Re: [PATCH 02/16] debug_vm_pgtable/ppc64: Avoid setting top bits in radom value

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 8/12/20 12:10 PM, Christophe Leroy wrote:


Le 12/08/2020 à 08:33, Aneesh Kumar K.V a écrit :
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 <aneesh.kumar@xxxxxxxxxxxxx>
---
  mm/debug_vm_pgtable.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 086309fb9b6f..4c32063a8acf 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -45,9 +45,12 @@
   * 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.
+ *
+ * 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 PPC_MASK_BITS    2
+#define RANDOM_ORVALUE    GENMASK(BITS_PER_LONG - 1 - PPC_MASK_BITS, S390_MASK_BITS)

Do you mean:

#define RANDOM_ORVALUE    GENMASK(BITS_PER_LONG - 1, PPC_MASK_BITS | S390_MASK_BITS)


IIUC GENMASK(hi, low) generate a mask from hi to low bits. Since i want to avoid bit 62, I am forcing it to generate bits from (61, 4)


-aneesh





[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux