arch/cris/mm/fault.c - maze/linux - Git at Google

 /*
  *  arch/cris/mm/fault.c
  *
  *  Copyright (C) 2000-2010  Axis Communications AB
  */

 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <asm/uaccess.h>
 #include <arch/system.h>

 extern int find_fixup_code(struct pt_regs *);
 extern void die_if_kernel(const char *, struct pt_regs *, long);
 extern void show_registers(struct pt_regs *regs);

 /* debug of low-level TLB reload */
 #undef DEBUG

 #ifdef DEBUG
 #define D(x) x
 #else
 #define D(x)
 #endif

 /* debug of higher-level faults */
 #define DPG(x)

 /* current active page directory */

 DEFINE_PER_CPU(pgd_t *, current_pgd);
 unsigned long cris_signal_return_page;

 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
  *
  * Notice that the address we're given is aligned to the page the fault
  * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
  * address.
  *
  * error_code:
  *      bit 0 == 0 means no page found, 1 means protection fault
  *      bit 1 == 0 means read, 1 means write
  *
  * If this routine detects a bad access, it returns 1, otherwise it
  * returns 0.
  */

 asmlinkage void
 do_page_fault(unsigned long address, struct pt_regs *regs,
 	      int protection, int writeaccess)
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
 	struct vm_area_struct * vma;
 	siginfo_t info;
 	int fault;

 	D(printk(KERN_DEBUG
 		 "Page fault for %lX on %X at %lX, prot %d write %d\n",
 		 address, smp_processor_id(), instruction_pointer(regs),
 		 protection, writeaccess));

 	tsk = current;

 	/*
 	 * 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.
 	 *
 	 * NOTE2: This is done so that, when updating the vmalloc
 	 * mappings we don't have to walk all processes pgdirs and
 	 * add the high mappings all at once. Instead we do it as they
 	 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
 	 * bit set so sometimes the TLB can use a lingering entry.
 	 *
 	 * This verifies that the fault happens in kernel space
 	 * and that the fault was not a protection error (error_code & 1).
 	 */

 	if (address >= VMALLOC_START &&
 	    !protection &&
 	    !user_mode(regs))
 		goto vmalloc_fault;

 	/* When stack execution is not allowed we store the signal
 	 * trampolines in the reserved cris_signal_return_page.
 	 * Handle this in the exact same way as vmalloc (we know
 	 * that the mapping is there and is valid so no need to
 	 * call handle_mm_fault).
 	 */
 	if (cris_signal_return_page &&
 	    address == cris_signal_return_page &&
 	    !protection && user_mode(regs))
 		goto vmalloc_fault;

 	/* we can and should enable interrupts at this point */
 	local_irq_enable();

 	mm = tsk->mm;
 	info.si_code = SEGV_MAPERR;

 	/*
 	 * If we're in an interrupt or "atomic" operation or have no
 	 * user context, we must not take the fault.
 	 */

 	if (in_atomic() || !mm)
 		goto no_context;

 	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 (user_mode(regs)) {
 		/*
 		 * accessing the stack below usp is always a bug.
 		 * we get page-aligned addresses so we can only check
 		 * if we're within a page from usp, but that might be
 		 * enough to catch brutal errors at least.
 		 */
 		if (address + PAGE_SIZE < rdusp())
 			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:
 	info.si_code = SEGV_ACCERR;

 	/* first do some preliminary protection checks */

 	if (writeaccess == 2){
 		if (!(vma->vm_flags & VM_EXEC))
 			goto bad_area;
 	} else if (writeaccess == 1) {
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 	} else {
 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 			goto bad_area;
 	}

 	/*
 	 * 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, address, (writeaccess & 1) ? FAULT_FLAG_WRITE : 0);
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)
 			goto out_of_memory;
 		else if (fault & VM_FAULT_SIGBUS)
 			goto do_sigbus;
 		BUG();
 	}
 	if (fault & VM_FAULT_MAJOR)
 		tsk->maj_flt++;
 	else
 		tsk->min_flt++;

