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Commit 40f9249a authored by K.Prasad's avatar K.Prasad Committed by Frederic Weisbecker
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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: default avatarK.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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 1e12a4a7

arch/x86/include/asm/debugreg.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/traps.c

+3 −0
Original line number Diff line number Diff line
@@ -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;