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authorK.Prasad <prasad@linux.vnet.ibm.com>2010-01-28 16:44:01 +0530
committerFrederic Weisbecker <fweisbec@gmail.com>2010-01-29 02:26:10 +0100
commit40f9249a73f6c251adea492b1c3d19d39e2a9bda (patch)
treec60a605bdd1ca6981de926234dffd93a3f9b970f
parent1e12a4a7a3a78bc9c3aaf3486dde3b8ab1cdf465 (diff)
x86/debug: Clear reserved bits of DR6 in do_debug()
Clear the reserved bits from the stored copy of debug status register (DR6). This will help easy bitwise operations such as quick testing of a debug event origin. Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> Cc: Roland McGrath <roland@redhat.com> Cc: Jan Kiszka <jan.kiszka@siemens.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Ingo Molnar <mingo@elte.hu> LKML-Reference: <20100128111401.GB13935@in.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
-rw-r--r--arch/x86/include/asm/debugreg.h3
-rw-r--r--arch/x86/kernel/traps.c3
2 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 8240f76b531..b81002f2361 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -14,6 +14,9 @@
which debugging register was responsible for the trap. The other bits
are either reserved or not of interest to us. */
+/* Define reserved bits in DR6 which are always set to 1 */
+#define DR6_RESERVED (0xFFFF0FF0)
+
#define DR_TRAP0 (0x1) /* db0 */
#define DR_TRAP1 (0x2) /* db1 */
#define DR_TRAP2 (0x4) /* db2 */
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 33399176512..1168e445418 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -534,6 +534,9 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
get_debugreg(dr6, 6);
+ /* Filter out all the reserved bits which are preset to 1 */
+ dr6 &= ~DR6_RESERVED;
+
/* Catch kmemcheck conditions first of all! */
if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
return;