linux-kernel - [PATCH 9/9] kgdb: Always process the whole breakpoint list on activate or deactivate

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Date:	Fri, 11 Dec 2009 09:36:17 -0600
From:	Jason Wessel <jason.wessel@...driver.com>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	Jason Wessel <jason.wessel@...driver.com>
Subject: [PATCH 9/9] kgdb: Always process the whole breakpoint list on activate or deactivate

This patch fixes 2 edge cases in using kgdb in conjunction with gdb.

1) kgdb_deactivate_sw_breakpoints() should process the entire array of
   breakpoints.  The failure to do so results in breakpoints that you
   cannot remove, because a break point can only be removed if its
   state flag is set to BP_SET.

   The easy way to duplicate this problem is to plant a break point in
   a kernel module and then unload the kernel module.

2) kgdb_activate_sw_breakpoints() should process the entire array of
   breakpoints.  The failure to do so results in missed breakpoints
   when a breakpoint cannot be activated.

Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
---
 kernel/kgdb.c |   23 +++++++++++++++--------
 1 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 8584eac..2eb517e 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -625,7 +625,8 @@ static void kgdb_flush_swbreak_addr(unsigned long addr)
 static int kgdb_activate_sw_breakpoints(void)
 {
 	unsigned long addr;
-	int error = 0;
+	int error;
+	int ret = 0;
 	int i;
 
 	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
@@ -635,13 +636,16 @@ static int kgdb_activate_sw_breakpoints(void)
 		addr = kgdb_break[i].bpt_addr;
 		error = kgdb_arch_set_breakpoint(addr,
 				kgdb_break[i].saved_instr);
-		if (error)
-			return error;
+		if (error) {
+			ret = error;
+			printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
+			continue;
+		}
 
 		kgdb_flush_swbreak_addr(addr);
 		kgdb_break[i].state = BP_ACTIVE;
 	}
-	return 0;
+	return ret;
 }
 
 static int kgdb_set_sw_break(unsigned long addr)
@@ -688,7 +692,8 @@ static int kgdb_set_sw_break(unsigned long addr)
 static int kgdb_deactivate_sw_breakpoints(void)
 {
 	unsigned long addr;
-	int error = 0;
+	int error;
+	int ret = 0;
 	int i;
 
 	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
@@ -697,13 +702,15 @@ static int kgdb_deactivate_sw_breakpoints(void)
 		addr = kgdb_break[i].bpt_addr;
 		error = kgdb_arch_remove_breakpoint(addr,
 					kgdb_break[i].saved_instr);
-		if (error)
-			return error;
+		if (error) {
+			printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
+			ret = error;
+		}
 
 		kgdb_flush_swbreak_addr(addr);
 		kgdb_break[i].state = BP_SET;
 	}
-	return 0;
+	return ret;
 }
 
 static int kgdb_remove_sw_break(unsigned long addr)
-- 
1.6.4.rc1

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