releases/4.5.7/mips-fix-watchpoint-restoration.patch

   1 From a7e89326b415b5d81c4b1016fd4a40db861eb58d Mon Sep 17 00:00:00 2001
   2 From: James Hogan <james.hogan@imgtec.com>
   3 Date: Tue, 1 Mar 2016 22:19:36 +0000
   4 Subject: MIPS: Fix watchpoint restoration
   5
   6 From: James Hogan <james.hogan@imgtec.com>
   7
   8 commit a7e89326b415b5d81c4b1016fd4a40db861eb58d upstream.
   9
  10 Commit f51246efee2b ("MIPS: Get rid of finish_arch_switch().") moved the
  11 __restore_watch() call from finish_arch_switch() (i.e. after resume()
  12 returns) to before the resume() call in switch_to(). This results in
  13 watchpoints only being restored when a task is descheduled, preventing
  14 the watchpoints from being effective most of the time, except due to
  15 chance before the watchpoints are lazily removed.
  16
  17 Fix the call sequence from switch_to() through to
  18 mips_install_watch_registers() to pass the task_struct pointer of the
  19 next task, instead of using current. This allows the watchpoints for the
  20 next (non-current) task to be restored without reintroducing
  21 finish_arch_switch().
  22
  23 Fixes: f51246efee2b ("MIPS: Get rid of finish_arch_switch().")
  24 Signed-off-by: James Hogan <james.hogan@imgtec.com>
  25 Cc: Paul Burton <paul.burton@imgtec.com>
  26 Cc: linux-mips@linux-mips.org
  27 Patchwork: https://patchwork.linux-mips.org/patch/12726/
  28 Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  arch/mips/include/asm/switch_to.h |    2 +-
  33  arch/mips/include/asm/watch.h     |   10 +++++-----
  34  arch/mips/kernel/pm.c             |    2 +-
  35  arch/mips/kernel/watch.c          |    5 ++---
  36  4 files changed, 9 insertions(+), 10 deletions(-)
  37
  38 --- a/arch/mips/include/asm/switch_to.h
  39 +++ b/arch/mips/include/asm/switch_to.h
  40 @@ -105,7 +105,7 @@ do {                                                                        \
  41         __clear_software_ll_bit();                                      \
  42         if (cpu_has_userlocal)                                          \
  43                 write_c0_userlocal(task_thread_info(next)->tp_value);   \
  44 -       __restore_watch();                                              \
  45 +       __restore_watch(next);                                          \
  46         (last) = resume(prev, next, task_thread_info(next));            \
  47  } while (0)
  48
  49 --- a/arch/mips/include/asm/watch.h
  50 +++ b/arch/mips/include/asm/watch.h
  51 @@ -12,21 +12,21 @@
  52
  53  #include <asm/mipsregs.h>
  54
  55 -void mips_install_watch_registers(void);
  56 +void mips_install_watch_registers(struct task_struct *t);
  57  void mips_read_watch_registers(void);
  58  void mips_clear_watch_registers(void);
  59  void mips_probe_watch_registers(struct cpuinfo_mips *c);
  60
  61  #ifdef CONFIG_HARDWARE_WATCHPOINTS
  62 -#define __restore_watch() do {                                         \
  63 +#define __restore_watch(task) do {                                     \
  64         if (unlikely(test_bit(TIF_LOAD_WATCH,                           \
  65 -                             &current_thread_info()->flags))) {        \
  66 -               mips_install_watch_registers();                         \
  67 +                             &task_thread_info(task)->flags))) {       \
  68 +               mips_install_watch_registers(task);                     \
  69         }                                                               \
  70  } while (0)
  71
  72  #else
  73 -#define __restore_watch() do {} while (0)
  74 +#define __restore_watch(task) do {} while (0)
  75  #endif
  76
  77  #endif /* _ASM_WATCH_H */
  78 --- a/arch/mips/kernel/pm.c
  79 +++ b/arch/mips/kernel/pm.c
  80 @@ -56,7 +56,7 @@ static void mips_cpu_restore(void)
  81                 write_c0_userlocal(current_thread_info()->tp_value);
  82
  83         /* Restore watch registers */
  84 -       __restore_watch();
  85 +       __restore_watch(current);
  86  }
  87
  88  /**
  89 --- a/arch/mips/kernel/watch.c
  90 +++ b/arch/mips/kernel/watch.c
  91 @@ -15,10 +15,9 @@
  92   * Install the watch registers for the current thread. A maximum of
  93   * four registers are installed although the machine may have more.
  94   */
  95 -void mips_install_watch_registers(void)
  96 +void mips_install_watch_registers(struct task_struct *t)
  97  {
  98 -       struct mips3264_watch_reg_state *watches =
  99 -               &current->thread.watch.mips3264;
 100 +       struct mips3264_watch_reg_state *watches = &t->thread.watch.mips3264;
 101         switch (current_cpu_data.watch_reg_use_cnt) {
 102         default:
 103                 BUG();