3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
5 * Derived from "arch/i386/mm/fault.c"
6 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * Modified by Cort Dougan and Paul Mackerras.
10 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
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.
18 #include <linux/signal.h>
19 #include <linux/sched.h>
20 #include <linux/sched/task_stack.h>
21 #include <linux/kernel.h>
22 #include <linux/errno.h>
23 #include <linux/string.h>
24 #include <linux/types.h>
25 #include <linux/pagemap.h>
26 #include <linux/ptrace.h>
27 #include <linux/mman.h>
29 #include <linux/interrupt.h>
30 #include <linux/highmem.h>
31 #include <linux/extable.h>
32 #include <linux/kprobes.h>
33 #include <linux/kdebug.h>
34 #include <linux/perf_event.h>
35 #include <linux/ratelimit.h>
36 #include <linux/context_tracking.h>
37 #include <linux/hugetlb.h>
38 #include <linux/uaccess.h>
40 #include <asm/firmware.h>
42 #include <asm/pgtable.h>
44 #include <asm/mmu_context.h>
45 #include <asm/siginfo.h>
46 #include <asm/debug.h>
48 static inline bool notify_page_fault(struct pt_regs
*regs
)
53 /* kprobe_running() needs smp_processor_id() */
54 if (!user_mode(regs
)) {
56 if (kprobe_running() && kprobe_fault_handler(regs
, 11))
60 #endif /* CONFIG_KPROBES */
62 if (unlikely(debugger_fault_handler(regs
)))
69 * Check whether the instruction inst is a store using
70 * an update addressing form which will update r1.
72 static bool store_updates_sp(unsigned int inst
)
74 /* check for 1 in the rA field */
75 if (((inst
>> 16) & 0x1f) != 1)
77 /* check major opcode */
85 case OP_STD
: /* std or stdu */
86 return (inst
& 3) == 1;
88 /* check minor opcode */
89 switch ((inst
>> 1) & 0x3ff) {
94 case OP_31_XOP_STFSUX
:
95 case OP_31_XOP_STFDUX
:
102 * do_page_fault error handling helpers
106 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long address
, int si_code
)
109 * If we are in kernel mode, bail out with a SEGV, this will
110 * be caught by the assembly which will restore the non-volatile
111 * registers before calling bad_page_fault()
113 if (!user_mode(regs
))
116 _exception(SIGSEGV
, regs
, si_code
, address
);
121 static noinline
int bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long address
)
123 return __bad_area_nosemaphore(regs
, address
, SEGV_MAPERR
);
126 static int __bad_area(struct pt_regs
*regs
, unsigned long address
, int si_code
)
128 struct mm_struct
*mm
= current
->mm
;
131 * Something tried to access memory that isn't in our memory map..
132 * Fix it, but check if it's kernel or user first..
134 up_read(&mm
->mmap_sem
);
136 return __bad_area_nosemaphore(regs
, address
, si_code
);
139 static noinline
int bad_area(struct pt_regs
*regs
, unsigned long address
)
141 return __bad_area(regs
, address
, SEGV_MAPERR
);
144 static int bad_key_fault_exception(struct pt_regs
*regs
, unsigned long address
,
148 * If we are in kernel mode, bail out with a SEGV, this will
149 * be caught by the assembly which will restore the non-volatile
150 * registers before calling bad_page_fault()
152 if (!user_mode(regs
))
155 _exception_pkey(regs
, address
, pkey
);
160 static noinline
int bad_access(struct pt_regs
*regs
, unsigned long address
)
162 return __bad_area(regs
, address
, SEGV_ACCERR
);
165 static int do_sigbus(struct pt_regs
*regs
, unsigned long address
,
168 if (!user_mode(regs
))
171 current
->thread
.trap_nr
= BUS_ADRERR
;
172 #ifdef CONFIG_MEMORY_FAILURE
173 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
174 unsigned int lsb
= 0; /* shutup gcc */
176 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
177 current
->comm
, current
->pid
, address
);
179 if (fault
& VM_FAULT_HWPOISON_LARGE
)
180 lsb
= hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault
));
181 if (fault
& VM_FAULT_HWPOISON
)
184 force_sig_mceerr(BUS_MCEERR_AR
, (void __user
*)address
, lsb
,
190 force_sig_fault(SIGBUS
, BUS_ADRERR
, (void __user
*)address
, current
);
194 static int mm_fault_error(struct pt_regs
*regs
, unsigned long addr
,
198 * Kernel page fault interrupted by SIGKILL. We have no reason to
199 * continue processing.
