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))
86 * Unlock any spinlocks which will prevent us from getting the
89 void bust_spinlocks(int yes)
94 int loglevel_save = console_loglevel;
98 * OK, the message is on the console. Now we call printk()
99 * without oops_in_progress set so that printk will give klogd
100 * a poke. Hold onto your hats...
102 console_loglevel = 15;
104 console_loglevel = loglevel_save;
109 * Find out which address space caused the exception.
110 * Access register mode is impossible, ignore space == 3.
112 static inline enum fault_type get_fault_type(struct pt_regs *regs)
114 unsigned long trans_exc_code;
116 trans_exc_code = regs->int_parm_long & 3;
117 if (likely(trans_exc_code == 0)) {
118 /* primary space exception */
119 if (IS_ENABLED(CONFIG_PGSTE) &&
120 test_pt_regs_flag(regs, PIF_GUEST_FAULT))
122 if (current->thread.mm_segment == USER_DS)
126 if (trans_exc_code == 2) {
127 /* secondary space exception */
128 if (current->thread.mm_segment & 1) {
129 if (current->thread.mm_segment == USER_DS_SACF)
135 /* home space exception -> access via kernel ASCE */
139 static int bad_address(void *p)
143 return probe_kernel_address((unsigned long *)p, dummy);
146 static void dump_pagetable(unsigned long asce, unsigned long address)
148 unsigned long *table = __va(asce & _ASCE_ORIGIN);
150 pr_alert("AS:%016lx ", asce);
151 switch (asce & _ASCE_TYPE_MASK) {
152 case _ASCE_TYPE_REGION1:
153 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
154 if (bad_address(table))
156 pr_cont("R1:%016lx ", *table);
157 if (*table & _REGION_ENTRY_INVALID)
159 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
161 case _ASCE_TYPE_REGION2:
162 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
163 if (bad_address(table))
165 pr_cont("R2:%016lx ", *table);
166 if (*table & _REGION_ENTRY_INVALID)
168 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
170 case _ASCE_TYPE_REGION3:
171 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
172 if (bad_address(table))
174 pr_cont("R3:%016lx ", *table);
175 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
177 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
179 case _ASCE_TYPE_SEGMENT:
180 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
181 if (bad_address(table))
183 pr_cont("S:%016lx ", *table);
184 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
186 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
188 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT;
189 if (bad_address(table))
191 pr_cont("P:%016lx ", *table);
199 static void dump_fault_info(struct pt_regs *regs)
203 pr_alert("Failing address: %016lx TEID: %016lx\n",
204 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long);
205 pr_alert("Fault in ");
206 switch (regs->int_parm_long & 3) {
208 pr_cont("home space ");
211 pr_cont("secondary space ");
214 pr_cont("access register ");
217 pr_cont("primary space ");
220 pr_cont("mode while using ");
221 switch (get_fault_type(regs)) {
223 asce = S390_lowcore.user_asce;
227 asce = S390_lowcore.vdso_asce;
231 asce = ((struct gmap *) S390_lowcore.gmap)->asce;
235 asce = S390_lowcore.kernel_asce;
240 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK);
243 int show_unhandled_signals = 1;
245 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
247 if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
249 if (!unhandled_signal(current, signr))
251 if (!printk_ratelimit())
253 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ",
254 regs->int_code & 0xffff, regs->int_code >> 17);
255 print_vma_addr(KERN_CONT "in ", regs->psw.addr);
256 printk(KERN_CONT "\n");
258 dump_fault_info(regs);
263 * Send SIGSEGV to task. This is an external routine
264 * to keep the stack usage of do_page_fault small.
266 static noinline void do_sigsegv(struct pt_regs *regs, int si_code)
268 report_user_fault(regs, SIGSEGV, 1);
269 force_sig_fault(SIGSEGV, si_code,
270 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK),
274 static noinline void do_no_context(struct pt_regs *regs)
276 const struct exception_table_entry *fixup;
278 /* Are we prepared to handle this kernel fault? */
279 fixup = search_exception_tables(regs->psw.addr);
281 regs->psw.addr = extable_fixup(fixup);
286 * Oops. The kernel tried to access some bad page. We'll have to
287 * terminate things with extreme prejudice.
