1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1995 Linus Torvalds
4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
7 #include <linux/sched.h> /* test_thread_flag(), ... */
8 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */
9 #include <linux/kdebug.h> /* oops_begin/end, ... */
10 #include <linux/extable.h> /* search_exception_tables */
11 #include <linux/memblock.h> /* max_low_pfn */
12 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
13 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
14 #include <linux/perf_event.h> /* perf_sw_event */
15 #include <linux/hugetlb.h> /* hstate_index_to_shift */
16 #include <linux/prefetch.h> /* prefetchw */
17 #include <linux/context_tracking.h> /* exception_enter(), ... */
18 #include <linux/uaccess.h> /* faulthandler_disabled() */
19 #include <linux/efi.h> /* efi_recover_from_page_fault()*/
20 #include <linux/mm_types.h>
22 #include <asm/cpufeature.h> /* boot_cpu_has, ... */
23 #include <asm/traps.h> /* dotraplinkage, ... */
24 #include <asm/pgalloc.h> /* pgd_*(), ... */
25 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
26 #include <asm/vsyscall.h> /* emulate_vsyscall */
27 #include <asm/vm86.h> /* struct vm86 */
28 #include <asm/mmu_context.h> /* vma_pkey() */
29 #include <asm/efi.h> /* efi_recover_from_page_fault()*/
30 #include <asm/desc.h> /* store_idt(), ... */
31 #include <asm/cpu_entry_area.h> /* exception stack */
32 #include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
33 #include <asm/kvm_para.h> /* kvm_handle_async_pf */
35 #define CREATE_TRACE_POINTS
36 #include <asm/trace/exceptions.h>
39 * Returns 0 if mmiotrace is disabled, or if the fault is not
40 * handled by mmiotrace:
42 static nokprobe_inline int
43 kmmio_fault(struct pt_regs *regs, unsigned long addr)
45 if (unlikely(is_kmmio_active()))
46 if (kmmio_handler(regs, addr) == 1)
56 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
57 * Check that here and ignore it.
61 * Sometimes the CPU reports invalid exceptions on prefetch.
62 * Check that here and ignore it.
64 * Opcode checker based on code by Richard Brunner.
67 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
68 unsigned char opcode, int *prefetch)
70 unsigned char instr_hi = opcode & 0xf0;
71 unsigned char instr_lo = opcode & 0x0f;
77 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
78 * In X86_64 long mode, the CPU will signal invalid
79 * opcode if some of these prefixes are present so
80 * X86_64 will never get here anyway
82 return ((instr_lo & 7) == 0x6);
86 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
87 * Need to figure out under what instruction mode the
88 * instruction was issued. Could check the LDT for lm,
89 * but for now it's good enough to assume that long
90 * mode only uses well known segments or kernel.
92 return (!user_mode(regs) || user_64bit_mode(regs));
95 /* 0x64 thru 0x67 are valid prefixes in all modes. */
96 return (instr_lo & 0xC) == 0x4;
98 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
99 return !instr_lo || (instr_lo>>1) == 1;
101 /* Prefetch instruction is 0x0F0D or 0x0F18 */
102 if (probe_kernel_address(instr, opcode))
105 *prefetch = (instr_lo == 0xF) &&
106 (opcode == 0x0D || opcode == 0x18);
114 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
116 unsigned char *max_instr;
117 unsigned char *instr;
121 * If it was a exec (instruction fetch) fault on NX page, then
122 * do not ignore the fault:
124 if (error_code & X86_PF_INSTR)
127 instr = (void *)convert_ip_to_linear(current, regs);
128 max_instr = instr + 15;
130 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
133 while (instr < max_instr) {
134 unsigned char opcode;
136 if (probe_kernel_address(instr, opcode))
141 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
147 DEFINE_SPINLOCK(pgd_lock);
151 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
153 unsigned index = pgd_index(address);
160 pgd_k = init_mm.pgd + index;
162 if (!pgd_present(*pgd_k))
166 * set_pgd(pgd, *pgd_k); here would be useless on PAE
167 * and redundant with the set_pmd() on non-PAE. As would
170 p4d = p4d_offset(pgd, address);
171 p4d_k = p4d_offset(pgd_k, address);
172 if (!p4d_present(*p4d_k))
175 pud = pud_offset(p4d, address);
176 pud_k = pud_offset(p4d_k, address);
177 if (!pud_present(*pud_k))
180 pmd = pmd_offset(pud, address);
181 pmd_k = pmd_offset(pud_k, address);
183 if (pmd_present(*pmd) != pmd_present(*pmd_k))
184 set_pmd(pmd, *pmd_k);
186 if (!pmd_present(*pmd_k))
189 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
194 void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
198 for (addr = start & PMD_MASK;
199 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
203 spin_lock(&pgd_lock);
204 list_for_each_entry(page, &pgd_list, lru) {
205 spinlock_t *pgt_lock;
207 /* the pgt_lock only for Xen */
208 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
211 vmalloc_sync_one(page_address(page), addr);
212 spin_unlock(pgt_lock);
214 spin_unlock(&pgd_lock);
219 * Did it hit the DOS screen memory VA from vm86 mode?
