with "
270 "in_atomic() = %d mm = %p\n", in_atomic(), mm);
271 printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
272 regs->nip, regs->msr);
273 die("Weird page fault", regs, SIGSEGV);
274 }
275
276 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
277
278 /* When running in the kernel we expect faults to occur only to
279 * addresses in user space. All other faults represent errors in the
280 * kernel and should generate an OOPS. Unfortunately, in the case of an
281 * erroneous fault occurring in a code path which already holds mmap_sem
282 * we will deadlock attempting to validate the fault against the
283 * address space. Luckily the kernel only validly references user
284 * space from well defined areas of code, which are listed in the
285 * exceptions table.
286 *
287 * As the vast majority of faults will be valid we will only perform
288 * the source reference check when there is a possibility of a deadlock.
289 * Attempt to lock the address space, if we cannot we then validate the
290 * source. If this is invalid we can skip the address space check,
291 * thus avoiding the deadlock.
292 */
293 if (!down_read_trylock(&mm->mmap_sem)) {
294 if (!user_mode(regs) && !search_exception_tables(regs->nip))
295 goto bad_area_nosemaphore;
296
297 retry:
298 down_read(&mm->mmap_sem);
299 } else {
300 /*
301 * The above down_read_trylock() might have succeeded in
302 * which case we'll have missed the might_sleep() from
303 * down_read():
304 */
305 might_sleep();
306 }
307
308 vma = find_vma(mm, address);
309 if (!vma)
310 goto bad_area;
311 if (vma->vm_start <= address)
312 goto good_area;
313 if (!(vma->vm_flags & VM_GROWSDOWN))
314 goto bad_area;
315
316 /*
317 * N.B. The POWER/Open ABI allows programs to access up to
318 * 288 bytes below the stack pointer.
319 * The kernel signal delivery code writes up to about 1.5kB
320 * below the stack pointer (r1) before decrementing it.
321 * The exec code can write slightly over 640kB to the stack
322 * before setting the user r1. Thus we allow the stack to
323 * expand to 1MB without further checks.
324 */
325 if (address + 0x100000 < vma->vm_end) {
326 /* get user regs even if this fault is in kernel mode */
327 struct pt_regs *uregs = current->thread.regs;
328 if (uregs == NULL)
329 goto bad_area;
330
331 /*
332 * A user-mode access to an address a long way below
333 * the stack pointer is only valid if the instruction
334 * is one which would update the stack pointer to the
335 * address accessed if the instruction completed,
336 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
337 * (or the byte, halfword, float or double forms).
338 *
339 * If we don't check this then any write to the area
340 * between the last mapped region and the stack will
341 * expand the stack rather than segfaulting.
342 */
343 if (address + 2048 < uregs->gpr[1]
344 && (!user_mode(regs) || !store_updates_sp(regs)))
345 goto bad_area;
346 }
347 if (expand_stack(vma, address))
348 goto bad_area;
349
350 good_area:
351 code = SEGV_ACCERR;
352 #if defined(CONFIG_6xx)
353 if (error_code & 0x95700000)
354 /* an error such as lwarx to I/O controller space,
355 address matching DABR, eciwx, etc. */
356 goto bad_area;
357 #endif /* CONFIG_6xx */
358 #if defined(CONFIG_8xx)
359 /* 8xx sometimes need to load a invalid/non-present TLBs.
360 * These must be invalidated separately as linux mm don't.
361 */
362 if (error_code & 0x40000000) /* no translation? */
363 _tlbil_va(address, 0, 0, 0);
364
365 /* The MPC8xx seems to always set 0x80000000, which is
366 * "undefined". Of those that can be set, this is the only
367 * one which seems bad.
368 */
369 if (error_code & 0x10000000)
370 /* Guarded storage error. */
371 goto bad_area;
372 #endif /* CONFIG_8xx */
373
374 if (is_exec) {
375 #ifdef CONFIG_PPC_STD_MMU
376 /* Protection fault on exec go straight to failure on
377 * Hash based MMUs as they either don't support per-page
378 * execute permission, or if they do, it's handled already
379 * at the hash level. This test would probably have to
380 * be removed if we change the way this works to make hash
381 * processors use the same I/D cache coherency mechanism
382 * as embedded.
