1 // SPDX-License-Identifier: GPL-2.0
4 * Copyright IBM Corp. 1999
5 * Author(s): Hartmut Penner (hp@de.ibm.com)
6 * Ulrich Weigand (uweigand@de.ibm.com)
8 * Derived from "arch/i386/mm/fault.c"
9 * Copyright (C) 1995 Linus Torvalds
12 #include <linux/kernel_stat.h>
13 #include <linux/perf_event.h>
14 #include <linux/signal.h>
15 #include <linux/sched.h>
16 #include <linux/sched/debug.h>
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21 #include <linux/ptrace.h>
22 #include <linux/mman.h>
24 #include <linux/compat.h>
25 #include <linux/smp.h>
26 #include <linux/kdebug.h>
27 #include <linux/init.h>
28 #include <linux/console.h>
29 #include <linux/extable.h>
30 #include <linux/hardirq.h>
31 #include <linux/kprobes.h>
32 #include <linux/uaccess.h>
33 #include <linux/hugetlb.h>
34 #include <asm/asm-offsets.h>
36 #include <asm/pgtable.h>
39 #include <asm/mmu_context.h>
40 #include <asm/facility.h>
41 #include "../kernel/entry.h"
43 #define __FAIL_ADDR_MASK -4096L
44 #define __SUBCODE_MASK 0x0600
45 #define __PF_RES_FIELD 0x8000000000000000ULL
47 #define VM_FAULT_BADCONTEXT 0x010000
48 #define VM_FAULT_BADMAP 0x020000
49 #define VM_FAULT_BADACCESS 0x040000
50 #define VM_FAULT_SIGNAL 0x080000
51 #define VM_FAULT_PFAULT 0x100000
60 static unsigned long store_indication __read_mostly
;
62 static int __init
fault_init(void)
64 if (test_facility(75))
65 store_indication
= 0xc00;
68 early_initcall(fault_init
);
70 static inline int notify_page_fault(struct pt_regs
*regs
)
74 /* kprobe_running() needs smp_processor_id() */
75 if (kprobes_built_in() && !user_mode(regs
)) {
77 if (kprobe_running() && kprobe_fault_handler(regs
, 14))
85 * Find out which address space caused the exception.
87 static enum fault_type
get_fault_type(struct pt_regs
*regs
)
89 unsigned long trans_exc_code
;
91 trans_exc_code
= regs
->int_parm_long
& 3;
92 if (likely(trans_exc_code
== 0)) {
93 /* primary space exception */
94 if (IS_ENABLED(CONFIG_PGSTE
) &&
95 test_pt_regs_flag(regs
, PIF_GUEST_FAULT
))
97 if (current
->thread
.mm_segment
== USER_DS
)
101 if (trans_exc_code
== 2) {
102 /* secondary space exception */
103 if (current
->thread
.mm_segment
& 1) {
104 if (current
->thread
.mm_segment
== USER_DS_SACF
)
110 if (trans_exc_code
== 1) {
111 /* access register mode, not used in the kernel */
114 /* home space exception -> access via kernel ASCE */
118 static int bad_address(void *p
)
122 return probe_kernel_address((unsigned long *)p
, dummy
);
125 static void dump_pagetable(unsigned long asce
, unsigned long address
)
127 unsigned long *table
= __va(asce
& _ASCE_ORIGIN
);
129 pr_alert("AS:%016lx ", asce
);
130 switch (asce
& _ASCE_TYPE_MASK
) {
131 case _ASCE_TYPE_REGION1
:
132 table
+= (address
& _REGION1_INDEX
) >> _REGION1_SHIFT
;
133 if (bad_address(table
))
135 pr_cont("R1:%016lx ", *table
);
136 if (*table
& _REGION_ENTRY_INVALID
)
138 table
= (unsigned long *)(*table
& _REGION_ENTRY_ORIGIN
);
140 case _ASCE_TYPE_REGION2
:
141 table
+= (address
& _REGION2_INDEX
) >> _REGION2_SHIFT
;