201 if (fatal_signal_pending(current
) && !user_mode(regs
))
205 if (fault
& VM_FAULT_OOM
) {
207 * We ran out of memory, or some other thing happened to us that
208 * made us unable to handle the page fault gracefully.
210 if (!user_mode(regs
))
212 pagefault_out_of_memory();
214 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
215 VM_FAULT_HWPOISON_LARGE
))
216 return do_sigbus(regs
, addr
, fault
);
217 else if (fault
& VM_FAULT_SIGSEGV
)
218 return bad_area_nosemaphore(regs
, addr
);
225 /* Is this a bad kernel fault ? */
226 static bool bad_kernel_fault(bool is_exec
, unsigned long error_code
,
227 unsigned long address
)
229 if (is_exec
&& (error_code
& (DSISR_NOEXEC_OR_G
| DSISR_KEYFAULT
))) {
230 printk_ratelimited(KERN_CRIT
"kernel tried to execute"
231 " exec-protected page (%lx) -"
232 "exploit attempt? (uid: %d)\n",
233 address
, from_kuid(&init_user_ns
,
236 return is_exec
|| (address
>= TASK_SIZE
);
239 static bool bad_stack_expansion(struct pt_regs
*regs
, unsigned long address
,
240 struct vm_area_struct
*vma
, unsigned int flags
,
244 * N.B. The POWER/Open ABI allows programs to access up to
245 * 288 bytes below the stack pointer.
246 * The kernel signal delivery code writes up to about 1.5kB
247 * below the stack pointer (r1) before decrementing it.
248 * The exec code can write slightly over 640kB to the stack
249 * before setting the user r1. Thus we allow the stack to
250 * expand to 1MB without further checks.
252 if (address
+ 0x100000 < vma
->vm_end
) {
253 unsigned int __user
*nip
= (unsigned int __user
*)regs
->nip
;
254 /* get user regs even if this fault is in kernel mode */
255 struct pt_regs
*uregs
= current
->thread
.regs
;
260 * A user-mode access to an address a long way below
261 * the stack pointer is only valid if the instruction
262 * is one which would update the stack pointer to the
263 * address accessed if the instruction completed,
264 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
265 * (or the byte, halfword, float or double forms).
267 * If we don't check this then any write to the area
268 * between the last mapped region and the stack will
269 * expand the stack rather than segfaulting.
271 if (address
+ 2048 >= uregs
->gpr
[1])
274 if ((flags
& FAULT_FLAG_WRITE
) && (flags
& FAULT_FLAG_USER
) &&
275 access_ok(VERIFY_READ
, nip
, sizeof(*nip
))) {
280 res
= __get_user_inatomic(inst
, nip
);
283 return !store_updates_sp(inst
);
291 static bool access_error(bool is_write
, bool is_exec
,
292 struct vm_area_struct
*vma
)
295 * Allow execution from readable areas if the MMU does not
296 * provide separate controls over reading and executing.
298 * Note: That code used to not be enabled for 4xx/BookE.
299 * It is now as I/D cache coherency for these is done at
300 * set_pte_at() time and I see no reason why the test
301 * below wouldn't be valid on those processors. This -may-
302 * break programs compiled with a really old ABI though.
305 return !(vma
->vm_flags
& VM_EXEC
) &&
306 (cpu_has_feature(CPU_FTR_NOEXECUTE
) ||
307 !(vma
->vm_flags
& (VM_READ
| VM_WRITE
)));
311 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
316 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
319 * We should ideally do the vma pkey access check here. But in the
320 * fault path, handle_mm_fault() also does the same check. To avoid
321 * these multiple checks, we skip it here and handle access error due
327 #ifdef CONFIG_PPC_SMLPAR
328 static inline void cmo_account_page_fault(void)
330 if (firmware_has_feature(FW_FEATURE_CMO
)) {
334 page_ins
= be32_to_cpu(get_lppaca()->page_ins
);
335 page_ins
+= 1 << PAGE_FACTOR
;
336 get_lppaca()->page_ins
= cpu_to_be32(page_ins
);
341 static inline void cmo_account_page_fault(void) { }
342 #endif /* CONFIG_PPC_SMLPAR */
344 #ifdef CONFIG_PPC_STD_MMU
345 static void sanity_check_fault(bool is_write
, unsigned long error_code
)
348 * For hash translation mode, we should never get a
349 * PROTFAULT. Any update to pte to reduce access will result in us
350 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
351 * fault instead of DSISR_PROTFAULT.
