arch/nios2/mm/fault.c - linux - Git at Google

 /*
  * Copyright (C) 2009 Wind River Systems Inc
  *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
  *
  * based on arch/mips/mm/fault.c which is:
  *
  * Copyright (C) 1995-2000 Ralf Baechle
  *
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  */

 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/ptrace.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/extable.h>
 #include <linux/uaccess.h>

 #include <asm/mmu_context.h>
 #include <asm/traps.h>

 #define EXC_SUPERV_INSN_ACCESS	9  /* Supervisor only instruction address */
 #define EXC_SUPERV_DATA_ACCESS	11 /* Supervisor only data address */
 #define EXC_X_PROTECTION_FAULT	13 /* TLB permission violation (x) */
 #define EXC_R_PROTECTION_FAULT	14 /* TLB permission violation (r) */
 #define EXC_W_PROTECTION_FAULT	15 /* TLB permission violation (w) */

 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
  */
 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 				unsigned long address)
 {
 	struct vm_area_struct *vma = NULL;
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
 	int code = SEGV_MAPERR;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

 	cause >>= 2;

 	/* Restart the instruction */
 	regs->ea -= 4;

 	/*
 	 * We fault-in kernel-space virtual memory on-demand. The
 	 * 'reference' page table is init_mm.pgd.
 	 *
 	 * 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.
 	 */
 	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
 		if (user_mode(regs))
 			goto bad_area_nosemaphore;
 		else
 			goto vmalloc_fault;
 	}

 	if (unlikely(address >= TASK_SIZE))
 		goto bad_area_nosemaphore;

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

 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;

 	if (!down_read_trylock(&mm->mmap_sem)) {
 		if (!user_mode(regs) && !search_exception_tables(regs->ea))
 			goto bad_area_nosemaphore;
 retry:
 		down_read(&mm->mmap_sem);
 	}

 	vma = find_vma(mm, address);
 	if (!vma)
 		goto bad_area;
 	if (vma->vm_start <= address)
 		goto good_area;
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
 	if (expand_stack(vma, address))
 		goto bad_area;
 /*
  * Ok, we have a good vm_area for this memory access, so
  * we can handle it..
  */
 good_area:
 	code = SEGV_ACCERR;

 	switch (cause) {
 	case EXC_SUPERV_INSN_ACCESS:
 		goto bad_area;
 	case EXC_SUPERV_DATA_ACCESS:
 		goto bad_area;
 	case EXC_X_PROTECTION_FAULT:
 		if (!(vma->vm_flags & VM_EXEC))
 			goto bad_area;
 		break;
 	case EXC_R_PROTECTION_FAULT:
 		if (!(vma->vm_flags & VM_READ))
 			goto bad_area;
 		break;
 	case EXC_W_PROTECTION_FAULT:
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 		flags = FAULT_FLAG_WRITE;
 		break;
 	}

 	/*
 	 * 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(vma, address, flags);

 	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 		return;

 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)
 			goto out_of_memory;
 		else if (fault & VM_FAULT_SIGSEGV)
 			goto bad_area;
 		else if (fault & VM_FAULT_SIGBUS)
 			goto do_sigbus;
 		BUG();
 	}

 	/*
 	 * Major/minor page fault accounting is only done on the
 	 * initial attempt. If we go through a retry, it is extremely
 	 * likely that the page will be found in page cache at that point.
 	 */
 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
 		if (fault & VM_FAULT_MAJOR)
 			current->maj_flt++;
 		else
 			current->min_flt++;
 		if (fault & VM_FAULT_RETRY) {
 			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 			 * of starvation. */
 			flags &= ~FAULT_FLAG_ALLOW_RETRY;
 			flags |= FAULT_FLAG_TRIED;

 			/*
 			 * No need to up_read(&mm->mmap_sem) as we would
 			 * have already released it in __lock_page_or_retry
 			 * in mm/filemap.c.
 			 */

 			goto retry;
 		}
 	}

 	up_read(&mm->mmap_sem);
 	return;