222 check_v8086_mode(struct pt_regs *regs, unsigned long address,
223 struct task_struct *tsk)
228 if (!v8086_mode(regs) || !tsk->thread.vm86)
231 bit = (address - 0xA0000) >> PAGE_SHIFT;
233 tsk->thread.vm86->screen_bitmap |= 1 << bit;
237 static bool low_pfn(unsigned long pfn)
239 return pfn < max_low_pfn;
242 static void dump_pagetable(unsigned long address)
244 pgd_t *base = __va(read_cr3_pa());
245 pgd_t *pgd = &base[pgd_index(address)];
251 #ifdef CONFIG_X86_PAE
252 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
253 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
255 #define pr_pde pr_cont
257 #define pr_pde pr_info
259 p4d = p4d_offset(pgd, address);
260 pud = pud_offset(p4d, address);
261 pmd = pmd_offset(pud, address);
262 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
266 * We must not directly access the pte in the highpte
267 * case if the page table is located in highmem.
268 * And let's rather not kmap-atomic the pte, just in case
269 * it's allocated already:
271 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
274 pte = pte_offset_kernel(pmd, address);
275 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
280 #else /* CONFIG_X86_64: */
282 #ifdef CONFIG_CPU_SUP_AMD
283 static const char errata93_warning[] =
285 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
286 "******* Working around it, but it may cause SEGVs or burn power.\n"
287 "******* Please consider a BIOS update.\n"
288 "******* Disabling USB legacy in the BIOS may also help.\n";
292 * No vm86 mode in 64-bit mode:
295 check_v8086_mode(struct pt_regs *regs, unsigned long address,
296 struct task_struct *tsk)
300 static int bad_address(void *p)
304 return probe_kernel_address((unsigned long *)p, dummy);
307 static void dump_pagetable(unsigned long address)
309 pgd_t *base = __va(read_cr3_pa());
310 pgd_t *pgd = base + pgd_index(address);
316 if (bad_address(pgd))
319 pr_info("PGD %lx ", pgd_val(*pgd));
321 if (!pgd_present(*pgd))
324 p4d = p4d_offset(pgd, address);
325 if (bad_address(p4d))
328 pr_cont("P4D %lx ", p4d_val(*p4d));
329 if (!p4d_present(*p4d) || p4d_large(*p4d))
332 pud = pud_offset(p4d, address);
333 if (bad_address(pud))
336 pr_cont("PUD %lx ", pud_val(*pud));
337 if (!pud_present(*pud) || pud_large(*pud))
340 pmd = pmd_offset(pud, address);
341 if (bad_address(pmd))
344 pr_cont("PMD %lx ", pmd_val(*pmd));
345 if (!pmd_present(*pmd) || pmd_large(*pmd))
348 pte = pte_offset_kernel(pmd, address);
349 if (bad_address(pte))
352 pr_cont("PTE %lx", pte_val(*pte));
360 #endif /* CONFIG_X86_64 */
363 * Workaround for K8 erratum #93 & buggy BIOS.
