arch/arm/mm/fault.c - kernel/msm-4.19 - Gitiles

 /*
  *  linux/arch/arm/mm/fault.c
  *
  *  Copyright (C) 1995  Linus Torvalds
  *  Modifications for ARM processor (c) 1995-2004 Russell King
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
 #include <linux/module.h>
 #include <linux/signal.h>
 #include <linux/mm.h>
 #include <linux/hardirq.h>
 #include <linux/init.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/page-flags.h>
 #include <linux/sched.h>
 #include <linux/highmem.h>
 #include <linux/perf_event.h>

 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>

 #include "fault.h"

 /*
  * Fault status register encodings.  We steal bit 31 for our own purposes.
  */
 #define FSR_LNX_PF		(1 << 31)
 #define FSR_WRITE		(1 << 11)
 #define FSR_FS4			(1 << 10)
 #define FSR_FS3_0		(15)

 static inline int fsr_fs(unsigned int fsr)
 {
 	return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6;
 }

 #ifdef CONFIG_MMU

 #ifdef CONFIG_KPROBES
 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
 {
 	int ret = 0;

 	if (!user_mode(regs)) {
 		/* kprobe_running() needs smp_processor_id() */
 		preempt_disable();
 		if (kprobe_running() && kprobe_fault_handler(regs, fsr))
 			ret = 1;
 		preempt_enable();
 	}

 	return ret;
 }
 #else
 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
 {
 	return 0;
 }
 #endif

 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
  */
 void show_pte(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;

 	if (!mm)
 		mm = &init_mm;

 	printk(KERN_ALERT "pgd = %p\n", mm->pgd);
 	pgd = pgd_offset(mm, addr);
 	printk(KERN_ALERT "[%08lx] *pgd=%08llx",
 			addr, (long long)pgd_val(*pgd));

 	do {
 		pud_t *pud;
 		pmd_t *pmd;
 		pte_t *pte;

 		if (pgd_none(*pgd))
 			break;

 		if (pgd_bad(*pgd)) {
 			printk("(bad)");
 			break;
 		}

 		pud = pud_offset(pgd, addr);
 		if (PTRS_PER_PUD != 1)
 			printk(", *pud=%08lx", pud_val(*pud));

 		if (pud_none(*pud))
 			break;

 		if (pud_bad(*pud)) {
 			printk("(bad)");
 			break;
 		}

 		pmd = pmd_offset(pud, addr);
 		if (PTRS_PER_PMD != 1)
 			printk(", *pmd=%08llx", (long long)pmd_val(*pmd));

 		if (pmd_none(*pmd))
 			break;

 		if (pmd_bad(*pmd)) {
 			printk("(bad)");
 			break;
 		}

 		/* We must not map this if we have highmem enabled */
 		if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 			break;

 		pte = pte_offset_map(pmd, addr);
 		printk(", *pte=%08llx", (long long)pte_val(*pte));
 		printk(", *ppte=%08llx",
 		       (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
 		pte_unmap(pte);
 	} while(0);

 	printk("\n");
 }
 #else					/* CONFIG_MMU */
 void show_pte(struct mm_struct *mm, unsigned long addr)
 { }
 #endif					/* CONFIG_MMU */

 /*
  * Oops.  The kernel tried to access some page that wasn't present.
  */
 static void
 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 		  struct pt_regs *regs)
 {
 	/*
 	 * Are we prepared to handle this kernel fault?
 	 */
 	if (fixup_exception(regs))
 		return;

 	/*
 	 * No handler, we'll have to terminate things with extreme prejudice.
 	 */
 	bust_spinlocks(1);
 	printk(KERN_ALERT
 		"Unable to handle kernel %s at virtual address %08lx\n",
 		(addr < PAGE_SIZE) ? "NULL pointer dereference" :
 		"paging request", addr);

 	show_pte(mm, addr);
 	die("Oops", regs, fsr);
 	bust_spinlocks(0);
 	do_exit(SIGKILL);
 }

 /*
  * Something tried to access memory that isn't in our memory map..
  * User mode accesses just cause a SIGSEGV
  */
 static void
 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 		unsigned int fsr, unsigned int sig, int code,
 		struct pt_regs *regs)
 {
 	struct siginfo si;

 #ifdef CONFIG_DEBUG_USER
 	if (user_debug & UDBG_SEGV) {
 		printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 		       tsk->comm, sig, addr, fsr);
 		show_pte(tsk->mm, addr);
 		show_regs(regs);
 	}
 #endif

 	tsk->thread.address = addr;
 	tsk->thread.error_code = fsr;
 	tsk->thread.trap_no = 14;
 	si.si_signo = sig;
 	si.si_errno = 0;
 	si.si_code = code;
 	si.si_addr = (void __user *)addr;
 	force_sig_info(sig, &si, tsk);
 }

