x86/debug: Clear reserved bits of DR6 in do_debug() (40f9249a) · Commits · 戴 / test

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>

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;

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