[patch 05/52] [PATCH] fault handler access flags check.

Martin Schwidefsky
2009-11-13T15:17:05Z

[-- Attachment #1: 104-mm-fault-access.diff --]
[-- Type: text/plain, Size: 2701 bytes --]

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

Simplify the check of the vma->flags in do_exception for the
different fault types.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

arch/s390/mm/fault.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)

Index: quilt-2.6/arch/s390/mm/fault.c
===================================================================
--- quilt-2.6.orig/arch/s390/mm/fault.c 2009-11-13 16:08:12.000000000 +0100
+++ quilt-2.6/arch/s390/mm/fault.c 2009-11-13 16:08:12.000000000 +0100
@@ -286,7 +286,7 @@
* 11 Page translation -> Not present (nullification)
* 3b Region third trans. -> Not present (nullification)
*/
-static inline int do_exception(struct pt_regs *regs, int write,
+static inline int do_exception(struct pt_regs *regs, int access,
unsigned long trans_exc_code)
{
struct task_struct *tsk;
@@ -337,19 +337,8 @@
* we can handle it..
*/
fault = VM_FAULT_BADACCESS;
-#ifdef CONFIG_S390_EXEC_PROTECT
- if (unlikely((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY &&
- (trans_exc_code & 3) == 0 && !(vma->vm_flags & VM_EXEC)))
+ if (unlikely(!(vma->vm_flags & access)))
goto out_up;
-#endif
- if (!write) {
- /* page not present, check vm flags */
- if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
- goto out_up;
- } else {
- if (!(vma->vm_flags & VM_WRITE))
- goto out_up;
- }

if (is_vm_hugetlb_page(vma))
address &= HPAGE_MASK;
@@ -358,7 +347,8 @@
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
- fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
+ fault = handle_mm_fault(mm, vma, address,
+ (access == VM_WRITE) ? FAULT_FLAG_WRITE : 0);
if (unlikely(fault & VM_FAULT_ERROR))
goto out_up;

@@ -399,7 +389,7 @@
do_low_address(regs, int_code, trans_exc_code);
return;
}
- fault = do_exception(regs, 1, trans_exc_code);
+ fault = do_exception(regs, VM_WRITE, trans_exc_code);
if (unlikely(fault))
do_fault_error(regs, 4, trans_exc_code, fault);
}
@@ -407,9 +397,15 @@
void __kprobes do_dat_exception(struct pt_regs *regs, long int_code)
{
unsigned long trans_exc_code = S390_lowcore.trans_exc_code;
- int fault;
+ int access, fault;

- fault = do_exception(regs, 0, trans_exc_code);
+ access = VM_READ | VM_EXEC | VM_WRITE;
+#ifdef CONFIG_S390_EXEC_PROTECT
+ if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY &&
+ (trans_exc_code & 3) == 0)
+ access = VM_EXEC;
+#endif
+ fault = do_exception(regs, access, trans_exc_code);
if (unlikely(fault))
do_fault_error(regs, int_code & 255, trans_exc_code, fault);
}