383 */
384 if (error_code & DSISR_PROTFAULT)
385 goto bad_area;
386 #endif /* CONFIG_PPC_STD_MMU */
387
388 /*
389 * Allow execution from readable areas if the MMU does not
390 * provide separate controls over reading and executing.
391 *
392 * Note: That code used to not be enabled for 4xx/BookE.
393 * It is now as I/D cache coherency for these is done at
394 * set_pte_at() time and I see no reason why the test
395 * below wouldn't be valid on those processors. This -may-
396 * break programs compiled with a really old ABI though.
397 */
398 if (!(vma->vm_flags & VM_EXEC) &&
399 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
400 !(vma->vm_flags & (VM_READ | VM_WRITE))))
401 goto bad_area;
402 /* a write */
403 } else if (is_write) {
404 if (!(vma->vm_flags & VM_WRITE))
405 goto bad_area;
406 /* a read */
407 } else {
408 /* protection fault */
409 if (error_code & 0x08000000)
410 goto bad_area;
411 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
412 goto bad_area;
413 }
414
415 /*
416 * If for any reason at all we couldn't handle the fault,
417 * make sure we exit gracefully rather than endlessly redo
418 * the fault.
419 */
420 fault = handle_mm_fault(mm, vma, address, flags);
421 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
422 int rc = mm_fault_error(regs, address, fault);
423 if (rc >= MM_FAULT_RETURN)
424 return rc;
425 }
426
427 /*
428 * Major/minor page fault accounting is only done on the
429 * initial attempt. If we go through a retry, it is extremely
430 * likely that the page will be found in page cache at that point.
431 */
432 if (flags & FAULT_FLAG_ALLOW_RETRY) {
433 if (fault & VM_FAULT_MAJOR) {
434 current->maj_flt++;
435 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
436 regs, address);
437 #ifdef CONFIG_PPC_SMLPAR
438 if (firmware_has_feature(FW_FEATURE_CMO)) {
439 preempt_disable();
440 get_lppaca()->page_ins += (1 << PAGE_FACTOR);
441 preempt_enable();
442 }
443 #endif /* CONFIG_PPC_SMLPAR */
444 } else {
445 current->min_flt++;
446 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
447 regs, address);
448 }
449 if (fault & VM_FAULT_RETRY) {
450 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
451 * of starvation. */
452 flags &= ~FAULT_FLAG_ALLOW_RETRY;
453 goto retry;
454 }
455 }
456
457 up_read(&mm->mmap_sem);
458 return 0;
459
460 bad_area:
461 up_read(&mm->mmap_sem);
462
463 bad_area_nosemaphore:
464 /* User mode accesses cause a SIGSEGV */
465 if (user_mode(regs)) {
466 _exception(SIGSEGV, regs, code, address);
467 return 0;
468 }
469
470 if (is_exec && (error_code & DSISR_PROTFAULT))
471 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
472 " page (%lx) - exploit attempt? (uid: %d)\n",
473 address, current_uid());
474
475 return SIGSEGV;
476
477 }
478
479 /*
480 * bad_page_fault is called when we have a bad access from the kernel.
481 * It is called from the DSI and ISI handlers in head.S and from some
482 * of the procedures in traps.c.
483 */
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)484 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
485 {
486 const struct exception_table_entry *entry;
487 unsigned long *stackend;
488
489 /* Are we prepared to handle this fault? */
490 if ((entry = search_exception_tables(regs->nip)) != NULL) {
491 regs->nip = entry->fixup;
492 return;
493 }
494
495 /* kernel has accessed a bad area */
496
497 switch (regs->trap) {
498 case 0x300:
499 case 0x380:
500 printk(KERN_ALERT "Unable to handle kernel paging request for "
501 "data at address 0x%08lx\n", regs->dar);
502 break;
503 case 0x400:
504 case 0x480:
505 printk(KERN_ALERT "Unable to handle kernel paging request for "
506 "instruction fetch\n");
507 break;
508 default:
509 printk(KERN_ALERT "Unable to handle kernel paging request for "
510 "unknown fault\n");
511 break;
512 }
513 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
514 regs->nip);
515
516 stackend = end_of_stack(current);
517 if (current != &init_task && *stackend != STACK_END_MAGIC)
518 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
519
520 die("Kernel access of bad area", regs, sig);
521 }
522