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Subject[PATCH 04/10] ppc64: Add paranoid warnings for unexpected DSISR_PROTFAULT
Date
ppc64 should not be depending on DSISR_PROTFAULT and it's unexpected
if they are triggered. This patch adds warnings just in case they
are being accidentally depended upon.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
arch/powerpc/mm/copro_fault.c | 8 ++++++--
arch/powerpc/mm/fault.c | 20 +++++++++-----------
2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
index 5a236f0..0450d68 100644
--- a/arch/powerpc/mm/copro_fault.c
+++ b/arch/powerpc/mm/copro_fault.c
@@ -64,10 +64,14 @@ int copro_handle_mm_fault(struct mm_struct *mm, unsigned long ea,
if (!(vma->vm_flags & VM_WRITE))
goto out_unlock;
} else {
- if (dsisr & DSISR_PROTFAULT)
- goto out_unlock;
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
goto out_unlock;
+ /*
+ * protfault should only happen due to us
+ * mapping a region readonly temporarily. PROT_NONE
+ * is also covered by the VMA check above.
+ */
+ WARN_ON_ONCE(dsisr & DSISR_PROTFAULT);
}

ret = 0;
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index b434153..1bcd378 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -389,17 +389,6 @@ good_area:
#endif /* CONFIG_8xx */

if (is_exec) {
-#ifdef CONFIG_PPC_STD_MMU
- /* Protection fault on exec go straight to failure on
- * Hash based MMUs as they either don't support per-page
- * execute permission, or if they do, it's handled already
- * at the hash level. This test would probably have to
- * be removed if we change the way this works to make hash
- * processors use the same I/D cache coherency mechanism
- * as embedded.
- */
-#endif /* CONFIG_PPC_STD_MMU */
-
/*
* Allow execution from readable areas if the MMU does not
* provide separate controls over reading and executing.
@@ -414,6 +403,14 @@ good_area:
(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
!(vma->vm_flags & (VM_READ | VM_WRITE))))
goto bad_area;
+#ifdef CONFIG_PPC_STD_MMU
+ /*
+ * protfault should only happen due to us
+ * mapping a region readonly temporarily. PROT_NONE
+ * is also covered by the VMA check above.
+ */
+ WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+#endif /* CONFIG_PPC_STD_MMU */
/* a write */
} else if (is_write) {
if (!(vma->vm_flags & VM_WRITE))
@@ -423,6 +420,7 @@ good_area:
} else {
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
+ WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
}

/*
--
2.1.2


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