142 if (bad_address(table
))
144 pr_cont("R2:%016lx ", *table
);
145 if (*table
& _REGION_ENTRY_INVALID
)
147 table
= (unsigned long *)(*table
& _REGION_ENTRY_ORIGIN
);
149 case _ASCE_TYPE_REGION3
:
150 table
+= (address
& _REGION3_INDEX
) >> _REGION3_SHIFT
;
151 if (bad_address(table
))
153 pr_cont("R3:%016lx ", *table
);
154 if (*table
& (_REGION_ENTRY_INVALID
| _REGION3_ENTRY_LARGE
))
156 table
= (unsigned long *)(*table
& _REGION_ENTRY_ORIGIN
);
158 case _ASCE_TYPE_SEGMENT
:
159 table
+= (address
& _SEGMENT_INDEX
) >> _SEGMENT_SHIFT
;
160 if (bad_address(table
))
162 pr_cont("S:%016lx ", *table
);
163 if (*table
& (_SEGMENT_ENTRY_INVALID
| _SEGMENT_ENTRY_LARGE
))
165 table
= (unsigned long *)(*table
& _SEGMENT_ENTRY_ORIGIN
);
167 table
+= (address
& _PAGE_INDEX
) >> _PAGE_SHIFT
;
168 if (bad_address(table
))
170 pr_cont("P:%016lx ", *table
);
178 static void dump_fault_info(struct pt_regs
*regs
)
182 pr_alert("Failing address: %016lx TEID: %016lx\n",
183 regs
->int_parm_long
& __FAIL_ADDR_MASK
, regs
->int_parm_long
);
184 pr_alert("Fault in ");
185 switch (regs
->int_parm_long
& 3) {
187 pr_cont("home space ");
190 pr_cont("secondary space ");
193 pr_cont("access register ");
196 pr_cont("primary space ");
199 pr_cont("mode while using ");
200 switch (get_fault_type(regs
)) {
202 asce
= S390_lowcore
.user_asce
;
206 asce
= S390_lowcore
.vdso_asce
;
210 asce
= ((struct gmap
*) S390_lowcore
.gmap
)->asce
;
214 asce
= S390_lowcore
.kernel_asce
;
221 dump_pagetable(asce
, regs
->int_parm_long
& __FAIL_ADDR_MASK
);
224 int show_unhandled_signals
= 1;
226 void report_user_fault(struct pt_regs
*regs
, long signr
, int is_mm_fault
)
228 if ((task_pid_nr(current
) > 1) && !show_unhandled_signals
)
230 if (!unhandled_signal(current
, signr
))
232 if (!printk_ratelimit())
234 printk(KERN_ALERT
"User process fault: interruption code %04x ilc:%d ",
235 regs
->int_code
& 0xffff, regs
->int_code
>> 17);
236 print_vma_addr(KERN_CONT
"in ", regs
->psw
.addr
);
237 printk(KERN_CONT
"\n");
239 dump_fault_info(regs
);
244 * Send SIGSEGV to task. This is an external routine
245 * to keep the stack usage of do_page_fault small.
247 static noinline
void do_sigsegv(struct pt_regs
*regs
, int si_code
)
249 report_user_fault(regs
, SIGSEGV
, 1);
250 force_sig_fault(SIGSEGV
, si_code
,
251 (void __user
*)(regs
->int_parm_long
& __FAIL_ADDR_MASK
),
255 const struct exception_table_entry
*s390_search_extables(unsigned long addr
)
257 const struct exception_table_entry
*fixup
;
259 fixup
= search_extable(__start_dma_ex_table
,
260 __stop_dma_ex_table
- __start_dma_ex_table
,
263 fixup
= search_exception_tables(addr
);
267 static noinline
void do_no_context(struct pt_regs
*regs
)
269 const struct exception_table_entry
*fixup
;
271 /* Are we prepared to handle this kernel fault? */
272 fixup
= s390_search_extables(regs
->psw
.addr
);
274 regs
->psw
.addr
= extable_fixup(fixup
);
279 * Oops. The kernel tried to access some bad page. We'll have to
280 * terminate things with extreme prejudice.
