Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/arch/x86/mm/fault.c

  1 /*
  2  *  Copyright (C) 1995  Linus Torvalds
  3  *  Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
  4  *  Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
  5  */
  6 #include <linux/sched.h>                /* test_thread_flag(), ...      */
  7 #include <linux/kdebug.h>               /* oops_begin/end, ...          */
  8 #include <linux/extable.h>              /* search_exception_tables      */
  9 #include <linux/bootmem.h>              /* max_low_pfn                  */
 10 #include <linux/kprobes.h>              /* NOKPROBE_SYMBOL, ...         */
 11 #include <linux/mmiotrace.h>            /* kmmio_handler, ...           */
 12 #include <linux/perf_event.h>           /* perf_sw_event                */
 13 #include <linux/hugetlb.h>              /* hstate_index_to_shift        */
 14 #include <linux/prefetch.h>             /* prefetchw                    */
 15 #include <linux/context_tracking.h>     /* exception_enter(), ...       */
 16 #include <linux/uaccess.h>              /* faulthandler_disabled()      */
 17 
 18 #include <asm/cpufeature.h>             /* boot_cpu_has, ...            */
 19 #include <asm/traps.h>                  /* dotraplinkage, ...           */
 20 #include <asm/pgalloc.h>                /* pgd_*(), ...                 */
 21 #include <asm/kmemcheck.h>              /* kmemcheck_*(), ...           */
 22 #include <asm/fixmap.h>                 /* VSYSCALL_ADDR                */
 23 #include <asm/vsyscall.h>               /* emulate_vsyscall             */
 24 #include <asm/vm86.h>                   /* struct vm86                  */
 25 #include <asm/mmu_context.h>            /* vma_pkey()                   */
 26 
 27 #define CREATE_TRACE_POINTS
 28 #include <asm/trace/exceptions.h>
 29 
 30 /*
 31  * Page fault error code bits:
 32  *
 33  *   bit 0 ==    0: no page found       1: protection fault
 34  *   bit 1 ==    0: read access         1: write access
 35  *   bit 2 ==    0: kernel-mode access  1: user-mode access
 36  *   bit 3 ==                           1: use of reserved bit detected
 37  *   bit 4 ==                           1: fault was an instruction fetch
 38  *   bit 5 ==                           1: protection keys block access
 39  */
 40 enum x86_pf_error_code {
 41 
 42         PF_PROT         =               1 << 0,
 43         PF_WRITE        =               1 << 1,
 44         PF_USER         =               1 << 2,
 45         PF_RSVD         =               1 << 3,
 46         PF_INSTR        =               1 << 4,
 47         PF_PK           =               1 << 5,
 48 };
 49 
 50 /*
 51  * Returns 0 if mmiotrace is disabled, or if the fault is not
 52  * handled by mmiotrace:
 53  */
 54 static nokprobe_inline int
 55 kmmio_fault(struct pt_regs *regs, unsigned long addr)
 56 {
 57         if (unlikely(is_kmmio_active()))
 58                 if (kmmio_handler(regs, addr) == 1)
 59                         return -1;
 60         return 0;
 61 }
 62 
 63 static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
 64 {
 65         int ret = 0;
 66 
 67         /* kprobe_running() needs smp_processor_id() */
 68         if (kprobes_built_in() && !user_mode(regs)) {
 69                 preempt_disable();
 70                 if (kprobe_running() && kprobe_fault_handler(regs, 14))
 71                         ret = 1;
 72                 preempt_enable();
 73         }
 74 
 75         return ret;
 76 }
 77 
 78 /*
 79  * Prefetch quirks:
 80  *
 81  * 32-bit mode:
 82  *
 83  *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 84  *   Check that here and ignore it.
 85  *
 86  * 64-bit mode:
 87  *
 88  *   Sometimes the CPU reports invalid exceptions on prefetch.
 89  *   Check that here and ignore it.
 90  *
 91  * Opcode checker based on code by Richard Brunner.
 92  */
 93 static inline int
 94 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
 95                       unsigned char opcode, int *prefetch)
 96 {
 97         unsigned char instr_hi = opcode & 0xf0;
 98         unsigned char instr_lo = opcode & 0x0f;
 99 
100         switch (instr_hi) {
101         case 0x20:
102         case 0x30:
103                 /*
104                  * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
105                  * In X86_64 long mode, the CPU will signal invalid
106                  * opcode if some of these prefixes are present so
107                  * X86_64 will never get here anyway
108                  */
109                 return ((instr_lo & 7) == 0x6);
110 #ifdef CONFIG_X86_64
111         case 0x40:
112                 /*
113                  * In AMD64 long mode 0x40..0x4F are valid REX prefixes
114                  * Need to figure out under what instruction mode the
115                  * instruction was issued. Could check the LDT for lm,
116                  * but for now it's good enough to assume that long
117                  * mode only uses well known segments or kernel.
118                  */
119                 return (!user_mode(regs) || user_64bit_mode(regs));
120 #endif
121         case 0x60:
122                 /* 0x64 thru 0x67 are valid prefixes in all modes. */
123                 return (instr_lo & 0xC) == 0x4;
124         case 0xF0:
125                 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
126                 return !instr_lo || (instr_lo>>1) == 1;
127         case 0x00:
128                 /* Prefetch instruction is 0x0F0D or 0x0F18 */
129                 if (probe_kernel_address(instr, opcode))
130                         return 0;
131 
132                 *prefetch = (instr_lo == 0xF) &&
133                         (opcode == 0x0D || opcode == 0x18);
134                 return 0;
135         default:
136                 return 0;
137         }
138 }
139 
140 static int
141 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
142 {
143         unsigned char *max_instr;
144         unsigned char *instr;
145         int prefetch = 0;
146 
147         /*
148          * If it was a exec (instruction fetch) fault on NX page, then
149          * do not ignore the fault:
150          */
151         if (error_code & PF_INSTR)
152                 return 0;
153 
154         instr = (void *)convert_ip_to_linear(current, regs);
155         max_instr = instr + 15;
156 
157         if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
158                 return 0;
159 
160         while (instr < max_instr) {
161                 unsigned char opcode;
162 
163                 if (probe_kernel_address(instr, opcode))
164                         break;
165 
166                 instr++;
167 
168                 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
169                         break;
170         }
171         return prefetch;
172 }
173 
174 /*
175  * A protection key fault means that the PKRU value did not allow
176  * access to some PTE.  Userspace can figure out what PKRU was
177  * from the XSAVE state, and this function fills out a field in
178  * siginfo so userspace can discover which protection key was set
179  * on the PTE.
