[Skiboot] [PATCH] core: Catch attempts to branch through a NULL pointer

[Benjamin Herrenschmidt]

Display an assertion and a backtrace

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
 core/init.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/core/init.c b/core/init.c
index 8acc44c..1ed7501 100644
--- a/core/init.c
+++ b/core/init.c
@@ -501,6 +501,17 @@ static void dt_init_misc(void)
 	dt_fixups();
 }
 
+static void branch_null(void)
+{
+	assert_fail("Branch to NULL !");
+}
+
+static void setup_branch_null_catcher(void)
+{
+	void (*bn)(void) = branch_null;
+	memcpy(0, bn, 16);
+}
+
 /* Called from head.S, thus no prototype. */
 void __noreturn main_cpu_entry(const void *fdt, u32 master_cpu);
 
@@ -527,6 +538,11 @@ void __noreturn main_cpu_entry(const void *fdt, u32 master_cpu)
 	 */
 	clear_console();
 
+	/* Put at 0 an OPD to a warning function in case we branch through
+	 * a NULL function pointer
+	 */
+	setup_branch_null_catcher();
+
 	printf("SkiBoot %s starting...\n", version);
 	printf("initial console log level: memory %d, driver %d\n",
 	       (debug_descriptor.console_log_levels >> 4),