 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->active_mm;

 	/*
 	 * If we are in kernel mode at this point, we
 	 * have no context to handle this fault with.
 	 */
 	if (user_mode(regs))
 		__do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 	else
 		__do_kernel_fault(mm, addr, fsr, regs);
 }

 #ifdef CONFIG_MMU
 #define VM_FAULT_BADMAP		0x010000
 #define VM_FAULT_BADACCESS	0x020000

 /*
  * Check that the permissions on the VMA allow for the fault which occurred.
  * If we encountered a write fault, we must have write permission, otherwise
  * we allow any permission.
  */
 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 {
 	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;

 	if (fsr & FSR_WRITE)
 		mask = VM_WRITE;
 	if (fsr & FSR_LNX_PF)
 		mask = VM_EXEC;

 	return vma->vm_flags & mask ? false : true;
 }

 static int __kprobes
 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 		struct task_struct *tsk)
 {
 	struct vm_area_struct *vma;
 	int fault;

 	vma = find_vma(mm, addr);
 	fault = VM_FAULT_BADMAP;
 	if (unlikely(!vma))
 		goto out;
 	if (unlikely(vma->vm_start > addr))
 		goto check_stack;

 	/*
 	 * Ok, we have a good vm_area for this
 	 * memory access, so we can handle it.
 	 */
 good_area:
 	if (access_error(fsr, vma)) {
 		fault = VM_FAULT_BADACCESS;
 		goto out;
 	}

 	/*
 	 * If for any reason at all we couldn't handle the fault, make
 	 * sure we exit gracefully rather than endlessly redo the fault.
 	 */
 	fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0);
 	if (unlikely(fault & VM_FAULT_ERROR))
 		return fault;
 	if (fault & VM_FAULT_MAJOR)
 		tsk->maj_flt++;
 	else
 		tsk->min_flt++;
 	return fault;

 check_stack:
 	if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 		goto good_area;
 out:
 	return fault;
 }

 static int __kprobes
 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
 	int fault, sig, code;

 	if (notify_page_fault(regs, fsr))
 		return 0;

 	tsk = current;
 	mm  = tsk->mm;

 	/* Enable interrupts if they were enabled in the parent context. */
 	if (interrupts_enabled(regs))
 		local_irq_enable();

 	/*
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
 	if (in_atomic() || !mm)
 		goto no_context;

 	/*
 	 * As per x86, we may deadlock here.  However, since the kernel only
 	 * validly references user space from well defined areas of the code,
 	 * we can bug out early if this is from code which shouldn't.
 	 */
 	if (!down_read_trylock(&mm->mmap_sem)) {
 		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
 			goto no_context;
 		down_read(&mm->mmap_sem);
 	} else {
 		/*
 		 * The above down_read_trylock() might have succeeded in
 		 * which case, we'll have missed the might_sleep() from
 		 * down_read()
 		 */
 		might_sleep();
 #ifdef CONFIG_DEBUG_VM
 		if (!user_mode(regs) &&
 		    !search_exception_tables(regs->ARM_pc))
 			goto no_context;
 #endif
 	}

 	fault = __do_page_fault(mm, addr, fsr, tsk);
 	up_read(&mm->mmap_sem);

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, addr);
 	if (fault & VM_FAULT_MAJOR)
 		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, regs, addr);
 	else if (fault & VM_FAULT_MINOR)
 		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, regs, addr);

 	/*
 	 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 	 */
 	if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 		return 0;

 	if (fault & VM_FAULT_OOM) {
 		/*
 		 * We ran out of memory, call the OOM killer, and return to
 		 * userspace (which will retry the fault, or kill us if we
 		 * got oom-killed)
 		 */
 		pagefault_out_of_memory();
 		return 0;
 	}

 	/*
 	 * If we are in kernel mode at this point, we
 	 * have no context to handle this fault with.
 	 */
 	if (!user_mode(regs))
 		goto no_context;

 	if (fault & VM_FAULT_SIGBUS) {
 		/*
 		 * We had some memory, but were unable to
 		 * successfully fix up this page fault.
 		 */
 		sig = SIGBUS;
 		code = BUS_ADRERR;
 	} else {
 		/*
 		 * Something tried to access memory that
 		 * isn't in our memory map..
 		 */
 		sig = SIGSEGV;
 		code = fault == VM_FAULT_BADACCESS ?
 			SEGV_ACCERR : SEGV_MAPERR;
 	}

