linux-kernel - [PATCH 14/17] mm,kdb,kgdb: Add a debug reference for the kdb kmap usage

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Date:	Thu,  5 Aug 2010 09:37:55 -0500
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>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-mm@...ck.org
Subject: [PATCH 14/17] mm,kdb,kgdb: Add a debug reference for the kdb kmap usage

The kdb kmap should never get used outside of the kernel debugger
exception context.

Signed-off-by: Jason Wessel<jason.wessel@...driver.com>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Ingo Molnar <mingo@...e.hu>
CC: linux-mm@...ck.org
---
 mm/highmem.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/mm/highmem.c b/mm/highmem.c
index 66baa20..7a0aa1b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -26,6 +26,7 @@
 #include <linux/init.h>
 #include <linux/hash.h>
 #include <linux/highmem.h>
+#include <linux/kgdb.h>
 #include <asm/tlbflush.h>
 
 /*
@@ -470,6 +471,12 @@ void debug_kmap_atomic(enum km_type type)
 			warn_count--;
 		}
 	}
+#ifdef CONFIG_KGDB_KDB
+	if (unlikely(type == KM_KDB && atomic_read(&kgdb_active) == -1)) {
+		WARN_ON(1);
+		warn_count--;
+	}
+#endif /* CONFIG_KGDB_KDB */
 }
 
 #endif
-- 
1.6.3.3

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