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hw-breakpoints: Keep track of user disabled breakpoints

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When we disable a breakpoint through dr7, we unregister it right
away, making us lose track of its corresponding address
register value.

It means that the following sequence would be unsupported:

 - set address in dr0
 - enable it through dr7
 - disable it through dr7
 - enable it through dr7

because we lost the address register value when we disabled the
breakpoint.

Don't unregister the disabled breakpoints but rather disable
them.

Reported-by: "K.Prasad" <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1259735536-9236-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2009-12-02 07:32:16 +01:00 committed by Ingo Molnar
parent 6b62fe019e
commit 1cedae7290
1 changed files with 12 additions and 4 deletions
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16
arch/x86/kernel/ptrace.c
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@ -595,7 +595,7 @@ static unsigned long ptrace_get_dr7(struct perf_event *bp[])
static struct perf_event *
ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
struct task_struct *tsk)
struct task_struct *tsk, int disabled)
{
int err;
int gen_len, gen_type;
@ -616,7 +616,7 @@ ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
attr = bp->attr;
attr.bp_len = gen_len;
attr.bp_type = gen_type;
attr.disabled = 0;
attr.disabled = disabled;
return modify_user_hw_breakpoint(bp, &attr, bp->callback, tsk);
}
@ -655,13 +655,21 @@ restore:
*/
if (!second_pass)
continue;
thread->ptrace_bps[i] = NULL;
unregister_hw_breakpoint(bp);
bp = ptrace_modify_breakpoint(bp, len, type,
tsk, 1);
if (IS_ERR(bp)) {
rc = PTR_ERR(bp);
thread->ptrace_bps[i] = NULL;
break;
}
thread->ptrace_bps[i] = bp;
}
continue;
}
bp = ptrace_modify_breakpoint(bp, len, type, tsk);
bp = ptrace_modify_breakpoint(bp, len, type, tsk, 0);
/* Incorrect bp, or we have a bug in bp API */
if (IS_ERR(bp)) {