289 if (get_fault_type(regs) == KERNEL_FAULT)
290 printk(KERN_ALERT "Unable to handle kernel pointer dereference"
291 " in virtual kernel address space\n");
293 printk(KERN_ALERT "Unable to handle kernel paging request"
294 " in virtual user address space\n");
295 dump_fault_info(regs);
300 static noinline void do_low_address(struct pt_regs *regs)
302 /* Low-address protection hit in kernel mode means
303 NULL pointer write access in kernel mode. */
304 if (regs->psw.mask & PSW_MASK_PSTATE) {
305 /* Low-address protection hit in user mode 'cannot happen'. */
306 die (regs, "Low-address protection");
313 static noinline void do_sigbus(struct pt_regs *regs)
316 * Send a sigbus, regardless of whether we were in kernel
319 force_sig_fault(SIGBUS, BUS_ADRERR,
320 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK),
324 static noinline int signal_return(struct pt_regs *regs)
329 rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
332 if (instruction == 0x0a77) {
333 set_pt_regs_flag(regs, PIF_SYSCALL);
334 regs->int_code = 0x00040077;
336 } else if (instruction == 0x0aad) {
337 set_pt_regs_flag(regs, PIF_SYSCALL);
338 regs->int_code = 0x000400ad;
344 static noinline void do_fault_error(struct pt_regs *regs, int access,
350 case VM_FAULT_BADACCESS:
351 if (access == VM_EXEC && signal_return(regs) == 0)
353 case VM_FAULT_BADMAP:
354 /* Bad memory access. Check if it is kernel or user space. */
355 if (user_mode(regs)) {
356 /* User mode accesses just cause a SIGSEGV */
357 si_code = (fault == VM_FAULT_BADMAP) ?
358 SEGV_MAPERR : SEGV_ACCERR;
359 do_sigsegv(regs, si_code);
362 case VM_FAULT_BADCONTEXT:
363 case VM_FAULT_PFAULT:
366 case VM_FAULT_SIGNAL:
367 if (!user_mode(regs))
370 default: /* fault & VM_FAULT_ERROR */
371 if (fault & VM_FAULT_OOM) {
372 if (!user_mode(regs))
375 pagefault_out_of_memory();
376 } else if (fault & VM_FAULT_SIGSEGV) {
377 /* Kernel mode? Handle exceptions or die */
378 if (!user_mode(regs))
381 do_sigsegv(regs, SEGV_MAPERR);
382 } else if (fault & VM_FAULT_SIGBUS) {
383 /* Kernel mode? Handle exceptions or die */
384 if (!user_mode(regs))
395 * This routine handles page faults. It determines the address,
396 * and the problem, and then passes it off to one of the appropriate
399 * interruption code (int_code):
400 * 04 Protection -> Write-Protection (suprression)
401 * 10 Segment translation -> Not present (nullification)
402 * 11 Page translation -> Not present (nullification)
403 * 3b Region third trans. -> Not present (nullification)
405 static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
408 struct task_struct *tsk;
409 struct mm_struct *mm;
410 struct vm_area_struct *vma;
411 enum fault_type type;
412 unsigned long trans_exc_code;
413 unsigned long address;
419 * The instruction that caused the program check has
420 * been nullified. Don't signal single step via SIGTRAP.
422 clear_pt_regs_flag(regs, PIF_PER_TRAP);
424 if (notify_page_fault(regs))
428 trans_exc_code = regs->int_parm_long;
431 * Verify that the fault happened in user space, that
432 * we are not in an interrupt and that there is a
435 fault = VM_FAULT_BADCONTEXT;
436 type = get_fault_type(regs);
441 fault = VM_FAULT_BADMAP;
445 if (faulthandler_disabled() || !mm)
450 address = trans_exc_code & __FAIL_ADDR_MASK;
451 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
452 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
454 flags |= FAULT_FLAG_USER;
455 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
456 flags |= FAULT_FLAG_WRITE;
457 down_read(&mm->mmap_sem);
460 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) {
461 gmap = (struct gmap *) S390_lowcore.gmap;
462 current->thread.gmap_addr = address;
463 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE);
464 current->thread.gmap_int_code = regs->int_code & 0xffff;
465 address = __gmap_translate(gmap, address);
466 if (address == -EFAULT) {
467 fault = VM_FAULT_BADMAP;
470 if (gmap->pfault_enabled)
471 flags |= FAULT_FLAG_RETRY_NOWAIT;
475 fault = VM_FAULT_BADMAP;
476 vma = find_vma(mm, address);
480 if (unlikely(vma->vm_start > address)) {
481 if (!(vma->vm_flags & VM_GROWSDOWN))
483 if (expand_stack(vma, address))
488 * Ok, we have a good vm_area for this memory access, so
491 fault = VM_FAULT_BADACCESS;
492 if (unlikely(!(vma->vm_flags & access)))
495 if (is_vm_hugetlb_page(vma))
496 address &= HPAGE_MASK;
498 * If for any reason at all we couldn't handle the fault,
499 * make sure we exit gracefully rather than endlessly redo
502 fault = handle_mm_fault(vma, address, flags);
503 /* No reason to continue if interrupted by SIGKILL. */
504 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
505 fault = VM_FAULT_SIGNAL;
506 if (flags & FAULT_FLAG_RETRY_NOWAIT)
510 if (unlikely(fault & VM_FAULT_ERROR))
514 * Major/minor page fault accounting is only done on the
515 * initial attempt. If we go through a retry, it is extremely
516 * likely that the page will be found in page cache at that point.
