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hw-breakpoints: reset bits in dr6 after the corresponding exception is handled

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This patch resets the bit in dr6 after the corresponding exception is
handled in code, so that we keep a clean track of the current virtual debug
status register.

[ Impact: keep track of breakpoints triggering completion ]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
K.Prasad
2009-06-01 23:47:06 +05:30
committed by Frederic Weisbecker
parent 0722db015c
commit 62edab9056
5 changed files with 34 additions and 6 deletions
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13
arch/x86/kernel/hw_breakpoint.c
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@@ -314,8 +314,12 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
{
int i, cpu, rc = NOTIFY_STOP;
struct hw_breakpoint *bp;
/* The DR6 value is stored in args->err */
unsigned long dr7, dr6 = args->err;
unsigned long dr7, dr6;
unsigned long *dr6_p;
/* The DR6 value is pointed by args->err */
dr6_p = (unsigned long *)ERR_PTR(args->err);
dr6 = *dr6_p;
/* Do an early return if no trap bits are set in DR6 */
if ((dr6 & DR_TRAP_BITS) == 0)
@@ -351,6 +355,11 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
if (bp)
rc = NOTIFY_DONE;
}
/*
* Reset the 'i'th TRAP bit in dr6 to denote completion of
* exception handling
*/
(*dr6_p) &= ~(DR_TRAP0 << i);
/*
* bp can be NULL due to lazy debug register switching
* or due to the delay between updates of hbp_kernel_pos