 /*
  * Something tried to access memory that isn't in our memory map..
  * Fix it, but check if it's kernel or user first..
  */
 bad_area:
 	up_read(&mm->mmap_sem);

 bad_area_nosemaphore:
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
 			pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
 				"cause %ld\n", current->comm, SIGSEGV, address, cause);
 			show_regs(regs);
 		}
 		_exception(SIGSEGV, regs, code, address);
 		return;
 	}

 no_context:
 	/* Are we prepared to handle this kernel fault? */
 	if (fixup_exception(regs))
 		return;

 	/*
 	 * Oops. The kernel tried to access some bad page. We'll have to
 	 * terminate things with extreme prejudice.
 	 */
 	bust_spinlocks(1);

 	pr_alert("Unable to handle kernel %s at virtual address %08lx",
 		address < PAGE_SIZE ? "NULL pointer dereference" :
 		"paging request", address);
 	pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
 		cause);
 	panic("Oops");
 	return;

 /*
  * We ran out of memory, or some other thing happened to us that made
  * us unable to handle the page fault gracefully.
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
 	if (!user_mode(regs))
 		goto no_context;
 	pagefault_out_of_memory();
 	return;

 do_sigbus:
 	up_read(&mm->mmap_sem);

 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs))
 		goto no_context;

 	_exception(SIGBUS, regs, BUS_ADRERR, address);
 	return;

 vmalloc_fault:
 	{
 		/*
 		 * Synchronize this task's top level page-table
 		 * with the 'reference' page table.
 		 *
 		 * Do _not_ use "tsk" here. We might be inside
 		 * an interrupt in the middle of a task switch..
 		 */
 		int offset = pgd_index(address);
 		pgd_t *pgd, *pgd_k;
 		pud_t *pud, *pud_k;
 		pmd_t *pmd, *pmd_k;
 		pte_t *pte_k;

 		pgd = pgd_current + offset;
 		pgd_k = init_mm.pgd + offset;

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

 		pud = pud_offset(pgd, address);
 		pud_k = pud_offset(pgd_k, address);
 		if (!pud_present(*pud_k))
 			goto no_context;
 		pmd = pmd_offset(pud, address);
 		pmd_k = pmd_offset(pud_k, address);
 		if (!pmd_present(*pmd_k))
 			goto no_context;
 		set_pmd(pmd, *pmd_k);

 		pte_k = pte_offset_kernel(pmd_k, address);
 		if (!pte_present(*pte_k))
 			goto no_context;

 		flush_tlb_kernel_page(address);
 		return;
 	}
 }
	/*
	* Copyright (C) 2009 Wind River Systems Inc
	* Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
	*
	* based on arch/mips/mm/fault.c which is:
	*
	* Copyright (C) 1995-2000 Ralf Baechle
	*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*/

	#include <linux/signal.h>
	#include <linux/sched.h>
	#include <linux/sched/debug.h>
	#include <linux/interrupt.h>
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/ptrace.h>
	#include <linux/mman.h>
	#include <linux/mm.h>
	#include <linux/extable.h>
	#include <linux/uaccess.h>

	#include <asm/mmu_context.h>
	#include <asm/traps.h>

	#define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */
	#define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */
	#define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */
	#define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */
	#define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */

	/*
	* This routine handles page faults. It determines the address,
	* and the problem, and then passes it off to one of the appropriate
	* routines.
	*/
	asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
	unsigned long address)
	{
	struct vm_area_struct *vma = NULL;
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;
	int code = SEGV_MAPERR;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_ALLOW_RETRY \| FAULT_FLAG_KILLABLE;

	cause >>= 2;

	/* Restart the instruction */
	regs->ea -= 4;

	/*
	* We fault-in kernel-space virtual memory on-demand. The
	* 'reference' page table is init_mm.pgd.
	*
	* 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.
	*/
	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
	if (user_mode(regs))
	goto bad_area_nosemaphore;
	else
	goto vmalloc_fault;
	}

	if (unlikely(address >= TASK_SIZE))
	goto bad_area_nosemaphore;