353 * A pte update to relax the access will not result in a hash page table
354 * entry invalidate and hence can result in DSISR_PROTFAULT.
355 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
356 * the special !is_write in the below conditional.
358 * For platforms that doesn't supports coherent icache and do support
359 * per page noexec bit, we do setup things such that we do the
360 * sync between D/I cache via fault. But that is handled via low level
361 * hash fault code (hash_page_do_lazy_icache()) and we should not reach
364 * For wrong access that can result in PROTFAULT, the above vma->vm_flags
365 * check should handle those and hence we should fall to the bad_area
366 * handling correctly.
368 * For embedded with per page exec support that doesn't support coherent
369 * icache we do get PROTFAULT and we handle that D/I cache sync in
370 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
371 * is conditional for server MMU.
373 * For radix, we can get prot fault for autonuma case, because radix
374 * page table will have them marked noaccess for user.
376 if (!radix_enabled() && !is_write
)
377 WARN_ON_ONCE(error_code
& DSISR_PROTFAULT
);
380 static void sanity_check_fault(bool is_write
, unsigned long error_code
) { }
381 #endif /* CONFIG_PPC_STD_MMU */
384 * Define the correct "is_write" bit in error_code based
385 * on the processor family
387 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
388 #define page_fault_is_write(__err) ((__err) & ESR_DST)
389 #define page_fault_is_bad(__err) (0)
391 #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
392 #if defined(CONFIG_PPC_8xx)
393 #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
394 #elif defined(CONFIG_PPC64)
395 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
397 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
402 * For 600- and 800-family processors, the error_code parameter is DSISR
403 * for a data fault, SRR1 for an instruction fault. For 400-family processors
404 * the error_code parameter is ESR for a data fault, 0 for an instruction
406 * For 64-bit processors, the error_code parameter is
407 * - DSISR for a non-SLB data access fault,
408 * - SRR1 & 0x08000000 for a non-SLB instruction access fault
411 * The return value is 0 if the fault was handled, or the signal
412 * number if this is a kernel fault that can't be handled here.
414 static int __do_page_fault(struct pt_regs
*regs
, unsigned long address
,
415 unsigned long error_code
)
417 struct vm_area_struct
* vma
;
418 struct mm_struct
*mm
= current
->mm
;
419 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
420 int is_exec
= TRAP(regs
) == 0x400;
421 int is_user
= user_mode(regs
);
422 int is_write
= page_fault_is_write(error_code
);
423 vm_fault_t fault
, major
= 0;
424 bool must_retry
= false;
426 if (notify_page_fault(regs
))
429 if (unlikely(page_fault_is_bad(error_code
))) {
431 _exception(SIGBUS
, regs
, BUS_OBJERR
, address
);
437 /* Additional sanity check(s) */
438 sanity_check_fault(is_write
, error_code
);
441 * The kernel should never take an execute fault nor should it
442 * take a page fault to a kernel address.
444 if (unlikely(!is_user
&& bad_kernel_fault(is_exec
, error_code
, address
)))
448 * If we're in an interrupt, have no user context or are running
449 * in a region with pagefaults disabled then we must not take the fault
451 if (unlikely(faulthandler_disabled() || !mm
)) {
453 printk_ratelimited(KERN_ERR
"Page fault in user mode"
454 " with faulthandler_disabled()=%d"
456 faulthandler_disabled(), mm
);
457 return bad_area_nosemaphore(regs
, address
);
460 /* We restore the interrupt state now */
461 if (!arch_irq_disabled_regs(regs
))
464 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
466 if (error_code
& DSISR_KEYFAULT
)
467 return bad_key_fault_exception(regs
, address
,
468 get_mm_addr_key(mm
, address
));
471 * We want to do this outside mmap_sem, because reading code around nip
472 * can result in fault, which will cause a deadlock when called with
476 flags
|= FAULT_FLAG_USER
;
478 flags
|= FAULT_FLAG_WRITE
;
480 flags
|= FAULT_FLAG_INSTRUCTION
;
482 /* When running in the kernel we expect faults to occur only to
483 * addresses in user space. All other faults represent errors in the
484 * kernel and should generate an OOPS. Unfortunately, in the case of an
485 * erroneous fault occurring in a code path which already holds mmap_sem
486 * we will deadlock attempting to validate the fault against the
487 * address space. Luckily the kernel only validly references user
488 * space from well defined areas of code, which are listed in the
491 * As the vast majority of faults will be valid we will only perform
492 * the source reference check when there is a possibility of a deadlock.
