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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
View File

@ -314,8 +314,12 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
{ {
int i, cpu, rc = NOTIFY_STOP; int i, cpu, rc = NOTIFY_STOP;
struct hw_breakpoint *bp; struct hw_breakpoint *bp;
/* The DR6 value is stored in args->err */ unsigned long dr7, dr6;
unsigned long dr7, dr6 = args->err; 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 */ /* Do an early return if no trap bits are set in DR6 */
if ((dr6 & DR_TRAP_BITS) == 0) if ((dr6 & DR_TRAP_BITS) == 0)
@ -351,6 +355,11 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
if (bp) if (bp)
rc = NOTIFY_DONE; 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 * bp can be NULL due to lazy debug register switching
* or due to the delay between updates of hbp_kernel_pos * or due to the delay between updates of hbp_kernel_pos

6
arch/x86/kernel/kgdb.c
View File

@ -43,6 +43,7 @@
#include <linux/smp.h> #include <linux/smp.h>
#include <linux/nmi.h> #include <linux/nmi.h>
#include <asm/debugreg.h>
#include <asm/apicdef.h> #include <asm/apicdef.h>
#include <asm/system.h> #include <asm/system.h>
@ -434,6 +435,11 @@ single_step_cont(struct pt_regs *regs, struct die_args *args)
"resuming...\n"); "resuming...\n");
kgdb_arch_handle_exception(args->trapnr, args->signr, kgdb_arch_handle_exception(args->trapnr, args->signr,
args->err, "c", "", regs); args->err, "c", "", regs);
/*
* Reset the BS bit in dr6 (pointed by args->err) to
* denote completion of processing
*/
(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
return NOTIFY_STOP; return NOTIFY_STOP;
} }

9
arch/x86/kernel/kprobes.c
View File

@ -54,6 +54,7 @@
#include <asm/pgtable.h> #include <asm/pgtable.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
#include <asm/alternative.h> #include <asm/alternative.h>
#include <asm/debugreg.h>
void jprobe_return_end(void); void jprobe_return_end(void);
@ -967,8 +968,14 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
ret = NOTIFY_STOP; ret = NOTIFY_STOP;
break; break;
case DIE_DEBUG: case DIE_DEBUG:
if (post_kprobe_handler(args->regs)) if (post_kprobe_handler(args->regs)) {
/*
* Reset the BS bit in dr6 (pointed by args->err) to
* denote completion of processing
*/
(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
ret = NOTIFY_STOP; ret = NOTIFY_STOP;
}
break; break;
case DIE_GPF: case DIE_GPF:
/* /*

4
arch/x86/kernel/traps.c
View File

@ -545,8 +545,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
/* Store the virtualized DR6 value */ /* Store the virtualized DR6 value */
tsk->thread.debugreg6 = dr6; tsk->thread.debugreg6 = dr6;
if (notify_die(DIE_DEBUG, "debug", regs, dr6, error_code, if (notify_die(DIE_DEBUG, "debug", regs, PTR_ERR(&dr6), error_code,
SIGTRAP) == NOTIFY_STOP) SIGTRAP) == NOTIFY_STOP)
return; return;
/* It's safe to allow irq's after DR6 has been saved */ /* It's safe to allow irq's after DR6 has been saved */

8
arch/x86/mm/kmmio.c
View File

@ -540,8 +540,14 @@ kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args)
struct die_args *arg = args; struct die_args *arg = args;
if (val == DIE_DEBUG && (arg->err & DR_STEP)) if (val == DIE_DEBUG && (arg->err & DR_STEP))
if (post_kmmio_handler(arg->err, arg->regs) == 1) if (post_kmmio_handler(arg->err, arg->regs) == 1) {
/*
* Reset the BS bit in dr6 (pointed by args->err) to
* denote completion of processing
*/
(*(unsigned long *)ERR_PTR(arg->err)) &= ~DR_STEP;
return NOTIFY_STOP; return NOTIFY_STOP;
}
return NOTIFY_DONE; return NOTIFY_DONE;
} }