linux-kernel - [RFC Patch 7/9] Modify signal handling code to refrain from re-enabling HW Breakpoints

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Message-ID: <20081008192611.GG4989@in.ibm.com>
Date:	Thu, 9 Oct 2008 00:56:11 +0530
From:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Roland McGrath <roland@...hat.com>, akpm@...ux-foundation.org,
	mingo@...e.hu, jason.wessel@...driver.com, avi@...ranet.com,
	richardj_moore@...ibm.com
Subject: [RFC Patch 7/9] Modify signal handling code to refrain from
	re-enabling HW Breakpoints

This patch disables re-enabling of Hardware Breakpoint registers through the 
signal handling code. This is now during hw_breakpoint_handler().

Signed-off-by: K.Prasad <prasad@...ux.vnet.ibm.com>
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
---
 arch/x86/kernel/signal_32.c |    9 ---------
 arch/x86/kernel/signal_64.c |    8 --------
 2 files changed, 17 deletions(-)

Index: linux-bkpt-lkml-27-rc9/arch/x86/kernel/signal_32.c
===================================================================
--- linux-bkpt-lkml-27-rc9.orig/arch/x86/kernel/signal_32.c
+++ linux-bkpt-lkml-27-rc9/arch/x86/kernel/signal_32.c
@@ -600,15 +600,6 @@ static void do_signal(struct pt_regs *re
 
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
-		/*
-		 * Re-enable any watchpoints before delivering the
-		 * signal to user space. The processor register will
-		 * have been cleared if the watchpoint triggered
-		 * inside the kernel.
-		 */
-		if (current->thread.debugreg7)
-			set_debugreg(current->thread.debugreg7, 7);
-
 		/* Whee! Actually deliver the signal.  */
 		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 			/*
Index: linux-bkpt-lkml-27-rc9/arch/x86/kernel/signal_64.c
===================================================================
--- linux-bkpt-lkml-27-rc9.orig/arch/x86/kernel/signal_64.c
+++ linux-bkpt-lkml-27-rc9/arch/x86/kernel/signal_64.c
@@ -496,14 +496,6 @@ static void do_signal(struct pt_regs *re
 
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
-		/* Re-enable any watchpoints before delivering the
-		 * signal to user space. The processor register will
-		 * have been cleared if the watchpoint triggered
-		 * inside the kernel.
-		 */
-		if (current->thread.debugreg7)
-			set_debugreg(current->thread.debugreg7, 7);
-
 		/* Whee!  Actually deliver the signal.  */
 		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 			/*
--
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