@@ -221,6 +221,29 @@ extern int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt);
*/
extern void kgdb_arch_late(void);
+/**
+ * kgdb_arch_enable_nmi - Enable or disable KGDB-entry NMI
+ * @on: Flag to either enable or disable an NMI
+ *
+ * This is an architecture-specific "back-end" for kgdb_enable_nmi(). The
+ * call does not count disable/enable requests, do not use it directly.
+ */
+extern void kgdb_arch_enable_nmi(bool on);
+
+/**
+ * kgdb_enable_nmi - Enable or disable KGDB-entry NMI
+ * @on: Flag to either enable or disable an NMI
+ *
+ * This function manages NMIs that usually cause KGDB to enter. That is,
+ * not all NMIs should be enabled or disabled, but only those that issue
+ * kgdb_handle_exception().
+ *
+ * The call counts disable requests, and thus allows to nest disables.
+ * But trying to enable already enabled NMI is an error. The call returns
+ * 1 if NMI has been actually enabled after the call, and a value <= 0 if
+ * it is still disabled.
+ */
+extern int kgdb_enable_nmi(bool on);
/**
* struct kgdb_arch - Describe architecture specific values.
@@ -214,6 +214,30 @@ int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
return 0;
}
+void __weak kgdb_arch_enable_nmi(bool on)
+{
+}
+
+int kgdb_enable_nmi(bool on)
+{
+ static atomic_t cnt;
+ int ret;
+
+ ret = atomic_add_return(on ? 1 : -1, &cnt);
+ if (ret > 1 && on) {
+ /*
+ * There should be only one instance that calls this function
+ * in "enable, disable" order. All other users must call
+ * disable first, then enable. If not, something is wrong.
+ */
+ WARN_ON(1);
+ return 1;
+ }
+
+ kgdb_arch_enable_nmi(ret > 0);
+ return ret;
+}
+
/*
* Some architectures need cache flushes when we set/clear a
* breakpoint:
@@ -672,6 +696,9 @@ 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;
+
+ kgdb_enable_nmi(0);
ks->cpu = raw_smp_processor_id();
ks->ex_vector = evector;
@@ -681,11 +708,14 @@ 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:
+ kgdb_enable_nmi(1);
+ return ret;
}
int kgdb_nmicallback(int cpu, void *regs)
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> --- include/linux/kgdb.h | 23 +++++++++++++++++++++++ kernel/debug/debug_core.c | 36 +++++++++++++++++++++++++++++++++--- 2 files changed, 56 insertions(+), 3 deletions(-)