365 * BIOS SMM functions are required to use a specific workaround
366 * to avoid corruption of the 64bit RIP register on C stepping K8.
368 * A lot of BIOS that didn't get tested properly miss this.
370 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
371 * Try to work around it here.
373 * Note we only handle faults in kernel here.
374 * Does nothing on 32-bit.
376 static int is_errata93(struct pt_regs *regs, unsigned long address)
378 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
379 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
380 || boot_cpu_data.x86 != 0xf)
383 if (address != regs->ip)
386 if ((address >> 32) != 0)
389 address |= 0xffffffffUL << 32;
390 if ((address >= (u64)_stext && address <= (u64)_etext) ||
391 (address >= MODULES_VADDR && address <= MODULES_END)) {
392 printk_once(errata93_warning);
401 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
402 * to illegal addresses >4GB.
404 * We catch this in the page fault handler because these addresses
405 * are not reachable. Just detect this case and return. Any code
406 * segment in LDT is compatibility mode.
408 static int is_errata100(struct pt_regs *regs, unsigned long address)
411 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
417 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
419 #ifdef CONFIG_X86_F00F_BUG
423 * Pentium F0 0F C7 C8 bug workaround:
425 if (boot_cpu_has_bug(X86_BUG_F00F)) {
426 nr = (address - idt_descr.address) >> 3;
429 do_invalid_op(regs, 0);
437 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
439 u32 offset = (index >> 3) * sizeof(struct desc_struct);
441 struct ldttss_desc desc;
444 pr_alert("%s: NULL\n", name);
448 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
449 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
453 if (probe_kernel_read(&desc, (void *)(gdt->address + offset),
454 sizeof(struct ldttss_desc))) {
455 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
460 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
462 addr |= ((u64)desc.base3 << 32);
464 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
465 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
469 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
471 if (!oops_may_print())
474 if (error_code & X86_PF_INSTR) {
479 pgd = __va(read_cr3_pa());
480 pgd += pgd_index(address);
482 pte = lookup_address_in_pgd(pgd, address, &level);
484 if (pte && pte_present(*pte) && !pte_exec(*pte))
485 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
486 from_kuid(&init_user_ns, current_uid()));
487 if (pte && pte_present(*pte) && pte_exec(*pte) &&
488 (pgd_flags(*pgd) & _PAGE_USER) &&
489 (__read_cr4() & X86_CR4_SMEP))
490 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
491 from_kuid(&init_user_ns, current_uid()));
494 if (address < PAGE_SIZE && !user_mode(regs))
495 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
498 pr_alert("BUG: unable to handle page fault for address: %px\n",
501 pr_alert("#PF: %s %s in %s mode\n",
502 (error_code & X86_PF_USER) ? "user" : "supervisor",
503 (error_code & X86_PF_INSTR) ? "instruction fetch" :
504 (error_code & X86_PF_WRITE) ? "write access" :
506 user_mode(regs) ? "user" : "kernel");
507 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
508 !(error_code & X86_PF_PROT) ? "not-present page" :
509 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
510 (error_code & X86_PF_PK) ? "protection keys violation" :
511 "permissions violation");
513 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
514 struct desc_ptr idt, gdt;
518 * This can happen for quite a few reasons. The more obvious
519 * ones are faults accessing the GDT, or LDT. Perhaps
520 * surprisingly, if the CPU tries to deliver a benign or
521 * contributory exception from user code and gets a page fault
522 * during delivery, the page fault can be delivered as though
523 * it originated directly from user code. This could happen
524 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
525 * kernel or IST stack.