282 if (get_fault_type(regs
) == KERNEL_FAULT
)
283 printk(KERN_ALERT
"Unable to handle kernel pointer dereference"
284 " in virtual kernel address space\n");
286 printk(KERN_ALERT
"Unable to handle kernel paging request"
287 " in virtual user address space\n");
288 dump_fault_info(regs
);
293 static noinline
void do_low_address(struct pt_regs
*regs
)
295 /* Low-address protection hit in kernel mode means
296 NULL pointer write access in kernel mode. */
297 if (regs
->psw
.mask
& PSW_MASK_PSTATE
) {
298 /* Low-address protection hit in user mode 'cannot happen'. */
299 die (regs
, "Low-address protection");
306 static noinline
void do_sigbus(struct pt_regs
*regs
)
309 * Send a sigbus, regardless of whether we were in kernel
312 force_sig_fault(SIGBUS
, BUS_ADRERR
,
313 (void __user
*)(regs
->int_parm_long
& __FAIL_ADDR_MASK
),
317 static noinline
int signal_return(struct pt_regs
*regs
)
322 rc
= __get_user(instruction
, (u16 __user
*) regs
->psw
.addr
);
325 if (instruction
== 0x0a77) {
326 set_pt_regs_flag(regs
, PIF_SYSCALL
);
327 regs
->int_code
= 0x00040077;
329 } else if (instruction
== 0x0aad) {
330 set_pt_regs_flag(regs
, PIF_SYSCALL
);
331 regs
->int_code
= 0x000400ad;
337 static noinline
void do_fault_error(struct pt_regs
*regs
, int access
,
343 case VM_FAULT_BADACCESS
:
344 if (access
== VM_EXEC
&& signal_return(regs
) == 0)
346 case VM_FAULT_BADMAP
:
347 /* Bad memory access. Check if it is kernel or user space. */
348 if (user_mode(regs
)) {
349 /* User mode accesses just cause a SIGSEGV */
350 si_code
= (fault
== VM_FAULT_BADMAP
) ?
351 SEGV_MAPERR
: SEGV_ACCERR
;
352 do_sigsegv(regs
, si_code
);
355 case VM_FAULT_BADCONTEXT
:
356 case VM_FAULT_PFAULT
:
359 case VM_FAULT_SIGNAL
:
360 if (!user_mode(regs
))
363 default: /* fault & VM_FAULT_ERROR */
364 if (fault
& VM_FAULT_OOM
) {
365 if (!user_mode(regs
))
368 pagefault_out_of_memory();
369 } else if (fault
& VM_FAULT_SIGSEGV
) {
370 /* Kernel mode? Handle exceptions or die */
371 if (!user_mode(regs
))
374 do_sigsegv(regs
, SEGV_MAPERR
);
375 } else if (fault
& VM_FAULT_SIGBUS
) {
376 /* Kernel mode? Handle exceptions or die */
377 if (!user_mode(regs
))
388 * This routine handles page faults. It determines the address,
389 * and the problem, and then passes it off to one of the appropriate
392 * interruption code (int_code):
393 * 04 Protection -> Write-Protection (suprression)
394 * 10 Segment translation -> Not present (nullification)
395 * 11 Page translation -> Not present (nullification)
396 * 3b Region third trans. -> Not present (nullification)
398 static inline vm_fault_t
do_exception(struct pt_regs
*regs
, int access
)
401 struct task_struct
*tsk
;
402 struct mm_struct
*mm
;
403 struct vm_area_struct
*vma
;
404 enum fault_type type
;
405 unsigned long trans_exc_code
;
406 unsigned long address
;
412 * The instruction that caused the program check has
413 * been nullified. Don't signal single step via SIGTRAP.