 	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:
 	DPG(show_registers(regs));

 	/* User mode accesses just cause a SIGSEGV */

 	if (user_mode(regs)) {
 		printk(KERN_NOTICE "%s (pid %d) segfaults for page "
 			"address %08lx at pc %08lx\n",
 			tsk->comm, tsk->pid,
 			address, instruction_pointer(regs));

 		/* With DPG on, we've already dumped registers above.  */
 		DPG(if (0))
 			show_registers(regs);

 #ifdef CONFIG_NO_SEGFAULT_TERMINATION
 		DECLARE_WAIT_QUEUE_HEAD(wq);
 		wait_event_interruptible(wq, 0 == 1);
 #else
 		info.si_signo = SIGSEGV;
 		info.si_errno = 0;
 		/* info.si_code has been set above */
 		info.si_addr = (void *)address;
 		force_sig_info(SIGSEGV, &info, tsk);
 #endif
 		return;
 	}

  no_context:

 	/* Are we prepared to handle this kernel fault?
 	 *
 	 * (The kernel has valid exception-points in the source
 	 *  when it accesses user-memory. When it fails in one
 	 *  of those points, we find it in a table and do a jump
 	 *  to some fixup code that loads an appropriate error
 	 *  code)
 	 */

 	if (find_fixup_code(regs))
 		return;

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

 	if (!oops_in_progress) {
 		oops_in_progress = 1;
 		if ((unsigned long) (address) < PAGE_SIZE)
 			printk(KERN_ALERT "Unable to handle kernel NULL "
 				"pointer dereference");
 		else
 			printk(KERN_ALERT "Unable to handle kernel access"
 				" at virtual address %08lx\n", address);

 		die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
 		oops_in_progress = 0;
 	}

 	do_exit(SIGKILL);

 	/*
 	 * 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);

 	/*
 	 * Send a sigbus, regardless of whether we were in kernel
 	 * or user mode.
 	 */
 	info.si_signo = SIGBUS;
 	info.si_errno = 0;
 	info.si_code = BUS_ADRERR;
 	info.si_addr = (void *)address;
 	force_sig_info(SIGBUS, &info, tsk);

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

 vmalloc_fault:
 	{
 		/*
 		 * Synchronize this task's top level page-table
 		 * with the 'reference' page table.
 		 *
 		 * Use current_pgd instead of tsk->active_mm->pgd
 		 * since the latter might be unavailable if this
 		 * code is executed in a misfortunately run irq
 		 * (like inside schedule() between switch_mm and
 		 *  switch_to...).
 		 */

 		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_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
 		pgd_k = init_mm.pgd + offset;

 		/* Since we're two-level, we don't need to do both
 		 * set_pgd and set_pmd (they do the same thing). If
 		 * we go three-level at some point, do the right thing
 		 * with pgd_present and set_pgd here.
 		 *
 		 * Also, since the vmalloc area is global, we don't
 		 * need to copy individual PTE's, it is enough to
 		 * copy the pgd pointer into the pte page of the
 		 * root task. If that is there, we'll find our pte if
 		 * it exists.
 		 */

 		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 bad_area_nosemaphore;

 		set_pmd(pmd, *pmd_k);

 		/* Make sure the actual PTE exists as well to
 		 * catch kernel vmalloc-area accesses to non-mapped
 		 * addresses. If we don't do this, this will just
 		 * silently loop forever.
 		 */

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

 		return;
 	}
 }

 /* Find fixup code. */
 int
 find_fixup_code(struct pt_regs *regs)
 {
 	const struct exception_table_entry *fixup;
 	/* in case of delay slot fault (v32) */
 	unsigned long ip = (instruction_pointer(regs) & ~0x1);

 	fixup = search_exception_tables(ip);
 	if (fixup != 0) {
 		/* Adjust the instruction pointer in the stackframe. */
 		instruction_pointer(regs) = fixup->fixup;
 		arch_fixup(regs);
 		return 1;
 	}

 	return 0;
 }
	/*
	* arch/cris/mm/fault.c
	*
	* Copyright (C) 2000-2010 Axis Communications AB
	*/

