Messages in this thread Patch in this message | | | Date | Sat, 26 Dec 2009 23:57:25 +0530 | From | "K.Prasad" <> | Subject | [RFC Patch 1/2][Bugfix][x86][hw-breakpoint] Clear reserved bits of DR6 in do_debug() |
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Clear the reserved bits from the stored copy of debug status register (DR6). This will help easy bitwise operations.
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> --- arch/x86/include/asm/debugreg.h | 3 +++ arch/x86/kernel/traps.c | 3 +++ 2 files changed, 6 insertions(+)
Index: linux-2.6-tip/arch/x86/include/asm/debugreg.h =================================================================== --- linux-2.6-tip.orig/arch/x86/include/asm/debugreg.h +++ linux-2.6-tip/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 */ Index: linux-2.6-tip/arch/x86/kernel/traps.c =================================================================== --- linux-2.6-tip.orig/arch/x86/kernel/traps.c +++ linux-2.6-tip/arch/x86/kernel/traps.c @@ -534,6 +534,9 @@ dotraplinkage void __kprobes do_debug(st 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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