 	__do_user_fault(tsk, addr, fsr, sig, code, regs);
 	return 0;

 no_context:
 	__do_kernel_fault(mm, addr, fsr, regs);
 	return 0;
 }
 #else					/* CONFIG_MMU */
 static int
 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	return 0;
 }
 #endif					/* CONFIG_MMU */

 /*
  * First Level Translation Fault Handler
  *
  * We enter here because the first level page table doesn't contain
  * a valid entry for the address.
  *
  * If the address is in kernel space (>= TASK_SIZE), then we are
  * probably faulting in the vmalloc() area.
  *
  * If the init_task's first level page tables contains the relevant
  * entry, we copy the it to this task.  If not, we send the process
  * a signal, fixup the exception, or oops the kernel.
  *
  * NOTE! We MUST NOT take any locks for this case. We may be in an
  * interrupt or a critical region, and should only copy the information
  * from the master page table, nothing more.
  */
 #ifdef CONFIG_MMU
 static int __kprobes
 do_translation_fault(unsigned long addr, unsigned int fsr,
 		     struct pt_regs *regs)
 {
 	unsigned int index;
 	pgd_t *pgd, *pgd_k;
 	pud_t *pud, *pud_k;
 	pmd_t *pmd, *pmd_k;

 	if (addr < TASK_SIZE)
 		return do_page_fault(addr, fsr, regs);

 	if (user_mode(regs))
 		goto bad_area;

 	index = pgd_index(addr);

 	/*
 	 * FIXME: CP15 C1 is write only on ARMv3 architectures.
 	 */
 	pgd = cpu_get_pgd() + index;
 	pgd_k = init_mm.pgd + index;

 	if (pgd_none(*pgd_k))
 		goto bad_area;
 	if (!pgd_present(*pgd))
 		set_pgd(pgd, *pgd_k);

 	pud = pud_offset(pgd, addr);
 	pud_k = pud_offset(pgd_k, addr);

 	if (pud_none(*pud_k))
 		goto bad_area;
 	if (!pud_present(*pud))
 		set_pud(pud, *pud_k);

 	pmd = pmd_offset(pud, addr);
 	pmd_k = pmd_offset(pud_k, addr);

 	/*
 	 * On ARM one Linux PGD entry contains two hardware entries (see page
 	 * tables layout in pgtable.h). We normally guarantee that we always
 	 * fill both L1 entries. But create_mapping() doesn't follow the rule.
 	 * It can create inidividual L1 entries, so here we have to call
 	 * pmd_none() check for the entry really corresponded to address, not
 	 * for the first of pair.
 	 */
 	index = (addr >> SECTION_SHIFT) & 1;
 	if (pmd_none(pmd_k[index]))
 		goto bad_area;

 	copy_pmd(pmd, pmd_k);
 	return 0;

 bad_area:
 	do_bad_area(addr, fsr, regs);
 	return 0;
 }
 #else					/* CONFIG_MMU */
 static int
 do_translation_fault(unsigned long addr, unsigned int fsr,
 		     struct pt_regs *regs)
 {
 	return 0;
 }
 #endif					/* CONFIG_MMU */

 /*
  * Some section permission faults need to be handled gracefully.
  * They can happen due to a __{get,put}_user during an oops.
  */
 static int
 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	do_bad_area(addr, fsr, regs);
 	return 0;
 }

 /*
  * This abort handler always returns "fault".
  */
 static int
 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	return 1;
 }

 static struct fsr_info {
 	int	(*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 	int	sig;
 	int	code;
 	const char *name;
 } fsr_info[] = {
 	/*
 	 * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 	 * defines these to be "precise" aborts.
 	 */
 	{ do_bad,		SIGSEGV, 0,		"vector exception"		   },
 	{ do_bad,		SIGBUS,	 BUS_ADRALN,	"alignment exception"		   },
 	{ do_bad,		SIGKILL, 0,		"terminal exception"		   },
 	{ do_bad,		SIGBUS,	 BUS_ADRALN,	"alignment exception"		   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on linefetch"	   },
 	{ do_translation_fault,	SIGSEGV, SEGV_MAPERR,	"section translation fault"	   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on linefetch"	   },
 	{ do_page_fault,	SIGSEGV, SEGV_MAPERR,	"page translation fault"	   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on non-linefetch"  },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section domain fault"		   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on non-linefetch"  },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page domain fault"		   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
 	{ do_sect_fault,	SIGSEGV, SEGV_ACCERR,	"section permission fault"	   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
 	{ do_page_fault,	SIGSEGV, SEGV_ACCERR,	"page permission fault"		   },
 	/*
 	 * The following are "imprecise" aborts, which are signalled by bit
 	 * 10 of the FSR, and may not be recoverable.  These are only
 	 * supported if the CPU abort handler supports bit 10.
 	 */
 	{ do_bad,		SIGBUS,  0,		"unknown 16"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 17"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 18"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 19"			   },
 	{ do_bad,		SIGBUS,  0,		"lock abort"			   }, /* xscale */
 	{ do_bad,		SIGBUS,  0,		"unknown 21"			   },
 	{ do_bad,		SIGBUS,  BUS_OBJERR,	"imprecise external abort"	   }, /* xscale */
 	{ do_bad,		SIGBUS,  0,		"unknown 23"			   },
 	{ do_bad,		SIGBUS,  0,		"dcache parity error"		   }, /* xscale */
 	{ do_bad,		SIGBUS,  0,		"unknown 25"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 26"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 27"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 28"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 29"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 30"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 31"			   }
 };