529 /* Usable even on Xen PV -- it's just slow. */
530 native_store_gdt(&gdt);
532 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
533 idt.address, idt.size, gdt.address, gdt.size);
536 show_ldttss(&gdt, "LDTR", ldtr);
539 show_ldttss(&gdt, "TR", tr);
542 dump_pagetable(address);
546 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
547 unsigned long address)
549 struct task_struct *tsk;
553 flags = oops_begin();
557 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
559 dump_pagetable(address);
561 if (__die("Bad pagetable", regs, error_code))
564 oops_end(flags, regs, sig);
567 static void set_signal_archinfo(unsigned long address,
568 unsigned long error_code)
570 struct task_struct *tsk = current;
573 * To avoid leaking information about the kernel page
574 * table layout, pretend that user-mode accesses to
575 * kernel addresses are always protection faults.
577 * NB: This means that failed vsyscalls with vsyscall=none
578 * will have the PROT bit. This doesn't leak any
579 * information and does not appear to cause any problems.
581 if (address >= TASK_SIZE_MAX)
582 error_code |= X86_PF_PROT;
584 tsk->thread.trap_nr = X86_TRAP_PF;
585 tsk->thread.error_code = error_code | X86_PF_USER;
586 tsk->thread.cr2 = address;
590 no_context(struct pt_regs *regs, unsigned long error_code,
591 unsigned long address, int signal, int si_code)
593 struct task_struct *tsk = current;
597 if (user_mode(regs)) {
599 * This is an implicit supervisor-mode access from user
600 * mode. Bypass all the kernel-mode recovery code and just
606 /* Are we prepared to handle this kernel fault? */
607 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
609 * Any interrupt that takes a fault gets the fixup. This makes
610 * the below recursive fault logic only apply to a faults from
617 * Per the above we're !in_interrupt(), aka. task context.
619 * In this case we need to make sure we're not recursively
620 * faulting through the emulate_vsyscall() logic.
622 if (current->thread.sig_on_uaccess_err && signal) {
623 set_signal_archinfo(address, error_code);
625 /* XXX: hwpoison faults will set the wrong code. */
626 force_sig_fault(signal, si_code, (void __user *)address);
630 * Barring that, we can do the fixup and be happy.
635 #ifdef CONFIG_VMAP_STACK
637 * Stack overflow? During boot, we can fault near the initial
638 * stack in the direct map, but that's not an overflow -- check
639 * that we're in vmalloc space to avoid this.
641 if (is_vmalloc_addr((void *)address) &&
642 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
643 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
644 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
646 * We're likely to be running with very little stack space
647 * left. It's plausible that we'd hit this condition but
648 * double-fault even before we get this far, in which case
649 * we're fine: the double-fault handler will deal with it.
651 * We don't want to make it all the way into the oops code
652 * and then double-fault, though, because we're likely to
653 * break the console driver and lose most of the stack dump.
655 asm volatile ("movq %[stack], %%rsp\n\t"
656 "call handle_stack_overflow\n\t"
658 : ASM_CALL_CONSTRAINT
659 : "D" ("kernel stack overflow (page fault)"),
660 "S" (regs), "d" (address),
661 [stack] "rm" (stack));
669 * Valid to do another page fault here, because if this fault
670 * had been triggered by is_prefetch fixup_exception would have
675 * Hall of shame of CPU/BIOS bugs.
677 if (is_prefetch(regs, error_code, address))
680 if (is_errata93(regs, address))
684 * Buggy firmware could access regions which might page fault, try to
685 * recover from such faults.
687 if (IS_ENABLED(CONFIG_EFI))
688 efi_recover_from_page_fault(address);
692 * Oops. The kernel tried to access some bad page. We'll have to
693 * terminate things with extreme prejudice:
695 flags = oops_begin();
697 show_fault_oops(regs, error_code, address);
699 if (task_stack_end_corrupted(tsk))
700 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
703 if (__die("Oops", regs, error_code))
706 /* Executive summary in case the body of the oops scrolled away */
707 printk(KERN_DEFAULT "CR2: %016lx\n", address);
709 oops_end(flags, regs, sig);
713 * Print out info about fatal segfaults, if the show_unhandled_signals
717 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
718 unsigned long address, struct task_struct *tsk)
720 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
722 if (!unhandled_signal(tsk, SIGSEGV))
725 if (!printk_ratelimit())
728 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
729 loglvl, tsk->comm, task_pid_nr(tsk), address,
730 (void *)regs->ip, (void *)regs->sp, error_code);
732 print_vma_addr(KERN_CONT " in ", regs->ip);
734 printk(KERN_CONT "\n");
736 show_opcodes(regs, loglvl);
740 * The (legacy) vsyscall page is the long page in the kernel portion
741 * of the address space that has user-accessible permissions.
