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>

3 files changed, 18 insertions, 7 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.
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 31425e0fbf20..85b7e5b934a7 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -600,7 +600,7 @@ static void kgdb_flush_swbreak_addr(unsigned long addr)
         if (!CACHE_FLUSH_IS_SAFE)
                 return;
 
-        if (current->mm) {
+        if (current->mm && current->mm->mmap_cache) {
                 flush_cache_range(current->mm->mmap_cache,
                                   addr, addr + BREAK_INSTR_SIZE);
         } else {
@@ -729,14 +729,16 @@ int remove_all_break(void)
 
         /* Clear memory breakpoints. */
         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
-                if (kgdb_break[i].state != BP_SET)
-                        continue;
+                if (kgdb_break[i].state != BP_ACTIVE)
+                        goto setundefined;
                 addr = kgdb_break[i].bpt_addr;
                 error = kgdb_arch_remove_breakpoint(addr,
                                 kgdb_break[i].saved_instr);
                 if (error)
-                        return error;
-                kgdb_break[i].state = BP_REMOVED;
+                        printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
+                           addr);
+setundefined:
+                kgdb_break[i].state = BP_UNDEFINED;
         }
 
         /* Clear hardware breakpoints. */
@@ -1605,7 +1607,7 @@ static void kgdb_initial_breakpoint(void)
 }
 
 /**
- *      kkgdb_register_io_module - register KGDB IO module
+ *      kgdb_register_io_module - register KGDB IO module
  *      @new_kgdb_io_ops: the io ops vector
  *
  *      Register it with the KGDB core.