 void __init
 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 		int sig, int code, const char *name)
 {
 	if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
 		BUG();

 	fsr_info[nr].fn   = fn;
 	fsr_info[nr].sig  = sig;
 	fsr_info[nr].code = code;
 	fsr_info[nr].name = name;
 }

 /*
  * Dispatch a data abort to the relevant handler.
  */
 asmlinkage void __exception
 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
 	struct siginfo info;

 	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 		return;

 	printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 		inf->name, fsr, addr);

 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code  = inf->code;
 	info.si_addr  = (void __user *)addr;
 	arm_notify_die("", regs, &info, fsr, 0);
 }


 static struct fsr_info ifsr_info[] = {
 	{ do_bad,		SIGBUS,  0,		"unknown 0"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 1"			   },
 	{ do_bad,		SIGBUS,  0,		"debug event"			   },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section access flag fault"	   },
 	{ do_bad,		SIGBUS,  0,		"unknown 4"			   },
 	{ do_translation_fault,	SIGSEGV, SEGV_MAPERR,	"section translation fault"	   },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page access flag fault"	   },
 	{ do_page_fault,	SIGSEGV, SEGV_MAPERR,	"page translation fault"	   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on non-linefetch"  },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section domain fault"		   },
 	{ do_bad,		SIGBUS,  0,		"unknown 10"			   },
 	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page domain fault"		   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
 	{ do_sect_fault,	SIGSEGV, SEGV_ACCERR,	"section permission fault"	   },
 	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
 	{ do_page_fault,	SIGSEGV, SEGV_ACCERR,	"page permission fault"		   },
 	{ do_bad,		SIGBUS,  0,		"unknown 16"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 17"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 18"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 19"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 20"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 21"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 22"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 23"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 24"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 25"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 26"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 27"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 28"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 29"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 30"			   },
 	{ do_bad,		SIGBUS,  0,		"unknown 31"			   },
 };

 void __init
 hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 		 int sig, int code, const char *name)
 {
 	if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
 		BUG();

 	ifsr_info[nr].fn   = fn;
 	ifsr_info[nr].sig  = sig;
 	ifsr_info[nr].code = code;
 	ifsr_info[nr].name = name;
 }

 asmlinkage void __exception
 do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
 {
 	const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
 	struct siginfo info;

 	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 		return;

 	printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 		inf->name, ifsr, addr);

 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code  = inf->code;
 	info.si_addr  = (void __user *)addr;
 	arm_notify_die("", regs, &info, ifsr, 0);
 }

 static int __init exceptions_init(void)
 {
 	if (cpu_architecture() >= CPU_ARCH_ARMv6) {
 		hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
 				"I-cache maintenance fault");
 	}

 	if (cpu_architecture() >= CPU_ARCH_ARMv7) {
 		/*
 		 * TODO: Access flag faults introduced in ARMv6K.
 		 * Runtime check for 'K' extension is needed
 		 */
 		hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
 				"section access flag fault");
 		hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
 				"section access flag fault");
 	}

 	return 0;
 }

 arch_initcall(exceptions_init);
	/*
	* linux/arch/arm/mm/fault.c
	*
	* Copyright (C) 1995 Linus Torvalds
	* Modifications for ARM processor (c) 1995-2004 Russell King
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/
	#include <linux/module.h>
	#include <linux/signal.h>
	#include <linux/mm.h>
	#include <linux/hardirq.h>
	#include <linux/init.h>
	#include <linux/kprobes.h>
	#include <linux/uaccess.h>
	#include <linux/page-flags.h>
	#include <linux/sched.h>
	#include <linux/highmem.h>
	#include <linux/perf_event.h>

	#include <asm/system.h>
	#include <asm/pgtable.h>
	#include <asm/tlbflush.h>

	#include "fault.h"

