linux-kernel - [PATCH 4/6] Watch exception handling for HARDWARE

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Date:	Mon, 28 Apr 2008 18:37:31 -0700
From:	David Daney <ddaney@...rex.com>
To:	linux-mips@...ux-mips.org
Cc:	Linux kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/6] Watch exception handling for HARDWARE_WATCHPOINTS.

Watch exception handling for HARDWARE_WATCHPOINTS.

Here we hook up the watch exception handler so that it sends SIGTRAP when
the hardware watch registers are triggered.

Signed-off-by: David Daney <ddaney@...rex.com>
---
 arch/mips/kernel/genex.S |    4 ++++
 arch/mips/kernel/traps.c |   14 ++++++++++++++
 2 files changed, 18 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 824b187..22bb053 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -39,6 +39,7 @@
 #include <asm/tlbdebug.h>
 #include <asm/traps.h>
 #include <asm/uaccess.h>
+#include <asm/watch.h>
 #include <asm/mmu_context.h>
 #include <asm/types.h>
 #include <asm/stacktrace.h>
@@ -871,6 +872,18 @@ 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;
@@ -883,6 +896,7 @@ 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

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