releases/4.14.69/powerpc-pseries-fix-endianness-while-restoring-of-r3-in-mce-handler.patch

   1 From cd813e1cd7122f2c261dce5b54d1e0c97f80e1a5 Mon Sep 17 00:00:00 2001
   2 From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
   3 Date: Tue, 7 Aug 2018 19:46:46 +0530
   4 Subject: powerpc/pseries: Fix endianness while restoring of r3 in MCE handler.
   5
   6 From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
   7
   8 commit cd813e1cd7122f2c261dce5b54d1e0c97f80e1a5 upstream.
   9
  10 During Machine Check interrupt on pseries platform, register r3 points
  11 RTAS extended event log passed by hypervisor. Since hypervisor uses r3
  12 to pass pointer to rtas log, it stores the original r3 value at the
  13 start of the memory (first 8 bytes) pointed by r3. Since hypervisor
  14 stores this info and rtas log is in BE format, linux should make
  15 sure to restore r3 value in correct endian format.
  16
  17 Without this patch when MCE handler, after recovery, returns to code that
  18 that caused the MCE may end up with Data SLB access interrupt for invalid
  19 address followed by kernel panic or hang.
  20
  21   Severe Machine check interrupt [Recovered]
  22     NIP [d00000000ca301b8]: init_module+0x1b8/0x338 [bork_kernel]
  23     Initiator: CPU
  24     Error type: SLB [Multihit]
  25       Effective address: d00000000ca70000
  26   cpu 0xa: Vector: 380 (Data SLB Access) at [c0000000fc7775b0]
  27       pc: c0000000009694c0: vsnprintf+0x80/0x480
  28       lr: c0000000009698e0: vscnprintf+0x20/0x60
  29       sp: c0000000fc777830
  30      msr: 8000000002009033
  31      dar: a803a30c000000d0
  32     current = 0xc00000000bc9ef00
  33     paca    = 0xc00000001eca5c00         softe: 3        irq_happened: 0x01
  34       pid   = 8860, comm = insmod
  35   vscnprintf+0x20/0x60
  36   vprintk_emit+0xb4/0x4b0
  37   vprintk_func+0x5c/0xd0
  38   printk+0x38/0x4c
  39   init_module+0x1c0/0x338 [bork_kernel]
  40   do_one_initcall+0x54/0x230
  41   do_init_module+0x8c/0x248
  42   load_module+0x12b8/0x15b0
  43   sys_finit_module+0xa8/0x110
  44   system_call+0x58/0x6c
  45   --- Exception: c00 (System Call) at 00007fff8bda0644
  46   SP (7fffdfbfe980) is in userspace
  47
  48 This patch fixes this issue.
  49
  50 Fixes: a08a53ea4c97 ("powerpc/le: Enable RTAS events support")
  51 Cc: stable@vger.kernel.org # v3.15+
  52 Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
  53 Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
  54 Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
  55 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  56
  57 ---
  58  arch/powerpc/platforms/pseries/ras.c |    2 +-
  59  1 file changed, 1 insertion(+), 1 deletion(-)
  60
  61 --- a/arch/powerpc/platforms/pseries/ras.c
  62 +++ b/arch/powerpc/platforms/pseries/ras.c
  63 @@ -360,7 +360,7 @@ static struct rtas_error_log *fwnmi_get_
  64         }
  65
  66         savep = __va(regs->gpr[3]);
  67 -       regs->gpr[3] = savep[0];        /* restore original r3 */
  68 +       regs->gpr[3] = be64_to_cpu(savep[0]);   /* restore original r3 */
  69
  70         /* If it isn't an extended log we can use the per cpu 64bit buffer */
  71         h = (struct rtas_error_log *)&savep[1];