This code matches a fault condition up with the VMA and ensures
that the VMA allows the fault to be handled instead of just
erroring out.
We will be extending this in a moment to comprehend protection
keys.
---
b/mm/gup.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff -puN mm/gup.c~pkeys-10-pte-fault mm/gup.c
--- a/mm/gup.c~pkeys-10-pte-fault 2015-09-16 10:48:16.591207512 -0700
+++ b/mm/gup.c 2015-09-16 10:48:16.595207693 -0700
@@ -554,6 +554,17 @@ next_page:
}
EXPORT_SYMBOL(__get_user_pages);
+bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
+{
+ vm_flags_t vm_flags =
+ (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
+
+ if (!(vm_flags & vma->vm_flags))
+ return false;
+
+ return true;
+}
+
/*
* fixup_user_fault() - manually resolve a user page fault
* @tsk: the task_struct to use for page fault accounting, or
@@ -585,15 +596,13 @@ int fixup_user_fault(struct task_struct
unsigned long address, unsigned int fault_flags)
{
struct vm_area_struct *vma;
- vm_flags_t vm_flags;
int ret;
vma = find_extend_vma(mm, address);
if (!vma || address < vma->vm_start)
return -EFAULT;
- vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
- if (!(vm_flags & vma->vm_flags))
+ if (!vma_permits_fault(vma, fault_flags))
return -EFAULT;
ret = handle_mm_fault(mm, vma, address, fault_flags);
_
--
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