518 if (flags & FAULT_FLAG_ALLOW_RETRY) {
519 if (fault & VM_FAULT_MAJOR) {
521 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
525 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
528 if (fault & VM_FAULT_RETRY) {
529 if (IS_ENABLED(CONFIG_PGSTE) && gmap &&
530 (flags & FAULT_FLAG_RETRY_NOWAIT)) {
531 /* FAULT_FLAG_RETRY_NOWAIT has been set,
532 * mmap_sem has not been released */
533 current->thread.gmap_pfault = 1;
534 fault = VM_FAULT_PFAULT;
537 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
539 flags &= ~(FAULT_FLAG_ALLOW_RETRY |
540 FAULT_FLAG_RETRY_NOWAIT);
541 flags |= FAULT_FLAG_TRIED;
542 down_read(&mm->mmap_sem);
546 if (IS_ENABLED(CONFIG_PGSTE) && gmap) {
547 address = __gmap_link(gmap, current->thread.gmap_addr,
549 if (address == -EFAULT) {
550 fault = VM_FAULT_BADMAP;
553 if (address == -ENOMEM) {
554 fault = VM_FAULT_OOM;
560 up_read(&mm->mmap_sem);
565 void do_protection_exception(struct pt_regs *regs)
567 unsigned long trans_exc_code;
571 trans_exc_code = regs->int_parm_long;
573 * Protection exceptions are suppressing, decrement psw address.
574 * The exception to this rule are aborted transactions, for these
575 * the PSW already points to the correct location.
577 if (!(regs->int_code & 0x200))
578 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
580 * Check for low-address protection. This needs to be treated
581 * as a special case because the translation exception code
582 * field is not guaranteed to contain valid data in this case.
584 if (unlikely(!(trans_exc_code & 4))) {
585 do_low_address(regs);
588 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) {
589 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) |
590 (regs->psw.addr & PAGE_MASK);
592 fault = VM_FAULT_BADACCESS;
595 fault = do_exception(regs, access);
598 do_fault_error(regs, access, fault);
600 NOKPROBE_SYMBOL(do_protection_exception);
602 void do_dat_exception(struct pt_regs *regs)
607 access = VM_READ | VM_EXEC | VM_WRITE;
608 fault = do_exception(regs, access);
610 do_fault_error(regs, access, fault);
612 NOKPROBE_SYMBOL(do_dat_exception);
616 * 'pfault' pseudo page faults routines.
618 static int pfault_disable;
620 static int __init nopfault(char *str)
626 __setup("nopfault", nopfault);
628 struct pfault_refbk {
637 } __attribute__ ((packed, aligned(8)));
639 static struct pfault_refbk pfault_init_refbk = {
644 .refgaddr = __LC_LPP,
645 .refselmk = 1ULL << 48,
646 .refcmpmk = 1ULL << 48,
647 .reserved = __PF_RES_FIELD
650 int pfault_init(void)
656 diag_stat_inc(DIAG_STAT_X258);
658 " diag %1,%0,0x258\n"
664 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc");
668 static struct pfault_refbk pfault_fini_refbk = {
675 void pfault_fini(void)
680 diag_stat_inc(DIAG_STAT_X258);
685 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc");
688 static DEFINE_SPINLOCK(pfault_lock);
689 static LIST_HEAD(pfault_list);
691 #define PF_COMPLETE 0x0080
694 * The mechanism of our pfault code: if Linux is running as guest, runs a user
695 * space process and the user space process accesses a page that the host has
696 * paged out we get a pfault interrupt.
