kernel/debug: Mask KGDB NMI upon entry

The new arch callback should manage NMIs that usually cause KGDB to
enter. That is, not all NMIs should be enabled/disabled, but only
those that issue kgdb_handle_exception().

We must mask it as serial-line interrupt can be used as an NMI, so
if the original KGDB-entry cause was say a breakpoint, then every
input to KDB console will cause KGDB to reenter, which we don't want.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 0557f24c6bca..17e073c309e6 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -672,6 +672,10 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 {
         struct kgdb_state kgdb_var;
         struct kgdb_state *ks = &kgdb_var;
+        int ret = 0;
+
+        if (arch_kgdb_ops.enable_nmi)
+                arch_kgdb_ops.enable_nmi(0);
 
         ks->cpu                 = raw_smp_processor_id();
         ks->ex_vector           = evector;
@@ -681,11 +685,15 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
         ks->linux_regs          = regs;
 
         if (kgdb_reenter_check(ks))
-                return 0; /* Ouch, double exception ! */
+                goto out; /* Ouch, double exception ! */
         if (kgdb_info[ks->cpu].enter_kgdb != 0)
-                return 0;
+                goto out;
 
-        return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
+        ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
+out:
+        if (arch_kgdb_ops.enable_nmi)
+                arch_kgdb_ops.enable_nmi(1);
+        return ret;
 }
 
 int kgdb_nmicallback(int cpu, void *regs)