[PATCH 4.5 008/128] MIPS: Fix watchpoint restoration

Greg Kroah-Hartman
2016-06-05T22:44:13Z

From: James Hogan <james.hogan@imgtec.com>

commit a7e89326b415b5d81c4b1016fd4a40db861eb58d upstream.

Commit f51246efee2b ("MIPS: Get rid of finish_arch_switch().") moved the
__restore_watch() call from finish_arch_switch() (i.e. after resume()
returns) to before the resume() call in switch_to(). This results in
watchpoints only being restored when a task is descheduled, preventing
the watchpoints from being effective most of the time, except due to
chance before the watchpoints are lazily removed.

Fix the call sequence from switch_to() through to
mips_install_watch_registers() to pass the task_struct pointer of the
next task, instead of using current. This allows the watchpoints for the
next (non-current) task to be restored without reintroducing
finish_arch_switch().

Fixes: f51246efee2b ("MIPS: Get rid of finish_arch_switch().")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12726/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/mips/include/asm/switch_to.h | 2 +-
arch/mips/include/asm/watch.h | 10 +++++-----
arch/mips/kernel/pm.c | 2 +-
arch/mips/kernel/watch.c | 5 ++---
4 files changed, 9 insertions(+), 10 deletions(-)

--- a/arch/mips/include/asm/switch_to.h
+++ b/arch/mips/include/asm/switch_to.h
@@ -105,7 +105,7 @@ do { \
__clear_software_ll_bit(); \
if (cpu_has_userlocal) \
write_c0_userlocal(task_thread_info(next)->tp_value); \
- __restore_watch(); \
+ __restore_watch(next); \
(last) = resume(prev, next, task_thread_info(next)); \
} while (0)

--- a/arch/mips/include/asm/watch.h
+++ b/arch/mips/include/asm/watch.h
@@ -12,21 +12,21 @@

#include <asm/mipsregs.h>

-void mips_install_watch_registers(void);
+void mips_install_watch_registers(struct task_struct *t);
void mips_read_watch_registers(void);
void mips_clear_watch_registers(void);
void mips_probe_watch_registers(struct cpuinfo_mips *c);

#ifdef CONFIG_HARDWARE_WATCHPOINTS
-#define __restore_watch() do { \
+#define __restore_watch(task) do { \
if (unlikely(test_bit(TIF_LOAD_WATCH, \
- &current_thread_info()->flags))) { \
- mips_install_watch_registers(); \
+ &task_thread_info(task)->flags))) { \
+ mips_install_watch_registers(task); \
} \
} while (0)

#else
-#define __restore_watch() do {} while (0)
+#define __restore_watch(task) do {} while (0)
#endif

#endif /* _ASM_WATCH_H */
--- a/arch/mips/kernel/pm.c
+++ b/arch/mips/kernel/pm.c
@@ -56,7 +56,7 @@ static void mips_cpu_restore(void)
write_c0_userlocal(current_thread_info()->tp_value);

/* Restore watch registers */
- __restore_watch();
+ __restore_watch(current);
}

/**
--- a/arch/mips/kernel/watch.c
+++ b/arch/mips/kernel/watch.c
@@ -15,10 +15,9 @@
* Install the watch registers for the current thread. A maximum of
* four registers are installed although the machine may have more.
*/
-void mips_install_watch_registers(void)
+void mips_install_watch_registers(struct task_struct *t)
{
- struct mips3264_watch_reg_state *watches =
- &current->thread.watch.mips3264;
+ struct mips3264_watch_reg_state *watches = &t->thread.watch.mips3264;
switch (current_cpu_data.watch_reg_use_cnt) {
default:
BUG();