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;
+ }
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;
+ }
return 0;
}
--
2.14.3