180  *
181  * If we get here, we know that the hardware signaled a PF_PK
182  * fault and that there was a VMA once we got in the fault
183  * handler.  It does *not* guarantee that the VMA we find here
184  * was the one that we faulted on.
185  *
186  * 1. T1   : mprotect_key(foo, PAGE_SIZE, pkey=4);
187  * 2. T1   : set PKRU to deny access to pkey=4, touches page
188  * 3. T1   : faults...
189  * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
190  * 5. T1   : enters fault handler, takes mmap_sem, etc...
191  * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
192  *           faulted on a pte with its pkey=4.
193  */
194 static void fill_sig_info_pkey(int si_code, siginfo_t *info,
195                 struct vm_area_struct *vma)
196 {
197         /* This is effectively an #ifdef */
198         if (!boot_cpu_has(X86_FEATURE_OSPKE))
199                 return;
200 
201         /* Fault not from Protection Keys: nothing to do */
202         if (si_code != SEGV_PKUERR)
203                 return;
204         /*
205          * force_sig_info_fault() is called from a number of
206          * contexts, some of which have a VMA and some of which
207          * do not.  The PF_PK handing happens after we have a
208          * valid VMA, so we should never reach this without a
209          * valid VMA.
210          */
211         if (!vma) {
212                 WARN_ONCE(1, "PKU fault with no VMA passed in");
213                 info->si_pkey = 0;
214                 return;
215         }
216         /*
217          * si_pkey should be thought of as a strong hint, but not
218          * absolutely guranteed to be 100% accurate because of
219          * the race explained above.
220          */
221         info->si_pkey = vma_pkey(vma);
222 }
223 
224 static void
225 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
226                      struct task_struct *tsk, struct vm_area_struct *vma,
227                      int fault)
228 {
229         unsigned lsb = 0;
230         siginfo_t info;
231 
232         info.si_signo   = si_signo;
233         info.si_errno   = 0;
234         info.si_code    = si_code;
235         info.si_addr    = (void __user *)address;
236         if (fault & VM_FAULT_HWPOISON_LARGE)
237                 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
238         if (fault & VM_FAULT_HWPOISON)
239                 lsb = PAGE_SHIFT;
240         info.si_addr_lsb = lsb;
241 
242         fill_sig_info_pkey(si_code, &info, vma);
243 
244         force_sig_info(si_signo, &info, tsk);
245 }
246 
247 DEFINE_SPINLOCK(pgd_lock);
248 LIST_HEAD(pgd_list);
249 
250 #ifdef CONFIG_X86_32
251 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
252 {
253         unsigned index = pgd_index(address);
254         pgd_t *pgd_k;
255         pud_t *pud, *pud_k;
256         pmd_t *pmd, *pmd_k;
257 
258         pgd += index;
259         pgd_k = init_mm.pgd + index;
260 
261         if (!pgd_present(*pgd_k))
262                 return NULL;
263 
264         /*
265          * set_pgd(pgd, *pgd_k); here would be useless on PAE
266          * and redundant with the set_pmd() on non-PAE. As would
267          * set_pud.
268          */
269         pud = pud_offset(pgd, address);
270         pud_k = pud_offset(pgd_k, address);
271         if (!pud_present(*pud_k))
272                 return NULL;
273 
274         pmd = pmd_offset(pud, address);
275         pmd_k = pmd_offset(pud_k, address);
276         if (!pmd_present(*pmd_k))
277                 return NULL;
278 
279         if (!pmd_present(*pmd))
280                 set_pmd(pmd, *pmd_k);
281         else
282                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
283 
284         return pmd_k;
285 }
286 
287 void vmalloc_sync_all(void)
288 {
289         unsigned long address;
290 
291         if (SHARED_KERNEL_PMD)
292                 return;
293 
294         for (address = VMALLOC_START & PMD_MASK;
295              address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
296              address += PMD_SIZE) {
297                 struct page *page;
298 
299                 spin_lock(&pgd_lock);
300                 list_for_each_entry(page, &pgd_list, lru) {
301                         spinlock_t *pgt_lock;
302                         pmd_t *ret;
303 
304                         /* the pgt_lock only for Xen */
305                         pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
306 
307                         spin_lock(pgt_lock);
308                         ret = vmalloc_sync_one(page_address(page), address);
309                         spin_unlock(pgt_lock);
310 
311                         if (!ret)
312                                 break;
313                 }
314                 spin_unlock(&pgd_lock);
315         }
316 }
317 
318 /*
319  * 32-bit:
320  *
321  *   Handle a fault on the vmalloc or module mapping area
322  */
323 static noinline int vmalloc_fault(unsigned long address)
324 {
325         unsigned long pgd_paddr;
326         pmd_t *pmd_k;
327         pte_t *pte_k;
328 
329         /* Make sure we are in vmalloc area: */
330         if (!(address >= VMALLOC_START && address < VMALLOC_END))
331                 return -1;
332 
333         WARN_ON_ONCE(in_nmi());
334 
335         /*
336          * Synchronize this task's top level page-table
337          * with the 'reference' page table.
338          *
339          * Do _not_ use "current" here. We might be inside
340          * an interrupt in the middle of a task switch..