	#include <linux/mm.h>
	#include <linux/interrupt.h>
	#include <linux/module.h>
	#include <linux/wait.h>
	#include <asm/uaccess.h>
	#include <arch/system.h>

	extern int find_fixup_code(struct pt_regs *);
	extern void die_if_kernel(const char , struct pt_regs , long);
	extern void show_registers(struct pt_regs *regs);

	/* debug of low-level TLB reload */
	#undef DEBUG

	#ifdef DEBUG
	#define D(x) x
	#else
	#define D(x)
	#endif

	/* debug of higher-level faults */
	#define DPG(x)

	/* current active page directory */

	DEFINE_PER_CPU(pgd_t *, current_pgd);
	unsigned long cris_signal_return_page;

	/*
	* This routine handles page faults. It determines the address,
	* and the problem, and then passes it off to one of the appropriate
	* routines.
	*
	* Notice that the address we're given is aligned to the page the fault
	* occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
	* address.
	*
	* error_code:
	* bit 0 == 0 means no page found, 1 means protection fault
	* bit 1 == 0 means read, 1 means write
	*
	* If this routine detects a bad access, it returns 1, otherwise it
	* returns 0.
	*/

	asmlinkage void
	do_page_fault(unsigned long address, struct pt_regs *regs,
	int protection, int writeaccess)
	{
	struct task_struct *tsk;
	struct mm_struct *mm;
	struct vm_area_struct * vma;
	siginfo_t info;
	int fault;

	D(printk(KERN_DEBUG
	"Page fault for %lX on %X at %lX, prot %d write %d\n",
	address, smp_processor_id(), instruction_pointer(regs),
	protection, writeaccess));

	tsk = current;

	/*
	* 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.
	*
	* NOTE2: This is done so that, when updating the vmalloc
	* mappings we don't have to walk all processes pgdirs and
	* add the high mappings all at once. Instead we do it as they
	* are used. However vmalloc'ed page entries have the PAGE_GLOBAL
	* bit set so sometimes the TLB can use a lingering entry.
	*
	* This verifies that the fault happens in kernel space
	* and that the fault was not a protection error (error_code & 1).
	*/

	if (address >= VMALLOC_START &&
	!protection &&
	!user_mode(regs))
	goto vmalloc_fault;

	/* When stack execution is not allowed we store the signal
	* trampolines in the reserved cris_signal_return_page.
	* Handle this in the exact same way as vmalloc (we know
	* that the mapping is there and is valid so no need to
	* call handle_mm_fault).
	*/
	if (cris_signal_return_page &&
	address == cris_signal_return_page &&
	!protection && user_mode(regs))
	goto vmalloc_fault;

	/* we can and should enable interrupts at this point */
	local_irq_enable();

	mm = tsk->mm;
	info.si_code = SEGV_MAPERR;

	/*
	* If we're in an interrupt or "atomic" operation or have no
	* user context, we must not take the fault.
	*/

	if (in_atomic() \|\| !mm)
	goto no_context;

	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 (user_mode(regs)) {
	/*
	* accessing the stack below usp is always a bug.
	* we get page-aligned addresses so we can only check
	* if we're within a page from usp, but that might be
	* enough to catch brutal errors at least.
	*/
	if (address + PAGE_SIZE < rdusp())
	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:
	info.si_code = SEGV_ACCERR;

	/* first do some preliminary protection checks */

	if (writeaccess == 2){
	if (!(vma->vm_flags & VM_EXEC))
	goto bad_area;
	} else if (writeaccess == 1) {
	if (!(vma->vm_flags & VM_WRITE))
	goto bad_area;
	} else {
	if (!(vma->vm_flags & (VM_READ \| VM_EXEC)))
	goto bad_area;
	}

