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Linux/arch/x86/mm/fault.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  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
  6  */
  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>
 21 
 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 
 32 #define CREATE_TRACE_POINTS
 33 #include <asm/trace/exceptions.h>
 34 
 35 /*
 36  * Returns 0 if mmiotrace is disabled, or if the fault is not
 37  * handled by mmiotrace:
 38  */
 39 static nokprobe_inline int
 40 kmmio_fault(struct pt_regs *regs, unsigned long addr)
 41 {
 42         if (unlikely(is_kmmio_active()))
 43                 if (kmmio_handler(regs, addr) == 1)
 44                         return -1;
 45         return 0;
 46 }
 47 
 48 static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
 49 {
 50         if (!kprobes_built_in())
 51                 return 0;
 52         if (user_mode(regs))
 53                 return 0;
 54         /*
 55          * To be potentially processing a kprobe fault and to be allowed to call
 56          * kprobe_running(), we have to be non-preemptible.
 57          */
 58         if (preemptible())
 59                 return 0;
 60         if (!kprobe_running())
 61                 return 0;
 62         return kprobe_fault_handler(regs, X86_TRAP_PF);
 63 }
 64 
 65 /*
 66  * Prefetch quirks:
 67  *
 68  * 32-bit mode:
 69  *
 70  *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 71  *   Check that here and ignore it.
 72  *
 73  * 64-bit mode:
 74  *
 75  *   Sometimes the CPU reports invalid exceptions on prefetch.
 76  *   Check that here and ignore it.
 77  *
 78  * Opcode checker based on code by Richard Brunner.
 79  */
 80 static inline int
 81 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
 82                       unsigned char opcode, int *prefetch)
 83 {
 84         unsigned char instr_hi = opcode & 0xf0;
 85         unsigned char instr_lo = opcode & 0x0f;
 86 
 87         switch (instr_hi) {
 88         case 0x20:
 89         case 0x30:
 90                 /*
 91                  * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
 92                  * In X86_64 long mode, the CPU will signal invalid
 93                  * opcode if some of these prefixes are present so
 94                  * X86_64 will never get here anyway
 95                  */
 96                 return ((instr_lo & 7) == 0x6);
 97 #ifdef CONFIG_X86_64
 98         case 0x40:
 99                 /*
100                  * In AMD64 long mode 0x40..0x4F are valid REX prefixes
101                  * Need to figure out under what instruction mode the
102                  * instruction was issued. Could check the LDT for lm,
103                  * but for now it's good enough to assume that long
104                  * mode only uses well known segments or kernel.
105                  */
106                 return (!user_mode(regs) || user_64bit_mode(regs));
107 #endif
108         case 0x60:
109                 /* 0x64 thru 0x67 are valid prefixes in all modes. */
110                 return (instr_lo & 0xC) == 0x4;
111         case 0xF0:
112                 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
113                 return !instr_lo || (instr_lo>>1) == 1;
114         case 0x00:
115                 /* Prefetch instruction is 0x0F0D or 0x0F18 */
116                 if (probe_kernel_address(instr, opcode))
117                         return 0;
118 
119                 *prefetch = (instr_lo == 0xF) &&
120                         (opcode == 0x0D || opcode == 0x18);
121                 return 0;
122         default:
123                 return 0;
124         }
125 }
126 
127 static int
128 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
129 {
130         unsigned char *max_instr;
131         unsigned char *instr;
132         int prefetch = 0;
133 
134         /*
135          * If it was a exec (instruction fetch) fault on NX page, then
136          * do not ignore the fault:
137          */
138         if (error_code & X86_PF_INSTR)
139                 return 0;
140 
141         instr = (void *)convert_ip_to_linear(current, regs);
142         max_instr = instr + 15;
143 
144         if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
145                 return 0;
146 
147         while (instr < max_instr) {
148                 unsigned char opcode;
149 
150                 if (probe_kernel_address(instr, opcode))
151                         break;
152 
153                 instr++;
154 
155                 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
156                         break;
157         }
158         return prefetch;
159 }
160 
161 DEFINE_SPINLOCK(pgd_lock);
162 LIST_HEAD(pgd_list);
163 
164 #ifdef CONFIG_X86_32
165 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
166 {
167         unsigned index = pgd_index(address);
168         pgd_t *pgd_k;
169         p4d_t *p4d, *p4d_k;
170         pud_t *pud, *pud_k;
171         pmd_t *pmd, *pmd_k;
172 
173         pgd += index;
174         pgd_k = init_mm.pgd + index;
175 
176         if (!pgd_present(*pgd_k))
177                 return NULL;
178 
179         /*
180          * set_pgd(pgd, *pgd_k); here would be useless on PAE
181          * and redundant with the set_pmd() on non-PAE. As would
182          * set_p4d/set_pud.
183          */
184         p4d = p4d_offset(pgd, address);
185         p4d_k = p4d_offset(pgd_k, address);
186         if (!p4d_present(*p4d_k))
187                 return NULL;
188 
189         pud = pud_offset(p4d, address);
190         pud_k = pud_offset(p4d_k, address);
191         if (!pud_present(*pud_k))
192                 return NULL;
193 
194         pmd = pmd_offset(pud, address);
195         pmd_k = pmd_offset(pud_k, address);
196         if (!pmd_present(*pmd_k))
197                 return NULL;
198 
199         if (!pmd_present(*pmd))
200                 set_pmd(pmd, *pmd_k);
201         else
202                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
203 
204         return pmd_k;
205 }
206 
207 void vmalloc_sync_all(void)
208 {
209         unsigned long address;
210 
211         if (SHARED_KERNEL_PMD)
212                 return;
213 
214         for (address = VMALLOC_START & PMD_MASK;
215              address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
216              address += PMD_SIZE) {
217                 struct page *page;
218 
219                 spin_lock(&pgd_lock);
220                 list_for_each_entry(page, &pgd_list, lru) {
221                         spinlock_t *pgt_lock;
222                         pmd_t *ret;
223 
224                         /* the pgt_lock only for Xen */
225                         pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
226 
227                         spin_lock(pgt_lock);
228                         ret = vmalloc_sync_one(page_address(page), address);
229                         spin_unlock(pgt_lock);
230 
231                         if (!ret)
232                                 break;
233                 }
234                 spin_unlock(&pgd_lock);
235         }
236 }
237 
238 /*
239  * 32-bit:
240  *
241  *   Handle a fault on the vmalloc or module mapping area
242  */
243 static noinline int vmalloc_fault(unsigned long address)
244 {
245         unsigned long pgd_paddr;
246         pmd_t *pmd_k;
247         pte_t *pte_k;
248 
249         /* Make sure we are in vmalloc area: */
250         if (!(address >= VMALLOC_START && address < VMALLOC_END))
251                 return -1;
252 
253         /*
254          * Synchronize this task's top level page-table
255          * with the 'reference' page table.