743 static bool is_vsyscall_vaddr(unsigned long vaddr)
745 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
749 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
750 unsigned long address, u32 pkey, int si_code)
752 struct task_struct *tsk = current;
754 /* User mode accesses just cause a SIGSEGV */
755 if (user_mode(regs) && (error_code & X86_PF_USER)) {
757 * It's possible to have interrupts off here:
762 * Valid to do another page fault here because this one came
765 if (is_prefetch(regs, error_code, address))
768 if (is_errata100(regs, address))
772 * To avoid leaking information about the kernel page table
773 * layout, pretend that user-mode accesses to kernel addresses
774 * are always protection faults.
776 if (address >= TASK_SIZE_MAX)
777 error_code |= X86_PF_PROT;
779 if (likely(show_unhandled_signals))
780 show_signal_msg(regs, error_code, address, tsk);
782 set_signal_archinfo(address, error_code);
784 if (si_code == SEGV_PKUERR)
785 force_sig_pkuerr((void __user *)address, pkey);
787 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
792 if (is_f00f_bug(regs, address))
795 no_context(regs, error_code, address, SIGSEGV, si_code);
799 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
800 unsigned long address)
802 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
806 __bad_area(struct pt_regs *regs, unsigned long error_code,
807 unsigned long address, u32 pkey, int si_code)
809 struct mm_struct *mm = current->mm;
811 * Something tried to access memory that isn't in our memory map..
812 * Fix it, but check if it's kernel or user first..
814 mmap_read_unlock(mm);
816 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
820 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
822 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
825 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
826 struct vm_area_struct *vma)
828 /* This code is always called on the current mm */
829 bool foreign = false;
831 if (!boot_cpu_has(X86_FEATURE_OSPKE))
833 if (error_code & X86_PF_PK)
835 /* this checks permission keys on the VMA: */
836 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
837 (error_code & X86_PF_INSTR), foreign))
843 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
844 unsigned long address, struct vm_area_struct *vma)
847 * This OSPKE check is not strictly necessary at runtime.
848 * But, doing it this way allows compiler optimizations
849 * if pkeys are compiled out.
851 if (bad_area_access_from_pkeys(error_code, vma)) {
853 * A protection key fault means that the PKRU value did not allow
854 * access to some PTE. Userspace can figure out what PKRU was
855 * from the XSAVE state. This function captures the pkey from
856 * the vma and passes it to userspace so userspace can discover
857 * which protection key was set on the PTE.
859 * If we get here, we know that the hardware signaled a X86_PF_PK
860 * fault and that there was a VMA once we got in the fault
861 * handler. It does *not* guarantee that the VMA we find here
862 * was the one that we faulted on.
864 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
865 * 2. T1 : set PKRU to deny access to pkey=4, touches page
867 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
868 * 5. T1 : enters fault handler, takes mmap_sem, etc...
869 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
870 * faulted on a pte with its pkey=4.
