boot: New boot_go hook

This new hook allows external modules to override the choice of which
image to boot - it can be used, for instance, to load an image based on
some GPIO state.

If the hook returns FIH_BOOT_HOOK_REGULAR, then normal platform
boot_go() will be run to choose image to boot.

This hook is shielded by a different configuration than other hooks -
MCUBOOT_BOOT_GO_HOOKS, so that it can be enabled independently from
other available hooks.

Support for this new hook was added to Zephyr port.

Signed-off-by: Ederson de Souza <[email protected]>

Author: edersondisouza

boot/bootutil/include/bootutil/boot_hooks.h

@@ -34,25 +34,54 @@
 #ifndef H_BOOTUTIL_HOOKS
 #define H_BOOTUTIL_HOOKS
 
-#ifdef MCUBOOT_IMAGE_ACCESS_HOOKS
+#include "bootutil/bootutil.h"
+#include "bootutil/fault_injection_hardening.h"
 
-#define BOOT_HOOK_CALL(f, ret_default, ...) f(__VA_ARGS__)
+#define DO_HOOK_CALL(f, ret_default, ...) \
+    f(__VA_ARGS__)
 
-#define BOOT_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+#define DO_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
     do { \
         FIH_CALL(f, fih_rc, __VA_ARGS__); \
     } while(0);
 
-#else
-
-#define BOOT_HOOK_CALL(f, ret_default, ...) ret_default
+#define HOOK_CALL_NOP(f, ret_default, ...) ret_default
 
-#define BOOT_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+#define HOOK_CALL_FIH_NOP(f, fih_ret_default, fih_rc, ...) \
     do { \
         fih_rc = fih_ret_default; \
     } while(0);
 
-#endif
+#ifdef MCUBOOT_IMAGE_ACCESS_HOOKS
+
+#define BOOT_HOOK_CALL(f, ret_default, ...) \
+    DO_HOOK_CALL(f, ret_default, __VA_ARGS__)
+
+#define BOOT_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+    DO_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, __VA_ARGS__)
+
+#else
+
+#define BOOT_HOOK_CALL(f, ret_default, ...) \
+    HOOK_CALL_NOP(f, ret_default, __VA_ARGS__)
+
+#define BOOT_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+    HOOK_CALL_FIH_NOP(f, fih_ret_default, fih_rc, __VA_ARGS__)
+
+#endif /* MCUBOOT_IMAGE_ACCESS_HOOKS */
+
+#ifdef MCUBOOT_BOOT_GO_HOOKS
+
+#define BOOT_HOOK_GO_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+    DO_HOOK_CALL_FIH(f, fih_ret_default, fih_rc, __VA_ARGS__);
+
+#else
+
+#define BOOT_HOOK_GO_CALL_FIH(f, fih_ret_default, fih_rc, ...) \
+    HOOK_CALL_FIH_NOP(f, fih_ret_default, fih_rc, __VA_ARGS__)
+
+#endif /* MCUBOOT_BOOT_GO_HOOKS  */
+
 
 /** Hook for provide image header data.
  *
@@ -173,6 +202,19 @@ int boot_img_install_stat_hook(int image_index, int slot,
  */
 int boot_reset_request_hook(bool force);
 
+/**
+ * Hook to implement custom action before boot_go() function.
+ *
+ * @param rsp boot response structure.
+ *
+ * @retval FIH_SUCCESS: boot_go() should be skipped, boot response is already
+ *         filled.
+ *         FIH_FAILURE: boot_go() should be skipped, boot response is already
+ *         filled with error.
+ *         FIH_BOOT_HOOK_REGULAR: follow the normal execution path.
+ */
+fih_ret boot_go_hook(struct boot_rsp *rsp);
+
 #define BOOT_RESET_REQUEST_HOOK_BUSY		1
 #define BOOT_RESET_REQUEST_HOOK_TIMEOUT		2
 #define BOOT_RESET_REQUEST_HOOK_CHECK_FAILED	3

boot/zephyr/Kconfig

@@ -772,6 +772,13 @@ config BOOT_IMAGE_ACCESS_HOOKS
 	  update. It is up to the project customization to add required source
 	  files to the build.
 
+config BOOT_GO_HOOKS
+	bool "Enable hooks for overriding MCUBOOT's boot_go routine"
+	help
+	  Allow to provide procedures for override or extend native
+	  MCUboot's boot_go routine. It is up to the project customization to
+	  add required source files to the build.
+
 config MCUBOOT_ACTION_HOOKS
 	bool "Enable hooks for responding to MCUboot status changes"
 	help

boot/zephyr/include/mcuboot_config/mcuboot_config.h

@@ -227,6 +227,10 @@
 #define MCUBOOT_IMAGE_ACCESS_HOOKS
 #endif
 
+#ifdef CONFIG_BOOT_GO_HOOKS
+#define MCUBOOT_BOOT_GO_HOOKS
+#endif
+
 #ifdef CONFIG_MCUBOOT_VERIFY_IMG_ADDRESS
 #define MCUBOOT_VERIFY_IMG_ADDRESS
 #endif

boot/zephyr/main.c

@@ -41,6 +41,7 @@
 #include "bootutil/bootutil_log.h"
 #include "bootutil/image.h"
 #include "bootutil/bootutil.h"
+#include "bootutil/boot_hooks.h"
 #include "bootutil/fault_injection_hardening.h"
 #include "bootutil/mcuboot_status.h"
 #include "flash_map_backend/flash_map_backend.h"
@@ -525,7 +526,10 @@ int main(void)
 #endif
 #endif
 
-    FIH_CALL(boot_go, fih_rc, &rsp);
+    BOOT_HOOK_GO_CALL_FIH(boot_go_hook, FIH_BOOT_HOOK_REGULAR, fih_rc, &rsp);
+    if (FIH_EQ(fih_rc, FIH_BOOT_HOOK_REGULAR)) {
+        FIH_CALL(boot_go, fih_rc, &rsp);
+    }
 
 #ifdef CONFIG_BOOT_SERIAL_BOOT_MODE
     if (io_detect_boot_mode()) {