341          */
342         pgd_paddr = read_cr3();
343         pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
344         if (!pmd_k)
345                 return -1;
346 
347         if (pmd_huge(*pmd_k))
348                 return 0;
349 
350         pte_k = pte_offset_kernel(pmd_k, address);
351         if (!pte_present(*pte_k))
352                 return -1;
353 
354         return 0;
355 }
356 NOKPROBE_SYMBOL(vmalloc_fault);
357 
358 /*
359  * Did it hit the DOS screen memory VA from vm86 mode?
360  */
361 static inline void
362 check_v8086_mode(struct pt_regs *regs, unsigned long address,
363                  struct task_struct *tsk)
364 {
365 #ifdef CONFIG_VM86
366         unsigned long bit;
367 
368         if (!v8086_mode(regs) || !tsk->thread.vm86)
369                 return;
370 
371         bit = (address - 0xA0000) >> PAGE_SHIFT;
372         if (bit < 32)
373                 tsk->thread.vm86->screen_bitmap |= 1 << bit;
374 #endif
375 }
376 
377 static bool low_pfn(unsigned long pfn)
378 {
379         return pfn < max_low_pfn;
380 }
381 
382 static void dump_pagetable(unsigned long address)
383 {
384         pgd_t *base = __va(read_cr3());
385         pgd_t *pgd = &base[pgd_index(address)];
386         pmd_t *pmd;
387         pte_t *pte;
388 
389 #ifdef CONFIG_X86_PAE
390         printk("*pdpt = %016Lx ", pgd_val(*pgd));
391         if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
392                 goto out;
393 #endif
394         pmd = pmd_offset(pud_offset(pgd, address), address);
395         printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
396 
397         /*
398          * We must not directly access the pte in the highpte
399          * case if the page table is located in highmem.
400          * And let's rather not kmap-atomic the pte, just in case
401          * it's allocated already:
402          */
403         if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
404                 goto out;
405 
406         pte = pte_offset_kernel(pmd, address);
407         printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
408 out:
409         printk("\n");
410 }
411 
412 #else /* CONFIG_X86_64: */
413 
414 void vmalloc_sync_all(void)
415 {
416         sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
417 }
418 
419 /*
420  * 64-bit:
421  *
422  *   Handle a fault on the vmalloc area
423  */
424 static noinline int vmalloc_fault(unsigned long address)
425 {
426         pgd_t *pgd, *pgd_ref;
427         pud_t *pud, *pud_ref;
428         pmd_t *pmd, *pmd_ref;
429         pte_t *pte, *pte_ref;
430 
431         /* Make sure we are in vmalloc area: */
432         if (!(address >= VMALLOC_START && address < VMALLOC_END))
433                 return -1;
434 
435         WARN_ON_ONCE(in_nmi());
436 
437         /*
438          * Copy kernel mappings over when needed. This can also
439          * happen within a race in page table update. In the later
440          * case just flush:
441          */
442         pgd = (pgd_t *)__va(read_cr3()) + pgd_index(address);
443         pgd_ref = pgd_offset_k(address);
444         if (pgd_none(*pgd_ref))
445                 return -1;
446 
447         if (pgd_none(*pgd)) {
448                 set_pgd(pgd, *pgd_ref);
449                 arch_flush_lazy_mmu_mode();
450         } else {
451                 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
452         }
453 
454         /*
455          * Below here mismatches are bugs because these lower tables
456          * are shared:
457          */
458 
459         pud = pud_offset(pgd, address);
460         pud_ref = pud_offset(pgd_ref, address);
461         if (pud_none(*pud_ref))
462                 return -1;
463 
464         if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
465                 BUG();
466 
467         if (pud_huge(*pud))
468                 return 0;
469 
470         pmd = pmd_offset(pud, address);
471         pmd_ref = pmd_offset(pud_ref, address);
472         if (pmd_none(*pmd_ref))
473                 return -1;
474 
475         if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
476                 BUG();
477 
478         if (pmd_huge(*pmd))
479                 return 0;
480 
481         pte_ref = pte_offset_kernel(pmd_ref, address);
482         if (!pte_present(*pte_ref))
483                 return -1;
484 
485         pte = pte_offset_kernel(pmd, address);
486 
487         /*
488          * Don't use pte_page here, because the mappings can point
489          * outside mem_map, and the NUMA hash lookup cannot handle
490          * that:
491          */
492         if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
493                 BUG();
494 
495         return 0;
496 }
497 NOKPROBE_SYMBOL(vmalloc_fault);
498 
499 #ifdef CONFIG_CPU_SUP_AMD
500 static const char errata93_warning[] =
501 KERN_ERR 
502 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
503 "******* Working around it, but it may cause SEGVs or burn power.\n"
504 "******* Please consider a BIOS update.\n"
505 "******* Disabling USB legacy in the BIOS may also help.\n";
506 #endif
507 
508 /*
509  * No vm86 mode in 64-bit mode:
510  */
511 static inline void
512 check_v8086_mode(struct pt_regs *regs, unsigned long address,
513                  struct task_struct *tsk)
514 {
515 }
516 
517 static int bad_address(void *p)
518 {
519         unsigned long dummy;
520 
521         return probe_kernel_address((unsigned long *)p, dummy);
522 }
523 
524 static void dump_pagetable(unsigned long address)
525 {
526         pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
527         pgd_t *pgd = base + pgd_index(address);
528         pud_t *pud;
529         pmd_t *pmd;
530         pte_t *pte;
531 
532         if (bad_address(pgd))
533                 goto bad;
534 
535         printk("PGD %lx ", pgd_val(*pgd));
536 
537         if (!pgd_present(*pgd))
538                 goto out;
539 
540         pud = pud_offset(pgd, address);
541         if (bad_address(pud))
542                 goto bad;
543 
544         printk("PUD %lx ", pud_val(*pud));
545         if (!pud_present(*pud) || pud_large(*pud))
546                 goto out;
547 
548         pmd = pmd_offset(pud, address);
549         if (bad_address(pmd))
550                 goto bad;
551 
552         printk("PMD %lx ", pmd_val(*pmd));
553         if (!pmd_present(*pmd) || pmd_large(*pmd))
554                 goto out;
555 
556         pte = pte_offset_kernel(pmd, address);
557         if (bad_address(pte))
558                 goto bad;
559 
560         printk("PTE %lx", pte_val(*pte));
561 out:
562         printk("\n");
563         return;
564 bad:
565         printk("BAD\n");
566 }
567 
568 #endif /* CONFIG_X86_64 */
569 
570 /*
571  * Workaround for K8 erratum #93 & buggy BIOS.