872 u32 pkey = vma_pkey(vma);
874 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
876 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
881 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
884 /* Kernel mode? Handle exceptions or die: */
885 if (!(error_code & X86_PF_USER)) {
886 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
890 /* User-space => ok to do another page fault: */
891 if (is_prefetch(regs, error_code, address))
894 set_signal_archinfo(address, error_code);
896 #ifdef CONFIG_MEMORY_FAILURE
897 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
898 struct task_struct *tsk = current;
902 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
903 tsk->comm, tsk->pid, address);
904 if (fault & VM_FAULT_HWPOISON_LARGE)
905 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
906 if (fault & VM_FAULT_HWPOISON)
908 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
912 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
916 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
917 unsigned long address, vm_fault_t fault)
919 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
920 no_context(regs, error_code, address, 0, 0);
924 if (fault & VM_FAULT_OOM) {
925 /* Kernel mode? Handle exceptions or die: */
926 if (!(error_code & X86_PF_USER)) {
927 no_context(regs, error_code, address,
928 SIGSEGV, SEGV_MAPERR);
933 * We ran out of memory, call the OOM killer, and return the
934 * userspace (which will retry the fault, or kill us if we got
937 pagefault_out_of_memory();
939 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
940 VM_FAULT_HWPOISON_LARGE))
941 do_sigbus(regs, error_code, address, fault);
942 else if (fault & VM_FAULT_SIGSEGV)
943 bad_area_nosemaphore(regs, error_code, address);
949 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
951 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
954 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
961 * Handle a spurious fault caused by a stale TLB entry.
963 * This allows us to lazily refresh the TLB when increasing the
964 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
965 * eagerly is very expensive since that implies doing a full
966 * cross-processor TLB flush, even if no stale TLB entries exist
967 * on other processors.
969 * Spurious faults may only occur if the TLB contains an entry with
970 * fewer permission than the page table entry. Non-present (P = 0)
971 * and reserved bit (R = 1) faults are never spurious.
973 * There are no security implications to leaving a stale TLB when
974 * increasing the permissions on a page.
976 * Returns non-zero if a spurious fault was handled, zero otherwise.
978 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
979 * (Optional Invalidation).
982 spurious_kernel_fault(unsigned long error_code, unsigned long address)
992 * Only writes to RO or instruction fetches from NX may cause
995 * These could be from user or supervisor accesses but the TLB
996 * is only lazily flushed after a kernel mapping protection
997 * change, so user accesses are not expected to cause spurious
1000 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1001 error_code != (X86_PF_INSTR | X86_PF_PROT))
1004 pgd = init_mm.pgd + pgd_index(address);
1005 if (!pgd_present(*pgd))
1008 p4d = p4d_offset(pgd, address);
1009 if (!p4d_present(*p4d))
1012 if (p4d_large(*p4d))
1013 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1015 pud = pud_offset(p4d, address);
1016 if (!pud_present(*pud))
1019 if (pud_large(*pud))
1020 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1022 pmd = pmd_offset(pud, address);
1023 if (!pmd_present(*pmd))
1026 if (pmd_large(*pmd))
1027 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1029 pte = pte_offset_kernel(pmd, address);
1030 if (!pte_present(*pte))
1033 ret = spurious_kernel_fault_check(error_code, pte);
1038 * Make sure we have permissions in PMD.
1039 * If not, then there's a bug in the page tables:
1041 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1042 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1046 NOKPROBE_SYMBOL(spurious_kernel_fault);
1048 int show_unhandled_signals = 1;
1051 access_error(unsigned long error_code, struct vm_area_struct *vma)
1053 /* This is only called for the current mm, so: */
1054 bool foreign = false;
1057 * Read or write was blocked by protection keys. This is
1058 * always an unconditional error and can never result in
1059 * a follow-up action to resolve the fault, like a COW.
1061 if (error_code & X86_PF_PK)
1065 * Make sure to check the VMA so that we do not perform
1066 * faults just to hit a X86_PF_PK as soon as we fill in a
1069 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1070 (error_code & X86_PF_INSTR), foreign))
1073 if (error_code & X86_PF_WRITE) {
1074 /* write, present and write, not present: */
1075 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1080 /* read, present: */
1081 if (unlikely(error_code & X86_PF_PROT))
1084 /* read, not present: */
1085 if (unlikely(!vma_is_accessible(vma)))
1091 static int fault_in_kernel_space(unsigned long address)
1094 * On 64-bit systems, the vsyscall page is at an address above
1095 * TASK_SIZE_MAX, but is not considered part of the kernel
1098 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1101 return address >= TASK_SIZE_MAX;
1105 * Called for all faults where 'address' is part of the kernel address
1106 * space. Might get called for faults that originate from *code* that
1107 * ran in userspace or the kernel.
