6 files changed, 41 insertions, 2 deletions

diff --git a/arch/x86/include/asm/kgdb.h b/arch/x86/include/asm/kgdb.h
index e6c6c808489f..006da3687cdc 100644
--- a/arch/x86/include/asm/kgdb.h
+++ b/arch/x86/include/asm/kgdb.h
@@ -76,4 +76,7 @@ static inline void arch_kgdb_breakpoint(void)
 #define BREAK_INSTR_SIZE        1
 #define CACHE_FLUSH_IS_SAFE     1
 
+extern int kgdb_ll_trap(int cmd, const char *str,
+                        struct pt_regs *regs, long err, int trap, int sig);
+
 #endif /* _ASM_X86_KGDB_H */
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index acba57169938..95b89d4cb8f1 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -538,7 +538,7 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
                         return NOTIFY_DONE;
         }
 
-        if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
+        if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
                 return NOTIFY_DONE;
 
         /* Must touch watchdog before return to normal operation */
@@ -546,6 +546,26 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
         return NOTIFY_STOP;
 }
 
+#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
+int kgdb_ll_trap(int cmd, const char *str,
+                 struct pt_regs *regs, long err, int trap, int sig)
+{
+        struct die_args args = {
+                .regs   = regs,
+                .str    = str,
+                .err    = err,
+                .trapnr = trap,
+                .signr  = sig,
+
+        };
+
+        if (!kgdb_io_module_registered)
+                return NOTIFY_DONE;
+
+        return __kgdb_notify(&args, cmd);
+}
+#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
+
 static int
 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 {
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 02cfb9b8f5b1..7eaad4c5110a 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -15,6 +15,7 @@
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/kgdb.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/ptrace.h>
@@ -451,6 +452,11 @@ void restart_nmi(void)
 /* May run on IST stack. */
 dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
 {
+#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
+        if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
+                        == NOTIFY_STOP)
+                return;
+#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 #ifdef CONFIG_KPROBES
         if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
                         == NOTIFY_STOP)
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 406f6f9286f3..19d1b29a2694 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -60,6 +60,7 @@ struct uart_port;
 void kgdb_breakpoint(void);
 
 extern int kgdb_connected;
+extern int kgdb_io_module_registered;
 
 extern atomic_t                 kgdb_setting_breakpoint;
 extern atomic_t                 kgdb_cpu_doing_single_step;
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 88a83a225374..375e42f0baf0 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -66,7 +66,7 @@ int				kgdb_connected;
 EXPORT_SYMBOL_GPL(kgdb_connected);
 
 /* All the KGDB handlers are installed */
-static int                      kgdb_io_module_registered;
+int                     kgdb_io_module_registered;
 
 /* Guard for recursive entry */
 static int                      exception_level;
diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
index ee8ae7132f20..c56ccb4ad292 100644
--- a/lib/Kconfig.kgdb
+++ b/lib/Kconfig.kgdb
@@ -57,6 +57,15 @@ config KGDB_TESTS_BOOT_STRING
           information about other strings you could use beyond the
           default of V1F100.
 
+config KGDB_LOW_LEVEL_TRAP
+       bool "KGDB: Allow debugging with traps in notifiers"
+       depends on X86
+       default n
+       help
+         This will add an extra call back to kgdb for the breakpoint
+         exception handler on which will will allow kgdb to step
+         through a notify handler.
+
 config KGDB_KDB
         bool "KGDB_KDB: include kdb frontend for kgdb"
         default n