493 * Attempt to lock the address space, if we cannot we then validate the
494 * source. If this is invalid we can skip the address space check,
495 * thus avoiding the deadlock.
497 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
498 if (!is_user
&& !search_exception_tables(regs
->nip
))
499 return bad_area_nosemaphore(regs
, address
);
502 down_read(&mm
->mmap_sem
);
505 * The above down_read_trylock() might have succeeded in
506 * which case we'll have missed the might_sleep() from
512 vma
= find_vma(mm
, address
);
514 return bad_area(regs
, address
);
515 if (likely(vma
->vm_start
<= address
))
517 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
)))
518 return bad_area(regs
, address
);
520 /* The stack is being expanded, check if it's valid */
521 if (unlikely(bad_stack_expansion(regs
, address
, vma
, flags
,
524 return bad_area(regs
, address
);
526 up_read(&mm
->mmap_sem
);
527 if (fault_in_pages_readable((const char __user
*)regs
->nip
,
528 sizeof(unsigned int)))
529 return bad_area_nosemaphore(regs
, address
);
533 /* Try to expand it */
534 if (unlikely(expand_stack(vma
, address
)))
535 return bad_area(regs
, address
);
538 if (unlikely(access_error(is_write
, is_exec
, vma
)))
539 return bad_access(regs
, address
);
542 * If for any reason at all we couldn't handle the fault,
543 * make sure we exit gracefully rather than endlessly redo
546 fault
= handle_mm_fault(vma
, address
, flags
);
548 #ifdef CONFIG_PPC_MEM_KEYS
550 * we skipped checking for access error due to key earlier.
551 * Check that using handle_mm_fault error return.
553 if (unlikely(fault
& VM_FAULT_SIGSEGV
) &&
554 !arch_vma_access_permitted(vma
, is_write
, is_exec
, 0)) {
556 int pkey
= vma_pkey(vma
);
558 up_read(&mm
->mmap_sem
);
559 return bad_key_fault_exception(regs
, address
, pkey
);
561 #endif /* CONFIG_PPC_MEM_KEYS */
563 major
|= fault
& VM_FAULT_MAJOR
;
566 * Handle the retry right now, the mmap_sem has been released in that
569 if (unlikely(fault
& VM_FAULT_RETRY
)) {
570 /* We retry only once */
571 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
573 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
576 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
577 flags
|= FAULT_FLAG_TRIED
;
578 if (!fatal_signal_pending(current
))
583 * User mode? Just return to handle the fatal exception otherwise
584 * return to bad_page_fault
586 return is_user
? 0 : SIGBUS
;
589 up_read(¤t
->mm
->mmap_sem
);
591 if (unlikely(fault
& VM_FAULT_ERROR
))
592 return mm_fault_error(regs
, address
, fault
);
595 * Major/minor page fault accounting.
599 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1, regs
, address
);
600 cmo_account_page_fault();
603 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1, regs
, address
);
607 NOKPROBE_SYMBOL(__do_page_fault
);
609 int do_page_fault(struct pt_regs
*regs
, unsigned long address
,
610 unsigned long error_code
)
612 enum ctx_state prev_state
= exception_enter();
613 int rc
= __do_page_fault(regs
, address
, error_code
);
614 exception_exit(prev_state
);
617 NOKPROBE_SYMBOL(do_page_fault
);
620 * bad_page_fault is called when we have a bad access from the kernel.
621 * It is called from the DSI and ISI handlers in head.S and from some
622 * of the procedures in traps.c.
624 void bad_page_fault(struct pt_regs
*regs
, unsigned long address
, int sig
)
626 const struct exception_table_entry
*entry
;
628 /* Are we prepared to handle this fault? */
629 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
630 regs
->nip
= extable_fixup(entry
);
634 /* kernel has accessed a bad area */
636 switch (TRAP(regs
)) {
640 printk(KERN_ALERT
"Unable to handle kernel paging request for "
641 "data at address 0x%08lx\n", regs
->dar
);
645 printk(KERN_ALERT
"Unable to handle kernel paging request for "
646 "instruction fetch\n");
649 printk(KERN_ALERT
"Unable to handle kernel paging request for "
650 "unaligned access at address 0x%08lx\n", regs
->dar
);
653 printk(KERN_ALERT
"Unable to handle kernel paging request for "
657 printk(KERN_ALERT
"Faulting instruction address: 0x%08lx\n",
660 if (task_stack_end_corrupted(current
))
661 printk(KERN_ALERT
"Thread overran stack, or stack corrupted\n");
663 die("Kernel access of bad area", regs
, sig
);