572  *
573  * BIOS SMM functions are required to use a specific workaround
574  * to avoid corruption of the 64bit RIP register on C stepping K8.
575  *
576  * A lot of BIOS that didn't get tested properly miss this.
577  *
578  * The OS sees this as a page fault with the upper 32bits of RIP cleared.
579  * Try to work around it here.
580  *
581  * Note we only handle faults in kernel here.
582  * Does nothing on 32-bit.
583  */
584 static int is_errata93(struct pt_regs *regs, unsigned long address)
585 {
586 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
587         if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
588             || boot_cpu_data.x86 != 0xf)
589                 return 0;
590 
591         if (address != regs->ip)
592                 return 0;
593 
594         if ((address >> 32) != 0)
595                 return 0;
596 
597         address |= 0xffffffffUL << 32;
598         if ((address >= (u64)_stext && address <= (u64)_etext) ||
599             (address >= MODULES_VADDR && address <= MODULES_END)) {
600                 printk_once(errata93_warning);
601                 regs->ip = address;
602                 return 1;
603         }
604 #endif
605         return 0;
606 }
607 
608 /*
609  * Work around K8 erratum #100 K8 in compat mode occasionally jumps
610  * to illegal addresses >4GB.
611  *
612  * We catch this in the page fault handler because these addresses
613  * are not reachable. Just detect this case and return.  Any code
614  * segment in LDT is compatibility mode.
615  */
616 static int is_errata100(struct pt_regs *regs, unsigned long address)
617 {
618 #ifdef CONFIG_X86_64
619         if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
620                 return 1;
621 #endif
622         return 0;
623 }
624 
625 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
626 {
627 #ifdef CONFIG_X86_F00F_BUG
628         unsigned long nr;
629 
630         /*
631          * Pentium F0 0F C7 C8 bug workaround:
632          */
633         if (boot_cpu_has_bug(X86_BUG_F00F)) {
634                 nr = (address - idt_descr.address) >> 3;
635 
636                 if (nr == 6) {
637                         do_invalid_op(regs, 0);
638                         return 1;
639                 }
640         }
641 #endif
642         return 0;
643 }
644 
645 static const char nx_warning[] = KERN_CRIT
646 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
647 static const char smep_warning[] = KERN_CRIT
648 "unable to execute userspace code (SMEP?) (uid: %d)\n";
649 
650 static void
651 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
652                 unsigned long address)
653 {
654         if (!oops_may_print())
655                 return;
656 
657         if (error_code & PF_INSTR) {
658                 unsigned int level;
659                 pgd_t *pgd;
660                 pte_t *pte;
661 
662                 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
663                 pgd += pgd_index(address);
664 
665                 pte = lookup_address_in_pgd(pgd, address, &level);
666 
667                 if (pte && pte_present(*pte) && !pte_exec(*pte))
668                         printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
669                 if (pte && pte_present(*pte) && pte_exec(*pte) &&
670                                 (pgd_flags(*pgd) & _PAGE_USER) &&
671                                 (__read_cr4() & X86_CR4_SMEP))
672                         printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
673         }
674 
675         printk(KERN_ALERT "BUG: unable to handle kernel ");
676         if (address < PAGE_SIZE)
677                 printk(KERN_CONT "NULL pointer dereference");
678         else
679                 printk(KERN_CONT "paging request");
680 
681         printk(KERN_CONT " at %p\n", (void *) address);
682         printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);
683 
684         dump_pagetable(address);
685 }
686 
687 static noinline void
688 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
689             unsigned long address)
690 {
691         struct task_struct *tsk;
692         unsigned long flags;
693         int sig;
694 
695         flags = oops_begin();
696         tsk = current;
697         sig = SIGKILL;
698 
699         printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
700                tsk->comm, address);
701         dump_pagetable(address);
702 
703         tsk->thread.cr2         = address;
704         tsk->thread.trap_nr     = X86_TRAP_PF;
705         tsk->thread.error_code  = error_code;
706 
707         if (__die("Bad pagetable", regs, error_code))
708                 sig = 0;
709 
710         oops_end(flags, regs, sig);
711 }
712 
713 static noinline void
714 no_context(struct pt_regs *regs, unsigned long error_code,
715            unsigned long address, int signal, int si_code)
716 {
717         struct task_struct *tsk = current;
718         unsigned long flags;
719         int sig;
720         /* No context means no VMA to pass down */
721         struct vm_area_struct *vma = NULL;
722 
723         /* Are we prepared to handle this kernel fault? */
724         if (fixup_exception(regs, X86_TRAP_PF)) {
725                 /*
726                  * Any interrupt that takes a fault gets the fixup. This makes
727                  * the below recursive fault logic only apply to a faults from
728                  * task context.
729                  */
730                 if (in_interrupt())
731                         return;
732 
733                 /*
734                  * Per the above we're !in_interrupt(), aka. task context.
735                  *
736                  * In this case we need to make sure we're not recursively
737                  * faulting through the emulate_vsyscall() logic.
738                  */
739                 if (current->thread.sig_on_uaccess_err && signal) {
740                         tsk->thread.trap_nr = X86_TRAP_PF;
741                         tsk->thread.error_code = error_code | PF_USER;
742                         tsk->thread.cr2 = address;
743 
744                         /* XXX: hwpoison faults will set the wrong code. */
745                         force_sig_info_fault(signal, si_code, address,
746                                              tsk, vma, 0);
747                 }
748 
749                 /*
750                  * Barring that, we can do the fixup and be happy.