256          *
257          * Do _not_ use "current" here. We might be inside
258          * an interrupt in the middle of a task switch..
259          */
260         pgd_paddr = read_cr3_pa();
261         pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
262         if (!pmd_k)
263                 return -1;
264 
265         if (pmd_large(*pmd_k))
266                 return 0;
267 
268         pte_k = pte_offset_kernel(pmd_k, address);
269         if (!pte_present(*pte_k))
270                 return -1;
271 
272         return 0;
273 }
274 NOKPROBE_SYMBOL(vmalloc_fault);
275 
276 /*
277  * Did it hit the DOS screen memory VA from vm86 mode?
278  */
279 static inline void
280 check_v8086_mode(struct pt_regs *regs, unsigned long address,
281                  struct task_struct *tsk)
282 {
283 #ifdef CONFIG_VM86
284         unsigned long bit;
285 
286         if (!v8086_mode(regs) || !tsk->thread.vm86)
287                 return;
288 
289         bit = (address - 0xA0000) >> PAGE_SHIFT;
290         if (bit < 32)
291                 tsk->thread.vm86->screen_bitmap |= 1 << bit;
292 #endif
293 }
294 
295 static bool low_pfn(unsigned long pfn)
296 {
297         return pfn < max_low_pfn;
298 }
299 
300 static void dump_pagetable(unsigned long address)
301 {
302         pgd_t *base = __va(read_cr3_pa());
303         pgd_t *pgd = &base[pgd_index(address)];
304         p4d_t *p4d;
305         pud_t *pud;
306         pmd_t *pmd;
307         pte_t *pte;
308 
309 #ifdef CONFIG_X86_PAE
310         pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
311         if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
312                 goto out;
313 #define pr_pde pr_cont
314 #else
315 #define pr_pde pr_info
316 #endif
317         p4d = p4d_offset(pgd, address);
318         pud = pud_offset(p4d, address);
319         pmd = pmd_offset(pud, address);
320         pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
321 #undef pr_pde
322 
323         /*
324          * We must not directly access the pte in the highpte
325          * case if the page table is located in highmem.
326          * And let's rather not kmap-atomic the pte, just in case
327          * it's allocated already:
328          */
329         if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
330                 goto out;
331 
332         pte = pte_offset_kernel(pmd, address);
333         pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
334 out:
335         pr_cont("\n");
336 }
337 
338 #else /* CONFIG_X86_64: */
339 
340 void vmalloc_sync_all(void)
341 {
342         sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
343 }
344 
345 /*
346  * 64-bit:
347  *
348  *   Handle a fault on the vmalloc area
349  */
350 static noinline int vmalloc_fault(unsigned long address)
351 {
352         pgd_t *pgd, *pgd_k;
353         p4d_t *p4d, *p4d_k;
354         pud_t *pud;
355         pmd_t *pmd;
356         pte_t *pte;
357 
358         /* Make sure we are in vmalloc area: */
359         if (!(address >= VMALLOC_START && address < VMALLOC_END))
360                 return -1;
361 
362         WARN_ON_ONCE(in_nmi());
363 
364         /*
365          * Copy kernel mappings over when needed. This can also
366          * happen within a race in page table update. In the later
367          * case just flush:
368          */
369         pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
370         pgd_k = pgd_offset_k(address);
371         if (pgd_none(*pgd_k))
372                 return -1;
373 
374         if (pgtable_l5_enabled()) {
375                 if (pgd_none(*pgd)) {
376                         set_pgd(pgd, *pgd_k);
377                         arch_flush_lazy_mmu_mode();
378                 } else {
379                         BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k));
380                 }
381         }
382 
383         /* With 4-level paging, copying happens on the p4d level. */
384         p4d = p4d_offset(pgd, address);
385         p4d_k = p4d_offset(pgd_k, address);
386         if (p4d_none(*p4d_k))
387                 return -1;
388 
389         if (p4d_none(*p4d) && !pgtable_l5_enabled()) {
390                 set_p4d(p4d, *p4d_k);
391                 arch_flush_lazy_mmu_mode();
392         } else {
393                 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k));
394         }
395 
396         BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);
397 
398         pud = pud_offset(p4d, address);
399         if (pud_none(*pud))
400                 return -1;
401 
402         if (pud_large(*pud))
403                 return 0;
404 
405         pmd = pmd_offset(pud, address);
406         if (pmd_none(*pmd))
407                 return -1;
408 
409         if (pmd_large(*pmd))
410                 return 0;
411 
412         pte = pte_offset_kernel(pmd, address);
413         if (!pte_present(*pte))
414                 return -1;
415 
416         return 0;
417 }
418 NOKPROBE_SYMBOL(vmalloc_fault);
419 
420 #ifdef CONFIG_CPU_SUP_AMD
421 static const char errata93_warning[] =
422 KERN_ERR 
423 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
424 "******* Working around it, but it may cause SEGVs or burn power.\n"
425 "******* Please consider a BIOS update.\n"
426 "******* Disabling USB legacy in the BIOS may also help.\n";
427 #endif
428 
429 /*
430  * No vm86 mode in 64-bit mode:
431  */
432 static inline void
433 check_v8086_mode(struct pt_regs *regs, unsigned long address,
434                  struct task_struct *tsk)
435 {
436 }
437 
438 static int bad_address(void *p)
439 {
440         unsigned long dummy;
441 
442         return probe_kernel_address((unsigned long *)p, dummy);
443 }
444 
445 static void dump_pagetable(unsigned long address)
446 {
447         pgd_t *base = __va(read_cr3_pa());
448         pgd_t *pgd = base + pgd_index(address);
449         p4d_t *p4d;
450         pud_t *pud;
451         pmd_t *pmd;
452         pte_t *pte;
453 
454         if (bad_address(pgd))
455                 goto bad;
456 
457         pr_info("PGD %lx ", pgd_val(*pgd));
458 
459         if (!pgd_present(*pgd))
460                 goto out;
461 
462         p4d = p4d_offset(pgd, address);
463         if (bad_address(p4d))
464                 goto bad;
465 
466         pr_cont("P4D %lx ", p4d_val(*p4d));
467         if (!p4d_present(*p4d) || p4d_large(*p4d))