415 clear_pt_regs_flag(regs
, PIF_PER_TRAP
);
417 if (notify_page_fault(regs
))
421 trans_exc_code
= regs
->int_parm_long
;
424 * Verify that the fault happened in user space, that
425 * we are not in an interrupt and that there is a
428 fault
= VM_FAULT_BADCONTEXT
;
429 type
= get_fault_type(regs
);
434 fault
= VM_FAULT_BADMAP
;
438 if (faulthandler_disabled() || !mm
)
443 address
= trans_exc_code
& __FAIL_ADDR_MASK
;
444 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
445 flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
447 flags
|= FAULT_FLAG_USER
;
448 if (access
== VM_WRITE
|| (trans_exc_code
& store_indication
) == 0x400)
449 flags
|= FAULT_FLAG_WRITE
;
450 down_read(&mm
->mmap_sem
);
453 if (IS_ENABLED(CONFIG_PGSTE
) && type
== GMAP_FAULT
) {
454 gmap
= (struct gmap
*) S390_lowcore
.gmap
;
455 current
->thread
.gmap_addr
= address
;
456 current
->thread
.gmap_write_flag
= !!(flags
& FAULT_FLAG_WRITE
);
457 current
->thread
.gmap_int_code
= regs
->int_code
& 0xffff;
458 address
= __gmap_translate(gmap
, address
);
459 if (address
== -EFAULT
) {
460 fault
= VM_FAULT_BADMAP
;
463 if (gmap
->pfault_enabled
)
464 flags
|= FAULT_FLAG_RETRY_NOWAIT
;
468 fault
= VM_FAULT_BADMAP
;
469 vma
= find_vma(mm
, address
);
473 if (unlikely(vma
->vm_start
> address
)) {
474 if (!(vma
->vm_flags
& VM_GROWSDOWN
))
476 if (expand_stack(vma
, address
))
481 * Ok, we have a good vm_area for this memory access, so
484 fault
= VM_FAULT_BADACCESS
;
485 if (unlikely(!(vma
->vm_flags
& access
)))
488 if (is_vm_hugetlb_page(vma
))
489 address
&= HPAGE_MASK
;
491 * If for any reason at all we couldn't handle the fault,
492 * make sure we exit gracefully rather than endlessly redo
495 fault
= handle_mm_fault(vma
, address
, flags
);
496 /* No reason to continue if interrupted by SIGKILL. */
497 if ((fault
& VM_FAULT_RETRY
) && fatal_signal_pending(current
)) {
498 fault
= VM_FAULT_SIGNAL
;
499 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
503 if (unlikely(fault
& VM_FAULT_ERROR
))
507 * Major/minor page fault accounting is only done on the
508 * initial attempt. If we go through a retry, it is extremely
509 * likely that the page will be found in page cache at that point.
511 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
512 if (fault
& VM_FAULT_MAJOR
) {
514 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1,
518 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1,
521 if (fault
& VM_FAULT_RETRY
) {
522 if (IS_ENABLED(CONFIG_PGSTE
) && gmap
&&
523 (flags
& FAULT_FLAG_RETRY_NOWAIT
)) {
524 /* FAULT_FLAG_RETRY_NOWAIT has been set,
525 * mmap_sem has not been released */
526 current
->thread
.gmap_pfault
= 1;
527 fault
= VM_FAULT_PFAULT
;
530 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
532 flags
&= ~(FAULT_FLAG_ALLOW_RETRY
|
533 FAULT_FLAG_RETRY_NOWAIT
);
534 flags
|= FAULT_FLAG_TRIED
;
535 down_read(&mm
->mmap_sem
);
539 if (IS_ENABLED(CONFIG_PGSTE
) && gmap
) {
540 address
= __gmap_link(gmap
, current
->thread
.gmap_addr
,
542 if (address
== -EFAULT
) {
543 fault
= VM_FAULT_BADMAP
;
546 if (address
== -ENOMEM
) {
547 fault
= VM_FAULT_OOM
;
553 up_read(&mm
->mmap_sem
);
558 void do_protection_exception(struct pt_regs
*regs
)
560 unsigned long trans_exc_code
;
564 trans_exc_code
= regs
->int_parm_long
;
566 * Protection exceptions are suppressing, decrement psw address.