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

	if (user_mode(regs))
	flags \|= FAULT_FLAG_USER;

	if (!down_read_trylock(&mm->mmap_sem)) {
	if (!user_mode(regs) && !search_exception_tables(regs->ea))
	goto bad_area_nosemaphore;
	retry:
	down_read(&mm->mmap_sem);
	}

	vma = find_vma(mm, address);
	if (!vma)
	goto bad_area;
	if (vma->vm_start <= address)
	goto good_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
	goto bad_area;
	if (expand_stack(vma, address))
	goto bad_area;
	/*
	* Ok, we have a good vm_area for this memory access, so
	* we can handle it..
	*/
	good_area:
	code = SEGV_ACCERR;

	switch (cause) {
	case EXC_SUPERV_INSN_ACCESS:
	goto bad_area;
	case EXC_SUPERV_DATA_ACCESS:
	goto bad_area;
	case EXC_X_PROTECTION_FAULT:
	if (!(vma->vm_flags & VM_EXEC))
	goto bad_area;
	break;
	case EXC_R_PROTECTION_FAULT:
	if (!(vma->vm_flags & VM_READ))
	goto bad_area;
	break;
	case EXC_W_PROTECTION_FAULT:
	if (!(vma->vm_flags & VM_WRITE))
	goto bad_area;
	flags = FAULT_FLAG_WRITE;
	break;
	}

	/*
	* 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(vma, address, flags);

	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
	return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
	if (fault & VM_FAULT_OOM)
	goto out_of_memory;
	else if (fault & VM_FAULT_SIGSEGV)
	goto bad_area;
	else if (fault & VM_FAULT_SIGBUS)
	goto do_sigbus;
	BUG();
	}

	/*
	* Major/minor page fault accounting is only done on the
	* initial attempt. If we go through a retry, it is extremely
	* likely that the page will be found in page cache at that point.
	*/
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
	if (fault & VM_FAULT_MAJOR)
	current->maj_flt++;
	else
	current->min_flt++;
	if (fault & VM_FAULT_RETRY) {
	/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
	* of starvation. */
	flags &= ~FAULT_FLAG_ALLOW_RETRY;
	flags \|= FAULT_FLAG_TRIED;

	/*
	* No need to up_read(&mm->mmap_sem) as we would
	* have already released it in __lock_page_or_retry
	* in mm/filemap.c.
	*/

	goto retry;
	}
	}

	up_read(&mm->mmap_sem);
	return;

	/*
	* Something tried to access memory that isn't in our memory map..
	* Fix it, but check if it's kernel or user first..
	*/
	bad_area:
	up_read(&mm->mmap_sem);

	bad_area_nosemaphore:
	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs)) {
	if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
	pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
	"cause %ld\n", current->comm, SIGSEGV, address, cause);
	show_regs(regs);
	}
	_exception(SIGSEGV, regs, code, address);
	return;
	}

	no_context:
	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs))
	return;

	/*
	* Oops. The kernel tried to access some bad page. We'll have to
	* terminate things with extreme prejudice.
	*/
	bust_spinlocks(1);

	pr_alert("Unable to handle kernel %s at virtual address %08lx",
	address < PAGE_SIZE ? "NULL pointer dereference" :
	"paging request", address);
	pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
	cause);
	panic("Oops");
	return;

	/*
	* We ran out of memory, or some other thing happened to us that made
	* us unable to handle the page fault gracefully.
	*/
	out_of_memory:
	up_read(&mm->mmap_sem);
	if (!user_mode(regs))
	goto no_context;
	pagefault_out_of_memory();
	return;

	do_sigbus:
	up_read(&mm->mmap_sem);

	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs))
	goto no_context;

	_exception(SIGBUS, regs, BUS_ADRERR, address);
	return;

	vmalloc_fault:
	{
	/*
	* Synchronize this task's top level page-table
	* with the 'reference' page table.
	*
	* Do _not_ use "tsk" here. We might be inside
	* an interrupt in the middle of a task switch..
	*/
	int offset = pgd_index(address);
	pgd_t pgd, pgd_k;
	pud_t pud, pud_k;
	pmd_t pmd, pmd_k;
	pte_t *pte_k;

	pgd = pgd_current + offset;
	pgd_k = init_mm.pgd + offset;

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

	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
	goto no_context;
	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
	goto no_context;
	set_pmd(pmd, *pmd_k);

	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
	goto no_context;

	flush_tlb_kernel_page(address);
	return;
	}
	}