468                 goto out;
469 
470         pud = pud_offset(p4d, address);
471         if (bad_address(pud))
472                 goto bad;
473 
474         pr_cont("PUD %lx ", pud_val(*pud));
475         if (!pud_present(*pud) || pud_large(*pud))
476                 goto out;
477 
478         pmd = pmd_offset(pud, address);
479         if (bad_address(pmd))
480                 goto bad;
481 
482         pr_cont("PMD %lx ", pmd_val(*pmd));
483         if (!pmd_present(*pmd) || pmd_large(*pmd))
484                 goto out;
485 
486         pte = pte_offset_kernel(pmd, address);
487         if (bad_address(pte))
488                 goto bad;
489 
490         pr_cont("PTE %lx", pte_val(*pte));
491 out:
492         pr_cont("\n");
493         return;
494 bad:
495         pr_info("BAD\n");
496 }
497 
498 #endif /* CONFIG_X86_64 */
499 
500 /*
501  * Workaround for K8 erratum #93 & buggy BIOS.
502  *
503  * BIOS SMM functions are required to use a specific workaround
504  * to avoid corruption of the 64bit RIP register on C stepping K8.
505  *
506  * A lot of BIOS that didn't get tested properly miss this.
507  *
508  * The OS sees this as a page fault with the upper 32bits of RIP cleared.
509  * Try to work around it here.
510  *
511  * Note we only handle faults in kernel here.
512  * Does nothing on 32-bit.
513  */
514 static int is_errata93(struct pt_regs *regs, unsigned long address)
515 {
516 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
517         if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
518             || boot_cpu_data.x86 != 0xf)
519                 return 0;
520 
521         if (address != regs->ip)
522                 return 0;
523 
524         if ((address >> 32) != 0)
525                 return 0;
526 
527         address |= 0xffffffffUL << 32;
528         if ((address >= (u64)_stext && address <= (u64)_etext) ||
529             (address >= MODULES_VADDR && address <= MODULES_END)) {
530                 printk_once(errata93_warning);
531                 regs->ip = address;
532                 return 1;
533         }
534 #endif
535         return 0;
536 }
537 
538 /*
539  * Work around K8 erratum #100 K8 in compat mode occasionally jumps
540  * to illegal addresses >4GB.
541  *
542  * We catch this in the page fault handler because these addresses
543  * are not reachable. Just detect this case and return.  Any code
544  * segment in LDT is compatibility mode.
545  */
546 static int is_errata100(struct pt_regs *regs, unsigned long address)
547 {
548 #ifdef CONFIG_X86_64
549         if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
550                 return 1;
551 #endif
552         return 0;
553 }
554 
555 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
556 {
557 #ifdef CONFIG_X86_F00F_BUG
558         unsigned long nr;
559 
560         /*
561          * Pentium F0 0F C7 C8 bug workaround:
562          */
563         if (boot_cpu_has_bug(X86_BUG_F00F)) {
564                 nr = (address - idt_descr.address) >> 3;
565 
566                 if (nr == 6) {
567                         do_invalid_op(regs, 0);
568                         return 1;
569                 }
570         }
571 #endif
572         return 0;
573 }
574 
575 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
576 {
577         u32 offset = (index >> 3) * sizeof(struct desc_struct);
578         unsigned long addr;
579         struct ldttss_desc desc;
580 
581         if (index == 0) {
582                 pr_alert("%s: NULL\n", name);
583                 return;
584         }
585 
586         if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
587                 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
588                 return;
589         }
590 
591         if (probe_kernel_read(&desc, (void *)(gdt->address + offset),
592                               sizeof(struct ldttss_desc))) {
593                 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
594                          name, index);
595                 return;
596         }
597 
598         addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
599 #ifdef CONFIG_X86_64
600         addr |= ((u64)desc.base3 << 32);
601 #endif
602         pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
603                  name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
604 }
605 
606 /*
607  * This helper function transforms the #PF error_code bits into
608  * "[PROT] [USER]" type of descriptive, almost human-readable error strings:
609  */
610 static void err_str_append(unsigned long error_code, char *buf, unsigned long mask, const char *txt)
611 {
612         if (error_code & mask) {
613                 if (buf[0])
614                         strcat(buf, " ");
615                 strcat(buf, txt);
616         }
617 }
618 
619 static void
620 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
621 {
622         char err_txt[64];
623 
624         if (!oops_may_print())
625                 return;
626 
627         if (error_code & X86_PF_INSTR) {
628                 unsigned int level;
629                 pgd_t *pgd;
630                 pte_t *pte;
631 
632                 pgd = __va(read_cr3_pa());
633                 pgd += pgd_index(address);
634 
635                 pte = lookup_address_in_pgd(pgd, address, &level);
636 
637                 if (pte && pte_present(*pte) && !pte_exec(*pte))
638                         pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
639                                 from_kuid(&init_user_ns, current_uid()));
640                 if (pte && pte_present(*pte) && pte_exec(*pte) &&
641                                 (pgd_flags(*pgd) & _PAGE_USER) &&
642                                 (__read_cr4() & X86_CR4_SMEP))
643                         pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
644                                 from_kuid(&init_user_ns, current_uid()));
645         }
646 
647         pr_alert("BUG: unable to handle kernel %s at %px\n",
648                  address < PAGE_SIZE ? "NULL pointer dereference" : "paging request",
649                  (void *)address);
650 
651         err_txt[0] = 0;
652 
653         /*
654          * Note: length of these appended strings including the separation space and the
655          * zero delimiter must fit into err_txt[].