751                  */
752                 return;
753         }
754 
755 #ifdef CONFIG_VMAP_STACK
756         /*
757          * Stack overflow?  During boot, we can fault near the initial
758          * stack in the direct map, but that's not an overflow -- check
759          * that we're in vmalloc space to avoid this.
760          */
761         if (is_vmalloc_addr((void *)address) &&
762             (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
763              address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
764                 register void *__sp asm("rsp");
765                 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
766                 /*
767                  * We're likely to be running with very little stack space
768                  * left.  It's plausible that we'd hit this condition but
769                  * double-fault even before we get this far, in which case
770                  * we're fine: the double-fault handler will deal with it.
771                  *
772                  * We don't want to make it all the way into the oops code
773                  * and then double-fault, though, because we're likely to
774                  * break the console driver and lose most of the stack dump.
775                  */
776                 asm volatile ("movq %[stack], %%rsp\n\t"
777                               "call handle_stack_overflow\n\t"
778                               "1: jmp 1b"
779                               : "+r" (__sp)
780                               : "D" ("kernel stack overflow (page fault)"),
781                                 "S" (regs), "d" (address),
782                                 [stack] "rm" (stack));
783                 unreachable();
784         }
785 #endif
786 
787         /*
788          * 32-bit:
789          *
790          *   Valid to do another page fault here, because if this fault
791          *   had been triggered by is_prefetch fixup_exception would have
792          *   handled it.
793          *
794          * 64-bit:
795          *
796          *   Hall of shame of CPU/BIOS bugs.
797          */
798         if (is_prefetch(regs, error_code, address))
799                 return;
800 
801         if (is_errata93(regs, address))
802                 return;
803 
804         /*
805          * Oops. The kernel tried to access some bad page. We'll have to
806          * terminate things with extreme prejudice:
807          */
808         flags = oops_begin();
809 
810         show_fault_oops(regs, error_code, address);
811 
812         if (task_stack_end_corrupted(tsk))
813                 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
814 
815         tsk->thread.cr2         = address;
816         tsk->thread.trap_nr     = X86_TRAP_PF;
817         tsk->thread.error_code  = error_code;
818 
819         sig = SIGKILL;
820         if (__die("Oops", regs, error_code))
821                 sig = 0;
822 
823         /* Executive summary in case the body of the oops scrolled away */
824         printk(KERN_DEFAULT "CR2: %016lx\n", address);
825 
826         oops_end(flags, regs, sig);
827 }
828 
829 /*
830  * Print out info about fatal segfaults, if the show_unhandled_signals
831  * sysctl is set:
832  */
833 static inline void
834 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
835                 unsigned long address, struct task_struct *tsk)
836 {
837         if (!unhandled_signal(tsk, SIGSEGV))
838                 return;
839 
840         if (!printk_ratelimit())
841                 return;
842 
843         printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
844                 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
845                 tsk->comm, task_pid_nr(tsk), address,
846                 (void *)regs->ip, (void *)regs->sp, error_code);
847 
848         print_vma_addr(KERN_CONT " in ", regs->ip);
849 
850         printk(KERN_CONT "\n");
851 }
852 
853 static void
854 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
855                        unsigned long address, struct vm_area_struct *vma,
856                        int si_code)
857 {
858         struct task_struct *tsk = current;
859 
860         /* User mode accesses just cause a SIGSEGV */
861         if (error_code & PF_USER) {
862                 /*
863                  * It's possible to have interrupts off here:
864                  */
865                 local_irq_enable();
866 
867                 /*
868                  * Valid to do another page fault here because this one came
869                  * from user space:
870                  */
871                 if (is_prefetch(regs, error_code, address))
872                         return;
873 
874                 if (is_errata100(regs, address))
875                         return;
876 
877 #ifdef CONFIG_X86_64
878                 /*
879                  * Instruction fetch faults in the vsyscall page might need
880                  * emulation.
881                  */
882                 if (unlikely((error_code & PF_INSTR) &&
883                              ((address & ~0xfff) == VSYSCALL_ADDR))) {
884                         if (emulate_vsyscall(regs, address))
885                                 return;
886                 }
887 #endif
888 
889                 /*
890                  * To avoid leaking information about the kernel page table
891                  * layout, pretend that user-mode accesses to kernel addresses
892                  * are always protection faults.
893                  */
894                 if (address >= TASK_SIZE_MAX)
895                         error_code |= PF_PROT;
896 
897                 if (likely(show_unhandled_signals))
898                         show_signal_msg(regs, error_code, address, tsk);
899 
900                 tsk->thread.cr2         = address;
901                 tsk->thread.error_code  = error_code;
902                 tsk->thread.trap_nr     = X86_TRAP_PF;
903 
904                 force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0);
905 
906                 return;
907         }
908 
909         if (is_f00f_bug(regs, address))
910                 return;
911 
912         no_context(regs, error_code, address, SIGSEGV, si_code);
913 }
914 
915 static noinline void
916 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
917                      unsigned long address, struct vm_area_struct *vma)
918 {
919         __bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR);
920 }
921 
922 static void
923 __bad_area(struct pt_regs *regs, unsigned long error_code,
924            unsigned long address,  struct vm_area_struct *vma, int si_code)
925 {
926         struct mm_struct *mm = current->mm;
927 
928         /*
929          * Something tried to access memory that isn't in our memory map..
930          * Fix it, but check if it's kernel or user first..
931          */
932         up_read(&mm->mmap_sem);
933 
934         __bad_area_nosemaphore(regs, error_code, address, vma, si_code);
935 }
936 
937 static noinline void
938 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
939 {
940         __bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
941 }
942 
943 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
944                 struct vm_area_struct *vma)
945 {
946         /* This code is always called on the current mm */
947         bool foreign = false;
948 
949         if (!boot_cpu_has(X86_FEATURE_OSPKE))
950                 return false;
951         if (error_code & PF_PK)
952                 return true;
953         /* this checks permission keys on the VMA: */
954         if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
955                                 (error_code & PF_INSTR), foreign))
956                 return true;
957         return false;
958 }
959 
960 static noinline void
961 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
962                       unsigned long address, struct vm_area_struct *vma)
963 {
964         /*
965          * This OSPKE check is not strictly necessary at runtime.
