On Mon, 2018-02-26 at 17:06 +0530, Vaibhav Jain wrote:
> Presently sysrq key for xmon('x') is registered during kernel init
> irrespective of the value of kernel param 'xmon'. Thus xmon is enabled
> even if 'xmon=off' is passed on the kernel command line. However this
> doesn't enable the kernel debugger hooks needed for instruction or data
> breakpoints. Thus when a break-point is hit with xmon=off a kernel oops
> of the form below is reported:
>
> Oops: Exception in kernel mode, sig: 5 [#1]
> < snip >
> Trace/breakpoint trap
>
> To fix this the patch checks and enables debugger hooks when an
> instruction or data break-point is set via xmon console. It also clears
> all breakpoints when xmon is disabled via debugfs.
>
> Signed-off-by: Vaibhav Jain <vaib...@linux.vnet.ibm.com>
> ---
> arch/powerpc/xmon/xmon.c | 34 +++++++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 82e1a3ee6e0f..3679f5417a7e 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -1295,6 +1295,7 @@ bpt_cmds(void)
> switch (cmd) {
> #ifndef CONFIG_PPC_8xx
> static const char badaddr[] = "Only kernel addresses are permitted for
> breakpoints\n";
> + static const char warnxmon[] = "xmon: Enabling debugger hooks\n";
> int mode;
> case 'd': /* bd - hardware data breakpoint */
> mode = 7;
> @@ -1315,6 +1316,11 @@ bpt_cmds(void)
> dabr.address &= ~HW_BRK_TYPE_DABR;
> dabr.enabled = mode | BP_DABR;
> }
> + /* Enable xmon hooks if needed */
> + if (!xmon_on) {
> + printf(warnxmon);
> + xmon_on = 1;
> + }
Can we get this three liner into an inline function?
> break;
>
> case 'i': /* bi - hardware instr breakpoint */
> @@ -1335,6 +1341,12 @@ bpt_cmds(void)
> if (bp != NULL) {
> bp->enabled |= BP_CIABR;
> iabr = bp;
> +
> + /* Enable xmon hooks if needed */
> + if (!xmon_on) {
> + printf(warnxmon);
> + xmon_on = 1;
> + }
> }
> break;
> #endif
> @@ -1399,8 +1411,15 @@ bpt_cmds(void)
> if (!check_bp_loc(a))
> break;
> bp = new_breakpoint(a);
> - if (bp != NULL)
> + if (bp != NULL) {
> bp->enabled |= BP_TRAP;
> +
> + /* Enable xmon hooks if needed */
> + if (!xmon_on) {
> + printf(warnxmon);
> + xmon_on = 1;
> + }
> + }
> break;
> }
> }
> @@ -3651,9 +3670,22 @@ device_initcall(setup_xmon_sysrq);
> #ifdef CONFIG_DEBUG_FS
> static int xmon_dbgfs_set(void *data, u64 val)
> {
> + int i;
> +
> xmon_on = !!val;
> xmon_init(xmon_on);
>
> + /* make sure all breakpoints removed when disabling */
> + if (!xmon_on) {
> + for (i = 0; i < NBPTS; ++i)
> + bpts[i].enabled = 0;
> + /* if anything set inform user that breakpoints are cleared */
> + if (iabr || dabr.enabled)
> + pr_info("xmon: All breakpoints cleared\n");
> +
> + iabr = NULL;
> + dabr.enabled = 0;
Is this sufficient or do we need remove_bpts()
Balbir Singh