656          */
657         err_str_append(error_code, err_txt, X86_PF_PROT,  "[PROT]" );
658         err_str_append(error_code, err_txt, X86_PF_WRITE, "[WRITE]");
659         err_str_append(error_code, err_txt, X86_PF_USER,  "[USER]" );
660         err_str_append(error_code, err_txt, X86_PF_RSVD,  "[RSVD]" );
661         err_str_append(error_code, err_txt, X86_PF_INSTR, "[INSTR]");
662         err_str_append(error_code, err_txt, X86_PF_PK,    "[PK]"   );
663 
664         pr_alert("#PF error: %s\n", error_code ? err_txt : "[normal kernel read fault]");
665 
666         if (!(error_code & X86_PF_USER) && user_mode(regs)) {
667                 struct desc_ptr idt, gdt;
668                 u16 ldtr, tr;
669 
670                 pr_alert("This was a system access from user code\n");
671 
672                 /*
673                  * This can happen for quite a few reasons.  The more obvious
674                  * ones are faults accessing the GDT, or LDT.  Perhaps
675                  * surprisingly, if the CPU tries to deliver a benign or
676                  * contributory exception from user code and gets a page fault
677                  * during delivery, the page fault can be delivered as though
678                  * it originated directly from user code.  This could happen
679                  * due to wrong permissions on the IDT, GDT, LDT, TSS, or
680                  * kernel or IST stack.
681                  */
682                 store_idt(&idt);
683 
684                 /* Usable even on Xen PV -- it's just slow. */
685                 native_store_gdt(&gdt);
686 
687                 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
688                          idt.address, idt.size, gdt.address, gdt.size);
689 
690                 store_ldt(ldtr);
691                 show_ldttss(&gdt, "LDTR", ldtr);
692 
693                 store_tr(tr);
694                 show_ldttss(&gdt, "TR", tr);
695         }
696 
697         dump_pagetable(address);
698 }
699 
700 static noinline void
701 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
702             unsigned long address)
703 {
704         struct task_struct *tsk;
705         unsigned long flags;
706         int sig;
707 
708         flags = oops_begin();
709         tsk = current;
710         sig = SIGKILL;
711 
712         printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
713                tsk->comm, address);
714         dump_pagetable(address);
715 
716         if (__die("Bad pagetable", regs, error_code))
717                 sig = 0;
718 
719         oops_end(flags, regs, sig);
720 }
721 
722 static void set_signal_archinfo(unsigned long address,
723                                 unsigned long error_code)
724 {
725         struct task_struct *tsk = current;
726 
727         /*
728          * To avoid leaking information about the kernel page
729          * table layout, pretend that user-mode accesses to
730          * kernel addresses are always protection faults.
731          */
732         if (address >= TASK_SIZE_MAX)
733                 error_code |= X86_PF_PROT;
734 
735         tsk->thread.trap_nr = X86_TRAP_PF;
736         tsk->thread.error_code = error_code | X86_PF_USER;
737         tsk->thread.cr2 = address;
738 }
739 
740 static noinline void
741 no_context(struct pt_regs *regs, unsigned long error_code,
742            unsigned long address, int signal, int si_code)
743 {
744         struct task_struct *tsk = current;
745         unsigned long flags;
746         int sig;
747 
748         if (user_mode(regs)) {
749                 /*
750                  * This is an implicit supervisor-mode access from user
751                  * mode.  Bypass all the kernel-mode recovery code and just
752                  * OOPS.
753                  */
754                 goto oops;
755         }
756 
757         /* Are we prepared to handle this kernel fault? */
758         if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
759                 /*
760                  * Any interrupt that takes a fault gets the fixup. This makes
761                  * the below recursive fault logic only apply to a faults from
762                  * task context.
763                  */
764                 if (in_interrupt())
765                         return;
766 
767                 /*
768                  * Per the above we're !in_interrupt(), aka. task context.
769                  *
770                  * In this case we need to make sure we're not recursively
771                  * faulting through the emulate_vsyscall() logic.
772                  */
773                 if (current->thread.sig_on_uaccess_err && signal) {
774                         set_signal_archinfo(address, error_code);
775 
776                         /* XXX: hwpoison faults will set the wrong code. */
777                         force_sig_fault(signal, si_code, (void __user *)address,
778                                         tsk);
779                 }
780 
781                 /*
782                  * Barring that, we can do the fixup and be happy.
783                  */
784                 return;
785         }
786 
787 #ifdef CONFIG_VMAP_STACK
788         /*
789          * Stack overflow?  During boot, we can fault near the initial
790          * stack in the direct map, but that's not an overflow -- check
791          * that we're in vmalloc space to avoid this.
792          */
793         if (is_vmalloc_addr((void *)address) &&
794             (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
795              address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
796                 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
797                 /*
798                  * We're likely to be running with very little stack space
799                  * left.  It's plausible that we'd hit this condition but
800                  * double-fault even before we get this far, in which case
801                  * we're fine: the double-fault handler will deal with it.
802                  *
803                  * We don't want to make it all the way into the oops code
804                  * and then double-fault, though, because we're likely to
805                  * break the console driver and lose most of the stack dump.
806                  */
807                 asm volatile ("movq %[stack], %%rsp\n\t"
808                               "call handle_stack_overflow\n\t"
809                               "1: jmp 1b"
810                               : ASM_CALL_CONSTRAINT
811                               : "D" ("kernel stack overflow (page fault)"),
812                                 "S" (regs), "d" (address),
813                                 [stack] "rm" (stack));
814                 unreachable();
815         }
816 #endif
817 
818         /*
819          * 32-bit:
820          *
821          *   Valid to do another page fault here, because if this fault
822          *   had been triggered by is_prefetch fixup_exception would have
823          *   handled it.
