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Commit d374bf14 authored by Russell King's avatar Russell King
Browse files

ARM: Separate out access error checking 



Since we get notified separately about prefetch aborts, which may be
permission faults, we need to check for appropriate access permissions
when handling a fault.  This patch prepares us for doing this by
separating out the access error checking.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent bf456992

arch/arm/mm/fault.c

+22 −11
Original line number Diff line number Diff line
@@ -194,18 +194,33 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 
#define VM_FAULT_BADMAP		0x010000

#define VM_FAULT_BADACCESS	0x020000



static int

/*

 * 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;



	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, mask;

	int fault;



	vma = find_vma(mm, addr);

	fault = VM_FAULT_BADMAP;

	if (!vma)

	if (unlikely(!vma))

		goto out;

	if (vma->vm_start > addr)

	if (unlikely(vma->vm_start > addr))

		goto check_stack;



	/*
@@ -213,14 +228,10 @@ __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr, 
	 * memory access, so we can handle it.

	 */

good_area:

	if (fsr & FSR_WRITE)

		mask = VM_WRITE;

	else

		mask = VM_READ|VM_EXEC|VM_WRITE;



	if (access_error(fsr, vma)) {

		fault = VM_FAULT_BADACCESS;

	if (!(vma->vm_flags & mask))

		goto out;

	}



	/*

	 * If for any reason at all we couldn't handle the fault, make