966          * But, doing it this way allows compiler optimizations
967          * if pkeys are compiled out.
968          */
969         if (bad_area_access_from_pkeys(error_code, vma))
970                 __bad_area(regs, error_code, address, vma, SEGV_PKUERR);
971         else
972                 __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
973 }
974 
975 static void
976 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
977           struct vm_area_struct *vma, unsigned int fault)
978 {
979         struct task_struct *tsk = current;
980         int code = BUS_ADRERR;
981 
982         /* Kernel mode? Handle exceptions or die: */
983         if (!(error_code & PF_USER)) {
984                 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
985                 return;
986         }
987 
988         /* User-space => ok to do another page fault: */
989         if (is_prefetch(regs, error_code, address))
990                 return;
991 
992         tsk->thread.cr2         = address;
993         tsk->thread.error_code  = error_code;
994         tsk->thread.trap_nr     = X86_TRAP_PF;
995 
996 #ifdef CONFIG_MEMORY_FAILURE
997         if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
998                 printk(KERN_ERR
999         "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
1000                         tsk->comm, tsk->pid, address);
1001                 code = BUS_MCEERR_AR;
1002         }
1003 #endif
1004         force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault);
1005 }
1006 
1007 static noinline void
1008 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
1009                unsigned long address, struct vm_area_struct *vma,
1010                unsigned int fault)
1011 {
1012         if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
1013                 no_context(regs, error_code, address, 0, 0);
1014                 return;
1015         }
1016 
1017         if (fault & VM_FAULT_OOM) {
1018                 /* Kernel mode? Handle exceptions or die: */
1019                 if (!(error_code & PF_USER)) {
1020                         no_context(regs, error_code, address,
1021                                    SIGSEGV, SEGV_MAPERR);
1022                         return;
1023                 }
1024 
1025                 /*
1026                  * We ran out of memory, call the OOM killer, and return the
1027                  * userspace (which will retry the fault, or kill us if we got
1028                  * oom-killed):
1029                  */
1030                 pagefault_out_of_memory();
1031         } else {
1032                 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1033                              VM_FAULT_HWPOISON_LARGE))
1034                         do_sigbus(regs, error_code, address, vma, fault);
1035                 else if (fault & VM_FAULT_SIGSEGV)
1036                         bad_area_nosemaphore(regs, error_code, address, vma);
1037                 else
1038                         BUG();
1039         }
1040 }
1041 
1042 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
1043 {
1044         if ((error_code & PF_WRITE) && !pte_write(*pte))
1045                 return 0;
1046 
1047         if ((error_code & PF_INSTR) && !pte_exec(*pte))
1048                 return 0;
1049         /*
1050          * Note: We do not do lazy flushing on protection key
1051          * changes, so no spurious fault will ever set PF_PK.
1052          */
1053         if ((error_code & PF_PK))
1054                 return 1;
1055 
1056         return 1;
1057 }
1058 
1059 /*
1060  * Handle a spurious fault caused by a stale TLB entry.
1061  *
1062  * This allows us to lazily refresh the TLB when increasing the
1063  * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
1064  * eagerly is very expensive since that implies doing a full
1065  * cross-processor TLB flush, even if no stale TLB entries exist
1066  * on other processors.
1067  *
1068  * Spurious faults may only occur if the TLB contains an entry with
1069  * fewer permission than the page table entry.  Non-present (P = 0)
1070  * and reserved bit (R = 1) faults are never spurious.
1071  *
1072  * There are no security implications to leaving a stale TLB when
1073  * increasing the permissions on a page.
1074  *
1075  * Returns non-zero if a spurious fault was handled, zero otherwise.
1076  *
1077  * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1078  * (Optional Invalidation).
1079  */
1080 static noinline int
1081 spurious_fault(unsigned long error_code, unsigned long address)
1082 {
1083         pgd_t *pgd;
1084         pud_t *pud;
1085         pmd_t *pmd;
1086         pte_t *pte;
1087         int ret;
1088 
1089         /*
1090          * Only writes to RO or instruction fetches from NX may cause
1091          * spurious faults.
1092          *
1093          * These could be from user or supervisor accesses but the TLB
1094          * is only lazily flushed after a kernel mapping protection
1095          * change, so user accesses are not expected to cause spurious
1096          * faults.
1097          */
1098         if (error_code != (PF_WRITE | PF_PROT)
1099             && error_code != (PF_INSTR | PF_PROT))
1100                 return 0;
1101 
1102         pgd = init_mm.pgd + pgd_index(address);
1103         if (!pgd_present(*pgd))
1104                 return 0;
1105 
1106         pud = pud_offset(pgd, address);
1107         if (!pud_present(*pud))
1108                 return 0;
1109 
1110         if (pud_large(*pud))
1111                 return spurious_fault_check(error_code, (pte_t *) pud);
1112 
1113         pmd = pmd_offset(pud, address);
1114         if (!pmd_present(*pmd))
1115                 return 0;
1116 
1117         if (pmd_large(*pmd))
1118                 return spurious_fault_check(error_code, (pte_t *) pmd);
1119 
1120         pte = pte_offset_kernel(pmd, address);
1121         if (!pte_present(*pte))
1122                 return 0;
1123 
1124         ret = spurious_fault_check(error_code, pte);
1125         if (!ret)
1126                 return 0;
1127 
1128         /*
1129          * Make sure we have permissions in PMD.