824          *
825          * 64-bit:
826          *
827          *   Hall of shame of CPU/BIOS bugs.
828          */
829         if (is_prefetch(regs, error_code, address))
830                 return;
831 
832         if (is_errata93(regs, address))
833                 return;
834 
835         /*
836          * Buggy firmware could access regions which might page fault, try to
837          * recover from such faults.
838          */
839         if (IS_ENABLED(CONFIG_EFI))
840                 efi_recover_from_page_fault(address);
841 
842 oops:
843         /*
844          * Oops. The kernel tried to access some bad page. We'll have to
845          * terminate things with extreme prejudice:
846          */
847         flags = oops_begin();
848 
849         show_fault_oops(regs, error_code, address);
850 
851         if (task_stack_end_corrupted(tsk))
852                 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
853 
854         sig = SIGKILL;
855         if (__die("Oops", regs, error_code))
856                 sig = 0;
857 
858         /* Executive summary in case the body of the oops scrolled away */
859         printk(KERN_DEFAULT "CR2: %016lx\n", address);
860 
861         oops_end(flags, regs, sig);
862 }
863 
864 /*
865  * Print out info about fatal segfaults, if the show_unhandled_signals
866  * sysctl is set:
867  */
868 static inline void
869 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
870                 unsigned long address, struct task_struct *tsk)
871 {
872         const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
873 
874         if (!unhandled_signal(tsk, SIGSEGV))
875                 return;
876 
877         if (!printk_ratelimit())
878                 return;
879 
880         printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
881                 loglvl, tsk->comm, task_pid_nr(tsk), address,
882                 (void *)regs->ip, (void *)regs->sp, error_code);
883 
884         print_vma_addr(KERN_CONT " in ", regs->ip);
885 
886         printk(KERN_CONT "\n");
887 
888         show_opcodes(regs, loglvl);
889 }
890 
891 /*
892  * The (legacy) vsyscall page is the long page in the kernel portion
893  * of the address space that has user-accessible permissions.
894  */
895 static bool is_vsyscall_vaddr(unsigned long vaddr)
896 {
897         return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
898 }
899 
900 static void
901 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
902                        unsigned long address, u32 pkey, int si_code)
903 {
904         struct task_struct *tsk = current;
905 
906         /* User mode accesses just cause a SIGSEGV */
907         if (user_mode(regs) && (error_code & X86_PF_USER)) {
908                 /*
909                  * It's possible to have interrupts off here:
910                  */
911                 local_irq_enable();
912 
913                 /*
914                  * Valid to do another page fault here because this one came
915                  * from user space:
916                  */
917                 if (is_prefetch(regs, error_code, address))
918                         return;
919 
920                 if (is_errata100(regs, address))
921                         return;
922 
923                 /*
924                  * To avoid leaking information about the kernel page table
925                  * layout, pretend that user-mode accesses to kernel addresses
926                  * are always protection faults.
927                  */
928                 if (address >= TASK_SIZE_MAX)
929                         error_code |= X86_PF_PROT;
930 
931                 if (likely(show_unhandled_signals))
932                         show_signal_msg(regs, error_code, address, tsk);
933 
934                 set_signal_archinfo(address, error_code);
935 
936                 if (si_code == SEGV_PKUERR)
937                         force_sig_pkuerr((void __user *)address, pkey);
938 
939                 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk);
940 
941                 return;
942         }
943 
944         if (is_f00f_bug(regs, address))
945                 return;
946 
947         no_context(regs, error_code, address, SIGSEGV, si_code);
948 }
949 
950 static noinline void
951 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
952                      unsigned long address)
953 {
954         __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
955 }
956 
957 static void
958 __bad_area(struct pt_regs *regs, unsigned long error_code,
959            unsigned long address, u32 pkey, int si_code)
960 {
961         struct mm_struct *mm = current->mm;
962         /*
963          * Something tried to access memory that isn't in our memory map..
964          * Fix it, but check if it's kernel or user first..
965          */
966         up_read(&mm->mmap_sem);
967 
968         __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
969 }
970 
971 static noinline void
972 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
973 {
974         __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
975 }
976 
977 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
978                 struct vm_area_struct *vma)
979 {
980         /* This code is always called on the current mm */
981         bool foreign = false;
982 
983         if (!boot_cpu_has(X86_FEATURE_OSPKE))
984                 return false;
985         if (error_code & X86_PF_PK)
986                 return true;
987         /* this checks permission keys on the VMA: */
988         if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
989                                        (error_code & X86_PF_INSTR), foreign))
990                 return true;
991         return false;
992 }
993 
994 static noinline void
995 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
996                       unsigned long address, struct vm_area_struct *vma)
997 {
998         /*
999          * This OSPKE check is not strictly necessary at runtime.
1000          * But, doing it this way allows compiler optimizations
1001          * if pkeys are compiled out.
1002          */
1003         if (bad_area_access_from_pkeys(error_code, vma)) {
1004                 /*
1005                  * A protection key fault means that the PKRU value did not allow
1006                  * access to some PTE.  Userspace can figure out what PKRU was
1007                  * from the XSAVE state.  This function captures the pkey from
1008                  * the vma and passes it to userspace so userspace can discover
1009                  * which protection key was set on the PTE.
1010                  *
1011                  * If we get here, we know that the hardware signaled a X86_PF_PK
1012                  * fault and that there was a VMA once we got in the fault
1013                  * handler.  It does *not* guarantee that the VMA we find here
1014                  * was the one that we faulted on.
1015                  *
1016                  * 1. T1   : mprotect_key(foo, PAGE_SIZE, pkey=4);
1017                  * 2. T1   : set PKRU to deny access to pkey=4, touches page
1018                  * 3. T1   : faults...
1019                  * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
1020                  * 5. T1   : enters fault handler, takes mmap_sem, etc...
1021                  * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
1022                  *           faulted on a pte with its pkey=4.
