2018-03-04 17:36:51

by Vaibhav Jain

Subject: [PATCH] xmon: Clear all breakpoints when xmon is disabled via debugfs

Presently when xmon is disabled by debugfs any existing
instruction/data-access breakpoints set are not disabled. This may
lead to kernel oops when those breakpoints are hit as the necessary
debugger hooks aren't installed.

Hence this patch introduces a new function named clear_all_bpt()
which is called when xmon is disabled via debugfs. The function will
unpatch/clear all the trap and ciabr/dab based breakpoints.

Signed-off-by: Vaibhav Jain <[email protected]>
---
arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index e9c7ec8f15f8..f43aacd74625 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -903,6 +903,27 @@ static void remove_bpts(void)
}
}

+static void clear_all_bpt(void)
+{
+ int i;
+
+ /* clear/unpatch all breakpoints */
+ remove_bpts();
+ remove_cpu_bpts();
+
+ /* Disable all breakpoints */
+ for (i = 0; i < NBPTS; ++i)
+ bpts[i].enabled = 0;
+
+ /* Clear any data or iabr breakpoints */
+ if (iabr || dabr.enabled) {
+ iabr = NULL;
+ dabr.enabled = 0;
+ }
+
+ printf("xmon: All breakpoints cleared\n");
+}
+
static void remove_cpu_bpts(void)
{
hw_breakpoint_disable();
@@ -3671,6 +3692,9 @@ static int xmon_dbgfs_set(void *data, u64 val)
xmon_on = !!val;
xmon_init(xmon_on);

+ /* make sure all breakpoints removed when disabling */
+ if (!xmon_on)
+ clear_all_bpt();
return 0;
}

--
2.14.3

2018-03-04 21:48:54

by Balbir Singh

Subject: Re: [PATCH] xmon: Clear all breakpoints when xmon is disabled via debugfs

On Mon, Mar 5, 2018 at 4:31 AM, Vaibhav Jain <[email protected]> wrote:
> Presently when xmon is disabled by debugfs any existing
> instruction/data-access breakpoints set are not disabled. This may
> lead to kernel oops when those breakpoints are hit as the necessary
> debugger hooks aren't installed.
>
> Hence this patch introduces a new function named clear_all_bpt()
> which is called when xmon is disabled via debugfs. The function will
> unpatch/clear all the trap and ciabr/dab based breakpoints.
>
> Signed-off-by: Vaibhav Jain <[email protected]>
> ---

Reviewed-by: Balbir Singh <[email protected]>

Balbir

2018-03-14 09:31:15

by Michael Ellerman

Subject: Re: xmon: Clear all breakpoints when xmon is disabled via debugfs

On Sun, 2018-03-04 at 17:31:32 UTC, Vaibhav Jain wrote:
> Presently when xmon is disabled by debugfs any existing
> instruction/data-access breakpoints set are not disabled. This may
> lead to kernel oops when those breakpoints are hit as the necessary
> debugger hooks aren't installed.
>
> Hence this patch introduces a new function named clear_all_bpt()
> which is called when xmon is disabled via debugfs. The function will
> unpatch/clear all the trap and ciabr/dab based breakpoints.
>
> Signed-off-by: Vaibhav Jain <[email protected]>
> Reviewed-by: Balbir Singh <[email protected]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/1ff3b404019adf9d605224e1dce067

cheers