	/*
	* 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, address, (writeaccess & 1) ? FAULT_FLAG_WRITE : 0);
	if (unlikely(fault & VM_FAULT_ERROR)) {
	if (fault & VM_FAULT_OOM)
	goto out_of_memory;
	else if (fault & VM_FAULT_SIGBUS)
	goto do_sigbus;
	BUG();
	}
	if (fault & VM_FAULT_MAJOR)
	tsk->maj_flt++;
	else
	tsk->min_flt++;

	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:
	DPG(show_registers(regs));

	/* User mode accesses just cause a SIGSEGV */

	if (user_mode(regs)) {
	printk(KERN_NOTICE "%s (pid %d) segfaults for page "
	"address %08lx at pc %08lx\n",
	tsk->comm, tsk->pid,
	address, instruction_pointer(regs));

	/* With DPG on, we've already dumped registers above. */
	DPG(if (0))
	show_registers(regs);

	#ifdef CONFIG_NO_SEGFAULT_TERMINATION
	DECLARE_WAIT_QUEUE_HEAD(wq);
	wait_event_interruptible(wq, 0 == 1);
	#else
	info.si_signo = SIGSEGV;
	info.si_errno = 0;
	/* info.si_code has been set above */
	info.si_addr = (void *)address;
	force_sig_info(SIGSEGV, &info, tsk);
	#endif
	return;
	}

	no_context:

	/* Are we prepared to handle this kernel fault?
	*
	* (The kernel has valid exception-points in the source
	* when it accesses user-memory. When it fails in one
	* of those points, we find it in a table and do a jump
	* to some fixup code that loads an appropriate error
	* code)
	*/

	if (find_fixup_code(regs))
	return;

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

	if (!oops_in_progress) {
	oops_in_progress = 1;
	if ((unsigned long) (address) < PAGE_SIZE)
	printk(KERN_ALERT "Unable to handle kernel NULL "
	"pointer dereference");
	else
	printk(KERN_ALERT "Unable to handle kernel access"
	" at virtual address %08lx\n", address);

	die_if_kernel("Oops", regs, (writeaccess << 1) \| protection);
	oops_in_progress = 0;
	}

	do_exit(SIGKILL);

	/*
	* 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);

	/*
	* Send a sigbus, regardless of whether we were in kernel
	* or user mode.
	*/
	info.si_signo = SIGBUS;
	info.si_errno = 0;
	info.si_code = BUS_ADRERR;
	info.si_addr = (void *)address;
	force_sig_info(SIGBUS, &info, tsk);

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

	vmalloc_fault:
	{
	/*
	* Synchronize this task's top level page-table
	* with the 'reference' page table.
	*
	* Use current_pgd instead of tsk->active_mm->pgd
	* since the latter might be unavailable if this
	* code is executed in a misfortunately run irq
	* (like inside schedule() between switch_mm and
	* switch_to...).
	*/

	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_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
	pgd_k = init_mm.pgd + offset;

	/* Since we're two-level, we don't need to do both
	* set_pgd and set_pmd (they do the same thing). If
	* we go three-level at some point, do the right thing
	* with pgd_present and set_pgd here.
	*
	* Also, since the vmalloc area is global, we don't
	* need to copy individual PTE's, it is enough to
	* copy the pgd pointer into the pte page of the
	* root task. If that is there, we'll find our pte if
	* it exists.
	*/

	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 bad_area_nosemaphore;

	set_pmd(pmd, *pmd_k);

	/* Make sure the actual PTE exists as well to
	* catch kernel vmalloc-area accesses to non-mapped
	* addresses. If we don't do this, this will just
	* silently loop forever.
	*/

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

	return;
	}
	}

	/* Find fixup code. */
	int
	find_fixup_code(struct pt_regs *regs)
	{
	const struct exception_table_entry *fixup;
	/* in case of delay slot fault (v32) */
	unsigned long ip = (instruction_pointer(regs) & ~0x1);

	fixup = search_exception_tables(ip);
	if (fixup != 0) {
	/* Adjust the instruction pointer in the stackframe. */
	instruction_pointer(regs) = fixup->fixup;
	arch_fixup(regs);
	return 1;
	}

	return 0;
	}