1023                  */
1024                 u32 pkey = vma_pkey(vma);
1025 
1026                 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
1027         } else {
1028                 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
1029         }
1030 }
1031 
1032 static void
1033 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
1034           unsigned int fault)
1035 {
1036         struct task_struct *tsk = current;
1037 
1038         /* Kernel mode? Handle exceptions or die: */
1039         if (!(error_code & X86_PF_USER)) {
1040                 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1041                 return;
1042         }
1043 
1044         /* User-space => ok to do another page fault: */
1045         if (is_prefetch(regs, error_code, address))
1046                 return;
1047 
1048         set_signal_archinfo(address, error_code);
1049 
1050 #ifdef CONFIG_MEMORY_FAILURE
1051         if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
1052                 unsigned lsb = 0;
1053 
1054                 pr_err(
1055         "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
1056                         tsk->comm, tsk->pid, address);
1057                 if (fault & VM_FAULT_HWPOISON_LARGE)
1058                         lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
1059                 if (fault & VM_FAULT_HWPOISON)
1060                         lsb = PAGE_SHIFT;
1061                 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, tsk);
1062                 return;
1063         }
1064 #endif
1065         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk);
1066 }
1067 
1068 static noinline void
1069 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
1070                unsigned long address, vm_fault_t fault)
1071 {
1072         if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
1073                 no_context(regs, error_code, address, 0, 0);
1074                 return;
1075         }
1076 
1077         if (fault & VM_FAULT_OOM) {
1078                 /* Kernel mode? Handle exceptions or die: */
1079                 if (!(error_code & X86_PF_USER)) {
1080                         no_context(regs, error_code, address,
1081                                    SIGSEGV, SEGV_MAPERR);
1082                         return;
1083                 }
1084 
1085                 /*
1086                  * We ran out of memory, call the OOM killer, and return the
1087                  * userspace (which will retry the fault, or kill us if we got
1088                  * oom-killed):
1089                  */
1090                 pagefault_out_of_memory();
1091         } else {
1092                 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1093                              VM_FAULT_HWPOISON_LARGE))
1094                         do_sigbus(regs, error_code, address, fault);
1095                 else if (fault & VM_FAULT_SIGSEGV)
1096                         bad_area_nosemaphore(regs, error_code, address);
1097                 else
1098                         BUG();
1099         }
1100 }
1101 
1102 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
1103 {
1104         if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
1105                 return 0;
1106 
1107         if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
1108                 return 0;
1109 
1110         return 1;
1111 }
1112 
1113 /*
1114  * Handle a spurious fault caused by a stale TLB entry.
1115  *
1116  * This allows us to lazily refresh the TLB when increasing the
1117  * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
1118  * eagerly is very expensive since that implies doing a full
1119  * cross-processor TLB flush, even if no stale TLB entries exist
1120  * on other processors.
1121  *
1122  * Spurious faults may only occur if the TLB contains an entry with
1123  * fewer permission than the page table entry.  Non-present (P = 0)
1124  * and reserved bit (R = 1) faults are never spurious.
1125  *
1126  * There are no security implications to leaving a stale TLB when
1127  * increasing the permissions on a page.
1128  *
1129  * Returns non-zero if a spurious fault was handled, zero otherwise.
1130  *
1131  * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1132  * (Optional Invalidation).
1133  */
1134 static noinline int
1135 spurious_kernel_fault(unsigned long error_code, unsigned long address)
1136 {
1137         pgd_t *pgd;
1138         p4d_t *p4d;
1139         pud_t *pud;
1140         pmd_t *pmd;
1141         pte_t *pte;
1142         int ret;
1143 
1144         /*
1145          * Only writes to RO or instruction fetches from NX may cause
1146          * spurious faults.
1147          *
1148          * These could be from user or supervisor accesses but the TLB
1149          * is only lazily flushed after a kernel mapping protection
1150          * change, so user accesses are not expected to cause spurious
1151          * faults.
1152          */
1153         if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1154             error_code != (X86_PF_INSTR | X86_PF_PROT))
1155                 return 0;
1156 
1157         pgd = init_mm.pgd + pgd_index(address);
1158         if (!pgd_present(*pgd))
1159                 return 0;
1160 
1161         p4d = p4d_offset(pgd, address);
1162         if (!p4d_present(*p4d))
1163                 return 0;
1164 
1165         if (p4d_large(*p4d))
1166                 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1167 
1168         pud = pud_offset(p4d, address);
1169         if (!pud_present(*pud))
1170                 return 0;
1171 
1172         if (pud_large(*pud))
1173                 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1174 
1175         pmd = pmd_offset(pud, address);
1176         if (!pmd_present(*pmd))
1177                 return 0;
1178 
1179         if (pmd_large(*pmd))
1180                 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1181 
1182         pte = pte_offset_kernel(pmd, address);
1183         if (!pte_present(*pte))
1184                 return 0;
1185 
1186         ret = spurious_kernel_fault_check(error_code, pte);
1187         if (!ret)
1188                 return 0;
1189 
1190         /*
1191          * Make sure we have permissions in PMD.
1192          * If not, then there's a bug in the page tables:
1193          */
1194         ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1195         WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1196 
1197         return ret;
1198 }
1199 NOKPROBE_SYMBOL(spurious_kernel_fault);
1200 
1201 int show_unhandled_signals = 1;
1202 
1203 static inline int
1204 access_error(unsigned long error_code, struct vm_area_struct *vma)
1205 {
1206         /* This is only called for the current mm, so: */
1207         bool foreign = false;
1208 
1209         /*
1210          * Read or write was blocked by protection keys.  This is
1211          * always an unconditional error and can never result in
1212          * a follow-up action to resolve the fault, like a COW.
1213          */
1214         if (error_code & X86_PF_PK)
1215                 return 1;
1216 
1217         /*
1218          * Make sure to check the VMA so that we do not perform
1219          * faults just to hit a X86_PF_PK as soon as we fill in a
1220          * page.