	/*
	* Fault status register encodings. We steal bit 31 for our own purposes.
	*/
	#define FSR_LNX_PF (1 << 31)
	#define FSR_WRITE (1 << 11)
	#define FSR_FS4 (1 << 10)
	#define FSR_FS3_0 (15)

	static inline int fsr_fs(unsigned int fsr)
	{
	return (fsr & FSR_FS3_0) \| (fsr & FSR_FS4) >> 6;
	}

	#ifdef CONFIG_MMU

	#ifdef CONFIG_KPROBES
	static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
	{
	int ret = 0;

	if (!user_mode(regs)) {
	/* kprobe_running() needs smp_processor_id() */
	preempt_disable();
	if (kprobe_running() && kprobe_fault_handler(regs, fsr))
	ret = 1;
	preempt_enable();
	}

	return ret;
	}
	#else
	static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
	{
	return 0;
	}
	#endif

	/*
	* This is useful to dump out the page tables associated with
	* 'addr' in mm 'mm'.
	*/
	void show_pte(struct mm_struct *mm, unsigned long addr)
	{
	pgd_t *pgd;

	if (!mm)
	mm = &init_mm;

	printk(KERN_ALERT "pgd = %p\n", mm->pgd);
	pgd = pgd_offset(mm, addr);
	printk(KERN_ALERT "[%08lx] *pgd=%08llx",
	addr, (long long)pgd_val(*pgd));

	do {
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (pgd_none(*pgd))
	break;

	if (pgd_bad(*pgd)) {
	printk("(bad)");
	break;
	}

	pud = pud_offset(pgd, addr);
	if (PTRS_PER_PUD != 1)
	printk(", pud=%08lx", pud_val(pud));

	if (pud_none(*pud))
	break;

	if (pud_bad(*pud)) {
	printk("(bad)");
	break;
	}

	pmd = pmd_offset(pud, addr);
	if (PTRS_PER_PMD != 1)
	printk(", pmd=%08llx", (long long)pmd_val(pmd));

	if (pmd_none(*pmd))
	break;

	if (pmd_bad(*pmd)) {
	printk("(bad)");
	break;
	}

	/* We must not map this if we have highmem enabled */
	if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
	break;

	pte = pte_offset_map(pmd, addr);
	printk(", pte=%08llx", (long long)pte_val(pte));
	printk(", *ppte=%08llx",
	(long long)pte_val(pte[PTE_HWTABLE_PTRS]));
	pte_unmap(pte);
	} while(0);

	printk("\n");
	}
	#else /* CONFIG_MMU */
	void show_pte(struct mm_struct *mm, unsigned long addr)
	{ }
	#endif /* CONFIG_MMU */

	/*
	* Oops. The kernel tried to access some page that wasn't present.
	*/
	static void
	__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
	struct pt_regs *regs)
	{
	/*
	* Are we prepared to handle this kernel fault?
	*/
	if (fixup_exception(regs))
	return;

	/*
	* No handler, we'll have to terminate things with extreme prejudice.
	*/
	bust_spinlocks(1);
	printk(KERN_ALERT
	"Unable to handle kernel %s at virtual address %08lx\n",
	(addr < PAGE_SIZE) ? "NULL pointer dereference" :
	"paging request", addr);

	show_pte(mm, addr);
	die("Oops", regs, fsr);
	bust_spinlocks(0);
	do_exit(SIGKILL);
	}

	/*
	* Something tried to access memory that isn't in our memory map..
	* User mode accesses just cause a SIGSEGV
	*/
	static void
	__do_user_fault(struct task_struct *tsk, unsigned long addr,
	unsigned int fsr, unsigned int sig, int code,
	struct pt_regs *regs)
	{
	struct siginfo si;

	#ifdef CONFIG_DEBUG_USER
	if (user_debug & UDBG_SEGV) {
	printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
	tsk->comm, sig, addr, fsr);
	show_pte(tsk->mm, addr);
	show_regs(regs);
	}
	#endif

	tsk->thread.address = addr;
	tsk->thread.error_code = fsr;
	tsk->thread.trap_no = 14;
	si.si_signo = sig;
	si.si_errno = 0;
	si.si_code = code;
	si.si_addr = (void __user *)addr;
	force_sig_info(sig, &si, tsk);
	}

	void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->active_mm;

	/*
	* If we are in kernel mode at this point, we
	* have no context to handle this fault with.
	*/
	if (user_mode(regs))
	__do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
	else
	__do_kernel_fault(mm, addr, fsr, regs);
	}

	#ifdef CONFIG_MMU
	#define VM_FAULT_BADMAP 0x010000
	#define VM_FAULT_BADACCESS 0x020000