1110 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1111 unsigned long address)
1114 * Protection keys exceptions only happen on user pages. We
1115 * have no user pages in the kernel portion of the address
1116 * space, so do not expect them here.
1118 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1120 /* Was the fault spurious, caused by lazy TLB invalidation? */
1121 if (spurious_kernel_fault(hw_error_code, address))
1124 /* kprobes don't want to hook the spurious faults: */
1125 if (kprobe_page_fault(regs, X86_TRAP_PF))
1129 * Note, despite being a "bad area", there are quite a few
1130 * acceptable reasons to get here, such as erratum fixups
1131 * and handling kernel code that can fault, like get_user().
1133 * Don't take the mm semaphore here. If we fixup a prefetch
1134 * fault we could otherwise deadlock:
1136 bad_area_nosemaphore(regs, hw_error_code, address);
1138 NOKPROBE_SYMBOL(do_kern_addr_fault);
1140 /* Handle faults in the user portion of the address space */
1142 void do_user_addr_fault(struct pt_regs *regs,
1143 unsigned long hw_error_code,
1144 unsigned long address)
1146 struct vm_area_struct *vma;
1147 struct task_struct *tsk;
1148 struct mm_struct *mm;
1149 vm_fault_t fault, major = 0;
1150 unsigned int flags = FAULT_FLAG_DEFAULT;
1155 /* kprobes don't want to hook the spurious faults: */
1156 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
1160 * Reserved bits are never expected to be set on
1161 * entries in the user portion of the page tables.
1163 if (unlikely(hw_error_code & X86_PF_RSVD))
1164 pgtable_bad(regs, hw_error_code, address);
1167 * If SMAP is on, check for invalid kernel (supervisor) access to user
1168 * pages in the user address space. The odd case here is WRUSS,
1169 * which, according to the preliminary documentation, does not respect
1170 * SMAP and will have the USER bit set so, in all cases, SMAP
1171 * enforcement appears to be consistent with the USER bit.
1173 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1174 !(hw_error_code & X86_PF_USER) &&
1175 !(regs->flags & X86_EFLAGS_AC)))
1177 bad_area_nosemaphore(regs, hw_error_code, address);
1182 * If we're in an interrupt, have no user context or are running
1183 * in a region with pagefaults disabled then we must not take the fault
1185 if (unlikely(faulthandler_disabled() || !mm)) {
1186 bad_area_nosemaphore(regs, hw_error_code, address);
1191 * It's safe to allow irq's after cr2 has been saved and the
1192 * vmalloc fault has been handled.
1194 * User-mode registers count as a user access even for any
1195 * potential system fault or CPU buglet:
1197 if (user_mode(regs)) {
1199 flags |= FAULT_FLAG_USER;
1201 if (regs->flags & X86_EFLAGS_IF)
1205 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1207 if (hw_error_code & X86_PF_WRITE)
1208 flags |= FAULT_FLAG_WRITE;
1209 if (hw_error_code & X86_PF_INSTR)
1210 flags |= FAULT_FLAG_INSTRUCTION;
1212 #ifdef CONFIG_X86_64
1214 * Faults in the vsyscall page might need emulation. The
1215 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1216 * considered to be part of the user address space.
1218 * The vsyscall page does not have a "real" VMA, so do this
1219 * emulation before we go searching for VMAs.
1221 * PKRU never rejects instruction fetches, so we don't need
1222 * to consider the PF_PK bit.
1224 if (is_vsyscall_vaddr(address)) {
1225 if (emulate_vsyscall(hw_error_code, regs, address))
1231 * Kernel-mode access to the user address space should only occur
1232 * on well-defined single instructions listed in the exception
1233 * tables. But, an erroneous kernel fault occurring outside one of
1234 * those areas which also holds mmap_sem might deadlock attempting
1235 * to validate the fault against the address space.
1237 * Only do the expensive exception table search when we might be at
1238 * risk of a deadlock. This happens if we
1239 * 1. Failed to acquire mmap_sem, and
1240 * 2. The access did not originate in userspace.