1221          */
1222         if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1223                                        (error_code & X86_PF_INSTR), foreign))
1224                 return 1;
1225 
1226         if (error_code & X86_PF_WRITE) {
1227                 /* write, present and write, not present: */
1228                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1229                         return 1;
1230                 return 0;
1231         }
1232 
1233         /* read, present: */
1234         if (unlikely(error_code & X86_PF_PROT))
1235                 return 1;
1236 
1237         /* read, not present: */
1238         if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1239                 return 1;
1240 
1241         return 0;
1242 }
1243 
1244 static int fault_in_kernel_space(unsigned long address)
1245 {
1246         /*
1247          * On 64-bit systems, the vsyscall page is at an address above
1248          * TASK_SIZE_MAX, but is not considered part of the kernel
1249          * address space.
1250          */
1251         if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1252                 return false;
1253 
1254         return address >= TASK_SIZE_MAX;
1255 }
1256 
1257 /*
1258  * Called for all faults where 'address' is part of the kernel address
1259  * space.  Might get called for faults that originate from *code* that
1260  * ran in userspace or the kernel.
1261  */
1262 static void
1263 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1264                    unsigned long address)
1265 {
1266         /*
1267          * Protection keys exceptions only happen on user pages.  We
1268          * have no user pages in the kernel portion of the address
1269          * space, so do not expect them here.
1270          */
1271         WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1272 
1273         /*
1274          * We can fault-in kernel-space virtual memory on-demand. The
1275          * 'reference' page table is init_mm.pgd.
1276          *
1277          * NOTE! We MUST NOT take any locks for this case. We may
1278          * be in an interrupt or a critical region, and should
1279          * only copy the information from the master page table,
1280          * nothing more.
1281          *
1282          * Before doing this on-demand faulting, ensure that the
1283          * fault is not any of the following:
1284          * 1. A fault on a PTE with a reserved bit set.
1285          * 2. A fault caused by a user-mode access.  (Do not demand-
1286          *    fault kernel memory due to user-mode accesses).
1287          * 3. A fault caused by a page-level protection violation.
1288          *    (A demand fault would be on a non-present page which
1289          *     would have X86_PF_PROT==0).
1290          */
1291         if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1292                 if (vmalloc_fault(address) >= 0)
1293                         return;
1294         }
1295 
1296         /* Was the fault spurious, caused by lazy TLB invalidation? */
1297         if (spurious_kernel_fault(hw_error_code, address))
1298                 return;
1299 
1300         /* kprobes don't want to hook the spurious faults: */
1301         if (kprobes_fault(regs))
1302                 return;
1303 
1304         /*
1305          * Note, despite being a "bad area", there are quite a few
1306          * acceptable reasons to get here, such as erratum fixups
1307          * and handling kernel code that can fault, like get_user().
1308          *
1309          * Don't take the mm semaphore here. If we fixup a prefetch
1310          * fault we could otherwise deadlock:
1311          */
1312         bad_area_nosemaphore(regs, hw_error_code, address);
1313 }
1314 NOKPROBE_SYMBOL(do_kern_addr_fault);
1315 
1316 /* Handle faults in the user portion of the address space */
1317 static inline
1318 void do_user_addr_fault(struct pt_regs *regs,
1319                         unsigned long hw_error_code,
1320                         unsigned long address)
1321 {
1322         struct vm_area_struct *vma;
1323         struct task_struct *tsk;
1324         struct mm_struct *mm;
1325         vm_fault_t fault, major = 0;
1326         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1327 
1328         tsk = current;
1329         mm = tsk->mm;
1330 
1331         /* kprobes don't want to hook the spurious faults: */
1332         if (unlikely(kprobes_fault(regs)))
1333                 return;
1334 
1335         /*
1336          * Reserved bits are never expected to be set on
1337          * entries in the user portion of the page tables.
1338          */
1339         if (unlikely(hw_error_code & X86_PF_RSVD))
1340                 pgtable_bad(regs, hw_error_code, address);
1341 
1342         /*
1343          * If SMAP is on, check for invalid kernel (supervisor) access to user
1344          * pages in the user address space.  The odd case here is WRUSS,
1345          * which, according to the preliminary documentation, does not respect
1346          * SMAP and will have the USER bit set so, in all cases, SMAP
1347          * enforcement appears to be consistent with the USER bit.
1348          */
1349         if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1350                      !(hw_error_code & X86_PF_USER) &&
1351                      !(regs->flags & X86_EFLAGS_AC)))
1352         {
1353                 bad_area_nosemaphore(regs, hw_error_code, address);
1354                 return;
1355         }
1356 
1357         /*
1358          * If we're in an interrupt, have no user context or are running
1359          * in a region with pagefaults disabled then we must not take the fault
1360          */
1361         if (unlikely(faulthandler_disabled() || !mm)) {
1362                 bad_area_nosemaphore(regs, hw_error_code, address);
1363                 return;
1364         }
1365 
1366         /*
1367          * It's safe to allow irq's after cr2 has been saved and the
1368          * vmalloc fault has been handled.
1369          *
1370          * User-mode registers count as a user access even for any
1371          * potential system fault or CPU buglet:
1372          */
1373         if (user_mode(regs)) {
1374                 local_irq_enable();
1375                 flags |= FAULT_FLAG_USER;
1376         } else {
1377                 if (regs->flags & X86_EFLAGS_IF)
1378                         local_irq_enable();
1379         }
1380 
1381         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1382 
1383         if (hw_error_code & X86_PF_WRITE)
1384                 flags |= FAULT_FLAG_WRITE;
1385         if (hw_error_code & X86_PF_INSTR)
1386                 flags |= FAULT_FLAG_INSTRUCTION;
1387 
1388 #ifdef CONFIG_X86_64
1389         /*
1390          * Instruction fetch faults in the vsyscall page might need
1391          * emulation.  The vsyscall page is at a high address
1392          * (>PAGE_OFFSET), but is considered to be part of the user
1393          * address space.
1394          *
1395          * The vsyscall page does not have a "real" VMA, so do this
1396          * emulation before we go searching for VMAs.