	/*
	* Check that the permissions on the VMA allow for the fault which occurred.
	* If we encountered a write fault, we must have write permission, otherwise
	* we allow any permission.
	*/
	static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
	{
	unsigned int mask = VM_READ \| VM_WRITE \| VM_EXEC;

	if (fsr & FSR_WRITE)
	mask = VM_WRITE;
	if (fsr & FSR_LNX_PF)
	mask = VM_EXEC;

	return vma->vm_flags & mask ? false : true;
	}

	static int __kprobes
	__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
	struct task_struct *tsk)
	{
	struct vm_area_struct *vma;
	int fault;

	vma = find_vma(mm, addr);
	fault = VM_FAULT_BADMAP;
	if (unlikely(!vma))
	goto out;
	if (unlikely(vma->vm_start > addr))
	goto check_stack;

	/*
	* Ok, we have a good vm_area for this
	* memory access, so we can handle it.
	*/
	good_area:
	if (access_error(fsr, vma)) {
	fault = VM_FAULT_BADACCESS;
	goto out;
	}

	/*
	* If for any reason at all we couldn't handle the fault, make
	* sure we exit gracefully rather than endlessly redo the fault.
	*/
	fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0);
	if (unlikely(fault & VM_FAULT_ERROR))
	return fault;
	if (fault & VM_FAULT_MAJOR)
	tsk->maj_flt++;
	else
	tsk->min_flt++;
	return fault;

	check_stack:
	if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
	goto good_area;
	out:
	return fault;
	}

	static int __kprobes
	do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	struct task_struct *tsk;
	struct mm_struct *mm;
	int fault, sig, code;

	if (notify_page_fault(regs, fsr))
	return 0;

	tsk = current;
	mm = tsk->mm;

	/* Enable interrupts if they were enabled in the parent context. */
	if (interrupts_enabled(regs))
	local_irq_enable();

	/*
	* If we're in an interrupt or have no user
	* context, we must not take the fault..
	*/
	if (in_atomic() \|\| !mm)
	goto no_context;

	/*
	* As per x86, we may deadlock here. However, since the kernel only
	* validly references user space from well defined areas of the code,
	* we can bug out early if this is from code which shouldn't.
	*/
	if (!down_read_trylock(&mm->mmap_sem)) {
	if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
	goto no_context;
	down_read(&mm->mmap_sem);
	} else {
	/*
	* The above down_read_trylock() might have succeeded in
	* which case, we'll have missed the might_sleep() from
	* down_read()
	*/
	might_sleep();
	#ifdef CONFIG_DEBUG_VM
	if (!user_mode(regs) &&
	!search_exception_tables(regs->ARM_pc))
	goto no_context;
	#endif
	}

	fault = __do_page_fault(mm, addr, fsr, tsk);
	up_read(&mm->mmap_sem);

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, addr);
	if (fault & VM_FAULT_MAJOR)
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, regs, addr);
	else if (fault & VM_FAULT_MINOR)
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, regs, addr);

	/*
	* Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
	*/
	if (likely(!(fault & (VM_FAULT_ERROR \| VM_FAULT_BADMAP \| VM_FAULT_BADACCESS))))
	return 0;

	if (fault & VM_FAULT_OOM) {
	/*
	* We ran out of memory, call the OOM killer, and return to
	* userspace (which will retry the fault, or kill us if we
	* got oom-killed)
	*/
	pagefault_out_of_memory();
	return 0;
	}

	/*
	* If we are in kernel mode at this point, we
	* have no context to handle this fault with.
	*/
	if (!user_mode(regs))
	goto no_context;

	if (fault & VM_FAULT_SIGBUS) {
	/*
	* We had some memory, but were unable to
	* successfully fix up this page fault.
	*/
	sig = SIGBUS;
	code = BUS_ADRERR;
	} else {
	/*
	* Something tried to access memory that
	* isn't in our memory map..
	*/
	sig = SIGSEGV;
	code = fault == VM_FAULT_BADACCESS ?
	SEGV_ACCERR : SEGV_MAPERR;
	}

	__do_user_fault(tsk, addr, fsr, sig, code, regs);
	return 0;

	no_context:
	__do_kernel_fault(mm, addr, fsr, regs);
	return 0;
	}
	#else /* CONFIG_MMU */
	static int
	do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	return 0;
	}
	#endif /* CONFIG_MMU */

