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>
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@ -14,6 +14,9 @@
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which debugging register was responsible for the trap. The other bits
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are either reserved or not of interest to us. */
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/* Define reserved bits in DR6 which are always set to 1 */
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#define DR6_RESERVED (0xFFFF0FF0)
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#define DR_TRAP0 (0x1) /* db0 */
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#define DR_TRAP1 (0x2) /* db1 */
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#define DR_TRAP2 (0x4) /* db2 */
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@ -534,6 +534,9 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
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get_debugreg(dr6, 6);
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/* Filter out all the reserved bits which are preset to 1 */
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dr6 &= ~DR6_RESERVED;
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/* Catch kmemcheck conditions first of all! */
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if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
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return;
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