1130          * If not, then there's a bug in the page tables:
1131          */
1132         ret = spurious_fault_check(error_code, (pte_t *) pmd);
1133         WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1134 
1135         return ret;
1136 }
1137 NOKPROBE_SYMBOL(spurious_fault);
1138 
1139 int show_unhandled_signals = 1;
1140 
1141 static inline int
1142 access_error(unsigned long error_code, struct vm_area_struct *vma)
1143 {
1144         /* This is only called for the current mm, so: */
1145         bool foreign = false;
1146 
1147         /*
1148          * Read or write was blocked by protection keys.  This is
1149          * always an unconditional error and can never result in
1150          * a follow-up action to resolve the fault, like a COW.
1151          */
1152         if (error_code & PF_PK)
1153                 return 1;
1154 
1155         /*
1156          * Make sure to check the VMA so that we do not perform
1157          * faults just to hit a PF_PK as soon as we fill in a
1158          * page.
1159          */
1160         if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
1161                                 (error_code & PF_INSTR), foreign))
1162                 return 1;
1163 
1164         if (error_code & PF_WRITE) {
1165                 /* write, present and write, not present: */
1166                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1167                         return 1;
1168                 return 0;
1169         }
1170 
1171         /* read, present: */
1172         if (unlikely(error_code & PF_PROT))
1173                 return 1;
1174 
1175         /* read, not present: */
1176         if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1177                 return 1;
1178 
1179         return 0;
1180 }
1181 
1182 static int fault_in_kernel_space(unsigned long address)
1183 {
1184         return address >= TASK_SIZE_MAX;
1185 }
1186 
1187 static inline bool smap_violation(int error_code, struct pt_regs *regs)
1188 {
1189         if (!IS_ENABLED(CONFIG_X86_SMAP))
1190                 return false;
1191 
1192         if (!static_cpu_has(X86_FEATURE_SMAP))
1193                 return false;
1194 
1195         if (error_code & PF_USER)
1196                 return false;
1197 
1198         if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1199                 return false;
1200 
1201         return true;
1202 }
1203 
1204 /*
1205  * This routine handles page faults.  It determines the address,
1206  * and the problem, and then passes it off to one of the appropriate
1207  * routines.
1208  *
1209  * This function must have noinline because both callers
1210  * {,trace_}do_page_fault() have notrace on. Having this an actual function
1211  * guarantees there's a function trace entry.
1212  */
1213 static noinline void
1214 __do_page_fault(struct pt_regs *regs, unsigned long error_code,
1215                 unsigned long address)
1216 {
1217         struct vm_area_struct *vma;
1218         struct task_struct *tsk;
1219         struct mm_struct *mm;
1220         int fault, major = 0;
1221         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1222 
1223         tsk = current;
1224         mm = tsk->mm;
1225 
1226         /*
1227          * Detect and handle instructions that would cause a page fault for
1228          * both a tracked kernel page and a userspace page.
1229          */
1230         if (kmemcheck_active(regs))
1231                 kmemcheck_hide(regs);
1232         prefetchw(&mm->mmap_sem);
1233 
1234         if (unlikely(kmmio_fault(regs, address)))
1235                 return;
1236 
1237         /*
1238          * We fault-in kernel-space virtual memory on-demand. The
1239          * 'reference' page table is init_mm.pgd.
1240          *
1241          * NOTE! We MUST NOT take any locks for this case. We may
1242          * be in an interrupt or a critical region, and should
1243          * only copy the information from the master page table,
1244          * nothing more.
1245          *
1246          * This verifies that the fault happens in kernel space
1247          * (error_code & 4) == 0, and that the fault was not a
1248          * protection error (error_code & 9) == 0.
1249          */
1250         if (unlikely(fault_in_kernel_space(address))) {
1251                 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1252                         if (vmalloc_fault(address) >= 0)
1253                                 return;
1254 
1255                         if (kmemcheck_fault(regs, address, error_code))
1256                                 return;
1257                 }
1258 
1259                 /* Can handle a stale RO->RW TLB: */
1260                 if (spurious_fault(error_code, address))
1261                         return;
1262 
1263                 /* kprobes don't want to hook the spurious faults: */
1264                 if (kprobes_fault(regs))
1265                         return;
1266                 /*
1267                  * Don't take the mm semaphore here. If we fixup a prefetch
1268                  * fault we could otherwise deadlock:
1269                  */
1270                 bad_area_nosemaphore(regs, error_code, address, NULL);
1271 
1272                 return;
1273         }
1274 
1275         /* kprobes don't want to hook the spurious faults: */
1276         if (unlikely(kprobes_fault(regs)))
1277                 return;
1278 
1279         if (unlikely(error_code & PF_RSVD))
1280                 pgtable_bad(regs, error_code, address);
1281 
1282         if (unlikely(smap_violation(error_code, regs))) {
1283                 bad_area_nosemaphore(regs, error_code, address, NULL);
1284                 return;
1285         }
1286 
1287         /*
1288          * If we're in an interrupt, have no user context or are running
1289          * in a region with pagefaults disabled then we must not take the fault
1290          */
1291         if (unlikely(faulthandler_disabled() || !mm)) {
1292                 bad_area_nosemaphore(regs, error_code, address, NULL);
1293                 return;
1294         }
1295 
1296         /*
1297          * It's safe to allow irq's after cr2 has been saved and the
1298          * vmalloc fault has been handled.
1299          *
1300          * User-mode registers count as a user access even for any
1301          * potential system fault or CPU buglet:
1302          */
1303         if (user_mode(regs)) {
1304                 local_irq_enable();
1305                 error_code |= PF_USER;
1306                 flags |= FAULT_FLAG_USER;
1307         } else {
1308                 if (regs->flags & X86_EFLAGS_IF)
1309                         local_irq_enable();
1310         }
1311 
1312         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1313 
1314         if (error_code & PF_WRITE)
1315                 flags |= FAULT_FLAG_WRITE;
1316         if (error_code & PF_INSTR)
1317                 flags |= FAULT_FLAG_INSTRUCTION;
1318 
1319         /*
1320          * When running in the kernel we expect faults to occur only to
1321          * addresses in user space.  All other faults represent errors in
1322          * the kernel and should generate an OOPS.  Unfortunately, in the
1323          * case of an erroneous fault occurring in a code path which already
1324          * holds mmap_sem we will deadlock attempting to validate the fault
1325          * against the address space.  Luckily the kernel only validly
1326          * references user space from well defined areas of code, which are
1327          * listed in the exceptions table.