	/*
	* First Level Translation Fault Handler
	*
	* We enter here because the first level page table doesn't contain
	* a valid entry for the address.
	*
	* If the address is in kernel space (>= TASK_SIZE), then we are
	* probably faulting in the vmalloc() area.
	*
	* If the init_task's first level page tables contains the relevant
	* entry, we copy the it to this task. If not, we send the process
	* a signal, fixup the exception, or oops the kernel.
	*
	* NOTE! We MUST NOT take any locks for this case. We may be in an
	* interrupt or a critical region, and should only copy the information
	* from the master page table, nothing more.
	*/
	#ifdef CONFIG_MMU
	static int __kprobes
	do_translation_fault(unsigned long addr, unsigned int fsr,
	struct pt_regs *regs)
	{
	unsigned int index;
	pgd_t pgd, pgd_k;
	pud_t pud, pud_k;
	pmd_t pmd, pmd_k;

	if (addr < TASK_SIZE)
	return do_page_fault(addr, fsr, regs);

	if (user_mode(regs))
	goto bad_area;

	index = pgd_index(addr);

	/*
	* FIXME: CP15 C1 is write only on ARMv3 architectures.
	*/
	pgd = cpu_get_pgd() + index;
	pgd_k = init_mm.pgd + index;

	if (pgd_none(*pgd_k))
	goto bad_area;
	if (!pgd_present(*pgd))
	set_pgd(pgd, *pgd_k);

	pud = pud_offset(pgd, addr);
	pud_k = pud_offset(pgd_k, addr);

	if (pud_none(*pud_k))
	goto bad_area;
	if (!pud_present(*pud))
	set_pud(pud, *pud_k);

	pmd = pmd_offset(pud, addr);
	pmd_k = pmd_offset(pud_k, addr);

	/*
	* On ARM one Linux PGD entry contains two hardware entries (see page
	* tables layout in pgtable.h). We normally guarantee that we always
	* fill both L1 entries. But create_mapping() doesn't follow the rule.
	* It can create inidividual L1 entries, so here we have to call
	* pmd_none() check for the entry really corresponded to address, not
	* for the first of pair.
	*/
	index = (addr >> SECTION_SHIFT) & 1;
	if (pmd_none(pmd_k[index]))
	goto bad_area;

	copy_pmd(pmd, pmd_k);
	return 0;

	bad_area:
	do_bad_area(addr, fsr, regs);
	return 0;
	}
	#else /* CONFIG_MMU */
	static int
	do_translation_fault(unsigned long addr, unsigned int fsr,
	struct pt_regs *regs)
	{
	return 0;
	}
	#endif /* CONFIG_MMU */

	/*
	* Some section permission faults need to be handled gracefully.
	* They can happen due to a __{get,put}_user during an oops.
	*/
	static int
	do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	do_bad_area(addr, fsr, regs);
	return 0;
	}

	/*
	* This abort handler always returns "fault".
	*/
	static int
	do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	return 1;
	}

	static struct fsr_info {
	int (fn)(unsigned long addr, unsigned int fsr, struct pt_regs regs);
	int sig;
	int code;
	const char *name;
	} fsr_info[] = {
	/*
	* The following are the standard ARMv3 and ARMv4 aborts. ARMv5
	* defines these to be "precise" aborts.
	*/
	{ do_bad, SIGSEGV, 0, "vector exception" },
	{ do_bad, SIGBUS, BUS_ADRALN, "alignment exception" },
	{ do_bad, SIGKILL, 0, "terminal exception" },
	{ do_bad, SIGBUS, BUS_ADRALN, "alignment exception" },
	{ do_bad, SIGBUS, 0, "external abort on linefetch" },
	{ do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" },
	{ do_bad, SIGBUS, 0, "external abort on linefetch" },
	{ do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
	{ do_bad, SIGBUS, 0, "external abort on non-linefetch" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" },
	{ do_bad, SIGBUS, 0, "external abort on non-linefetch" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" },
	{ do_bad, SIGBUS, 0, "external abort on translation" },
	{ do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" },
	{ do_bad, SIGBUS, 0, "external abort on translation" },
	{ do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
	/*
	* The following are "imprecise" aborts, which are signalled by bit
	* 10 of the FSR, and may not be recoverable. These are only
	* supported if the CPU abort handler supports bit 10.
	*/
	{ do_bad, SIGBUS, 0, "unknown 16" },
	{ do_bad, SIGBUS, 0, "unknown 17" },
	{ do_bad, SIGBUS, 0, "unknown 18" },
	{ do_bad, SIGBUS, 0, "unknown 19" },
	{ do_bad, SIGBUS, 0, "lock abort" }, /* xscale */
	{ do_bad, SIGBUS, 0, "unknown 21" },
	{ do_bad, SIGBUS, BUS_OBJERR, "imprecise external abort" }, /* xscale */
	{ do_bad, SIGBUS, 0, "unknown 23" },
	{ do_bad, SIGBUS, 0, "dcache parity error" }, /* xscale */
	{ do_bad, SIGBUS, 0, "unknown 25" },
	{ do_bad, SIGBUS, 0, "unknown 26" },
	{ do_bad, SIGBUS, 0, "unknown 27" },
	{ do_bad, SIGBUS, 0, "unknown 28" },
	{ do_bad, SIGBUS, 0, "unknown 29" },
	{ do_bad, SIGBUS, 0, "unknown 30" },
	{ do_bad, SIGBUS, 0, "unknown 31" }
	};