1242 if (unlikely(!mmap_read_trylock(mm))) {
1243 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1245 * Fault from code in kernel from
1246 * which we do not expect faults.
1248 bad_area_nosemaphore(regs, hw_error_code, address);
1255 * The above down_read_trylock() might have succeeded in
1256 * which case we'll have missed the might_sleep() from
1262 vma = find_vma(mm, address);
1263 if (unlikely(!vma)) {
1264 bad_area(regs, hw_error_code, address);
1267 if (likely(vma->vm_start <= address))
1269 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1270 bad_area(regs, hw_error_code, address);
1273 if (unlikely(expand_stack(vma, address))) {
1274 bad_area(regs, hw_error_code, address);
1279 * Ok, we have a good vm_area for this memory access, so
1280 * we can handle it..
1283 if (unlikely(access_error(hw_error_code, vma))) {
1284 bad_area_access_error(regs, hw_error_code, address, vma);
1289 * If for any reason at all we couldn't handle the fault,
1290 * make sure we exit gracefully rather than endlessly redo
1291 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1292 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1294 * Note that handle_userfault() may also release and reacquire mmap_sem
1295 * (and not return with VM_FAULT_RETRY), when returning to userland to
1296 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1297 * (potentially after handling any pending signal during the return to
1298 * userland). The return to userland is identified whenever
1299 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1301 fault = handle_mm_fault(vma, address, flags);
1302 major |= fault & VM_FAULT_MAJOR;
1304 /* Quick path to respond to signals */
1305 if (fault_signal_pending(fault, regs)) {
1306 if (!user_mode(regs))
1307 no_context(regs, hw_error_code, address, SIGBUS,
1313 * If we need to retry the mmap_sem has already been released,
1314 * and if there is a fatal signal pending there is no guarantee
1315 * that we made any progress. Handle this case first.
1317 if (unlikely((fault & VM_FAULT_RETRY) &&
1318 (flags & FAULT_FLAG_ALLOW_RETRY))) {
1319 flags |= FAULT_FLAG_TRIED;
1323 mmap_read_unlock(mm);
1324 if (unlikely(fault & VM_FAULT_ERROR)) {
1325 mm_fault_error(regs, hw_error_code, address, fault);
1330 * Major/minor page fault accounting. If any of the events
1331 * returned VM_FAULT_MAJOR, we account it as a major fault.
1335 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1338 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1341 check_v8086_mode(regs, address, tsk);
1343 NOKPROBE_SYMBOL(do_user_addr_fault);
1345 static __always_inline void
1346 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1347 unsigned long address)
1349 if (!trace_pagefault_enabled())
1352 if (user_mode(regs))
1353 trace_page_fault_user(address, regs, error_code);
1355 trace_page_fault_kernel(address, regs, error_code);
1359 do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
1360 unsigned long address)
1362 prefetchw(¤t->mm->mmap_lock);
1364 * KVM has two types of events that are, logically, interrupts, but
1365 * are unfortunately delivered using the #PF vector. These events are
1366 * "you just accessed valid memory, but the host doesn't have it right
1367 * now, so I'll put you to sleep if you continue" and "that memory
1368 * you tried to access earlier is available now."
1370 * We are relying on the interrupted context being sane (valid RSP,
1371 * relevant locks not held, etc.), which is fine as long as the
1372 * interrupted context had IF=1. We are also relying on the KVM
1373 * async pf type field and CR2 being read consistently instead of
1374 * getting values from real and async page faults mixed up.
1378 if (kvm_handle_async_pf(regs, (u32)address))
1381 trace_page_fault_entries(regs, hw_error_code, address);
1383 if (unlikely(kmmio_fault(regs, address)))
1386 /* Was the fault on kernel-controlled part of the address space? */
1387 if (unlikely(fault_in_kernel_space(address)))
1388 do_kern_addr_fault(regs, hw_error_code, address);
1390 do_user_addr_fault(regs, hw_error_code, address);
1392 NOKPROBE_SYMBOL(do_page_fault);