1328          *
1329          * As the vast majority of faults will be valid we will only perform
1330          * the source reference check when there is a possibility of a
1331          * deadlock. Attempt to lock the address space, if we cannot we then
1332          * validate the source. If this is invalid we can skip the address
1333          * space check, thus avoiding the deadlock:
1334          */
1335         if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1336                 if ((error_code & PF_USER) == 0 &&
1337                     !search_exception_tables(regs->ip)) {
1338                         bad_area_nosemaphore(regs, error_code, address, NULL);
1339                         return;
1340                 }
1341 retry:
1342                 down_read(&mm->mmap_sem);
1343         } else {
1344                 /*
1345                  * The above down_read_trylock() might have succeeded in
1346                  * which case we'll have missed the might_sleep() from
1347                  * down_read():
1348                  */
1349                 might_sleep();
1350         }
1351 
1352         vma = find_vma(mm, address);
1353         if (unlikely(!vma)) {
1354                 bad_area(regs, error_code, address);
1355                 return;
1356         }
1357         if (likely(vma->vm_start <= address))
1358                 goto good_area;
1359         if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1360                 bad_area(regs, error_code, address);
1361                 return;
1362         }
1363         if (error_code & PF_USER) {
1364                 /*
1365                  * Accessing the stack below %sp is always a bug.
1366                  * The large cushion allows instructions like enter
1367                  * and pusha to work. ("enter $65535, $31" pushes
1368                  * 32 pointers and then decrements %sp by 65535.)
1369                  */
1370                 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1371                         bad_area(regs, error_code, address);
1372                         return;
1373                 }
1374         }
1375         if (unlikely(expand_stack(vma, address))) {
1376                 bad_area(regs, error_code, address);
1377                 return;
1378         }
1379 
1380         /*
1381          * Ok, we have a good vm_area for this memory access, so
1382          * we can handle it..
1383          */
1384 good_area:
1385         if (unlikely(access_error(error_code, vma))) {
1386                 bad_area_access_error(regs, error_code, address, vma);
1387                 return;
1388         }
1389 
1390         /*
1391          * If for any reason at all we couldn't handle the fault,
1392          * make sure we exit gracefully rather than endlessly redo
1393          * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1394          * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1395          */
1396         fault = handle_mm_fault(vma, address, flags);
1397         major |= fault & VM_FAULT_MAJOR;
1398 
1399         /*
1400          * If we need to retry the mmap_sem has already been released,
1401          * and if there is a fatal signal pending there is no guarantee
1402          * that we made any progress. Handle this case first.
1403          */
1404         if (unlikely(fault & VM_FAULT_RETRY)) {
1405                 /* Retry at most once */
1406                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1407                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
1408                         flags |= FAULT_FLAG_TRIED;
1409                         if (!fatal_signal_pending(tsk))
1410                                 goto retry;
1411                 }
1412 
1413                 /* User mode? Just return to handle the fatal exception */
1414                 if (flags & FAULT_FLAG_USER)
1415                         return;
1416 
1417                 /* Not returning to user mode? Handle exceptions or die: */
1418                 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1419                 return;
1420         }
1421 
1422         up_read(&mm->mmap_sem);
1423         if (unlikely(fault & VM_FAULT_ERROR)) {
1424                 mm_fault_error(regs, error_code, address, vma, fault);
1425                 return;
1426         }
1427 
1428         /*
1429          * Major/minor page fault accounting. If any of the events
1430          * returned VM_FAULT_MAJOR, we account it as a major fault.
1431          */
1432         if (major) {
1433                 tsk->maj_flt++;
1434                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1435         } else {
1436                 tsk->min_flt++;
1437                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1438         }
1439 
1440         check_v8086_mode(regs, address, tsk);
1441 }
1442 NOKPROBE_SYMBOL(__do_page_fault);
1443 
1444 dotraplinkage void notrace
1445 do_page_fault(struct pt_regs *regs, unsigned long error_code)
1446 {
1447         unsigned long address = read_cr2(); /* Get the faulting address */
1448         enum ctx_state prev_state;
1449 
1450         /*
1451          * We must have this function tagged with __kprobes, notrace and call
1452          * read_cr2() before calling anything else. To avoid calling any kind
1453          * of tracing machinery before we've observed the CR2 value.
1454          *
1455          * exception_{enter,exit}() contain all sorts of tracepoints.
1456          */
1457 
1458         prev_state = exception_enter();
1459         __do_page_fault(regs, error_code, address);
1460         exception_exit(prev_state);
1461 }
1462 NOKPROBE_SYMBOL(do_page_fault);
1463 
1464 #ifdef CONFIG_TRACING
1465 static nokprobe_inline void
1466 trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1467                          unsigned long error_code)
1468 {
1469         if (user_mode(regs))
1470                 trace_page_fault_user(address, regs, error_code);
1471         else
1472                 trace_page_fault_kernel(address, regs, error_code);
1473 }
1474 
1475 dotraplinkage void notrace
1476 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1477 {
1478         /*
1479          * The exception_enter and tracepoint processing could
1480          * trigger another page faults (user space callchain
1481          * reading) and destroy the original cr2 value, so read
1482          * the faulting address now.
1483          */
1484         unsigned long address = read_cr2();
1485         enum ctx_state prev_state;
1486 
1487         prev_state = exception_enter();
1488         trace_page_fault_entries(address, regs, error_code);
1489         __do_page_fault(regs, error_code, address);
1490         exception_exit(prev_state);
1491 }
1492 NOKPROBE_SYMBOL(trace_do_page_fault);
1493 #endif /* CONFIG_TRACING */
1494 

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