	void __init
	hook_fault_code(int nr, int (fn)(unsigned long, unsigned int, struct pt_regs ),
	int sig, int code, const char *name)
	{
	if (nr < 0 \|\| nr >= ARRAY_SIZE(fsr_info))
	BUG();

	fsr_info[nr].fn = fn;
	fsr_info[nr].sig = sig;
	fsr_info[nr].code = code;
	fsr_info[nr].name = name;
	}

	/*
	* Dispatch a data abort to the relevant handler.
	*/
	asmlinkage void __exception
	do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
	struct siginfo info;

	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
	return;

	printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
	inf->name, fsr, addr);

	info.si_signo = inf->sig;
	info.si_errno = 0;
	info.si_code = inf->code;
	info.si_addr = (void __user *)addr;
	arm_notify_die("", regs, &info, fsr, 0);
	}


	static struct fsr_info ifsr_info[] = {
	{ do_bad, SIGBUS, 0, "unknown 0" },
	{ do_bad, SIGBUS, 0, "unknown 1" },
	{ do_bad, SIGBUS, 0, "debug event" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "section access flag fault" },
	{ do_bad, SIGBUS, 0, "unknown 4" },
	{ do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "page access flag fault" },
	{ do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
	{ do_bad, SIGBUS, 0, "external abort on non-linefetch" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" },
	{ do_bad, SIGBUS, 0, "unknown 10" },
	{ do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" },
	{ do_bad, SIGBUS, 0, "external abort on translation" },
	{ do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" },
	{ do_bad, SIGBUS, 0, "external abort on translation" },
	{ do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
	{ do_bad, SIGBUS, 0, "unknown 16" },
	{ do_bad, SIGBUS, 0, "unknown 17" },
	{ do_bad, SIGBUS, 0, "unknown 18" },
	{ do_bad, SIGBUS, 0, "unknown 19" },
	{ do_bad, SIGBUS, 0, "unknown 20" },
	{ do_bad, SIGBUS, 0, "unknown 21" },
	{ do_bad, SIGBUS, 0, "unknown 22" },
	{ do_bad, SIGBUS, 0, "unknown 23" },
	{ do_bad, SIGBUS, 0, "unknown 24" },
	{ do_bad, SIGBUS, 0, "unknown 25" },
	{ do_bad, SIGBUS, 0, "unknown 26" },
	{ do_bad, SIGBUS, 0, "unknown 27" },
	{ do_bad, SIGBUS, 0, "unknown 28" },
	{ do_bad, SIGBUS, 0, "unknown 29" },
	{ do_bad, SIGBUS, 0, "unknown 30" },
	{ do_bad, SIGBUS, 0, "unknown 31" },
	};

	void __init
	hook_ifault_code(int nr, int (fn)(unsigned long, unsigned int, struct pt_regs ),
	int sig, int code, const char *name)
	{
	if (nr < 0 \|\| nr >= ARRAY_SIZE(ifsr_info))
	BUG();

	ifsr_info[nr].fn = fn;
	ifsr_info[nr].sig = sig;
	ifsr_info[nr].code = code;
	ifsr_info[nr].name = name;
	}

	asmlinkage void __exception
	do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
	{
	const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
	struct siginfo info;

	if (!inf->fn(addr, ifsr \| FSR_LNX_PF, regs))
	return;

	printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
	inf->name, ifsr, addr);

	info.si_signo = inf->sig;
	info.si_errno = 0;
	info.si_code = inf->code;
	info.si_addr = (void __user *)addr;
	arm_notify_die("", regs, &info, ifsr, 0);
	}

	static int __init exceptions_init(void)
	{
	if (cpu_architecture() >= CPU_ARCH_ARMv6) {
	hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
	"I-cache maintenance fault");
	}

	if (cpu_architecture() >= CPU_ARCH_ARMv7) {
	/*
	* TODO: Access flag faults introduced in ARMv6K.
	* Runtime check for 'K' extension is needed
	*/
	hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
	"section access flag fault");
	hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
	"section access flag fault");
	}

	return 0;
	}

	arch_initcall(exceptions_init);