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

 // TODO VM_EXEC flag work-around, cache aliasing
 /*
  * arch/xtensa/mm/fault.c
  *
  * 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.
  *
  * Copyright (C) 2001 - 2010 Tensilica Inc.
  *
  * Chris Zankel <chris@zankel.net>
  * Joe Taylor	<joe@tensilica.com, joetylr@yahoo.com>
  */

 #include <linux/mm.h>
 #include <linux/extable.h>
 #include <linux/hardirq.h>
 #include <linux/perf_event.h>
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/hardirq.h>
 #include <asm/pgalloc.h>

 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
 void bad_page_fault(struct pt_regs*, unsigned long, int);

 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
  *
  * Note: does not handle Miss and MultiHit.
  */

 void do_page_fault(struct pt_regs *regs)
 {
 	struct vm_area_struct * vma;
 	struct mm_struct *mm = current->mm;
 	unsigned int exccause = regs->exccause;
 	unsigned int address = regs->excvaddr;
 	int code;

 	int is_write, is_exec;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

 	code = SEGV_MAPERR;

 	/* We fault-in kernel-space virtual memory on-demand. The
 	 * 'reference' page table is init_mm.pgd.
 	 */
 	if (address >= TASK_SIZE && !user_mode(regs))
 		goto vmalloc_fault;

 	/* If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
 	if (faulthandler_disabled() || !mm) {
 		bad_page_fault(regs, address, SIGSEGV);
 		return;
 	}

 	is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
 	is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
 		    exccause == EXCCAUSE_ITLB_MISS ||
 		    exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;

 	pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
 		 current->comm, current->pid,
 		 address, exccause, regs->pc,
 		 is_write ? "w" : "", is_exec ? "x" : "");

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

 	if (is_write) {
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 		flags |= FAULT_FLAG_WRITE;
 	} else if (is_exec) {
 		if (!(vma->vm_flags & VM_EXEC))
 			goto bad_area;
 	} else	/* Allow read even from write-only pages. */
 		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 			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(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();
 	}
 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
 		if (fault & VM_FAULT_MAJOR)
 			current->maj_flt++;
 		else
 			current->min_flt++;
 		if (fault & VM_FAULT_RETRY) {
 			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);
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 	if (flags & VM_FAULT_MAJOR)
 		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
 	else
 		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);

 	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);
 	if (user_mode(regs)) {
 		current->thread.bad_vaddr = address;
 		current->thread.error_code = is_write;
 		force_sig_fault(SIGSEGV, code, (void *) address, current);
 		return;
 	}
 	bad_page_fault(regs, address, SIGSEGV);
 	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))
 		bad_page_fault(regs, address, SIGKILL);
 	else
 		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.
 	 */
 	current->thread.bad_vaddr = address;
 	force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address, current);

 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs))
 		bad_page_fault(regs, address, SIGBUS);
 	return;

 vmalloc_fault:
 	{
 		/* Synchronize this task's top level page-table
 		 * with the 'reference' page table.
 		 */
 		struct mm_struct *act_mm = current->active_mm;
 		int index = pgd_index(address);
 		pgd_t *pgd, *pgd_k;
 		pmd_t *pmd, *pmd_k;
 		pte_t *pte_k;

 		if (act_mm == NULL)
 			goto bad_page_fault;

 		pgd = act_mm->pgd + index;
 		pgd_k = init_mm.pgd + index;

 		if (!pgd_present(*pgd_k))
 			goto bad_page_fault;

 		pgd_val(*pgd) = pgd_val(*pgd_k);

 		pmd = pmd_offset(pgd, address);
 		pmd_k = pmd_offset(pgd_k, address);
 		if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 			goto bad_page_fault;

 		pmd_val(*pmd) = pmd_val(*pmd_k);
 		pte_k = pte_offset_kernel(pmd_k, address);

 		if (!pte_present(*pte_k))
 			goto bad_page_fault;
 		return;
 	}
 bad_page_fault:
 	bad_page_fault(regs, address, SIGKILL);
 	return;
 }


 void
 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 {
 	extern void die(const char*, struct pt_regs*, long);
 	const struct exception_table_entry *entry;

 	/* Are we prepared to handle this kernel fault?  */
 	if ((entry = search_exception_tables(regs->pc)) != NULL) {
 		pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
 			 current->comm, regs->pc, entry->fixup);
 		current->thread.bad_uaddr = address;
 		regs->pc = entry->fixup;
 		return;
 	}

 	/* Oops. The kernel tried to access some bad page. We'll have to
 	 * terminate things with extreme prejudice.
 	 */
 	pr_alert("Unable to handle kernel paging request at virtual "
 		 "address %08lx\n pc = %08lx, ra = %08lx\n",
 		 address, regs->pc, regs->areg[0]);
 	die("Oops", regs, sig);
 	do_exit(sig);
 }
	// TODO VM_EXEC flag work-around, cache aliasing
	/*
	* arch/xtensa/mm/fault.c
	*
	* 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.
	*
	* Copyright (C) 2001 - 2010 Tensilica Inc.
	*
	* Chris Zankel <chris@zankel.net>
	* Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
	*/

