[nrf fromlist] boot: zephyr: RAM cleanup debug loop

Option to put execution in infinite loop.
Meant to be used for debug.

Upstream PR #: 2370

Signed-off-by: Mateusz Michalek <mateusz.michalek@nordicsemi.no>
(cherry picked from commit b9274db5791c58c8e2172331c9e14594d18e7617)

Author: michalek-no

boot/zephyr/Kconfig

@@ -412,6 +412,13 @@ config MCUBOOT_CLEANUP_RAM
 	help
 	  Sets contents of memory to 0 before jumping to application.
 
+config MCUBOOT_INFINITE_LOOP_AFTER_RAM_CLEANUP
+	bool "Infinite loop after RAM cleanup"
+	depends on MCUBOOT_CLEANUP_RAM
+	help
+	  Verification option that keeps execution in infinite loop after
+	  RAM cleanup has been performed.
+
 # Disable MBEDTLS from being selected if NRF_SECURITY is enabled, and use default NRF_SECURITY
 # configuration file for MBEDTLS
 config MBEDTLS

boot/zephyr/main.c

@@ -294,6 +294,9 @@ static void do_boot(struct boot_rsp *rsp)
         "   b       clear\n"
         "out:\n"
         "   dsb\n"
+#if CONFIG_MCUBOOT_INFINITE_LOOP_AFTER_RAM_CLEANUP
+        "   b       out\n"
+#endif /*CONFIG_MCUBOOT_INFINITE_LOOP_AFTER_RAM_CLEANUP */
         /* jump to reset vector of an app */
         "   bx      r0\n"
         :