567 * The exception to this rule are aborted transactions, for these
568 * the PSW already points to the correct location.
570 if (!(regs
->int_code
& 0x200))
571 regs
->psw
.addr
= __rewind_psw(regs
->psw
, regs
->int_code
>> 16);
573 * Check for low-address protection. This needs to be treated
574 * as a special case because the translation exception code
575 * field is not guaranteed to contain valid data in this case.
577 if (unlikely(!(trans_exc_code
& 4))) {
578 do_low_address(regs
);
581 if (unlikely(MACHINE_HAS_NX
&& (trans_exc_code
& 0x80))) {
582 regs
->int_parm_long
= (trans_exc_code
& ~PAGE_MASK
) |
583 (regs
->psw
.addr
& PAGE_MASK
);
585 fault
= VM_FAULT_BADACCESS
;
588 fault
= do_exception(regs
, access
);
591 do_fault_error(regs
, access
, fault
);
593 NOKPROBE_SYMBOL(do_protection_exception
);
595 void do_dat_exception(struct pt_regs
*regs
)
600 access
= VM_READ
| VM_EXEC
| VM_WRITE
;
601 fault
= do_exception(regs
, access
);
603 do_fault_error(regs
, access
, fault
);
605 NOKPROBE_SYMBOL(do_dat_exception
);
609 * 'pfault' pseudo page faults routines.
611 static int pfault_disable
;
613 static int __init
nopfault(char *str
)
619 __setup("nopfault", nopfault
);
621 struct pfault_refbk
{
630 } __attribute__ ((packed
, aligned(8)));
632 static struct pfault_refbk pfault_init_refbk
= {
637 .refgaddr
= __LC_LPP
,
638 .refselmk
= 1ULL << 48,
639 .refcmpmk
= 1ULL << 48,
640 .reserved
= __PF_RES_FIELD
643 int pfault_init(void)
649 diag_stat_inc(DIAG_STAT_X258
);
651 " diag %1,%0,0x258\n"
657 : "a" (&pfault_init_refbk
), "m" (pfault_init_refbk
) : "cc");
661 static struct pfault_refbk pfault_fini_refbk
= {
668 void pfault_fini(void)
673 diag_stat_inc(DIAG_STAT_X258
);
678 : : "a" (&pfault_fini_refbk
), "m" (pfault_fini_refbk
) : "cc");
681 static DEFINE_SPINLOCK(pfault_lock
);
682 static LIST_HEAD(pfault_list
);
684 #define PF_COMPLETE 0x0080
687 * The mechanism of our pfault code: if Linux is running as guest, runs a user
688 * space process and the user space process accesses a page that the host has
689 * paged out we get a pfault interrupt.
691 * This allows us, within the guest, to schedule a different process. Without
692 * this mechanism the host would have to suspend the whole virtual cpu until
693 * the page has been paged in.
695 * So when we get such an interrupt then we set the state of the current task
696 * to uninterruptible and also set the need_resched flag. Both happens within
697 * interrupt context(!). If we later on want to return to user space we
698 * recognize the need_resched flag and then call schedule(). It's not very
699 * obvious how this works...
701 * Of course we have a lot of additional fun with the completion interrupt (->
702 * host signals that a page of a process has been paged in and the process can
703 * continue to run). This interrupt can arrive on any cpu and, since we have
704 * virtual cpus, actually appear before the interrupt that signals that a page
707 static void pfault_interrupt(struct ext_code ext_code
,
708 unsigned int param32
, unsigned long param64
)
710 struct task_struct
*tsk
;
715 * Get the external interruption subcode & pfault initial/completion
716 * signal bit. VM stores this in the 'cpu address' field associated
717 * with the external interrupt.