	#include <linux/mm.h>
	#include <linux/extable.h>
	#include <linux/hardirq.h>
	#include <linux/perf_event.h>
	#include <linux/uaccess.h>
	#include <asm/mmu_context.h>
	#include <asm/cacheflush.h>
	#include <asm/hardirq.h>
	#include <asm/pgalloc.h>

	DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
	void bad_page_fault(struct pt_regs*, unsigned long, int);

	/*
	* This routine handles page faults. It determines the address,
	* and the problem, and then passes it off to one of the appropriate
	* routines.
	*
	* Note: does not handle Miss and MultiHit.
	*/

	void do_page_fault(struct pt_regs *regs)
	{
	struct vm_area_struct * vma;
	struct mm_struct *mm = current->mm;
	unsigned int exccause = regs->exccause;
	unsigned int address = regs->excvaddr;
	int code;

	int is_write, is_exec;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_ALLOW_RETRY \| FAULT_FLAG_KILLABLE;

	code = SEGV_MAPERR;

	/* We fault-in kernel-space virtual memory on-demand. The
	* 'reference' page table is init_mm.pgd.
	*/
	if (address >= TASK_SIZE && !user_mode(regs))
	goto vmalloc_fault;

	/* If we're in an interrupt or have no user
	* context, we must not take the fault..
	*/
	if (faulthandler_disabled() \|\| !mm) {
	bad_page_fault(regs, address, SIGSEGV);
	return;
	}

	is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
	is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE \|\|
	exccause == EXCCAUSE_ITLB_MISS \|\|
	exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;

	pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
	current->comm, current->pid,
	address, exccause, regs->pc,
	is_write ? "w" : "", is_exec ? "x" : "");

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

	if (is_write) {
	if (!(vma->vm_flags & VM_WRITE))
	goto bad_area;
	flags \|= FAULT_FLAG_WRITE;
	} else if (is_exec) {
	if (!(vma->vm_flags & VM_EXEC))
	goto bad_area;
	} else /* Allow read even from write-only pages. */
	if (!(vma->vm_flags & (VM_READ \| VM_WRITE)))
	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(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();
	}
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
	if (fault & VM_FAULT_MAJOR)
	current->maj_flt++;
	else
	current->min_flt++;
	if (fault & VM_FAULT_RETRY) {
	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);
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
	if (flags & VM_FAULT_MAJOR)
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
	else
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);

	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);
	if (user_mode(regs)) {
	current->thread.bad_vaddr = address;
	current->thread.error_code = is_write;
	force_sig_fault(SIGSEGV, code, (void *) address, current);
	return;
	}
	bad_page_fault(regs, address, SIGSEGV);
	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))
	bad_page_fault(regs, address, SIGKILL);
	else
	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.
	*/
	current->thread.bad_vaddr = address;
	force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address, current);

	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs))
	bad_page_fault(regs, address, SIGBUS);
	return;

	vmalloc_fault:
	{
	/* Synchronize this task's top level page-table
	* with the 'reference' page table.
	*/
	struct mm_struct *act_mm = current->active_mm;
	int index = pgd_index(address);
	pgd_t pgd, pgd_k;
	pmd_t pmd, pmd_k;
	pte_t *pte_k;

	if (act_mm == NULL)
	goto bad_page_fault;

	pgd = act_mm->pgd + index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
	goto bad_page_fault;

	pgd_val(pgd) = pgd_val(pgd_k);

	pmd = pmd_offset(pgd, address);
	pmd_k = pmd_offset(pgd_k, address);
	if (!pmd_present(pmd) \|\| !pmd_present(pmd_k))
	goto bad_page_fault;

	pmd_val(pmd) = pmd_val(pmd_k);
	pte_k = pte_offset_kernel(pmd_k, address);

	if (!pte_present(*pte_k))
	goto bad_page_fault;
	return;
	}
	bad_page_fault:
	bad_page_fault(regs, address, SIGKILL);
	return;
	}


	void
	bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
	{
	extern void die(const char, struct pt_regs, long);
	const struct exception_table_entry *entry;

	/* Are we prepared to handle this kernel fault? */
	if ((entry = search_exception_tables(regs->pc)) != NULL) {
	pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
	current->comm, regs->pc, entry->fixup);
	current->thread.bad_uaddr = address;
	regs->pc = entry->fixup;
	return;
	}

	/* Oops. The kernel tried to access some bad page. We'll have to
	* terminate things with extreme prejudice.
	*/
	pr_alert("Unable to handle kernel paging request at virtual "
	"address %08lx\n pc = %08lx, ra = %08lx\n",
	address, regs->pc, regs->areg[0]);
	die("Oops", regs, sig);
	do_exit(sig);
	}