soc/nordic/nrf54h/pm_s2ram: S2RAM resume hardening

Added support for hardening decision on resume from
S2RAM by MCUboot bootloader.

Signed-off-by: Andrzej Puzdrowski <[email protected]>

Author: nvlsianpu

boards/nordic/nrf54h20dk/nrf54h20dk_nrf54h20_cpuapp.dts

@@ -349,11 +349,11 @@ zephyr_udc0: &usbhs {
 
 / {
 	soc {
-		/* run-time common S2RAM cpu context RAM */
-		pm_s2ram: cpuapp_s2ram@22007fe0  {
+		/* run-time common mcuboot S2RAM support section */
+		mcuboot_s2ram: cpuapp_s2ram@22007fe0  {
 			compatible = "zephyr,memory-region", "mmio-sram";
 			reg = <0x22007fe0 32>;
-			zephyr,memory-region = "pm_s2ram_context";
+			zephyr,memory-region = "mcuboot_s2ram_context";
 		};
 	};
 };

soc/nordic/nrf54h/pm_s2ram.c

@@ -219,10 +219,24 @@ static void fpu_restore(_fpu_context_t *backup)
 #endif /* !defined(CONFIG_FPU_SHARING) */
 #endif /* defined(CONFIG_FPU) */
 
+#if DT_NODE_EXISTS(DT_NODELABEL(mcuboot_s2ram)) &&\
+	DT_NODE_HAS_COMPAT(DT_NODELABEL(mcuboot_s2ram), zephyr_memory_region)
+/* Linker section name is given by `zephyr,memory-region` property of
+ * `zephyr,memory-region` compatible DT node with nodelabel `mcuboot_s2ram`.
+ */
+__attribute__((section(DT_PROP(DT_NODELABEL(mcuboot_s2ram), zephyr_memory_region))))
+struct mcuboot_resume_s _mcuboot_resume;
+
+#define SET_MCUBOOT_RESUME_MAGIC() do {_mcuboot_resume.magic = MCUBOOT_S2RAM_RESUME_MAGIC;} while (0)
+#else
+#define SET_MCUBOOT_RESUME_MAGIC()
+#endif
+
 int soc_s2ram_suspend(pm_s2ram_system_off_fn_t system_off)
 {
 	int ret;
 
+	SET_MCUBOOT_RESUME_MAGIC();
 	scb_save(&backup_data.scb_context);
 #if defined(CONFIG_FPU)
 #if !defined(CONFIG_FPU_SHARING)

soc/nordic/nrf54h/pm_s2ram.h

@@ -10,6 +10,12 @@
 #ifndef _ZEPHYR_SOC_ARM_NORDIC_NRF_PM_S2RAM_H_
 #define _ZEPHYR_SOC_ARM_NORDIC_NRF_PM_S2RAM_H_
 
+#define MCUBOOT_S2RAM_RESUME_MAGIC 0x75832419
+
+struct mcuboot_resume_s {
+    uint32_t magic;    /* magic value to identify valid structure */
+};
+
 /**
  * @brief Save CPU state on suspend
  *