719 subcode
= ext_code
.subcode
;
720 if ((subcode
& 0xff00) != __SUBCODE_MASK
)
722 inc_irq_stat(IRQEXT_PFL
);
723 /* Get the token (= pid of the affected task). */
724 pid
= param64
& LPP_PID_MASK
;
726 tsk
= find_task_by_pid_ns(pid
, &init_pid_ns
);
728 get_task_struct(tsk
);
732 spin_lock(&pfault_lock
);
733 if (subcode
& PF_COMPLETE
) {
734 /* signal bit is set -> a page has been swapped in by VM */
735 if (tsk
->thread
.pfault_wait
== 1) {
736 /* Initial interrupt was faster than the completion
737 * interrupt. pfault_wait is valid. Set pfault_wait
738 * back to zero and wake up the process. This can
739 * safely be done because the task is still sleeping
740 * and can't produce new pfaults. */
741 tsk
->thread
.pfault_wait
= 0;
742 list_del(&tsk
->thread
.list
);
743 wake_up_process(tsk
);
744 put_task_struct(tsk
);
746 /* Completion interrupt was faster than initial
747 * interrupt. Set pfault_wait to -1 so the initial
748 * interrupt doesn't put the task to sleep.
749 * If the task is not running, ignore the completion
750 * interrupt since it must be a leftover of a PFAULT
751 * CANCEL operation which didn't remove all pending
752 * completion interrupts. */
753 if (tsk
->state
== TASK_RUNNING
)
754 tsk
->thread
.pfault_wait
= -1;
757 /* signal bit not set -> a real page is missing. */
758 if (WARN_ON_ONCE(tsk
!= current
))
760 if (tsk
->thread
.pfault_wait
== 1) {
761 /* Already on the list with a reference: put to sleep */
763 } else if (tsk
->thread
.pfault_wait
== -1) {
764 /* Completion interrupt was faster than the initial
765 * interrupt (pfault_wait == -1). Set pfault_wait
766 * back to zero and exit. */
767 tsk
->thread
.pfault_wait
= 0;
769 /* Initial interrupt arrived before completion
770 * interrupt. Let the task sleep.
771 * An extra task reference is needed since a different
772 * cpu may set the task state to TASK_RUNNING again
773 * before the scheduler is reached. */
774 get_task_struct(tsk
);
775 tsk
->thread
.pfault_wait
= 1;
776 list_add(&tsk
->thread
.list
, &pfault_list
);
778 /* Since this must be a userspace fault, there
779 * is no kernel task state to trample. Rely on the
780 * return to userspace schedule() to block. */
781 __set_current_state(TASK_UNINTERRUPTIBLE
);
782 set_tsk_need_resched(tsk
);
783 set_preempt_need_resched();
787 spin_unlock(&pfault_lock
);
788 put_task_struct(tsk
);
791 static int pfault_cpu_dead(unsigned int cpu
)
793 struct thread_struct
*thread
, *next
;
794 struct task_struct
*tsk
;
796 spin_lock_irq(&pfault_lock
);
797 list_for_each_entry_safe(thread
, next
, &pfault_list
, list
) {
798 thread
->pfault_wait
= 0;
799 list_del(&thread
->list
);
800 tsk
= container_of(thread
, struct task_struct
, thread
);
801 wake_up_process(tsk
);
802 put_task_struct(tsk
);
804 spin_unlock_irq(&pfault_lock
);
808 static int __init
pfault_irq_init(void)
812 rc
= register_external_irq(EXT_IRQ_CP_SERVICE
, pfault_interrupt
);
815 rc
= pfault_init() == 0 ? 0 : -EOPNOTSUPP
;
818 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL
);
819 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD
, "s390/pfault:dead",
820 NULL
, pfault_cpu_dead
);
824 unregister_external_irq(EXT_IRQ_CP_SERVICE
, pfault_interrupt
);
829 early_initcall(pfault_irq_init
);
831 #endif /* CONFIG_PFAULT */