mm/debug_vm_pgtable/ppc64: avoid setting top bits in radom value

ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in random value. Signed-off-by: Aneesh Kumar K.V <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Reviewed-by: Anshuman Khandual <[email protected]> Cc: Christophe Leroy <[email protected]> Cc: Michael Ellerman <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
wafgo · Oct 16, 2020 · cfc5bbc · cfc5bbc
1 parent 379c926
commit cfc5bbc
Showing 1 changed file with 10 additions and 3 deletions.
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
@@ -44,10 +44,17 @@
  * entry type. But these bits might affect the ability to clear entries with
  * pxx_clear() because of how dynamic page table folding works on s390. So
  * while loading up the entries do not change the lower 4 bits. It does not
- * have affect any other platform.
+ * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
+ * used to mark a pte entry.
  */
-#define S390_MASK_BITS	4
-#define RANDOM_ORVALUE	GENMASK(BITS_PER_LONG - 1, S390_MASK_BITS)
+#define S390_SKIP_MASK		GENMASK(3, 0)
+#if __BITS_PER_LONG == 64
+#define PPC64_SKIP_MASK		GENMASK(62, 62)
+#else
+#define PPC64_SKIP_MASK		0x0
+#endif
+#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
+#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
 #define RANDOM_NZVALUE	GENMASK(7, 0)
 
 static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)