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powerpc/xmon: Setup debugger hooks when first break-point is set 

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.

Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
[mpe: Just printf directly, no need for static const char[]]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Vaibhav Jain 2018-03-04 23:00:25 +05:30 committed by Michael Ellerman
parent b395e55b49
commit e1368d0c9e
1 changed files with 16 additions and 1 deletions
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17
arch/powerpc/xmon/xmon.c
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@ -1273,6 +1273,16 @@ static long check_bp_loc(unsigned long addr)
return 1; return 1;
} }
/* Force enable xmon if not already enabled */
static inline void force_enable_xmon(void)
{
/* Enable xmon hooks if needed */
if (!xmon_on) {
printf("xmon: Enabling debugger hooks\n");
xmon_on = 1;
}
}
static char *breakpoint_help_string = static char *breakpoint_help_string =
"Breakpoint command usage:\n" "Breakpoint command usage:\n"
"b show breakpoints\n" "b show breakpoints\n"
@ -1315,6 +1325,8 @@ bpt_cmds(void)
dabr.address &= ~HW_BRK_TYPE_DABR; dabr.address &= ~HW_BRK_TYPE_DABR;
dabr.enabled = mode | BP_DABR; dabr.enabled = mode | BP_DABR;
} }
force_enable_xmon();
break; break;
case 'i': /* bi - hardware instr breakpoint */ case 'i': /* bi - hardware instr breakpoint */
@ -1335,6 +1347,7 @@ bpt_cmds(void)
if (bp != NULL) { if (bp != NULL) {
bp->enabled |= BP_CIABR; bp->enabled |= BP_CIABR;
iabr = bp; iabr = bp;
force_enable_xmon();
} }
break; break;
#endif #endif
@ -1399,8 +1412,10 @@ bpt_cmds(void)
if (!check_bp_loc(a)) if (!check_bp_loc(a))
break; break;
bp = new_breakpoint(a); bp = new_breakpoint(a);
if (bp != NULL) if (bp != NULL) {
bp->enabled |= BP_TRAP; bp->enabled |= BP_TRAP;
force_enable_xmon();
}
break; break;
} }
} }