[Patch 4/6] Watch trap handling for HARDWARE_WATCHPOINTS.

[David Daney <ddaney@avtrex.com>]

In this portion of the patch we hook up the watch trap handler.  When the
trap occurs, we copy the register contents into the thread_struct and 
send SIGTRAP.  If the current thread was not expecting the trap, the
watch register values must have been left over from a different context and
we just clear the registers and return.

Also I turn off the message the prints on each trap, as these traps are now
expected.

Signed-off-by: David Daney <ddaney@avtrex.com>
---
 arch/mips/kernel/genex.S |    4 ++++
 arch/mips/kernel/traps.c |   13 +++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index c6ada98..15a9bde 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -416,7 +416,11 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	BUILD_HANDLER tr tr sti silent			/* #13 */
 	BUILD_HANDLER fpe fpe fpe silent		/* #15 */
 	BUILD_HANDLER mdmx mdmx sti silent		/* #22 */
+#ifdef 	CONFIG_HARDWARE_WATCHPOINTS
+	BUILD_HANDLER watch watch sti silent		/* #23 */
+#else
 	BUILD_HANDLER watch watch sti verbose		/* #23 */
+#endif
 	BUILD_HANDLER mcheck mcheck cli verbose		/* #24 */
 	BUILD_HANDLER mt mt sti silent			/* #25 */
 	BUILD_HANDLER dsp dsp sti silent		/* #26 */
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 984c0d0..6a5f3f0 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -887,6 +887,18 @@ asmlinkage void do_mdmx(struct pt_regs *regs)
 
 asmlinkage void do_watch(struct pt_regs *regs)
 {
+#ifdef CONFIG_HARDWARE_WATCHPOINTS
+	/*
+	 * If the current thread has the watch registers loaded, save
+	 * their values and send SIGTRAP.  Otherwise another thread
+	 * left the registers set, clear them and continue.
+	 */
+	if (test_tsk_thread_flag(current, TIF_LOAD_WATCH)) {
+		mips_read_watch_registers();
+		force_sig(SIGTRAP, current);
+	} else
+		mips_clear_watch_registers();
+#else
 	if (board_watchpoint_handler) {
 		(*board_watchpoint_handler)(regs);
 		return;
@@ -899,6 +911,7 @@ asmlinkage void do_watch(struct pt_regs *regs)
 	dump_tlb_all();
 	show_regs(regs);
 	panic("Caught WATCH exception - probably caused by stack overflow.");
+#endif
 }
 
 asmlinkage void do_mcheck(struct pt_regs *regs)
-- 
1.5.5