[PATCH] powerpc: Better pmd_bad() and pud_bad() checks

At present, the powerpc pmd_bad() and pud_bad() macros return false
unless the given pmd or pud is zero.  This patch makes these tests
more thorough, checking if the given pmd or pud looks like a plausible
pte page or pmd page pointer respectively.  This can result in helpful
error messages when messing with the pagetable code.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/asm-powerpc/pgtable.h b/include/asm-powerpc/pgtable.h
index e38931379a72..8dc3eb54276f 100644
--- a/include/asm-powerpc/pgtable.h
+++ b/include/asm-powerpc/pgtable.h
@@ -188,9 +188,13 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t pgprot)
 #define pte_pfn(x)              ((unsigned long)((pte_val(x)>>PTE_RPN_SHIFT)))
 #define pte_page(x)             pfn_to_page(pte_pfn(x))
 
+#define PMD_BAD_BITS            (PTE_TABLE_SIZE-1)
+#define PUD_BAD_BITS            (PMD_TABLE_SIZE-1)
+
 #define pmd_set(pmdp, pmdval)   (pmd_val(*(pmdp)) = (pmdval))
 #define pmd_none(pmd)           (!pmd_val(pmd))
-#define pmd_bad(pmd)            (pmd_val(pmd) == 0)
+#define pmd_bad(pmd)            (!is_kernel_addr(pmd_val(pmd)) \
+                                 || (pmd_val(pmd) & PMD_BAD_BITS))
 #define pmd_present(pmd)        (pmd_val(pmd) != 0)
 #define pmd_clear(pmdp)         (pmd_val(*(pmdp)) = 0)
 #define pmd_page_kernel(pmd)    (pmd_val(pmd) & ~PMD_MASKED_BITS)
@@ -198,7 +202,8 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t pgprot)
 
 #define pud_set(pudp, pudval)   (pud_val(*(pudp)) = (pudval))
 #define pud_none(pud)           (!pud_val(pud))
-#define pud_bad(pud)            ((pud_val(pud)) == 0)
+#define pud_bad(pud)            (!is_kernel_addr(pud_val(pud)) \
+                                 || (pud_val(pud) & PUD_BAD_BITS))
 #define pud_present(pud)        (pud_val(pud) != 0)
 #define pud_clear(pudp)         (pud_val(*(pudp)) = 0)
 #define pud_page(pud)           (pud_val(pud) & ~PUD_MASKED_BITS)