1397          */
1398         if ((hw_error_code & X86_PF_INSTR) && is_vsyscall_vaddr(address)) {
1399                 if (emulate_vsyscall(regs, address))
1400                         return;
1401         }
1402 #endif
1403 
1404         /*
1405          * Kernel-mode access to the user address space should only occur
1406          * on well-defined single instructions listed in the exception
1407          * tables.  But, an erroneous kernel fault occurring outside one of
1408          * those areas which also holds mmap_sem might deadlock attempting
1409          * to validate the fault against the address space.
1410          *
1411          * Only do the expensive exception table search when we might be at
1412          * risk of a deadlock.  This happens if we
1413          * 1. Failed to acquire mmap_sem, and
1414          * 2. The access did not originate in userspace.
1415          */
1416         if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1417                 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1418                         /*
1419                          * Fault from code in kernel from
1420                          * which we do not expect faults.
1421                          */
1422                         bad_area_nosemaphore(regs, hw_error_code, address);
1423                         return;
1424                 }
1425 retry:
1426                 down_read(&mm->mmap_sem);
1427         } else {
1428                 /*
1429                  * The above down_read_trylock() might have succeeded in
1430                  * which case we'll have missed the might_sleep() from
1431                  * down_read():
1432                  */
1433                 might_sleep();
1434         }
1435 
1436         vma = find_vma(mm, address);
1437         if (unlikely(!vma)) {
1438                 bad_area(regs, hw_error_code, address);
1439                 return;
1440         }
1441         if (likely(vma->vm_start <= address))
1442                 goto good_area;
1443         if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1444                 bad_area(regs, hw_error_code, address);
1445                 return;
1446         }
1447         if (unlikely(expand_stack(vma, address))) {
1448                 bad_area(regs, hw_error_code, address);
1449                 return;
1450         }
1451 
1452         /*
1453          * Ok, we have a good vm_area for this memory access, so
1454          * we can handle it..
1455          */
1456 good_area:
1457         if (unlikely(access_error(hw_error_code, vma))) {
1458                 bad_area_access_error(regs, hw_error_code, address, vma);
1459                 return;
1460         }
1461 
1462         /*
1463          * If for any reason at all we couldn't handle the fault,
1464          * make sure we exit gracefully rather than endlessly redo
1465          * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1466          * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1467          *
1468          * Note that handle_userfault() may also release and reacquire mmap_sem
1469          * (and not return with VM_FAULT_RETRY), when returning to userland to
1470          * repeat the page fault later with a VM_FAULT_NOPAGE retval
1471          * (potentially after handling any pending signal during the return to
1472          * userland). The return to userland is identified whenever
1473          * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1474          */
1475         fault = handle_mm_fault(vma, address, flags);
1476         major |= fault & VM_FAULT_MAJOR;
1477 
1478         /*
1479          * If we need to retry the mmap_sem has already been released,
1480          * and if there is a fatal signal pending there is no guarantee
1481          * that we made any progress. Handle this case first.
1482          */
1483         if (unlikely(fault & VM_FAULT_RETRY)) {
1484                 /* Retry at most once */
1485                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1486                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
1487                         flags |= FAULT_FLAG_TRIED;
1488                         if (!fatal_signal_pending(tsk))
1489                                 goto retry;
1490                 }
1491 
1492                 /* User mode? Just return to handle the fatal exception */
1493                 if (flags & FAULT_FLAG_USER)
1494                         return;
1495 
1496                 /* Not returning to user mode? Handle exceptions or die: */
1497                 no_context(regs, hw_error_code, address, SIGBUS, BUS_ADRERR);
1498                 return;
1499         }
1500 
1501         up_read(&mm->mmap_sem);
1502         if (unlikely(fault & VM_FAULT_ERROR)) {
1503                 mm_fault_error(regs, hw_error_code, address, fault);
1504                 return;
1505         }
1506 
1507         /*
1508          * Major/minor page fault accounting. If any of the events
1509          * returned VM_FAULT_MAJOR, we account it as a major fault.
1510          */
1511         if (major) {
1512                 tsk->maj_flt++;
1513                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1514         } else {
1515                 tsk->min_flt++;
1516                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1517         }
1518 
1519         check_v8086_mode(regs, address, tsk);
1520 }
1521 NOKPROBE_SYMBOL(do_user_addr_fault);
1522 
1523 /*
1524  * This routine handles page faults.  It determines the address,
1525  * and the problem, and then passes it off to one of the appropriate
1526  * routines.
1527  */
1528 static noinline void
1529 __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
1530                 unsigned long address)
1531 {
1532         prefetchw(&current->mm->mmap_sem);
1533 
1534         if (unlikely(kmmio_fault(regs, address)))
1535                 return;
1536 
1537         /* Was the fault on kernel-controlled part of the address space? */
1538         if (unlikely(fault_in_kernel_space(address)))
1539                 do_kern_addr_fault(regs, hw_error_code, address);
1540         else
1541                 do_user_addr_fault(regs, hw_error_code, address);
1542 }
1543 NOKPROBE_SYMBOL(__do_page_fault);
1544 
1545 static nokprobe_inline void
1546 trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1547                          unsigned long error_code)
1548 {
1549         if (user_mode(regs))
1550                 trace_page_fault_user(address, regs, error_code);
1551         else
1552                 trace_page_fault_kernel(address, regs, error_code);
1553 }
1554 
1555 /*
1556  * We must have this function blacklisted from kprobes, tagged with notrace
1557  * and call read_cr2() before calling anything else. To avoid calling any
1558  * kind of tracing machinery before we've observed the CR2 value.
1559  *
1560  * exception_{enter,exit}() contains all sorts of tracepoints.
1561  */
1562 dotraplinkage void notrace
1563 do_page_fault(struct pt_regs *regs, unsigned long error_code)
1564 {
1565         unsigned long address = read_cr2(); /* Get the faulting address */
1566         enum ctx_state prev_state;
1567 
1568         prev_state = exception_enter();
1569         if (trace_pagefault_enabled())
1570                 trace_page_fault_entries(address, regs, error_code);
1571 
1572         __do_page_fault(regs, error_code, address);
1573         exception_exit(prev_state);
1574 }
1575 NOKPROBE_SYMBOL(do_page_fault);
1576 

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