Add support for GCC stack protection
Introduce new build option ENABLE_STACK_PROTECTOR. It enables
compilation of all BL images with one of the GCC -fstack-protector-*
options.
A new platform function plat_get_stack_protector_canary() is introduced.
It returns a value that is used to initialize the canary for stack
corruption detection. Returning a random value will prevent an attacker
from predicting the value and greatly increase the effectiveness of the
protection.
A message is printed at the ERROR level when a stack corruption is
detected.
To be effective, the global data must be stored at an address
lower than the base of the stacks. Failure to do so would allow an
attacker to overwrite the canary as part of an attack which would void
the protection.
FVP implementation of plat_get_stack_protector_canary is weak as
there is no real source of entropy on the FVP. It therefore relies on a
timer's value, which could be predictable.
Change-Id: Icaaee96392733b721fa7c86a81d03660d3c1bc06
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
diff --git a/include/common/aarch32/el3_common_macros.S b/include/common/aarch32/el3_common_macros.S
index f6b7527..d7e0b3f 100644
--- a/include/common/aarch32/el3_common_macros.S
+++ b/include/common/aarch32/el3_common_macros.S
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
@@ -278,6 +278,12 @@
* ---------------------------------------------------------------------
*/
bl plat_set_my_stack
+
+#if STACK_PROTECTOR_ENABLED
+ .if \_init_c_runtime
+ bl update_stack_protector_canary
+ .endif /* _init_c_runtime */
+#endif
.endm
#endif /* __EL3_COMMON_MACROS_S__ */
diff --git a/include/common/aarch64/el3_common_macros.S b/include/common/aarch64/el3_common_macros.S
index e085f9f..5c6aa06 100644
--- a/include/common/aarch64/el3_common_macros.S
+++ b/include/common/aarch64/el3_common_macros.S
@@ -283,6 +283,12 @@
* ---------------------------------------------------------------------
*/
bl plat_set_my_stack
+
+#if STACK_PROTECTOR_ENABLED
+ .if \_init_c_runtime
+ bl update_stack_protector_canary
+ .endif /* _init_c_runtime */
+#endif
.endm
#endif /* __EL3_COMMON_MACROS_S__ */
diff --git a/include/common/debug.h b/include/common/debug.h
index 41c8df0..c6f211f 100644
--- a/include/common/debug.h
+++ b/include/common/debug.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
@@ -84,6 +84,9 @@
void __dead2 do_panic(void);
#define panic() do_panic()
+/* Function called when stack protection check code detects a corrupted stack */
+void __dead2 __stack_chk_fail(void);
+
void tf_printf(const char *fmt, ...) __printflike(1, 2);
#endif /* __ASSEMBLY__ */
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index 73bb643..f13b30d 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -72,6 +72,16 @@
unsigned int plat_my_core_pos(void);
int plat_core_pos_by_mpidr(u_register_t mpidr);
+#if STACK_PROTECTOR_ENABLED
+/*
+ * Return a new value to be used for the stack protection's canary.
+ *
+ * Ideally, this value is a random number that is impossible to predict by an
+ * attacker.
+ */
+u_register_t plat_get_stack_protector_canary(void);
+#endif /* STACK_PROTECTOR_ENABLED */
+
/*******************************************************************************
* Mandatory interrupt management functions
******************************************************************************/
@@ -326,7 +336,7 @@
unsigned int plat_get_aff_count(unsigned int, unsigned long);
unsigned int plat_get_aff_state(unsigned int, unsigned long);
-#else
+#else /* __ENABLE_PLAT_COMPAT__ */
/*
* The below function enable Trusted Firmware components like SPDs which
* haven't migrated to the new platform API to compile on platforms which
@@ -335,4 +345,6 @@
unsigned int platform_get_core_pos(unsigned long mpidr) __deprecated;
#endif /* __ENABLE_PLAT_COMPAT__ */
+
#endif /* __PLATFORM_H__ */
+