698 * This allows us, within the guest, to schedule a different process. Without
699 * this mechanism the host would have to suspend the whole virtual cpu until
700 * the page has been paged in.
702 * So when we get such an interrupt then we set the state of the current task
703 * to uninterruptible and also set the need_resched flag. Both happens within
704 * interrupt context(!). If we later on want to return to user space we
705 * recognize the need_resched flag and then call schedule(). It's not very
706 * obvious how this works...
708 * Of course we have a lot of additional fun with the completion interrupt (->
709 * host signals that a page of a process has been paged in and the process can
710 * continue to run). This interrupt can arrive on any cpu and, since we have
711 * virtual cpus, actually appear before the interrupt that signals that a page
714 static void pfault_interrupt(struct ext_code ext_code,
715 unsigned int param32, unsigned long param64)
717 struct task_struct *tsk;
722 * Get the external interruption subcode & pfault initial/completion
723 * signal bit. VM stores this in the 'cpu address' field associated
724 * with the external interrupt.
726 subcode = ext_code.subcode;
727 if ((subcode & 0xff00) != __SUBCODE_MASK)
729 inc_irq_stat(IRQEXT_PFL);
730 /* Get the token (= pid of the affected task). */
731 pid = param64 & LPP_PID_MASK;
733 tsk = find_task_by_pid_ns(pid, &init_pid_ns);
735 get_task_struct(tsk);
739 spin_lock(&pfault_lock);
740 if (subcode & PF_COMPLETE) {
741 /* signal bit is set -> a page has been swapped in by VM */
742 if (tsk->thread.pfault_wait == 1) {
743 /* Initial interrupt was faster than the completion
744 * interrupt. pfault_wait is valid. Set pfault_wait
745 * back to zero and wake up the process. This can
746 * safely be done because the task is still sleeping
747 * and can't produce new pfaults. */
748 tsk->thread.pfault_wait = 0;
749 list_del(&tsk->thread.list);
750 wake_up_process(tsk);
751 put_task_struct(tsk);
753 /* Completion interrupt was faster than initial
754 * interrupt. Set pfault_wait to -1 so the initial
755 * interrupt doesn't put the task to sleep.
756 * If the task is not running, ignore the completion
757 * interrupt since it must be a leftover of a PFAULT
758 * CANCEL operation which didn't remove all pending
759 * completion interrupts. */
760 if (tsk->state == TASK_RUNNING)
761 tsk->thread.pfault_wait = -1;
764 /* signal bit not set -> a real page is missing. */
765 if (WARN_ON_ONCE(tsk != current))
767 if (tsk->thread.pfault_wait == 1) {
768 /* Already on the list with a reference: put to sleep */
770 } else if (tsk->thread.pfault_wait == -1) {
771 /* Completion interrupt was faster than the initial
772 * interrupt (pfault_wait == -1). Set pfault_wait
773 * back to zero and exit. */
774 tsk->thread.pfault_wait = 0;
776 /* Initial interrupt arrived before completion
777 * interrupt. Let the task sleep.
778 * An extra task reference is needed since a different
779 * cpu may set the task state to TASK_RUNNING again
780 * before the scheduler is reached. */
781 get_task_struct(tsk);
782 tsk->thread.pfault_wait = 1;
783 list_add(&tsk->thread.list, &pfault_list);
785 /* Since this must be a userspace fault, there
786 * is no kernel task state to trample. Rely on the
787 * return to userspace schedule() to block. */
788 __set_current_state(TASK_UNINTERRUPTIBLE);
789 set_tsk_need_resched(tsk);
790 set_preempt_need_resched();
794 spin_unlock(&pfault_lock);
795 put_task_struct(tsk);
798 static int pfault_cpu_dead(unsigned int cpu)
800 struct thread_struct *thread, *next;
801 struct task_struct *tsk;
803 spin_lock_irq(&pfault_lock);
804 list_for_each_entry_safe(thread, next, &pfault_list, list) {
805 thread->pfault_wait = 0;
806 list_del(&thread->list);
807 tsk = container_of(thread, struct task_struct, thread);
808 wake_up_process(tsk);
809 put_task_struct(tsk);
811 spin_unlock_irq(&pfault_lock);
815 static int __init pfault_irq_init(void)
819 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
822 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP;
825 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
826 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead",
827 NULL, pfault_cpu_dead);
831 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
836 early_initcall(pfault_irq_init);
838 #endif /* CONFIG_PFAULT */