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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: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2009-09-20 12:53:01 +01:00
parent bf4569922b
commit d374bf14a5
1 changed files with 22 additions and 11 deletions
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31
arch/arm/mm/fault.c
View File

@ -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_BADMAP 0x010000
#define VM_FAULT_BADACCESS 0x020000 #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, __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
struct task_struct *tsk) struct task_struct *tsk)
{ {
struct vm_area_struct *vma; struct vm_area_struct *vma;
int fault, mask; int fault;
vma = find_vma(mm, addr); vma = find_vma(mm, addr);
fault = VM_FAULT_BADMAP; fault = VM_FAULT_BADMAP;
if (!vma) if (unlikely(!vma))
goto out; goto out;
if (vma->vm_start > addr) if (unlikely(vma->vm_start > addr))
goto check_stack; 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. * memory access, so we can handle it.
*/ */
good_area: good_area:
if (fsr & FSR_WRITE) if (access_error(fsr, vma)) {
mask = VM_WRITE;
else
mask = VM_READ|VM_EXEC|VM_WRITE;
fault = VM_FAULT_BADACCESS; fault = VM_FAULT_BADACCESS;
if (!(vma->vm_flags & mask))
goto out; goto out;
}
/* /*
* If for any reason at all we couldn't handle the fault, make * If for any reason at all we couldn't handle the fault, make