kgdb: fix several kgdb regressions

kgdb core fixes:
- Check to see that mm->mmap_cache is not null before calling
  flush_cache_range(), else on arch=ARM it will cause a fatal
  fault.

- Breakpoints should only be restored if they are in the BP_ACTIVE
  state.

- Fix a typo in comments to "kgdb_register_io_module"

x86 kgdb fixes:
- Fix the x86 arch handler such that on a kill or detach that the
  appropriate cleanup on the single stepping flags gets run.

- Add in the DIE_NMIWATCHDOG call for x86_64

- Touch the nmi watchdog before returning the system to normal
  operation after performing any kind of kgdb operation, else
  the possibility exists to trigger the watchdog.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 7d651adcb222..8c7e555f6d39 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -370,6 +370,8 @@ int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
                 ptr = &remcomInBuffer[1];
                 if (kgdb_hex2long(&ptr, &addr))
                         linux_regs->ip = addr;
+        case 'D':
+        case 'k':
                 newPC = linux_regs->ip;
 
                 /* clear the trace bit */
@@ -480,6 +482,8 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
         if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
                 return NOTIFY_DONE;
 
+        /* Must touch watchdog before return to normal operation */
+        touch_nmi_watchdog();
         return NOTIFY_STOP;
 }
 
diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index 055b1650c69d..4e073320e70a 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -600,8 +600,13 @@ void die(const char * str, struct pt_regs * regs, long err)
 
 void __kprobes die_nmi(char *str, struct pt_regs *regs, int do_panic)
 {
-        unsigned long flags = oops_begin();
+        unsigned long flags;
+
+        if (notify_die(DIE_NMIWATCHDOG, str, regs, 0, 2, SIGINT) ==
+            NOTIFY_STOP)
+                return;
 
+        flags = oops_begin();
         /*
          * We are in trouble anyway, lets at least try
          * to get a message out.