linux-kernel - [PATCH] kdb: Add message about CONFIG_DEBUG_RODATA on failure to install breakpoint

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Message-ID: <4E7A4413.5000307@am.sony.com>
Date:	Wed, 21 Sep 2011 13:07:47 -0700
From:	Tim Bird <tim.bird@...sony.com>
To:	Jason Wessel <jason.wessel@...driver.com>
CC:	"kgdb-bugreport@...ts.sourceforge.net" 
	<kgdb-bugreport@...ts.sourceforge.net>,
	linux kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] kdb: Add message about CONFIG_DEBUG_RODATA on failure to
 install breakpoint

On x86, if CONFIG_DEBUG_RODATA is set, one cannot set breakpoints
via KDB.  Apparently this is a well-known problem, as at least one distribution
now ships with both KDB enabled and CONFIG_DEBUG_RODATA=y for security reasons.

This patch just adds an extra printk message to the breakpoint failure case,
in order to provide some useful diagnostics to the user.

Signed-off-by: Tim Bird <tim.bird@...sony.com>
---
 kernel/debug/kdb/kdb_bp.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c
index 20059ef..f015e79 100644
--- a/kernel/debug/kdb/kdb_bp.c
+++ b/kernel/debug/kdb/kdb_bp.c
@@ -153,6 +153,10 @@ static int _kdb_bp_install(struct pt_regs *regs, kdb_bp_t *bp)
 	} else {
 		kdb_printf("%s: failed to set breakpoint at 0x%lx\n",
 			   __func__, bp->bp_addr);
+#ifdef CONFIG_DEBUG_RODATA
+		kdb_printf("May need to disable CONFIG_DEBUG_RODATA in order"
+			" to set breakpoints\n");
+#endif
 		return 1;
 	}
 	return 0;
-- 
1.6.6


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