releases/4.7.3/arm64-kernel-fix-unmasked-debug-exceptions-when-restoring-mdscr_el1.patch

   1 From 744c6c37cc18705d19e179622f927f5b781fe9cc Mon Sep 17 00:00:00 2001
   2 From: James Morse <james.morse@arm.com>
   3 Date: Fri, 26 Aug 2016 16:03:42 +0100
   4 Subject: arm64: kernel: Fix unmasked debug exceptions when restoring mdscr_el1
   5
   6 From: James Morse <james.morse@arm.com>
   7
   8 commit 744c6c37cc18705d19e179622f927f5b781fe9cc upstream.
   9
  10 Changes to make the resume from cpu_suspend() code behave more like
  11 secondary boot caused debug exceptions to be unmasked early by
  12 __cpu_setup(). We then go on to restore mdscr_el1 in cpu_do_resume(),
  13 potentially taking break or watch points based on uninitialised registers.
  14
  15 Mask debug exceptions in cpu_do_resume(), which is specific to resume
  16 from cpu_suspend(). Debug exceptions will be restored to their original
  17 state by local_dbg_restore() in cpu_suspend(), which runs after
  18 hw_breakpoint_restore() has re-initialised the other registers.
  19
  20 Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
  21 Fixes: cabe1c81ea5b ("arm64: Change cpu_resume() to enable mmu early then access sleep_sp by va")
  22 Signed-off-by: James Morse <james.morse@arm.com>
  23 Acked-by: Will Deacon <will.deacon@arm.com>
  24 Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  arch/arm64/mm/proc.S |    9 +++++++++
  29  1 file changed, 9 insertions(+)
  30
  31 --- a/arch/arm64/mm/proc.S
  32 +++ b/arch/arm64/mm/proc.S
  33 @@ -100,7 +100,16 @@ ENTRY(cpu_do_resume)
  34
  35         msr     tcr_el1, x8
  36         msr     vbar_el1, x9
  37 +
  38 +       /*
  39 +        * __cpu_setup() cleared MDSCR_EL1.MDE and friends, before unmasking
  40 +        * debug exceptions. By restoring MDSCR_EL1 here, we may take a debug
  41 +        * exception. Mask them until local_dbg_restore() in cpu_suspend()
  42 +        * resets them.
  43 +        */
  44 +       disable_dbg
  45         msr     mdscr_el1, x10
  46 +
  47         msr     sctlr_el1, x12
  48         /*
  49          * Restore oslsr_el1 by writing oslar_el1