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>
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index b8b3bb4..b7ce07d 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -194,18 +194,33 @@
#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 @@
* memory access, so we can handle it.
*/
good_area:
- if (fsr & FSR_WRITE)
- mask = VM_WRITE;
- else
- mask = VM_READ|VM_EXEC|VM_WRITE;
-
- fault = VM_FAULT_BADACCESS;
- if (!(vma->vm_flags & mask))
+ if (access_error(fsr, vma)) {
+ fault = VM_FAULT_BADACCESS;
goto out;
+ }
/*
* If for any reason at all we couldn't handle the fault, make