kgdb: Add the ability to schedule a breakpoint via a tasklet

Some kgdb I/O modules require the ability to create a breakpoint
tasklet, such as kgdboc and external modules such as kgdboe.  The
breakpoint tasklet is used as an asynchronous entry point into the
debugger which will have a different function scope than the current
execution path where it might not be safe to have an inline
breakpoint.  This is true of some of the kgdb I/O drivers which share
code with kgdb and rest of the kernel users.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 19d1b29..ee007ea 100644 (file)
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -271,6 +271,7 @@ extern int kgdb_mem2hex(char *mem, char *buf, int count);
 extern int kgdb_hex2mem(char *buf, char *mem, int count);
 
 extern int kgdb_isremovedbreak(unsigned long addr);
+extern void kgdb_schedule_breakpoint(void);
 
 extern int
 kgdb_handle_exception(int ex_vector, int signo, int err_code,

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 375e42f..fff5901 100644 (file)
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -114,6 +114,7 @@ EXPORT_SYMBOL_GPL(kgdb_active);
  */
 static atomic_t                        passive_cpu_wait[NR_CPUS];
 static atomic_t                        cpu_in_kgdb[NR_CPUS];
+static atomic_t                        kgdb_break_tasklet_var;
 atomic_t                       kgdb_setting_breakpoint;
 
 struct task_struct             *kgdb_usethread;
@@ -789,6 +790,31 @@ static void kgdb_unregister_callbacks(void)
        }
 }
 
+/*
+ * There are times a tasklet needs to be used vs a compiled in
+ * break point so as to cause an exception outside a kgdb I/O module,
+ * such as is the case with kgdboe, where calling a breakpoint in the
+ * I/O driver itself would be fatal.
+ */
+static void kgdb_tasklet_bpt(unsigned long ing)
+{
+       kgdb_breakpoint();
+       atomic_set(&kgdb_break_tasklet_var, 0);
+}
+
+static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
+
+void kgdb_schedule_breakpoint(void)
+{
+       if (atomic_read(&kgdb_break_tasklet_var) ||
+               atomic_read(&kgdb_active) != -1 ||
+               atomic_read(&kgdb_setting_breakpoint))
+               return;
+       atomic_inc(&kgdb_break_tasklet_var);
+       tasklet_schedule(&kgdb_tasklet_breakpoint);
+}
+EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
+
 static void kgdb_initial_breakpoint(void)
 {
        kgdb_break_asap = 0;